Thread: Chisel Hardness Study, the first step.

I've been quietly following this thread with interest but I have to ask, am I reading correctly that the Funmatsu Nezumi cut over 4kg of shavings before it reached the 500g force limit?

Yes, you've read correctly. Keep in mind that these figures are linear extrapolations from the data I have. I cut anywhere from a few grams up to a maximum of about 60 grams to get the datapoints. Then I fit a straight line to them and extrapolated to the point on that line where 500 grams of force would be needed to cut the test filament. These figures are intended only to give an idea of the edge retention of the particular chisel, not to predict how many grams of wood could actually be cut to get to the 500 gram cutting force point.

In practice it's unpleasant to use a chisel with > 300 grams of cutting force and very difficult to use one at 500 grams. Some of the really poor chisels gave > 1000 grams of filament cutting force in testing and they were about as easy to use for paring as a shovel.

I don't yet know what's going on with those chisels that are showing negative extrapolations and slopes but I can conclude that the edges are changing. An example is the Woodcraft/Henry Taylor crank chisel. In pine it showed the negative slope but in oak it failed. Thus it may be that when a chisel shows a negative slope that it is an early indication that it will fail with extended use or that it can't cut wood that is harder.

Originally Posted by rob streeper

These results are from testing with oak.

Sharpness testing results 042018a_Page_136.jpg

Sharpness testing results 042018a_Page_150.jpg

Sharpness testing results 042018a_Page_151.jpg

Sharpness testing results 042018a_Page_152.jpg

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The S25 chisel gave up immediately, the first stroke raised a burr. The S30 held out longer but was still failing perceptibly at the end of testing. The H25 chisel, though the numbers show it doing pretty well, had about 5-6 mm of the edge fail visibly, just flaked off. The H30 held its edge well but dulling was apparent by feel toward the end.

Rob, The issue with the edges flaking is what I have been running into with these once hardened.... And they don't really stop chipping till they are quite soft. This may well be some problem with the way I am torch hardening them... I am not really sure what to do about it - but they end up not particularly useful as a result. Perhaps chasing them up to higher angles till they quit chipping....

One thing that is strange though... Even soft as they are - sharpen them up to 30 degrees and their predicted edge life is as good as the Pfeil and better than Lie Nielsen..... Not sure I believe that in use.... But still - strange....

Weather and life permitting I'm going to go back around on the hardened Bucks, flatten and sharpen them and re-test. May be that there's a little decarburization or oxidation layer at the edge.

I am also very interested in whether your sharpening method results in a more durable edge, especially finishing on water stones.... I am assuming you prepped these on your jig setup....

What's your impression of sharpening them? How do they feel to you compared to the others?

Originally Posted by rob streeper

These results are from testing with oak.

Sharpness testing results 042018a_Page_136.jpg

Sharpness testing results 042018a_Page_150.jpg

Sharpness testing results 042018a_Page_151.jpg

Sharpness testing results 042018a_Page_152.jpg

Sharpness testing results 042018a_Page_153.jpg

The S25 chisel gave up immediately, the first stroke raised a burr. The S30 held out longer but was still failing perceptibly at the end of testing. The H25 chisel, though the numbers show it doing pretty well, had about 5-6 mm of the edge fail visibly, just flaked off. The H30 held its edge well but dulling was apparent by feel toward the end.

pretty much appears that harder is better for paring (not surprised) in anything more than soft woods. I'm sure it's better for those, but the differentiation isn't as clear.

It also appears that a hard chisel upper 20s in degrees of edge holds up the best, even though it may not wow someone on the first few strokes due to wedging.

Interested in seeing where this goes in heavier work, as I had a set of ouchi chisels that were glass hard and they were great for light work, but the tables were turned when I used a few of them to do mortise work in beech (the corners broke off of them slowly, whereas it didn't with others).

Originally Posted by D.W.

Interested in seeing where this goes in heavier work, as I had a set of ouchi chisels that were glass hard and they were great for light work, but the tables were turned when I used a few of them to do mortise work in beech (the corners broke off of them slowly, whereas it didn't with others).

