Hardening of sawplates

[rob streeper]

All,

I've written some of this information elsewhere but decided to reproduce it here so that the thread will be complete, please forgive the repetition.

Having recently acquired a 36 inch heat treating oven and a Chinese Rockwell tester at a good price I have decided to do some testing on saw plate materials.
Why? Because it interests me and I am curious by nature. I like learning new things, I like building saws (among other things) and I want to build the best saws possible. This thread is in the same spirit as my threads on vacuum infusion of handles with resin and the use of bronze bushings/bearings for strengthening saw screw holes in handles. Why? Why not.

I have read elsewhere on the web that Disston hardened its saw plates to Rc 52.

As IsaacS and I have described in another thread on this site, the use of the C scale of Rockwell hardness, denoted "Rc", testing with the 120 degree Brale diamond indenter is limited by a combination of material hardness and thickness. Authorities differ somewhat on guidance but they state that the thickness of the material being tested should be at least three times the diameter of the indentation made by the indenter, other authorities call for 10X thickness. Thus, for a saw plate with a hardness of Rc 52 the minimum recommended thickness is 0.032". Rc testing of thinner or softer materials is not recommended as the scale becomes non-linear due to indenter induced stretching of the test article around the test point. However, I maintain that for materials of equal thickness that are harder than Rc 20 or so that the Rc test probably gives a good reading of relative hardness despite the invalidity of the Rc scale. I have decided to denote this scale Rc* indicating the application of Rc testing to materials that are regarded too thin to test by this method.

Thus, after setting up my Rockwell tester and calibrating it, delta = 0.5 U over the range 27.2 to 62.2, dead on at 46.1, I set about measuring the hardness of my personal stock of saws.

My first test was of an old (1917-1928 era I think) Disston D-8 I acquired on Ebay. The plate thickness measured at exactly 0.032" at the tooth line. Rc testing, at five different points, yielded five measurements of Rc 52.

My second set of tests was performed on the five commercially available dovetail saws in my collection. These are from two manufacturers. I have one from manufacturer 1 and four from manufacturer 2. I also have a strip of 0.015" 1095 spring steel that I use for my straight handle gents saws. I used this material as a standard. Like many 1095 strips, this one is reported to have a nominal Rc hardness between 48 and 52. I meausured Rc* 42-43 with my tester. The saw from manufacturer 1 gave back readings identical to those taken on the standard 1095 strip. I did multi-point measurements of manufacturer #2 saws and found that they ranged from Rc* 35-36+. All of the plates at the points tested were 0.015" to the best of my ability to read the micrometer. I conclude therefore that manufacturer 1 used 1095 straight from the roll or something of the same hardness even if the chemistry was not the same. Manufacturer #2, given the consistently lower Rc* readings, used steel that was significantly softer.

I then moved on to another saw, this on from manufacturer #3, that had a 0.030" thick plate at the test points. This plate gave the astonishingly low reading of Rc* 11. I have not been too pleased with the performance of this saw and visual inspection of the indentations produced by testing are consistent with the Rc* readings - it is soft.

Not wanting to spend too much time at this point examining the work of others I then began heat treating experiments. I haven't taken pictures because the process is visually boring so I will just report the results.

I have found that 0.015" 1095 steel can be hardened to Rc* 59+ using a range of soak times at temperatures from 749 to 807 Celsius. Soak times range from 45 minutes to 3 minutes for this material over this range. Given that I could produce adequate hardness I investigated annealing.

Googled values for 1095 and a quick Excel calculation (R squared of the fit line = 0.9957) revealed that 1095 could be annealed to Rc 52 with soaking at a temperature of 342 Celsius for two hours - longer than necessary but I am using residual heat for economy. This worked out according to the book, no problems at all. The hardening and annealing produced nice uniform hardness throughout the material and I was easily able to hit my mark of around Rc* 45-46.

Next comes the quenching. I started out using room temperature water. It was easy to get hard material but the temperature gradients that arose when the metal was transiting the surface of the quench bath caused severe distortion. I then proceeded to try hot water, cool brine, hot brine cool oil and hot oil. The best results so far have come with hot oil but I am still not satisfied.

Unfortunately I am stopped as I am waiting on the components needed to make a molten salt bath. I'll post more results when I have them.

Cheers,
Rob

[BobL]

Good work Rob. About 5 years ago I did some hardness measurements of a range of materials (mainly scraper blades) at local hardware shops to determine which could be used for saw blades. I bough a whole lot of stuff tested it and then returned it to the hardware stores for a full refund because the testing only left a pinprick indent in the material. The is how I discovered the Blue scraper material that quite a few Aussies are using as small saw blades.

Just a couple of points.
If you could set out your results on a table that would make it much easier to compare what is going on.

RC hardnesses measurements are very difficult to measure accurately below ~30 RC as the RC scale was not designed for harnesses below this. To measure hardness in this range other scales should be used. However as you say you can still use the results for comparative purposes.

Pictures are not at all boring especially if you can photograph the process, how you heat, transfer to quench bath, Orientation of material while quenching etc.

I'm not sure, but you seem to be confusing annealing with tempering?
Even if you are not your post might sound confusing to a newbie.,
The sequence is usual annealing to as soft as practicable, working the material, hardening, and then tempering.

For most tool steels, only hardening usually requires a quench.
Annealing and tempering are done by heating and usually letting the steel cooling off in air.
For SS its the reverse.

Quenching a big piece of flat steel is indeed very tricky.
It should be dunked as quickly as possible into the quench bath and moved around within the bath to cool the material off asap.
A sandwich between thicker material may help but will need longer heating times.
Ideally the bath should be consderably deeper than the dimension of the material being dunked so the material can be moved up and down to assist the quench.
Also the material does not need to be brought down to room temperature to be quenched so pre-heating the oil (~100ºC) may reduce distortion.

Be really careful with a molten salt bath, especially with any water as it explodes on contact with molten salt.

[Simplicity]

Rob
I won't say much.
But the reason is you have said it all and so much more in the last six months or so here.
Tho I may never but never say never go to the lengths you are.
They do make for some fascination reading.
Your enthusiasm for your art form and yes I mean art form is very encouraging.
Please keep posting
And will be trying some more ideas my self once I'm back in my creative zone(I hate the man cave thing lol)
Matt

[rob streeper]

Just a couple of points.
If you could set out your results on a table that would make it much easier to compare what is going on.

Pictures are not at all boring especially if you can photograph the process, how you heat, transfer to quench bath, Orientation of material while quenching etc.

I'm not sure, but you seem to be confusing annealing with tempering?
Even if you are not your post might sound confusing to a newbie.,
The sequence is usual annealing to as soft as practicable, working the material, hardening, and then tempering.


Quenching a big piece of flat steel is indeed very tricky.
It should be dunked as quickly as possible into the quench bath and moved around within the bath to cool the material off asap.


Be really careful with a molten salt bath, especially with any water as it explodes on contact with molten salt.

Hi Bob,

Yes, I plan data tables - I was at the end of the day at the time I posted the above and was too tired to make them up, I also want them to reflect all of the data I acquire.

Yes, technically the adjustment of hardness is tempering/ drawing, fatigue dulls the mind.

I am learning that heat distortion of thin sections can be dramatic. Cold water produced the worst, followed by warm water and so on up to hot oil which wasn't nearly as bad as cold water but still was unacceptable for a saw plate. I'm pretty close with hot oil so I think a bath that is just a little hotter will do the trick.

Yes, I forgot the safety admonition. Hot troughs of molten oxidizers can get exciting in a hurry. Water, sawdust, windblown leaves, fingers and other organic materials can combine with hot oxidizers in important, surprising and extraordinarily unpleasant ways. The usual firefighting measures will often make the problem worse as well. I keep a fire blanket, sand bucket and a dry chemical extinguisher ready in my work area. Amazingly however the reference I am reading on salt bath tempering states that water can be added to them. Sounds a little too exciting to me so I think I'll check the results without water first.

So no one who is not thoroughly familiar with safety techniques and the proper handling of dangerous processes such as I describe should try reproducing my projects. I have 30+ years of laboratory safety training and I still occasionally get my fingers nipped.

I'll post more later, this is turning into a busy week.

Cheers,
Rob

[jcge]

Please take this in the spirit it is intended - only to progress the discussion, and not in any way to detract from your good work. It's great to see actual measurement in action (as opposed to the usually more subjective posts that seem to proliferate)

Have you considered the effects of work hardening? (post heat treatment - pretensioning or hammering as applied to circ saw baldes, and roll straightening of sawplate or setting of the teeth on handsaws?)

I can imagine (...subjectively...) that setting (and perhaps reverse setting) teeth would have a significant work hardening effect at the tooth line. It is afterall only the teeth that are cutting.

Regards,
John

[rob streeper]

Please take this in the spirit it is intended - only to progress the discussion, and not in any way to detract from your good work. It's great to see actual measurement in action (as opposed to the usually more subjective posts that seem to proliferate)

Have you considered the effects of work hardening? (post heat treatment - pretensioning or hammering as applied to circ saw baldes, and roll straightening of sawplate or setting of the teeth on handsaws?)

I can imagine (...subjectively...) that setting (and perhaps reverse setting) teeth would have a significant work hardening effect at the tooth line. It is afterall only the teeth that are cutting.

Regards,
John

Hi John,

I agree completely. The cold working will certainly have an effect on the hardness of the saw plate.

I do projects like this because I want to know. I have a background in the sciences and I learn things through systematic and controlled studies. I reason that if Henry Disston did, or commissioned, studies that lead him to conclude that Rc 52 was the optimum hardness for saw blades he must have had very good reason to do so. However, over the intervening years his standard for hand saws has not evolved, at least publicly. I know that the blades of today's power driven saws using modern materials are true marvels, even those lacking tungsten carbide or other, now commonplace, exotica. But what of handsaws? What innovations have happened in the hand saw world in the last fifty years?

There seems to be a consensus among present day saw makers and wood workers that 1095 spring steel is the best available material for making saw blades and I do not dispute that some makers are turning out really fine products. However given my inquisitive nature, my strong technical bent and my interest in tool making I want to know if it can be done better. These studies may be dead ends, but if they are at least we know that.


Cheers,
Rob

[Ron Bontz]

Interesting read. I should send you a couple of my saw plates and see what you find. :)

[jcge]

These studies may be dead ends, but if they are at least we know that.
Cheers,
Rob

I really like your perspective Rob. There is clearly a defacto "standard" or benchmark but from where was it bourne? Was it established empirically, or by limitation or reason of economy, availability or applied study? And as to innovation beyond the benchmark ? Perhaps its all silently held close to the modern (boutique?) makers chests (who's work I also do admire).

