Saw sharpening. Historical information.

[planemaker]

I found this article by Brent Beach most interesting and thought it worth sharing. Further down he discusses the contents of the very early book The Art of Saw Filing by H. W. Holly, Gary Roberts scan on his Toolemera web site.

With great interest you will note from this book how the tooth geometry changes on cross-cut saws in relation to the type of wood being sawn. For example; for hard woods he recommends that "the back of the tooth be filed square". Including this statement; "Now the sharper each tooth is -- that is the more bevel on the point -- the deeper it will cut; but it must not cut any deeper than will crumble out across to the point of the other tooth. This is the difference between saws for soft or hard wood; if a saw for hard wood is too much bevel on the point, it will score deeper into the wood than it can carry out the chip, so that it will keep moving up and down in the same scores, and not accomplish anything."

Stewie;

Sloping Gullets (http://www3.telus.net/BrentBeach/sawjig/sloping%20gullets.html)

[RayG]

Hi Stewie,

Brent Beach does an excellent job, very thorough and detailed.

I have that book by Holly, it's interesting, but can be easily misunderstood, he promotes the idea of positive rake being essential, which is mostly true of power saws, but almost never true for handsaws.

If you are researching this, have a read of Grimshaw's book... here's a pdf http://www.evenfallstudios.com/woodworks_library/saws.pdf

There is an interesting pattern I'd personally like to try one day and that's the three tooth pattern, basically you have a sequence of cross-cut, cross-cut, rip, cross cut, cross cut rip repeated.

The idea is that the two cross cut teeth define the edges of the kerf and the rip tooth is a clearing tooth.

Regards
Ray

[planemaker]

Hi Stewie,

Brent Beach does an excellent job, very thorough and detailed.

I have that book by Holly, it's interesting, but can be easily misunderstood, he promotes the idea of positive rake being essential, which is mostly true of power saws, but almost never true for handsaws.

If you are researching this, have a read of Grimshaw's book... here's a pdf http://www.evenfallstudios.com/woodworks_library/saws.pdf

There is an interesting pattern I'd personally like to try one day and that's the three tooth pattern, basically you have a sequence of cross-cut, cross-cut, rip, cross cut, cross cut rip repeated.

The idea is that the two cross cut teeth define the edges of the kerf and the rip tooth is a clearing tooth.

Regards
Ray

Thanks Ray. I look forward to reading Grimshaws book. The 3 tooth pattern sounds most interesting. I wonder if the logic behind including the rip tooth within the pattern of crosscut teeth has a similar principal to that prescribed by H.W. Holly for leaving the back of the tooth flat on crosscut saws on hard wood timbers to aid wood chip dispersal.

"for hard woods he recommends that "the back of the tooth be filed square". Including this statement; "Now the sharper each tooth is -- that is the more bevel on the point -- the deeper it will cut; but it must not cut any deeper than will crumble out across to the point of the other tooth. This is the difference between saws for soft or hard wood; if a saw for hard wood is too much bevel on the point, it will score deeper into the wood than it can carry out the chip, so that it will keep moving up and down in the same scores, and not accomplish anything."

It also raises the general question as to how this indepth knowledge and understanding by early saw makers has been mostly forgotten about. Was this the result of translation lost through word of mouth. Or at some stage was it felt prudent to simplify saw sharpening back to to 2 basic principals of tooth patterns. Crosscut & rip. Did early H.Disston, shortly starting up Keystone Saw Works in 1840, have a role to play in this simplification of tooth patterns. He would most certainly have been aware of the principals outlined in H.W. Holly's book written in 1851.

Stewie;

[Isaac S]

"for hard woods he recommends that "the back of the tooth be filed square". Including this statement; "Now the sharper each tooth is -- that is the more bevel on the point -- the deeper it will cut; but it must not cut any deeper than will crumble out across to the point of the other tooth. This is the difference between saws for soft or hard wood; if a saw for hard wood is too much bevel on the point, it will score deeper into the wood than it can carry out the chip, so that it will keep moving up and down in the same scores, and not accomplish anything."

It also raises the general question as to how this indepth knowledge and understanding by early saw makers has been mostly forgotten about. Was this the result of translation lost through word of mouth. Or at some stage was it felt prudent to simplify saw sharpening back to to 2 basic principals of tooth patterns. Crosscut & rip. Did early H.Disston, shortly starting up Keystone Saw Works in 1840, have a role to play in this simplification of tooth patterns. He would most certainly have been aware of the principals outlined in H.W. Holly's book written in 1851.

Stewie;

As late as 1907, Disston talked about filing sloped gullets on hardwoods. Not to increase the gullet size, but to regulate the slope point. Sloping the gullets will make the point of the tooth less acute. The first picture below shows teeth filed without slope, the second has some (I don't recall how much, unfortunately).