My previous experience with these Buck chisels is that the re-hardened ones are pretty chippy compared to Two Cherries - which tend to run towards the hard side for western chisels... I have not been successful getting them to hold up under the mallet. Probably a lot to do with my technique, though... As plenty of Japanese chisels are considerably harder...

It would be nice to get an analysis on them. If they go high hardness but don't hold up that well there, it would suggest the possibility of not that much carbon. If you told me that they are 65 hundredths of a percent carbon, I wouldn't be surprised.

Same thing happens if people try to make irons out of 1070 (because it forge welds well) and then drive their hardness up where you'd put 1095. they just don't wear well.

I got yet another set of chisels today. Mifer. Spanish firm apparently out of business. they were $38 for six of them, unused with boxwood handles. Their literature said they were 59-61 hardness when they were made, and these are at least at the high side of that, but they do have some persistence with the wire edge (chromium-ish behavior). the thing about them, though, is that they have the most fabulous delicate bevels without resorting to the short side bevel from end to end like pfeil. They were also a little bit warped on the back, but I have a setup to deal with that. They'd have tortured someone using a 1k waterstone, and took me an extra 10 minutes or so to flatten (for the six).

Haven't gotten the craftsmans out yet, but will soon. I have three other sets of chisels that came in the last two weeks, but I think I'm getting close to the end of the jones and will resell a bunch of them.

I've bought some bigger laps and decided to use this one for flattening these chisels despite the fact that it's not quite flattened yet.

New two sided large lap.jpg

This one came from a surplus dealer and pictured is the flattest side. I have another large single-sided lap that isn't pictured to make the three surfaces needed for keeping them all flat.

Each of these larger units were used and each was more or less out of whack. The set of three Kent Moore laps were also used but very out of flat when they arrived. Maybe that the bad condition of the laps I was able to buy on the cheap gives some insight into why they were on the surplus market, i.e. the prior owners didn't know how to use them properly and went out of business as a result of general incompetence.

Nonetheless the Buck re-hardened chisels turned out pretty nice. These interferograms were acquired after 1 micron diamond.

H25 after flattening.JPG

H30 after flattening.JPG

They're about as flat as a BCTW plane blade.

For reference, this is the interferogram of a master flat.

Master flat interferogram.JPG

Attached is the NIST monograph of gauge blocks and flats.

The Gauge Block Handbook NIST 1991, Beers and Dorion.pdf

Very interesting. I threw the Buck chisels data into a DOE just to see what comes out... So caveat - limited data here.... 2nd caveat - data doesn't know what it doesn't know - and so hence neither does the simple model... So edge failure doesn't seem to be represented in the data except for the soft, low angle.....

Cutting edge hardness and angle both have very strong effects on cutting (no surprise...)
The effect is about the same strength for both within the same chisels. Aka - 1 hardness point gets you about the same improvement in cutting performance as 1 degree steeper bevel.... This is kinda a surprise to me... But it's probably not a surprise to people who have used a lot more chisels than I have....

Sounds like there's a sweet spot, or range, of angle and hardness. Makes sense and likely needs to be defined for each alloy.

Whether a chisel is too soft or too hard, the only solution is to increase the final bevel angle with a bevel that is thick enough to avoid failure in the final bevel.

So, you're right, just keep increasing the angle. if the angle that you have to go to to avoid strange failures is too steep, then it's time to move on to another chisel.

One of the reasons that I don't love magazine reviews is they don't follow my "give a chisel what it likes" principle, which sometimes means that giving a chisel what it likes is intolerable (if you have to go to 40 degrees to chop without chipping, no thanks, but if a chisel holds up worlds better at 31 degrees than it did at 28, jeez....hone it at 31).

the chisels that I've found that I like (apologies for repeating) aren't necessarily the ones that always do the best in fixed tests. Ouchi's old chisels (ouchi sr) were white 1 and ultra hard. In light work, they work great. Cut a plane mortise with them and they give up their corners, and then their hardness bites you in the rear. You can increase their angle so that they hold up as well as softer chisels, but you end up increasing the angle to a point where a basic stanley vintage chisel holds up just fine, and the touch-ups with the stanley chisel are agnostic on sharpening media and don't mind grinding. So what's the point with the ouchis? Well, if you're working mostly very soft wood that is very agreeable, they will hold bleeding edge sharpness better and be nicer for that work. Or if you're doing a lot of paring.