I'd not for a moment believe you're headed toward a dead end, and as you rightly say, at least we will know. I applaud your efforts and particularly your willingness to share your results.

Regards,
John

[rob streeper]

Interesting read. I should send you a couple of my saw plates and see what you find. :)

Hi Ron,

Sure, if you would like to send samples I am happy to help. I don't need a whole saw plate, just a couple of pieces a few square inches in size will do. The diamond indenter point makes a mark <1 mm to ~1.5/2mm in radius so I can test the area around the teeth easily.

Cheers,
Rob

[rob streeper]

I really like your perspective Rob. There is clearly a defacto "standard" or benchmark but from where was it bourne? Was it established empirically, or by limitation or reason of economy, availability or applied study? And as to innovation beyond the benchmark ? Perhaps its all silently held close to the modern (boutique?) makers chests (who's work I also do admire).

I'd not for a moment believe you're headed toward a dead end, and as you rightly say, at least we will know. I applaud your efforts and particularly your willingness to share your results.

Regards,
John

Thanks John,
The apparent disparity between the levels of development of handsaws vs. power saw blades is really what prompted me to begin here. I recently took delivery of some Lenox bandsaw blades, their Diemaster II, that are made from M42. The blades are amazing stuff - sharp, durable and amazing performers. Why not use such steel for handsaws? Is such a step needed? Is it worth the expense? Can 1095 be better than it comes from the mill?

Cheers,
Rob

[rob streeper]

Here is what NIST has to say about Rockwell testing.

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[Pagie]

When I was bricklaying we use to go into a shop to the trowel section and hit the trowels against each other edge to edge. The soft ones would be cut about 5mm. We only bought the hard ones that did the cutting.

[Sawdust Maker]

... But what of handsaws? What innovations have happened in the hand saw world in the last fifty years?

...
Cheers,
Rob

I can answer this one
Totes have become ugly and uncomfortable (and plastic)

sorry you were talking about steel etc, carry on :2tsup:

[pmcgee]

... I am learning that heat distortion of thin sections can be dramatic. Cold water produced the worst, followed by warm water and so on up to hot oil which wasn't nearly as bad as cold water but still was unacceptable for a saw plate. I'm pretty close with hot oil so I think a bath that is just a little hotter will do the trick.

William Clemson wanted me to point this out ... :)
http://www.wkfinetools.com/hus-saws/msw-wmc/pressBooks/1860-ScientAmerican/1860-ScienAmerican-01.asp
Great job here.
Cheers,
Paul

[pmcgee]

Clemson might have something to contribute here ... but he's lost in on the razor thing I think ...

http://www.wkfinetools.com/hus-saws/msw-wmc/pressBooks/1866-ScienAmerican-ChangesInSteel/12-08-1866-ScienAmerican-ChangesInSteel.asp

"SCIENTIFIC AMERICAN of December 8th, 1866

Messrs. Editors — "The singular quality of steel" alluded to in the SCIENTIFIC AMERICAN of Nov. 3d, is familiar to all saw makers.


When a hand saw is hardened and tempered it is crooked but elastic. Hammering it straight takes from it its elasticity, but not its hardness; for it yet grinds and files hard. Grinding and, polishing will destroy the spring nearly as effectively as the hammering, either of which affects soft steel in a manner exactly the reverse.


To restore the elasticity of saws, they are exposed to a degree of heat that will produce a straw color, and if not done too quickly this will be effectual. The color is removed with an acid; the presence or absence of it makes no difference in the elasticity of the saw; that is doubtless due to a certain definite arrangement of the grain of the steel."



This link reminded me of the japanese swordsmiths coating the backs (edge?) of the blades in clay so the edge became hard and the back remained softer. Any application to backsaws? would a difference in hardness make a difference in straightness while cooling?
http://www.wkfinetools.com/hus-saws/msw-wmc/pressBooks/1886-ScientAmerican/1886-ScientAmerican.asp

[jcge]

Just another thought...perhaps saw plate hardness was limited by the need to be able to sharpen the saw in service by the user with a hand file. I'm unsure of what that limit (on Rc scale) might be.

Regards,
John

[BobL]

Just another thought...perhaps saw plate hardness was limited by the need to be able to sharpen the saw in service by the user with a hand file. I'm unsure of what that limit (on Rc scale) might be.

Regards,
John

A difference in RC hardness of around 10 is needed between the file and the metal being filed to easily file the metal and not rapidly ruin the file.

The hardness is also limited by the need to create set in the teeth.
Hard teeth are much more likely to break during the setting process.
Although much less likely I'd much rather the teeth go blunt if they accidentally strike something hard than snap off.

[rob streeper]

A difference in RC hardness of around 10 is needed between the file and the metal being filed to easily file the metal and not rapidly ruin the file.

The hardness is also limited by the need to create set in the teeth.
Hard teeth are much more likely to break during the setting process.
Although much less likely I'd much rather the teeth go blunt if they accidentally strike something hard than snap off.

That's one of the reasons I want to do more here. Modern metallurgy has advanced tremendously since Disston's day so I am certain that handsaws can be better than they ever have been. Disston used Rc 52, which was best for the steel that was state of the art then.
I also have a couple of modern pull type saws with induction hardened teeth. They are fine for soft pine but the teeth tend to break on anything harder. Obviously the lowest possible specification steel for low materials cost.

[BobL]

I also have a couple of modern pull type saws with induction hardened teeth. They are fine for soft pine but the teeth tend to break on anything harder. Obviously the lowest possible specification steel for low materials cost.

I have a couple of those saw and have put one in particular through fair bit of often dirty aussie hardwood until it became very blunt, without breaking any teeth. What I have noticed with those blades is that they also seem to be made with minimal set so after a bit of wear they jam very easily.

[pmcgee]

I have a couple of those saw and have put one in particular through fair bit of often dirty aussie hardwood until it became very blunt, without breaking any teeth. What I have noticed with those blades is that they also seem to be made with minimal set so after a bit of wear they jam very easily.
Ditto for an Irwin, induction-hardened, japanese-style tooth, push-saw. about 40 thou sawblade untapered.

Rob - it would be interesting to know what reading you'd get from an Acme 120 or the equivalent Backsaw (77??)

Cheers,
Paul

(I have one if Bob is able to measure it. Would it be uniform across the whole sawblade?)

[Bushmiller]

Rob

Good thread. It gets us going

Regards
Paul

[jcge]

Would it be uniform across the whole sawblade?

That's a very interesting question Paul

Looking at http://www.disstonianinstitute.com/factorytour.html from Henry Disston and Sons, Inc., Lumberman Handbook, Published 1907, the saw plate is hardened "edge first", followed by hammering ("smithing" and "tensioning").


Regards
John

[Bushmiller]

My understanding of the constraints of a saw plate are twofold.

Firstly they have to be sharpenable with a standard triangular file.

Secondly you must be able to set the teeth without them snapping off or stress fracturing and breaking at a later date.

This pretty much dictated the maximum hardness that was practical, being RC52

They did experiment with no set saws such as the Disston 120 and that was harder although I don't know what it was. They also used a special shape file to sharpen and that is no longer available. Today with that 120 it has to be sharpened conventionally with a triangular file and, from what I have read, there is the distinct possibility that the teeth will break. Consequently I suspect they tend to be collector saws rather than user saws.

Even with modern steels there is still the issue of sharpening with a conventional file. Until file steel catches up with "modern" steels the limitation Henry and his descendants experienced up to and just after WW2 still exists today.

We do have machine sharpening available and quite possibly that can cope with harder steels, but I have no information on that. I also have to say that if we are chasing the supreme saw plate, we are rather defeating the object if we then have to machine sharpen which most seem to agree is inferior to hand sharpening by skilled persons.

Please don't misunderstand my comments as I think this is an admirable thread and I find information like this fascinating. I also suspect that the major saw makers of the early twentieth century relied heavily on flowery marketing phrases, which in the main part could not be easily verified. Consequently there was probably quite a wide range of variation in the product. Your testing may well de-bunk some of their more outlandish claims.

Much of the "excellence" in their high range saws was probably cosmetic (finish of the plate, etching, tote carving and tote material) and only a small part practical. By this I mean how much extra tempering, hammering and tapering went into a saw plate. Sure, tapering can be measured. Nowadays very easily with a digital vernier guage, but not so easily at the time of manufacture by the customer. Again, don't misunderstand me as I love those cosmetic touches and actively seek them out. It is a luxury the hardworking carpenter of the day could hardly justify. Today I still can't justify it, but it doesn't stop me :) .

Regards
Paul

[rob streeper]

Quick update:

The salts have arrived. I melted some today - no drama. The melt was well behaved, brown (technical grade KNO3) and did not react badly to the few leaves that fell in the pot while I was watching it. It is clear however that I need an insulated pot and higher wattage heaters. I used a 750W hotplate with the salt in a welded rectangular stainless pan. The hotplate was only able to bring the melt temperature to about 200 C. The references say 210+ for 1095 steel. I'm thinking dual pots with a sand bath to retain heat and a couple of more powerful hot plates. More updates as I make progress.

Cheers,
Rob

306031

[jcge]

Wow Rob that is quite an undertaking !! Bath salts sounded so relaxing...:)(

Regards
John

[pmcgee]

Hey - you might wanna go down this path ... http://www.wkfinetools.com/tMaking/z_reading/1913-SteelSelectAnnHardTemp/0_img-pdf/1913-Steel-Markham.pdf

Hardening in a Lead bath sounds like fun for all the family ... and ... don't forget the Cyanide of Potash.

306809

but actually on pg 178 it starts to talk about hardening thin plates ... and seems to favour compression between matching plates.

Cheers,
Paul

[Pagie]

I have read through a lot of that book, far too hard for me to harden steel. I'll stick to buying old saws at markets and retoothing them if I need to.

[rob streeper]

I have read through a lot of that book, far too hard for me to harden steel. I'll stick to buying old saws at markets and retoothing them if I need to.

306870

From life's school of war: what does not kill me makes me stronger

[GraemeCook]

.....
Firstly they have to be sharpenable with a standard triangular file.

Secondly you must be able to set the teeth without them snapping off or stress fracturing and breaking at a later date.

This pretty much dictated the maximum hardness that was practical, being RC52
............
Even with modern steels there is still the issue of sharpening with a conventional file. Until file steel catches up with "modern" steels the limitation Henry and his descendants experienced up to and just after WW2 still exists today.