297650 297651

You should also see that the back of the tooth in the second picture is filed nearly straight across. If one were to add a little more slope while filing, it is possible to make it exactly straight across. There is some more discussion of this is this article (http://www.blackburntools.com/articles/saw-tooth-geometry/index.html#point-slope).

Please note that all of this tooth geometry is accomplished with a standard triangular saw file. It's cool (in my little world, at least) to think of how much the tooth geometry can be manipulated by simply changing the rake, fleam, and slope. It's also a bit confusing at first.

I don't think Disston simplified sharpening at all. For at least the first 70 years of the company, they were aware of all this, and more. Don't forget about the teeth on their Acme saws, among others. So I don't think that much, if any, of the knowledge that they had about saw filing has been lost.

Today, anybody with a computer, some free time, and a bit of motivation can explore and diagram saw sharpening in SketchUp. The accuracy and magnification possible with this (and other) programs blows away anything available back then.

I guess the whole point of this is that it is just as dangerous to assume that they knew best in those days as it is to discount their knowledge. One advantage we have today is the conveyance of what we do know about filing. One has only to look at a few of the illustrations and descriptions in the old books to see that illustration was, at best, imprecise. Bad perspectives and impossible angles abound. Great illustrations and analysis of sharpening is readily available today in seconds if you know where to look.

Anyways, these are just a few incoherent thoughts from someone who is up too early to make much sense.

[planemaker]

Your thoughts add good value to the discussion Isaac. I fully agree with your statement, " it is just as dangerous to assume that they knew best in those days as it is to discount their knowledge."

Although we are getting better at understanding the basic principals of why early saw makers did as they did, we still have much more work to do to fully understand why. Its like playing with a jigsaw puzzle, where some of the key pieces are still missing. :doh:

Stewie;

[DSEL74]

What about this third tooth pattern that some people are using, and I've gone and forgotten the name of it. It is supposed to be a cross between Rip & Xcut.
Is it the 3 tooth pattern you refer to Ray being rediscovered?

[planemaker]

Hi Isaac. As a modern day saw maker I approach high tpi backsaw sharpening with a degree of difference to that of my counterparts. I prefer not to use fleam as I see it use as having an overall impact on the structural strength of each tooth especially on saw plates of thin gauge such as 0.015 and 0.020 saw plate. The use of fleam exposes the tooth to greater wear to the sharpened edge, causing loss of valuable tooth height that would result in more frequent sharpening to restore. As I see it, the alternate approach is to reduce the rake angle from that used primarily for rip tooth sawing, apply minimal set to reduce kerf width, and these thinner saw plates can be used very effectively to sever the crosscut fibers cleanly without messy tear out. What you would expect to gain in speed of cut with the sharper fleamed tooth profile is also of little benefit if the depth of cut is being hampered by poor chip dispersal within the kerf especially on hard woods or woods in general with high moisture levels. So what is the ideal tooth pattern for cross cut saws look like. Possibly a mixture of using both tooth types as by Ray with the 3 tooth pattern. "There is an interesting pattern I'd personally like to try one day and that's the three tooth pattern, basically you have a sequence of cross-cut, cross-cut, rip, cross cut, cross cut rip repeated. The idea is that the two cross cut teeth define the edges of the kerf and the rip tooth is a clearing tooth." I have yet to trial this type of tooth pattern so I can only speculate to its performance within the sawn kerf. An interesting topic.

Stewie,

[planemaker]

What about this third tooth pattern that some people are using, and I've gone and forgotten the name of it. It is supposed to be a cross between Rip & Xcut.
Is it the 3 tooth pattern you refer to Ray being rediscovered?

Are you referring to this Dale.

http://norsewoodsmith.com/files/file/Progressive.pdf

[RayG]

Are you referring to this Dale.

http://norsewoodsmith.com/files/file/Progressive.pdf



No, that's progressive pitch, What I'm thinking of is more like the B.M.T pattern, but with more conventional tooth profiles. The idea isn't new, the inspiration comes from here..

Montague-Woodrough Saw Company - Chicago, IL (http://www.wkfinetools.com/hus-saws/MontagueWoodrough/Montague-Woodrough-index.asp)

Regards
Ray

[DSEL74]

No I am aware of progressive pitch. I am pretty sure Matt Cianci is offering and teaching this tooth pattern, but I can't find the reference to it.

Can't remember the name, can't find the reference, I think I must be getting senile!

[DSEL74]

Ok found reference to it and it is rot related to Ray's post at all.


I have written and talked a lot about how I file these sash-style saws and the more I use them to build furniture, the more I love them. I think the combination of 10 degrees of rake and 10 degrees of fleam is the perfect compromise for ripping and crosscutting.

[planemaker]

No, that's progressive pitch, What I'm thinking of is more like the B.M.T pattern, but with more conventional tooth profiles. The idea isn't new, the inspiration comes from here..