We do have machine sharpening available and quite possibly that can cope with harder steels, but I have no information on that.

Regards
Paul


Good Morning Paul

All good stuff. Even if we can machine sharpen supremely hard "modern steels" we are still left with the brittleness issue, are we not?

Years ago I bought a set of stainless steel Gerber kitchen knives in a shield shaped wooden rack - looked really great, worked well, stayed shiny, held their edge really well - eventually they required sharpening and that was a real task due to the hardness of the steel. But I can wear that. A "bonus" and matching cleaver came with the set - I butchered a pig and finished up with three chips out of the blade of the cleaver and multiple fine cracks from the blade edge. Gerber's "life time" warrantee did not cover "abuse" such as chopping with a cleaver! Within a couple of years many similar fine cracks appeared in the cutting edges of the knives and two of the blades simply snapped. Gerbers standard answer was that it was not covered by warrantee as the knives had been abused.. That lovely looking stainless steel was simply too hard and too brittle for the task. Great to look at, but not fit for purpose.




Fair Winds

Graeme

I will never again buy crap tools.
I will never again buy crap tools.
I will never again buy crap tools.

[Bushmiller]

Good Morning Paul

All good stuff. Even if we can machine sharpen supremely hard "modern steels" we are still left with the brittleness issue, are we not?

Years ago I bought a set of stainless steel Gerber kitchen knives in a shield shaped wooden rack - looked really great, worked well, stayed shiny, held their edge really well - eventually they required sharpening and that was a real task due to the hardness of the steel. But I can wear that. A "bonus" and matching cleaver came with the set - I butchered a pig and finished up with three chips out of the blade of the cleaver and multiple fine cracks from the blade edge. Gerber's "life time" warrantee did not cover "abuse" such as chopping with a cleaver! Within a couple of years many similar fine cracks appeared in the cutting edges of the knives and two of the blades simply snapped. Gerbers standard answer was that it was not covered by warrantee as the knives had been abused.. That lovely looking stainless steel was simply too hard and too brittle for the task. Great to look at, but not fit for purpose.




Fair Winds

Graeme

I will never again buy crap tools.
I will never again buy crap tools.
I will never again buy crap tools.



Graeme

The short answer is that there was never much room to manoeuver regarding edge retention and brittleness.

Your experience with kitchen knives is a good example of as the "quality" of the knife increases, it's usefulness lessens and it's specialised nature becomes evident. Japanese kitchen knives are a good example of this in that they are super sharp, but you have to be extraordinarily careful what you cut with them as they will chip even if they look at a piece of bone. Incidentally, you have to try a Japanese kitchen knife if you really want to experience sharp :) .

I would suggest that Gerber's lifetime guarantee would have been challengeable, but hardly worth the effort.

Take the Disston 120, which had a harder saw plate, was carefully taper ground and consequently was sold requiring no set: It was recommended to be used in seasoned hardwoods as it had the potential to jam in green or fluffy softwoods. It had become more specialised. Disston were not the only manufacturer to try the no set approach. Atkins' No.52 was the same deal.

Regards
Paul

[Bushmiller]

Well I had a go at using my hardness guages today and my conclusion is that they are very hard to use :(.

I I started with the 60RC file which seemed to easily file the saw back. I progressively worked to down through 55RC, 50RC and 45RC. I could eliminate the 45RC quite easily. I felt the 55 file away, but I just wasn't sure about the 50 file.

I think BobL said that for a file to work comfortably the has to be a differential of at least 10RC. That probably puts the plate somewhere around the 50RC mark, which is pretty much what we were anticipating all along.

In other words the test is inconclusive, but amusing in a trivial way.

Oh, for those who aren't familiar with the guages:

307234

RC65 down to RC40

Regards
Paul

[pmcgee]

This won't be news to most people, but I forget some of the things I read ... or more where the info was ...

The manufacturing process at Disston is talked about a good deal in the 1912 catalogue from Rose Tools ...

http://www.roseantiquetools.com/sitebuildercontent/sitebuilderfiles/disston1912.pdf

Paul

[rob streeper]

This won't be news to most people, but I forget some of the things I read ... or more where the info was ...

The manufacturing process at Disston is talked about a good deal in the 1912 catalogue from Rose Tools ...

http://www.roseantiquetools.com/sitebuildercontent/sitebuilderfiles/disston1912.pdf

Paul

Thanks Paul, nice reading but short on details. It is clear that they put in a lot of research effort over the years and that they were doing the best work possible, albeit a century ago. I haven't had time to work on the hardening project, I've been making floats, but I have developed new ideas to test.

Cheers,
Rob

[pmcgee]

I was looking at the 1912 again ... I was referring to the pretty pictures section before ... but now I took in ...

307698

- Automatic progressive toother
- Harden saws under dies
- Temper saws under dies

[rob streeper]

I was looking at the 1912 again ... I was referring to the pretty pictures section before ... but now I took in ...

307698

- Automatic progressive toother
- Harden saws under dies
- Temper saws under dies

Reminiscent of the patent you cited earlier. Dies can mean a lot of different types of metal working tools, such as those I use for sawback forming. There are obviously lots of trade secrets lurking behind the text, unfortunately a lot of it is probably now lost.

[rob streeper]

It's been almost a year since I touched on this subject but recently I happened across a hardness tester for thin materials, otherwise known as a superficial hardness tester. This is an Ames model 2-S (http://www.amesportablehardnesstesters.com/product/model-2-s/).
This is a pretty simple to operate tester that, within it's limitations, gives results that are more than good enough for testing saw plate hardness.

336283

The kit consists of the tester, a diamond indenter, a 1/16" carbide ball indenter for softer materials, two test blocks one with a hardness of Rc49 +/- 0.5 and one that is Rc62 +/- 0.5, two anvil extensions, three anvils, and full documentation indicating that this tester was produced in 1969.

After reading through the directions and performing a couple of tests on each block I find that the instrument is perfectly calibrated and really pretty simple to use compared to the more conventional hardness testers although it has a somewhat larger measurement tolerance.

I cut samples of each thickness of saw plate material and tested each five times on the appropriate 15 kg loading scale, here are the results. I also did measurements on the 30 and 45 kg loading scales and came up with results that were substantially the same excepting the 0.015" material.

336284

So it turns out that commercially available 1095 sheet stock is actually pretty hard, measuring about 2-4% above the manufacturer specified hardness range of Rc 48-51.

Now to disassemble some saws and test them - should be very interesting.

[rob streeper]

Okay, here's the data for the saws. I picked these out from my collection. I have saws from three custom or boutique saw makers. Each saw plate was tested five times.
336288
Here's my interpretation: Somebody is using soft steel for making saws sold at premium prices.:((

[DSEL74]

One point that hasn't been considered is back in the day we had real files made of quality to file in the teeth, and sharpen the saws. If you make you saw more advanced and potentially harder…What are we to file with as most file today are made out of butter???

An advancement is saws would require an advancement in other tools that relate to it's manufacture & maintenance and we know files are going backwards not forwards. What are the other options?


I also wonder on saws with poor use that causes to buckle and flex the blade how much that introduces work hardening over time?

[rob streeper]

One point that hasn't been considered is back in the day we had real files made of quality to file in the teeth, and sharpen the saws. If you make you saw more advanced and potentially harder…What are we to file with as most file today are made out of butter???

An advancement is saws would require an advancement in other tools that relate to it's manufacture & maintenance and we know files are going backwards not forwards. What are the other options?


I also wonder on saws with poor use that causes to buckle and flex the blade how much that introduces work hardening over time?
Hi DSEL,

I got started on this direction firstly because of my other observations about poor performance of the oddball saw I describe above from Maker 3. Second, given the diversity of materials we use, ranging from sheets and rolls of steel of known or at least nominal characteristics to scraper blades ,I thought it a good idea to look into the properties of these materials. I like to test and measure things as I find doing so frequently helps me work better.
The other thing that struck me was the statements around the web that Disston had decided a century or more ago that Rc 52 was the best hardness for saw blades. I don't mindlessly challenge received wisdom but I thought that surely the state of the art had moved on some.
As to hardening, well there is an upper limit. In my heat treating experiments I found I could get 1095 steel so hard that it shattered under the testing diamond and then I could draw it back to any final hardness I wanted, unfortunately I was getting too much distortion. My next step in the hardening experiments is to go cryogenic because it has been found to both increase the hardness and the toughness of steels. Cryogenic hardening has been all the rage in gunsmithing circles for a number of years and the benefits there are apparently considerable.
As to sharpening, fortunately things like this exist http://www.ebay.com/itm/10Pcs-5-1-2-140MM-x-3MM-Diamond-Coated-Needle-TRIANGLE-File-Titanium-for-Filing-/171383777202?pt=US_Hand_Tools&hash=item27e744e7b2. Cheap enough to give them a shot.

Cheers,
Rob

[planemaker]

Hi Rob. With the softer saw plate you tested was there any visual difference. I say this because I received a very small batch of saw plates a while ago that had a distinct color variation to that I am normally use to. It had more of a slight dull gal steel appearance to it. I ended up putting those saw plates aside and have never used them over concerns they could actually be a softer saw plate. I ran a file across the edge of one of those saw plates and it seemed to validate my concerns.

Stewie;

[Heavansabove]

As to sharpening, fortunately things like this exist http://www.ebay.com/itm/10Pcs-5-1-2-140MM-x-3MM-Diamond-Coated-Needle-TRIANGLE-File-Titanium-for-Filing-/171383777202?pt=US_Hand_Tools&hash=item27e744e7b2. Cheap enough to give them a shot.
Rob, I have read negative reports on these (diamonds shear off), be interested to hear how you go with them.
Cheers Peter

[DSEL74]

Rob,

There was a major long running and long winded thread on saw file on this forum and I think diamond file were a part of that test also.

I'm all for testing and playing and research even if just for personal curiosity. I only made the comment that while some strive for excellence (the craftsman) industry strives for profit and the public in general for easy solutions. None of these work in favour of the craftsman and as some advancements are made in technology as you say, better materials or processes available. Others are degrading for greater profit.

An example is poorly made and uncomfortable injection moulded saw handles. There was a international petition made to manufacturers to improve the quality of saw files to be fit for purpose, which I recollect made no impression on the suppliers. Nearly all were made in China, India, Brazil despite branded country. This leads to limitations on what is practical for us to use in our saw making as these current files barely pass on the current materials. So other than for academic purpose and curiosity improved saw plate leads to the necessity of advancements in toothing and sharpening. Ok if you have a saw toother to punch the teeth but still need to file them sharp.

I'm just being philosophical in the state of industry I guess.

[rob streeper]

Hi Rob. With the softer saw plate you tested was there any visual difference. I say this because I received a very small batch of saw plates a while ago that had a distinct color variation to that I am normally use to. It had more of a slight dull gal steel appearance to it. I ended up putting those saw plates aside and have never used them over concerns they could actually be a softer saw plate. I ran a file across the edge of one of those saw plates and it seemed to validate my concerns.

Stewie;

Hi Stewie,

The weird plate does have a different hue to it. It appears to be slightly colored, maybe a little yellowish or gold toned. The effect is very slight but it looks very different from all of the pieces of 1095 I have and from the plates of all of my other saws.

Rob

[rob streeper]

Rob,

There was a major long running and long winded thread on saw file on this forum and I think diamond file were a part of that test also.

I'm all for testing and playing and research even if just for personal curiosity. I only made the comment that while some strive for excellence (the craftsman) industry strives for profit and the public in general for easy solutions. None of these work in favour of the craftsman and as some advancements are made in technology as you say, better materials or processes available. Others are degrading for greater profit.

An example is poorly made and uncomfortable injection moulded saw handles. There was a international petition made to manufacturers to improve the quality of saw files to be fit for purpose, which I recollect made no impression on the suppliers. Nearly all were made in China, India, Brazil despite branded country. This leads to limitations on what is practical for us to use in our saw making as these current files barely pass on the current materials. So other than for academic purpose and curiosity improved saw plate leads to the necessity of advancements in toothing and sharpening. Ok if you have a saw toother to punch the teeth but still need to file them sharp.

I'm just being philosophical in the state of industry I guess.


I agree. Part of the reason I'm able to get cheap high end tools like this tester is because of the ongoing de-industrialization of America. Industrial equipment brings 10 cents on the dollar these days here if you're lucky. The tester for instance has an old Ampex property tag on it. Ampex still exists but when was the last time you saw an Ampex branded electronic device? Makes me feel like a vulture feeding off of the remains of what America was.

[rob streeper]

Rob, I have read negative reports on these (diamonds shear off), be interested to hear how you go with them.
Cheers Peter

Hi Peter,

I figured as much. I've got to find some made by 3M - I love their products and use them extensively in my shop.

Cheers,
Rob

[Bushmiller]

Rob

That Ames tester looks like a beauty and I can envisage a whole number of myths being destroyed.

It was very disappointing to find a specialist saw maker using inferior grade product. When I first spied the chart with just maker numbers I knew what was coming.: One didn't measure up! It would be interesting to approach them for their comments. Maybe they would be interested in redeeming their reputation.

The hardness of saws has always been limited by two things: the ability to file them sharp and the ability to set the saw. Even back in the day Disston acknowledged this limitation. In fact the setting was even more problematical. Disston allegedly used a harder steel (well same steel, but tempered harder) in their "no-set" 120 ACME saws, which points to the setting more of an issue than filing at that time. Today, as DSEL points out, the files are inferior. I bought one from the local hardware store recently (Nicholson, I think) and it wouldn't touch my Simonds from the word go. I hadn't expected a gem, but that left me disgusted :(( !

Disston maintained that their premium saws used better steel, but there is some conjecture over this and if nothing else Disston were extremely adept at marketing. It would be interesting to compare a No7, a No.8 and a No.12 from the same era.

I feel sure your testing has not finished and it would be interesting to see more results. Thank you for the information already supplied.

Regards
Paul

[rob streeper]

Hi Paul,

Like everything saw plates involve compromises. I want to see if there's a better way. That's why I'm looking into cryogenic treatment - it both hardens the steel and increases it's resistance to abrasion. After hardening the steel can be drawn by heating back to Rc 52 or thereabouts but the scratch resistance is retained.
Saw files are a paradox. Given the resurgence in popularity of handsaws I'm somewhat surprised that one of the major file makers hasn't stepped up with a superior product. By searching I've been able to lay in a pretty good stock of older Nicholson three-squares but prices are going up and they're getting harder to find. The new Nicholsons such as are found in the home stores are totally unsuited for saw filing - rough, crooked and the teeth come off easily. They're fine for general use but are only useful for deburring in saw work.

Cheers,
Rob

[rob streeper]

Today I pulled out my Disston hand saws, disassembled them so that I could measure the hardness under the handle where the test dimples would be hidden and tabulated the results. I did not make any special effort to polish the test points but the steel was clean and free of visible contaminants.
336371
From these values I can see that Disston saw plates are pretty hard, harder than the 1095 that we use these days in the custom saw production.
The steel was nothing special according to the Disstonian Institute (http://www.disstonianinstitute.com/steel.html), similar in carbon content to our modern 1080 steel. In fact 1080 is likely superior in some ways due to it's slightly higher manganese content which confers better hardenability characteristics.

[RayG]

Good stuff Rob,

The stock standard 1095 spring temper is usually around 45-50 Rc, I've found that with 1095 coil product, the temper can be inconsistent across the sheet, and often the edges are harder. In any event, if the hardness is up around 60 it's going to be brittle, and should be avoided... also when it gets that hard it becomes very tough on files.

I'd think even 55 is starting to get too hard for saw plate.

How are you correcting for the material thickness with your testing?

Ray

[rob streeper]

Hi Ray,

These were all tested at 30 kg loading on the N scale. Referring to http://www.continentalht.com/userfiles/file/CHT-hardness-conversion-chart.pdf for the appropriate scale to use. I re-tested on 45 kg loading where permissible. The 0.015" stock produced consistent and repeatable readings, suggesting that, although it is not recommended, the 15 kg loading N scale is good enough. After all we're not talking about nuclear reactor pipes or turbine blades here, no issues of life and death.

Interesting that Disston used steel that was pretty consistently above the Rc52 hardness that everybody thinks is the benchmark. Perhaps a red herring?

Thanks,
Rob

[rob streeper]

I did some analysis of the results including t testing to get an idea of the statistical significance of my measurements. Students t test is a way of calculating the significance of the difference between two sets of measurements. The smaller the t statistic the more significant the difference.
336555
The conclusions I draw are:

1) 1095 steel is a consistent product. Despite the fact that the test materials were purchased from different sources over a period of several years the hardness values for the products were all very similar with a remarkably low standard deviation of 0.34 Rc points. Plus these tight results show you that both my technique and my hardness tester are working well.

2) Of the custom makers, only one is using 1095 steel. The other two makers represented in my collection are using softer material. Maker 3 is using very soft metal, 40% softer than 1095, - likely because it's cheaper and/or easier to work with. Maker 2 is using something that is about 7% softer. The highly significant t values (t < 0.05) for these measurements indicate a high degree of confidence that the measurements are not due to chance.
Maker 2's saws work just fine for me, but I'm not using them for production work. Maker 3's saw is a dog. Makers 2 and 3 are names that everybody in this area knows well so I won't reveal them. Let's see if either of them are willing to come clean.

3) Disston's products varied in hardness over the years. The Disston saws in my collection were manufactured in the period spanning post WW1 to post WW2. The variability is not too surprising because the concepts of industrial quality control were in their infancy in the early 20th century. Disston also used steel that is harder by just under 4%, or 2 Rc points, than is 1095 but the difference is on the edge of statistical significance (t = 0.04).

As far as saw files go, sharpening old Disston saws is going to be harder on your files than is sharpening modern saws. If you're really worried about the longevity of your files get some saws from Maker 3 and your files will last a long time but you may not get much wood cut.

Further, modern custom saws made with raw 1095 steel are not as hard as are older Disston saws. If the plate hardness is important and if Disston optimized his products we've actually taken a step backward in our unquestioning use of 1095.

I'm gonna go lick my wounds now.

[pmcgee]

Off topic, but I was a bit fascinated looking at the median rather than the mean over your measurements.

It's not important I know, but a non-parametric test in these circumstances might be the most appropriate choice.

Thanks for the info and the testing.
Lovely how 'facts' (physical observations) speak 'indisputedly' without emotion/opinion.

Cheers,
Paul

[rob streeper]

Off topic, but I was a bit fascinated looking at the median rather than the mean over your measurements.

It's not important I know, but a non-parametric test in these circumstances might be the most appropriate choice.

Thanks for the info and the testing.
Lovely how 'facts' (physical observations) speak 'indisputedly' without emotion/opinion.

Cheers,
Paul

Hi Paul,

I agree, I don't have an appreciation of the shape of the distribution. Probably a bit much for this forum. Nonetheless the data is what it is.
I was looking at the Disstonian website here http://www.disstonianinstitute.com/steel.html and noted this: "The saws with multiple values for hardness were hardest in the area under the handle, and softest in the area close to the teeth.". Hardness testing is sensitive to the surface finish, that's the reason why testing blocks are so nicely finished. The area under a saws handle, if it's not pitted or covered with goop is going to be the least scratched surface on the plate while the area near the teeth will have the roughest finish. Thus one would expect that Rockwell testing near the teeth would return anomalously low values because of the relatively rough surface. In other words, test the area under the handle and make sure the steel is clean or your readings are meaningless.

Cheers,
Rob

[rob streeper]

Here's the data with medians calculated. They're not much different from the means so the analysis is reasonable.


336646

[pmcgee]

Oh yes. It was the agreement that I was thinking over. :)

[rob streeper]

Oh yes. It was the agreement that I was thinking over. :)

I was hoping for normal distributions and it looks like they're pretty close.

[rob streeper]

I realized during dinner that I have saws from another custom maker, here Custom Maker 4. Custom maker 4 makes very hard saw blades, Rc 61.4. I also added measurements from the Atkins #26 pattern makers saw I have posted on this site in the past. It too has a very hard blade, Rc 57.4. I have a few more Disstons that I'll test later on when I have a chance.

336647

[pmcgee]

(Disston 240 median s/b 52)

[planemaker]

Hi Rob. What does concern me greatly is that by not naming Maker 3 your unfairly clouding the reputation of other Boutique Saw Makers (including myself).

Whats relevant is that you also making backsaws for sale. Now I personally believe its far from the case, but there may be other saw makers asking if your primary motive is more geared towards raising your own saw making profile.



On the Sawmill Creek Forum where you also posted this data, you stated;

Hi David,

People are getting sued by companies here for writing negative comments on the Internet. See: http://www.forbes.com/sites/investop...eview-on-yelp/ (http://www.forbes.com/sites/investopedia/2013/01/25/can-you-be-sued-if-you-give-a-bad-review-on-yelp/)

Speech is still free in America as long as nobody objects to what you have to say - that's why I have to be careful.