Montague-Woodrough Saw Company - Chicago, IL (http://www.wkfinetools.com/hus-saws/MontagueWoodrough/Montague-Woodrough-index.asp)

Regards
Ray

The description outlined for each repetitive set of 3 teeth reminds me of how Crown Teeth are shaped.

[DSEL74]

http://www.wkfinetools.com/hus-saws/MontagueWoodrough/0_img/1889-CarpentryAndBuilding-Saw-article.jpg

With scroll saw blades you can get some interesting tooth pattens also like skip tooth, and two up one down. I wonder if any of these could have applications in back saws, skip tooth in some ways would clear the dust like the slots in the blade above. Crown tooth would cut on both the push and the pull. It makes me think about how many of these had been tried but the market was to traditionalist and conservative to accept them and how many just didn't work any better.
http://www.woodcraft.com/images/articles/scrollsawblades2.jpg

[planemaker]

Not quite what I was referring to Dale. have a look at the crown teeth on this Atkins 93 Improved Universal saw. I used to have one of these in my hand saw collection.

Stewie;

WoodNet Forums: VERY large image of Atkins 93 Improved Universal saw (http://www.forums.woodnet.net/ubbthreads/showflat.php?Cat=&Number=6551862&page=8&view=collapsed&sb=5&o=)

WoodNet Forums: Saw Sharpening Advice - Atkins 93 (http://www.forums.woodnet.net/ubbthreads/showflat.php?Cat=&Number=6548628&page=&view=&sb=5&o=&fpart=all&vc=1)

[DSEL74]

Very interesting teeth Stewie.

Again I wonder if the would be practical or beneficial in a small scale for backsaws?

[planemaker]

Very interesting teeth Stewie.

Again I wonder if the would be practical or beneficial in a small scale for backsaws?

I would doubt its benefit, let alone the file work involved to shape these teeth in the 1st place.

[pmcgee]

Daryl Weir filed a BMT saw ... pictures ... bmt_hand_front.jpg Photo by daryl_weir | Photobucket (http://s279.photobucket.com/user/daryl_weir/media/BMT/bmt_hand_front.jpg.html)

I'm sure I remember a detailing posting on (guessing) woodnet about it.

Isaac gave an example of a front-fleamed tooth with the back of the tooth straight across, by sloping the file and consequently the gullets.

Stewie said he thought fleam weakened little teeth. There is the converse to Isaac's scenario - also through sloping the file - such that the front of the tooth is square across, but the back of the tooth is angled (or 'fleamed' if you like). So instead of the point-slope decreasing as in Isaac's example, some point-slope is introduced where there would otherwise be just the flat across top of a normal rip tooth.

I'd be intrigued to know whether that had any worthwhile effect for tiny teeth.

Daryl mentions that filing profile here (Old Vintage Antique Saws Restored (http://home.grics.net/~weir/Saws_for_sale.html)) in discussing the Simonds #5 handsaw.

BTW he also has a Disston #4 (12ppi) there that he describes as 'filed hybrid'. "This is a smooth cutting saw meant to work in either rip or cross cutting. "
There are plenty of pictures ... Disston No.4 16" by daryl_weir | Photobucket (http://s279.photobucket.com/user/daryl_weir/story/8657#)

Finally ... the Disston D17 "double duty" saw wasn't too different from the others mentioned (Online Reference of Disston Saws -- D-17 Saws (http://www.disstonianinstitute.com/d17page.html))
MarvW had an interesting view on it pretty recently (WoodNet Forums: Saw Sharpening Advice - Atkins 93 (http://www.forums.woodnet.net/ubbthreads/showflat.php?Cat=&Number=6548628&page=&view=&sb=5&o=&fpart=all&vc=1))
"I have had the misfortune of filing a couple of those type saws. They are in fact meant for double duty, ripping and crosscutting. If all you want is to use it for rough cutting, it will do exactly that. Due to there being way more crosscut teeth than there are rip teeth, the saw will rip pretty much the same as if you were using a crosscut saw. When you crosscut with it, the deep gullets act as if there is a missing tooth every 7th tooth. The gap, along with the two rip teeth it does about the worse job of crosscutting imaginable when sawing anything less than 4/4. I hated the saw and wouldn't recommend it even to someone I don't like. It might do ok in thicker stock. "

Cheers,
Paul

[planemaker]

Nice work Paul. Enjoyed the reading. I agree with Marv on his comments about the Atkins 93. The one I had was terrible to use. The only decent part of the saw was the handle with its wonderful detailed carvings. I ended up cutting the blade down to the size of a panel saw, and retoothing it to a high tpi rip saw. I really enjoy using this saw now.

Stewie;

[pmcgee]

I ended up cutting the blade down to the size of a panel saw, and retoothing it to a high tpi rip saw.
I really enjoy using this saw now.
Stewie;
<sob> You animal. You unfeeling bastord you!
:q