As to Maker 3 and the results I got, who knows. Maybe it's a one-off problem. Maybe one lot of steel was unevenly hardened. As to Maker 3 and the results I got, who knows. Maybe it's a one-off problem. Maybe one lot of steel was unevenly hardened.

While on this forum you are heading in a totally different direction by insinuating Maker 3 was aware his saw plate was below spec.

My suggestion Rob would be to email a copy of your data to Maker 3 and note your concerns. My bet is Maker 3 will be in contact with his saw plate supplier asap.

Nothing personal Rob.

regards; Stewie.

[hiroller]

Interesting findings. Are you going to share the results with the saw makers?
I think you should give the problem saw maker the feedback.

[rob streeper]

(Disston 240 median s/b 52)

Interesting isn't it? The 240 looks like a very late product. The etch actually looks like it is printed on the surface of the blade.

[rob streeper]

Hi Rob. What does concern me greatly is that by not naming Maker 3 your unfairly clouding the reputation of other Boutique Saw Makers (including myself).

Whats relevant is that you also making backsaws for sale. Now I personally believe its far from the case, but there may be other saw makers asking if your primary motive is more geared towards raising your own saw making profile.



On the Sawmill Creek Forum where you also posted this data, you stated;

Hi David,

People are getting sued by companies here for writing negative comments on the Internet. See: http://www.forbes.com/sites/investop...eview-on-yelp/ (http://www.forbes.com/sites/investopedia/2013/01/25/can-you-be-sued-if-you-give-a-bad-review-on-yelp/)

Speech is still free in America as long as nobody objects to what you have to say - that's why I have to be careful.

As to Maker 3 and the results I got, who knows. Maybe it's a one-off problem. Maybe one lot of steel was unevenly hardened. As to Maker 3 and the results I got, who knows. Maybe it's a one-off problem. Maybe one lot of steel was unevenly hardened.

While on this forum you are heading in a totally different direction by insinuating Maker 3 was aware his saw plate was below spec.

My suggestion Rob would be to email a copy of your data to Maker 3 and note your concerns. My bet is Maker 3 will be in contact with his saw plate supplier asap.

Nothing personal Rob.

regards; Stewie.

Hi Stewie,

I posted the results to Sawmill Creek because 1) I'm angry that I've been taken advantage of and 2) I feel that the community needs to know that there's a potential problem.

Maker 3's saw has other problems which I've detailed here on other threads suggesting that he or she knows what's going on with the product so contacting him/her would likely only lead to an angry response. Gappy inletting of the back to the handle and generally poor wood to metal fit, cosmetic problems with the metal work and poor performance relative to other custom makers. A saw made by another maker was recently sold on eBay that had obvious QC problems.

Don't forget that Maker 2 is also making saws with plates that are softer than Disstons optimum 52 and nobody has commented on that set of measurements. What about Maker 4 with the exceptionally hard blades? I haven't (yet) heard any comments of "That just can't be, you're crazy/mean/insane".

It seems my inquiry into this matter has divided the community into two groups, those that have chosen to attack me and those who thank me for my effort. I think that those who are on the attack may be motivated, at least in part, by a desire to not know what the facts are.

The community's unquestioning acceptance of Disston's "52" benchmark is an illustration of this kind of willful ignorance in my opinion. Would it be possible that the number "52" Disston threw out might be a red herring designed to throw off the competition? Maybe the truth was closer to 54/55 as my measurements indicate. Rockwell tester's weren't even available until the 1920's meaning that Disston could only have known about the magical 52 for the last 30 years or so that the company was in business.

As to the issues of liability, they're very real in America today. Might, in the form of money, makes right here and the link to the Forbes article above is an example. In your country I gather that there are pretty strong consumer protection laws in regard to 'fitness for use'. We don't effectively have such laws here. The laws are on the books but they are rarely if ever enforced. Thus, if you're a custom saw maker selling into the Australian market I think it would be advisable to test your raw materials to make sure that they truly are what you and your customers think they are. It's not very expensive or difficult. I've received a couple of private inquiries about the results and I've made offers to test questioned materials but notably nobody has taken me up on it yet.

This is not the first time or field in which I have knowingly published results that are contrary to what a community might prefer and it's not the first time that I have taken flak for it either. Given the comments I've received regarding my other experiments I've done I'm beginning to think that there is a fraction of the community of saw aficionado's who strongly dislike innovation and refuse to question cherished myths. I strongly disagree with this approach to life.

Here's an example of what may happen when we choose to be ignorant.
Years ago as part of my work I became aware that a certain grocery store chain had a program in place to test all incoming fruits and vegetables for the presence of pesticides exceeding government specified limits. Laboratory staff would go to the warehouses of the chain early in the morning and pick up sample lots of all incoming produce. This operation ran 7 days a week and the sample collectors were in the field at 4 in the morning. The produce specimens were taken back to the laboratory, processed and analyzed. The results were reported back to the QA department at the grocery chain. While the samples were in testing all of the produce was quarantined on the trucks - nothing was unloaded until the results were in. Lots that were accepted were then unloaded and distributed. Rejected lots were, according to my information, taken to the warehouses of other grocery chains and sold.
The end result of this was that the first grocery chain was ensuring that it's customers were not exposed to produce having illegal pesticide levels. Any and all of the other grocery chains in the region were therefore more likely to have produce on the shelves that did have excessive levels of pesticides.
The chain doing the testing was thereby taking a good step in the interests of it's customers, but only it's customers get the benefit, everybody else gets the dregs. The chain never spoke of the testing it was doing so the general public had no knowledge of it's screening program. But what about the larger problem of contaminated and possibly unsafe produce being in circulation? Don't people have a right to know of such issues?

If anybody who makes saws want's the results that I obtained in testing their saws only I'll tell them privately on the condition that they release me from all liability - in writing of course.

Cheers,
Rob

[planemaker]

Hi Rob. In my opinion you could have approached this subject a little more tactfully. Most boutique saw makers IMO are doing an excellent job with the overall quality of their work.

regards; Stewie

[rob streeper]

Hi Rob. In my opinion you could have approached this subject a little more tactfully. Most boutique saw makers IMO are doing an excellent job with the overall quality of their work.

regards; Stewie

Stewie

In the case of the saw in question it is very pretty, but the beauty fades on closer examination.
This issue of saw plate hardness has taken on some of the characteristics of a religion - something that everybody accepts but that nobody is willing to question. Debating the relative merits of saw plate hardness in the absence of measurements is like debating how many fairies are dancing on a pin head.
I spend my hard earned money on the saws I buy and I expect the best in craftsmanship, performance and materials.
From my data it is clear that three of the four custom saw makers represented in my collection are not using 1095 steel. The numbers don't lie.
If the problems with the Maker 3 saw are common to their other products then the truth will eventually out. If not then this saw is a unique problem and the boutique makers, users and collectors have no worries. Nonetheless my study points out the fact that improvement across the community is needed. Testing of raw materials is important and I see it as my duty to those I sell saws to.
I use 1095, which I now know is somewhat softer than the average for Disston. However I seem to be alone in trying to advance the field.

Cheers,
Rob

[rob streeper]

To be clear, if there's anybody who would like to have their raw materials tested before being used to make a saw I'll do it at no cost and communicate the results confidentially to the requester. All you need do is mail me a flat piece about 2 cm on a side of the material in question. I won't test saws that you own from other makers because of liability issues. Send me a PM for my address.

Cheers,
Rob

[rob streeper]

Interesting findings. Are you going to share the results with the saw makers?
I think you should give the problem saw maker the feedback.

The saw in question has some pretty obvious workmanship issues in my opinion suggesting, considered in light of the technical problem, at least QC issue and at worst a disregard for customer satisfaction. Defects obvious on casual visual examination should, for luxury items like boutique saws, be grounds for rejection of any particular item in my opinion.
If the defects in the Maker 3 saw are willful or the result negligence then contacting them may provoke a bad response.

[DSEL74]

Rob, I think part of the issue is everyone is guessing or presuming who these saw makers are. Most of us are probably wrong. You have your reason for not declaring this which is fine. However if we were in the market for a saw we are now suspicious of all sawmakers but most likely none have access to test the saw prior to purchase. This is damaging the whole of a small industry rather than helping advance & improve it as your obviously passionate to do.
He is an example. A bunch of thirsty people walk out of a desert and you put a table of glasses of water in front of them and say one glass is safe, most of them have a bit of poison and will make you very sick for months, but one will kill you. How many of those will want to drink? They will however want to know which will kill them, and which is water. They won't be happy knowing that you know & won't tell them, they are thirsty. All water is poison is the perception until more info is available.

[rob streeper]

Rob, I think part of the issue is everyone is guessing or presuming who these saw makers are. Most of us are probably wrong. You have your reason for not declaring this which is fine. However if we were in the market for a saw we are now suspicious of all sawmakers but most likely none have access to test the saw prior to purchase. This is damaging the whole of a small industry rather than helping advance & improve it as your obviously passionate to do.
He is an example. A bunch of thirsty people walk out of a desert and you put a table of glasses of water in front of them and say one glass is safe, most of them have a bit of poison and will make you very sick for months, but one will kill you. How many of those will want to drink? They will however want to know which will kill them, and which is water. They won't be happy knowing that you know & won't tell them, they are thirsty. All water is poison is the perception until more info is available.

Hi again DSEL,

In principle I agree with your sentiments. However I have learned that creating, publishing or posting information that challenges broadly held ideas about reality is often hazardous. Wouldn't it be great if people were fair and objective? Unfortunately they're not. The bad saw in my collection may be a one-off, I don't know. I've always made it clear that this single saw has problems. I discovered the problems the moment I opened the box. The functional problem became clear the first time I used it. Being possessed of an inquiring mind I wanted to know what was wrong with the saw and now I think I've proved it, at least to my satisfaction.
I posted this information over on Sawmill Creek despite a certain degree of trepidation because of things I have read about the users of that site. The majority of those who responded to my post decided to attack me as a person and dismissed my data. The reputation of that site is the primary reason that I post the vast majority of my hobby work on this site - Australians seem to be more open minded.
As I wrote above, if you're worried about a saw you are thinking of buying ask the seller what type of steel they use. If the saw you receive doesn't meet your expectations then I think my work here may be helpful. In the alternative go out and get a tester. They're not that expensive and I'm finding mine to be extremely useful. Maybe something for the governing bodies of your Men's Sheds to think about if there are enough interested members.
I think knowing is preferable to ignorance, even if the information is unpleasant.

Cheers,
Rob

[BobL]

I'd like to see some more extensive testing before making any firm conclusions - certainly before naming any manufacturer.
If one of my students was doing this as an undergraduate material science project I'd say even though 5 measurements might satisfy a standard procedure I still think 5 test points per saw is on the slim side to demonstrate hardness is normally distributed, especially if normal stats are going to be applied.

The first thing I would ask the student to do would be to demonstrate the method can generate a normal distribution on a reference material, both in several locations of the material and then using a reduced sampling regime across the surface of the material i.e. a hardness map. i.e. 20-30 measurements in a few locations and then 5 measurements at points event distributed across the material

I would then ask the student to to the same (hardness map) of at least one saw using the same method..
The surface finish issue can be addressed by sanding to the same level of smoothness.

The other concern is that typical "consumer testing" issue of just testing "one" of anything can be problematic. I would suggest the student investigate at least 5 saws of the same make and model from at least one manufacturer. i.e. no map but at least 20 measurements per saw.

To demonstrate "between sample" reproducibility I'd like to see the student repeatedly measuring the reference material between each different saw measurements to show there is nothing wrong with the apparatus or method. I'd also like to see one saw measured multiple times and in between revert to measuring the standard. A more representative value of the hardness would then be the external (or average of average values)

Although this might be difficult for you to do to further increase the confidence of measurements I'd also ask the student to perform sone repeat tests using a different apparatus. Ultimately a completely independent set of measurements would be useful.

I appreciate the time required to perform these measurements but I think even doing some of these it is one way to help reduce bias and hence criticism of the results

[RayG]

Hi Rob,

I've been following your hardness testing with interest, I have some real concerns about the conclusions you are drawing. I also have some concerns about validity of measuring the hardness of thin plate.

First off, Rockwell 60 is so hard that a file would skate off it... I get chisels hardened to 60-62 and there's no way that would be suitable material for saw plate. No I don't doubt that you are reading those numbers on your tester, what I know is that they can't be correct.

Second, 1095 maximum surface hardness in the "as quenched state" is around 66 Rc, that is as hard as you can get... and at that hardness it's as brittle as all get out, spring temper is usually down around 50 Rc... If you have a saw that's 60 Rc, I bet the teeth will snap like crazy.

Third, You seem to be suggesting that 30-40 Rc is too soft for saw plate... I disagree, I think it would be fine, while it wouldn't be my choice. Promoting the idea that the sawmaker is using sub standard material is a bit of a long bow to draw...

My hardness tester is an Avery 6402 , while I think I'd have trouble measuring 20 thou plate hardness accurately I'd still be able to get relative readings to compare with some of your results.

Ray

[rob streeper]

I'd like to see some more extensive testing before making any firm conclusions - certainly before naming any manufacturer.
If one of my students was doing this as an undergraduate material science project I'd say even though 5 measurements might satisfy a standard procedure I still think 5 test points per saw is on the slim side to demonstrate hardness is normally distributed, especially if normal stats are going to be applied.

The first thing I would ask the student to do would be to demonstrate the method can generate a normal distribution on a reference material, both in several locations of the material and then using a reduced sampling regime across the surface of the material i.e. a hardness map. i.e. 20-30 measurements in a few locations and then 5 measurements at points event distributed across the material

I would then ask the student to to the same (hardness map) of at least one saw using the same method..
The surface finish issue can be addressed by sanding to the same level of smoothness.

The other concern is that typical "consumer testing" issue of just testing "one" of anything can be problematic. I would suggest the student investigate at least 5 saws of the same make and model from at least one manufacturer. i.e. no map but at least 20 measurements per saw.

To demonstrate "between sample" reproducibility I'd like to see the student repeatedly measuring the reference material between each different saw measurements to show there is nothing wrong with the apparatus or method. I'd also like to see one saw measured multiple times and in between revert to measuring the standard. A more representative value of the hardness would then be the external (or average of average values)

Although this might be difficult for you to do to further increase the confidence of measurements I'd also ask the student to perform sone repeat tests using a different apparatus. Ultimately a completely independent set of measurements would be useful.

I appreciate the time required to perform these measurements but I think even doing some of these it is one way to help reduce bias and hence criticism of the results

Hi Bob,

I agree. I'm willing to make a controlled experiment on one of my saw plates, I don't really want to put prick marks all over a saw that I've paid hundreds of dollars for you know. Given the problems with thickness I propose to use a piece of 0.035" 1095 in it's as delivered state - no blue removal, and measure 25 or so test points with a distance between points of at least 5 mm. What do you think?

Cheers,
Rob

[BobL]

Hi Bob,

I agree. I'm willing to make a controlled experiment on one of my saw plates, I don't really want to put prick marks all over a saw that I've paid hundreds of dollars for you know. Given the problems with thickness I propose to use a piece of 0.035" 1095 in it's as delivered state - no blue removal, and measure 25 or so test points with a distance between points of at least 5 mm. What do you think?

Cheers,
Rob

Sounds good. I wouldn't do the saw map on a good saw, I'd just use an old or cheap saw.

[rob streeper]

Hi Rob,

I've been following your hardness testing with interest, I have some real concerns about the conclusions you are drawing. I also have some concerns about validity of measuring the hardness of thin plate.

First off, Rockwell 60 is so hard that a file would skate off it... I get chisels hardened to 60-62 and there's no way that would be suitable material for saw plate. No I don't doubt that you are reading those numbers on your tester, what I know is that they can't be correct.

Second, 1095 maximum surface hardness in the "as quenched state" is around 66 Rc, that is as hard as you can get... and at that hardness it's as brittle as all get out, spring temper is usually down around 50 Rc... If you have a saw that's 60 Rc, I bet the teeth will snap like crazy.

Third, You seem to be suggesting that 30-40 Rc is too soft for saw plate... I disagree, I think it would be fine, while it wouldn't be my choice. Promoting the idea that the sawmaker is using sub standard material is a bit of a long bow to draw...

My hardness tester is an Avery 6402 , while I think I'd have trouble measuring 20 thou plate hardness accurately I'd still be able to get relative readings to compare with some of your results.

Ray

Hi Ray,

I just posted some results of preliminary testing on one of the plates on the D-8 post that I hammered on. The hardness readings came out at roughly 63 in the region hammered and subsequently ground. Seems hammering has an enormous effect on the hardness.
The thin material concern is why I bought this tester - it is designed specifically for doing tests on thin hard materials. Most of my measurements have been on the 15N and 30N scales with 45N measurements only where the thickness of the test article warrants.

Cheers,
Rob

[rob streeper]

Just to refresh everyones memory, here is the NIST guidance on hardness testing, including for thin materials.

336780

[planemaker]

Hi Rob,

I've been following your hardness testing with interest, I have some real concerns about the conclusions you are drawing. I also have some concerns about validity of measuring the hardness of thin plate.

First off, Rockwell 60 is so hard that a file would skate off it... I get chisels hardened to 60-62 and there's no way that would be suitable material for saw plate. No I don't doubt that you are reading those numbers on your tester, what I know is that they can't be correct.

Second, 1095 maximum surface hardness in the "as quenched state" is around 66 Rc, that is as hard as you can get... and at that hardness it's as brittle as all get out, spring temper is usually down around 50 Rc... If you have a saw that's 60 Rc, I bet the teeth will snap like crazy.

Third, You seem to be suggesting that 30-40 Rc is too soft for saw plate... I disagree, I think it would be fine, while it wouldn't be my choice. Promoting the idea that the sawmaker is using sub standard material is a bit of a long bow to draw...

My hardness tester is an Avery 6402 , while I think I'd have trouble measuring 20 thou plate hardness accurately I'd still be able to get relative readings to compare with some of your results.

Ray

Hi Ray. On Sawmill Creek George Wilson and David Weaver raised similar concerns regarding the validity of the test results.

Having little knowledge on the subject of Metallurgy I am not in a position to form an opinion.

Stewie;

http://www.sawmillcreek.org/showthread.php?226091-Hardness-testing-of-saw-plates/page2

[rob streeper]

I just found that I had made an Excel error in calculating the standard deviations. I've corrected it in this table.

336784

[rob streeper]

I just found that I had made an Excel error in calculating the standard deviations. I've corrected it in this table.

336784

As to the high values on the Disston saws another thought just occurred to me. Given my posting on my D-8 replica page where I found that hammered areas of 1095 are remarkably hard and given the fact that I measured these hardnesses under the handles I wonder if I'm measuring in the hammer hardened zone of the blade? More testing tomorrow...

[RayG]

Hi Ray,
Most of my measurements have been on the 15N and 30N scales with 45N measurements only where the thickness of the test article warrants.



That's the wrong scale... Rockwell N scale not Rockwell C, you need to do a conversion. ( and a thickness correction. )

From the ames charts 50 on the 45-N scale is Rc 46, and 50 on the 30-N scale is Rc 30... lowest number on the 15-N scale in the conversion charts is 69.5, which is 20 Rc

Also, a superficial tester is not specifically designed for thin material, it's designed for surface hardness measurement.. You need to apply corrections for material thickness.

A general rule of thumb is that you can't measure materials where the depth of the indentation is more than 1/3 of the material thickness...

Ray

PS Here is a conversion chart to convert from Superficial N scales to Rockwell C
http://www.buehler-asia.com/brochure/download-02_Hardness_Table_01.pdf

[RayG]

Hi Ray. On Sawmill Creek George Wilson and David Weaver raised similar concerns regarding the validity of the test results.

Having little knowledge on the subject of Metallurgy I am not in a position to form an opinion.

Stewie;

http://www.sawmillcreek.org/showthread.php?226091-Hardness-testing-of-saw-plates/page2

Hi Stewie,

Thanks for that, I just quickly scanned the thread, I agree with what they are saying, something is seriously wrong with the measurements.

Ray

[rob streeper]

That's the wrong scale... Rockwell N scale not Rockwell C, you need to do a conversion. ( and a thickness correction. )

From the ames charts 50 on the 45-N scale is Rc 46

Also, a superficial tester is not specifically designed for thin material, it's designed for surface hardness measurement.. You need to apply corrections for material thickness.

Ray

Hi Ray,

I used the conversion charts to produce the Rc values reported. NIST recommends the N scale for thin hard materials and they recommend the highest loading permissible for a given test material thickness. Look here: http://qs-hardnesstester.com/hardness-minimum-thickness.html

Referring to the linked chart and given that we're talking about materials that should have Rc hardnesses of 45 or greater you can see that the minimum thickness recommended for a C scale measurement is 0.034" for Rc45. If the material is harder, say Rc 52 then the minimum thickness decreases to 0.032" and so on.
Look to the right side of the chart now at the N scales. You will see that for a 0.015" thick test article that the minimum Rc value is somewhere between 68 and 76. Thus N15 testing of 0.015" materials is not really that good. However, on the N30 and N45 scales you will see that the minimum thicknesses recommended are 0.022" and 0.024" respectively. All of the saws I tested have thicknesses equal to or greater than than 0.022".
To accurately measure 0.015" material I need to go to the 15T or 30T scales, something I need to do in the future obviously.

Please understand that I am doing these studies because I am interested. I have searched the web and have not found any systematic study of the hardness values of woodworking saw blades. I wonder why?

Cheers,
Rob

[RayG]

Hi Rob,

Thanks for that...

I haven't ever been able to do proper hardness testing on thin materials, On the Avery the Rockwell C standard load of 150Kg leaves an indentation too large. That's the area where you need the lighter loads of the superficial scales. But you still need to apply corrections for thickness.

That is a problem, since you usually have to add something for thickness, and your numbers are already way too high.... so I'm still mystified as to what could be wrong.

Ray

PS Can you post your raw data for the Sawmaker No4 and what scale you used.

[rob streeper]

336797

[rob streeper]

Ray,

I used the 30N scale for the majority of the measurements. Where the saws were thick enough I also used the 45N scale. The correspondence of the measurements was very good. I see now that I mistakenly said that the thinnest saw I tested was 0.022", in fact it was 0.020" but nonetheless for the hardness measured it was still within the acceptable thickness range for the N30 scale.

Aside from all of the bickering going on about whether I used the correct scale I haven't heard anybody opine on the consistency of my results. As I posted much earlier on this thread, if I used the C scale testing on material that was too thin and tested several samples the relative hardnesses would still be comparable even though the absolute values would be wrong.

Why pray tell is this such a contentious issue and why has nobody ever looked into this and posted some results?

Cheers,
Rob

[RayG]

Hi Rob,

That's not the raw data.. that's the data after conversion and correction. What I was interested to see is the actual numbers from the ames tester.

Ray

[rob streeper]

Hi Rob,

That's not the raw data.. that's the data after conversion and correction. What I was interested to see is the actual numbers from the ames tester.

Ray

I was doing the testing on the fly, meaning that I took the reading, looked at the chart and typed the result into the spreadsheet.

[RayG]

I was doing the testing on the fly, meaning that I took the reading, looked at the chart and typed the result into the spreadsheet.

Ok, next time you are doing a test, record the actual readings direct from the Ames out of interest.. maybe that will help unravel the mystery.


Why pray tell is this such a contentious issue and why has nobody ever looked into this and posted some results?

I don't know that it's all that contentious, certainly it's very interesting and not something that's been done all that much before.
The thing I do know for sure and that is that at least some of the data is wrong.. Rc 60 cannot be correct.

Ray

[rob streeper]

The thing I do know for sure and that is that at least some of the data is wrong.. Rc 60 cannot be correct.

Ray

You mean for maker number 4? If so I will tell you that it is a different saw design from the other saws. Any more and I could get even more trouble that I currently have.

BTW: The instrument I have was manufactured in 1969, well before the advent of USB connections. :o

[hiroller]

It would be interesting to do a map for an old Disston.
Despite the relatively recent development of a repeatable hardness test with Rockwell, I'm sure that the old saw makers could tell if a saw was hard or soft with out it.
Anecdotally, they could tell from the sound it made when struck.
If tensioning can locally increase the hardness of a thin plate then the hardness of the raw plate many be of less importance. This is certainly the case with modern hard point saws.

I suspect that saw plate for all saw makers was extremely varied in quality in flatness and hardness but this was evened out by the skilled saw maker in construction through grinding, toothing, setting and tensioning. Each process contributing to the smoothness and hardness of the saw.

[rob streeper]

Hi Stewie,

Thanks for that, I just quickly scanned the thread, I agree with what they are saying, something is seriously wrong with the measurements.

Ray

Now I know why Sawmill Creek has the reputation that it does. The posters there have formed a club and outsiders are not welcome. I checked the thread from yesterday and Prashun Patel, I assume one of the moderators, is going back and revising all of the posts and has deleted many. Auditing reality to make it pretty has a bad smell to me.

[rob streeper]

It would be interesting to do a map for an old Disston.
Despite the relatively recent development of a repeatable hardness test with Rockwell, I'm sure that the old saw makers could tell if a saw was hard or soft with out it.
Anecdotally, they could tell from the sound it made when struck.
If tensioning can locally increase the hardness of a thin plate then the hardness of the raw plate many be of less importance. This is certainly the case with modern hard point saws.

I suspect that saw plate for all saw makers was extremely varied in quality in flatness and hardness but this was evened out by the skilled saw maker in construction through grinding, toothing, setting and tensioning. Each process contributing to the smoothness and hardness of the saw.

If you've got an old Disston having a nice shiny blade I'd be happy to test it and report the results. Unfortunately the testing will leave little prick marks all over the plate which would have a detrimental effect on it's value. As I wrote above in correspondence with BobL I'm going to test a piece of 0.035" steel straight from the roll. I'll also take a piece and hammer one end, grind it flat and test the hammered and un-hammered portions. If the results I've seen for the D-8 saw plate I'm working on are reproduced the hammered end should be harder.

The problem with the sound tests, and I do those too, is that there's no intelligible way for me to report that kind of information on this website. I agree that the sound is different, generally higher in pitch but then again I'm sure that the plate is ringing in frequency bands well outside the range of human perception.

I think it's time that we banish these notions, meaning the various bits of received wisdom like Disston's 52, that we all think we know but that nobody has tested systematically. Everybody seems to have an opinion but nobody can offer any data. Why is that?

[RayG]

Now I know why Sawmill Creek has the reputation that it does. The posters there have formed a club and outsiders are not welcome. I checked the thread from yesterday and Prashun Patel, I assume one of the moderators, is going back and revising all of the posts and has deleted many. Auditing reality to make it pretty has a bad smell to me.

Moderators sometimes do that, mostly it's to delete personal attack type post, anyway, enough of that. Those guys over there were trying to tell you something, and that is....

The issue for me is the high hardness numbers that you are getting... the maximum hardness for 1095 as I've already posted is around 66 Rc, that's physically it!.... and that's surface hardness in the as quenched state. no tempering at all... and it will be glass hard, a file will skate off it without leaving a scratch. It's not able to be filed until you get down to maybe mid 50's, that's not just my opinion, that's just 1095 steel.

When you report results of 62,60,62,59,64 hardness for saw plate, there is something wrong with the methods you are using.

A simple test is to see if you can actually file that super hard saw, if it can be filed, then the hardness test must be wrong.

Ray

PS, The 1095 data I'm quoting comes from The ASM Heat Treaters Guide 2nd edition

http://www.asminternational.org/web/hts/heattreatersguide/-/journal_content/56/10192/06400G/PUBLICATION;jsessionid=3A2D7E58EA80CFC408C6C5164076B440?p_p_id=webcontentresults_WAR_webcontentsearchportlet_INSTANCE_nH8sZ8Ygz0Nq&p_p_lifecycle=0&p_p_state=normal&p_p_mode=view&p_p_col_id=column-2&p_p_col_pos=1&p_p_col_count=2

[rob streeper]

Moderators sometimes do that, mostly it's to delete personal attack type post, anyway, enough of that. Those guys over there were trying to tell you something, and that is....

The issue for me is the high hardness numbers that you are getting... the maximum hardness for 1095 as I've already posted is around 66 Rc, that's physically it!.... and that's surface hardness in the as quenched state. no tempering at all... and it will be glass hard, a file will skate off it without leaving a scratch. It's not able to be filed until you get down to maybe mid 50's, that's not just my opinion, that's just 1095 steel.

When you report results of 62,60,62,59,64 hardness for saw plate, there is something wrong with the methods you are using.

A simple test is to see if you can actually file that super hard saw, if it can be filed, then the hardness test must be wrong.

Ray

PS, The 1095 data I'm quoting comes from The ASM Heat Treaters Guide 2nd edition

http://www.asminternational.org/web/hts/heattreatersguide/-/journal_content/56/10192/06400G/PUBLICATION;jsessionid=3A2D7E58EA80CFC408C6C5164076B440?p_p_id=webcontentresults_WAR_webcontentsearchportlet_INSTANCE_nH8sZ8Ygz0Nq&p_p_lifecycle=0&p_p_state=normal&p_p_mode=view&p_p_col_id=column-2&p_p_col_pos=1&p_p_col_count=2

Ray,

I measured the hardness values for the old saws under the handles. I suspect they're harder there because they have been hammered in manufacture. I'll get after this issue later today.

Cheers,
Rob

[rob streeper]

I'd like to see some more extensive testing before making any firm conclusions - certainly before naming any manufacturer.
If one of my students was doing this as an undergraduate material science project I'd say even though 5 measurements might satisfy a standard procedure I still think 5 test points per saw is on the slim side to demonstrate hardness is normally distributed, especially if normal stats are going to be applied.

The first thing I would ask the student to do would be to demonstrate the method can generate a normal distribution on a reference material, both in several locations of the material and then using a reduced sampling regime across the surface of the material i.e. a hardness map. i.e. 20-30 measurements in a few locations and then 5 measurements at points event distributed across the material

I would then ask the student to to the same (hardness map) of at least one saw using the same method..
The surface finish issue can be addressed by sanding to the same level of smoothness.

The other concern is that typical "consumer testing" issue of just testing "one" of anything can be problematic. I would suggest the student investigate at least 5 saws of the same make and model from at least one manufacturer. i.e. no map but at least 20 measurements per saw.

To demonstrate "between sample" reproducibility I'd like to see the student repeatedly measuring the reference material between each different saw measurements to show there is nothing wrong with the apparatus or method. I'd also like to see one saw measured multiple times and in between revert to measuring the standard. A more representative value of the hardness would then be the external (or average of average values)

Although this might be difficult for you to do to further increase the confidence of measurements I'd also ask the student to perform sone repeat tests using a different apparatus. Ultimately a completely independent set of measurements would be useful.

I appreciate the time required to perform these measurements but I think even doing some of these it is one way to help reduce bias and hence criticism of the results

Hi again Bob,

Since this seems to be such a divisive issue I decided I'd better do this with an adequate number of samples. Thus I did a power analysis using the results tabulated above for standard deviation and differences in the means. Here's the log file of the calculation.

<PS logging enabled 1/13/2015 6:53:17 AM

Version 3.1.2
Suggested citation:
Dupont WD, Plummer WD: 'Power and Sample Size Calculations: A Review and Computer Program', Controlled Clinical Trials 1990; 11:116-28.
or
Dupont WD, Plummer WD: 'Power and Sample Size Calculations for Studies Involving Linear Regression', Controlled Clinical Trials 1998; 19:589-601.

--------------------------------------------------------
Type of study: T-test

Requested output: Sample size
Design: Paired

alpha=0.05 power=0.8 DIFF=0.9 SIGMA=1.92 M=0
Sample size=38

t-test confidence interval width=1.267477

We are planning a study of a continuous response variable from matched pairs of study subjects. Prior data indicate that the difference in the response of matched pairs is normally distributed with standard deviation 1.92. If the true difference in the mean response of matched pairs is 0.9, we will need to study 38 pairs of subjects to be able to reject the null hypothesis that this response difference is zero with probability (power) 0.8. The Type I error probability associated with this test of this null hypothesis is 0.05.>

Of course I'm not doing a clinical trial but the sample size number needed is larger than 25 so I'll do 50 measurements.

[Corneel]

It looks like Sawmilcreek closed the thread, just when I was outside to do some tests! How dare they? :U

I got my Disston D8, popped off the handle, grabbed a new sawfile (Bahco) and after 5 strokes I had filed the nick you can see in the first picture. Then I got a Stanley plane blade from a drawer (newish UK made stuff) and tried to file a nick into the edge of that one too. After 8 strokes I got only half as deep as on the Disston and more importantly, the feel was completely different. While you can feel the file really grabbing into the steel on the Disston, it feels like you are scratching on the plane blade. Also, when looking at my poor file's edge, you can clearly see the tell tale shiny spots of a worn out file.

Let's assume the Stanley plane blade is 58 HRc (I don't believe they would go much higher) then the Disston certainly is nowhere near that value.

Alas, I don't have any 1095 available at the moment.

336869336870

Just one data point of course, but it gives some color to the data.

[pmcgee]

Regardless of the absolute numbers, any test will show that there is a difference between the 30-ish numbers and the rest.

We should be welcoming this line of investigation ... even as a first step ... even if the method and data are not at a "peer-reviewable" level.

It asks and starts to investigate a question that maybe hasn't been looked at before ... which is what science is for.

As with any good experiment, there are any number of qns raised ... and it's valid, indeed essential, to question and query and improve and re-verify ... but people (elsewhere) approaching this with animosity is beyond me.

These are real measurements ... and internally consistent. There shouldn't be any backlash against publishing them ... only what to think of and do next.

[
One day ... for myself ... I'd like to know more about what "tension" means in the physical reality of a saw-plate. eg #12s (of which I have a couple dozen in varying ages and degrees of attrition) are dependably sonorous, and usually thin and flexible.
]


Cheers,
Paul

[rob streeper]

Regardless of the absolute numbers, any test will show that there is a difference between the 30-ish numbers and the rest.

We should be welcoming this line of investigation ... even as a first step ... even if the method and data are not at a "peer-reviewable" level.

It asks and starts to investigate a question that maybe hasn't been looked at before ... which is what science is for.

As with any good experiment, there are any number of qns raised ... and it's valid, indeed essential, to question and query and improve and re-verify ... but people (elsewhere) approaching this with animosity is beyond me.

These are real measurements ... and internally consistent. There shouldn't be any backlash against publishing them ... only what to think of and do next.

[
One day ... for myself ... I'd like to know more about what "tension" means in the physical reality of a saw-plate. eg #12s (of which I have a couple dozen in varying ages and degrees of attrition) are dependably sonorous, and usually thin and flexible.
]


Cheers,
Paul

Hi Paul,

I'm looking into that tension issue as well. See my D8 replica posts.

As to Sawmill Creek, well what can I say. I'd heard in several places some hints that the posters there could be difficult but I thought at least some people would appreciate the information. Some posted thanks openly but the majority sent me PM's suggesting that they didn't want to publicly thank me for my effort. I'll continue to go there and watch but I doubt I'll be posting anything more. My experience left me with a bad feeling.

Cheers,
Rob

[rob streeper]

It looks like Sawmilcreek closed the thread, just when I was outside to do some tests! How dare they? :U

I got my Disston D8, popped off the handle, grabbed a new sawfile (Bahco) and after 5 strokes I had filed the nick you can see in the first picture. Then I got a Stanley plane blade from a drawer (newish UK made stuff) and tried to file a nick into the edge of that one too. After 8 strokes I got only half as deep as on the Disston and more importantly, the feel was completely different. While you can feel the file really grabbing into the steel on the Disston, it feels like you are scratching on the plane blade. Also, when looking at my poor file's edge, you can clearly see the tell tale shiny spots of a worn out file.

Let's assume the Stanley plane blade is 58 HRc (I don't believe they would go much higher) then the Disston certainly is nowhere near that value.

Alas, I don't have any 1095 available at the moment.

336869336870

Just one data point of course, but it gives some color to the data.

Hi Corneel,

When I was testing and posting yesterday I was also doing some heat treating and annealing. I was hardening the round floats I posted about earlier in the year and they turned out quite well. I took some readings and got back values corresponding to Rc 58. An older file I had barely burnished the teeth of the hardened float. The steel I used was O1 if I'm remembering correctly. The thickness of the stock may play some role in perceived file-ability or the alloy may just be more abrasion resistant, at this point I don't know. Experiments and posting of results will continue however, here only though.

Cheers,
Rob

[D.W.]

Some of us do read more than one forum.

There is a misinterpretation of pressing people to provide correct data with it being a personal assault. It is nothing of the sort. It's the desire to see meaningful data and not just data.

As has been said previously in this thread, the high end of the hardness numbers provided for several western saws make no sense, and it's not worthwhile to push the data if the data is wrong. Incorrect data is worse than no data. I agree with that.

Kees just demonstrated why those high values aren't relevant, and quickly - even with a blade that may not even be 58 hardness.

As far as sawmakers making saws with various saw plates, it's not new news that some of the european manufacturers, and I'm sure western, too, do not use 1095 in their saws, and they do not harden 1070 or whatever other substitute is used to a high level (Certainly not the 48-52 range that 1095 is commonly found). One would expect if a boutique maker of saws doesn't specify the composition of the saw plate, you don't really have a reason to expect that a saw is 1095 and thus that it will be the same hardness as 1095 (be it a supply house that provides 48 hardness or 52, whatever it may be, either will make a good saw that is at least the equal of vintage backsaws from any era).

That said, 30 hardness is not acceptable, but providing that information without confirming that it's consistent and naming the maker doesn't do anything but indict all boutique makers who haven't been confirmed to not be that maker, and that is unfair. Especially when you are promoting your own saws and saw parts.

I have no objection to the data, but it has to be useful for something, and in order for it to be useful, it needs to be correct. Especially when another much more experienced professional toolmaker provided you with the actual results from strikes he made on saws with a much more sophisticated device (a versitron). What he provides as seeing saws between 40 and 45 hardness is data, and relevant. To suggest no other data has been provided is not accurate. It is less data, and less resolution, but much higher precision. With the direction that the aspersions are being cast, precision is awfully important.

I commend ray for directing you with exactly the same thoughts as I had, he is more mannerly than I am. It is not by chance that the most experienced folks are telling you that you have a problem to correct and the least experienced are cheering you on, correct or not.

[pmcgee]

Some of us do read more than one forum.

There's a good chance every reader here reads more than one forum.
It doesn't require reference to any other forum to discuss data and points that were presented here.


It's the desire to see meaningful data and not just data.

I would almost say *all* data is meaningful. This data clearly is.
At the very least it demonstrates at least separate groups in the recently manufactured items.
Rob could simply have posted ... "I have a number of custom saws ... and one of them doesn't perform."
That is opinion. So I'd say the call should be for "meaningful opinion, not just opinion".

There are various ways you go about trying to quantify performance or quality ... usage tests like Derek has pursued eg.
This is a perfectly reasonable step to take if the equipment is available.

In the first instance, the exact numbers do not matter ... even though there was a calibration stage.

If these numbers are "wrong" then the "real" ones are going to be a linear or near-linear or monotonic or non-linear function of the readings ... and for a virtual certainty ... the scores around 30 are going to remain clearly separate from the scores around 50-60.

This is not some offence against science ... this is exactly how it works. A first test is a first test.



As has been said previously in this thread, the high end of the hardness numbers provided for several western saws make no sense, and it's not worthwhile to push the data if the data is wrong. Incorrect data is worse than no data.

That is false. If the data is precise, then accuracy can be corrected.
It depends on what you are measuring and in what sense it is supposedly "incorrect".

A difference in means doesn't rely on accuracy ... precision is sufficient.
Medical risk statistics mostly never know what absolute level is observed ... it's proportionality that is investigated.
And most of all, we perform useful rough surveys all the time.

If I sort through my handsaws, some of them ring and some of them "thunk".
When you buy wood at a chain hardware store you sort through boards into "looks alright" and "not now, not ever".
It's useful at that level, and it is of course useful at this more explicitly quantified level.

If there's then more to investigate, then encourage more investigation ... and constructively suggest aspects that don't gel or could bear fruitful investigation.

This is a consistently supportive forum and a real good in the online world.
We don't do a bunch of negativity for very long around here.




That said, 30 hardness is not acceptable, but providing that information without confirming that it's consistent and naming the maker doesn't do anything but indict all boutique makers who haven't been confirmed to not be that maker, and that is unfair. Especially when you are promoting your own saws and saw parts.

Again I disagree. People will report on their purchases in the general areas all the time. "This is great", "This is a dog". There's nothing different going on here other than it is quantified. Plus this is a niche section of these forums. I doubt if there are thousands of trooping onlookers coming to carefully analyse the saw-making forum. This is where this should be posted, among the people who are interested in the details.

All this says to customers is that one individual saw out of four individual saws seems not to be up to functional expectations. It might be a maker, it might be a batch, it might be one-off. It might be unintentional. So customers learn to ask more questions, which they already had to learn anyway to know if they want a rip or xcut or hybrid saw. What pitch? What handle wood? So now they ask also about steel hardness. That's better for everyone.

[pmcgee]

Rob - do you know this forum? http://woodworkerszone.com/igits/forumdisplay.php?f=63

They're still american ... I don't suppose there would be more in the way of welcome of the data ... but they are keen on their saws.

Cheers,
Paul