I don't do a lot of either.

FWW one year stated that pfeil chisels were the ones to have. The next year, they stated that Lie Nielsen chisels were the ones to have, and that japanese chisels placed second. Instantly, the forums were lit with "common knowledge" that lie nielsen chisels held an edge better than anything else.

Then, pre-Woodcraft, Tommy Mac had his own show. He had a bombe chest in the background and a king stone with a piece of bare leather, and marples blue chips. he talked about his students coming in all the time with expensive tools and how much of a pain they were to sharpen. Blue chips would've placed near last in any magazine abuse test, but in his work, they were fine - fine to the point that he much preferred them over LN.

Long winded way of saying, there's lots of stuff to try before deciding a chisel is junk and relying on reviewers (which nobody in this group does to begin with, but I'll bet 95% of purchases due to reading are led by blog "experts" and woodworking magazines.)

(not surprised that hardness and cutting angle are the two biggest factors on a regression when other items are generally unknown. I am surprised that a couple of japanese chisels held up poorly at 30 degrees, but one never knows why that is. there *are* duds from every maker. I've got three kiyotada chisels, and one of the three is ....meh. It happens.)

So then.... What would be my track... Knowing woodworkers as well as a bit about buying....

Say you are a maker.....
Fill your quiver with several high quality offerings so that you can quickly get very good product offerings into the market to satisfy whatever itches people feel like they need to scratch based on whatever magazine article or web page happens to blow up the market next..

So sort out a good low alloy HCS, a high alloy HCS, and perhaps a flavor of HSS... Sort out heat treatment for a hard offering, medium, and softer offering.... Figure out several successful blade patterns/grinds and a couple handle profiles...

Then - when the magazine article or web page takes the web by storm - you have some product that's already worked out that you can quickly get out into the market to sell to folks... I think this is a whole lot better solution than constantly being surprised and caught with your pants down.... Or just doing nothing innovative...

I think of Two Cherries... You buy 1 set of their chisels and that's that for the rest of your life.... They have been selling more or less the same product line with basically the same handles and blades for 50+ years now... The main decison is plastic or wood handles...

But compare to Pfeil... They change handles and blade configurations on their chisels every so often... And they get you to circle back around and buy another set just to try them out...

Originally Posted by D.W.

One of the reasons that I don't love magazine reviews is they don't follow my "give a chisel what it likes" principle, which sometimes means that giving a chisel what it likes is intolerable (if you have to go to 40 degrees to chop without chipping, no thanks, but if a chisel holds up worlds better at 31 degrees than it did at 28, jeez....hone it at 31).

the chisels that I've found that I like (apologies for repeating) aren't necessarily the ones that always do the best in fixed tests.

FWW one year stated that pfeil chisels were the ones to have. The next year, they stated that Lie Nielsen chisels were the ones to have, and that japanese chisels placed second. Instantly, the forums were lit with "common knowledge" that lie nielsen chisels held an edge better than anything else.

Then, pre-Woodcraft, Tommy Mac had his own show. He had a bombe chest in the background and a king stone with a piece of bare leather, and marples blue chips. he talked about his students coming in all the time with expensive tools and how much of a pain they were to sharpen. Blue chips would've placed near last in any magazine abuse test, but in his work, they were fine - fine to the point that he much preferred them over LN.

Long winded way of saying, there's lots of stuff to try before deciding a chisel is junk and relying on reviewers (which nobody in this group does to begin with, but I'll bet 95% of purchases due to reading are led by blog "experts" and woodworking magazines.)

The reasons you state about 'opinions', 'reviews' and articles are the motivation for my studies. Instead of the b------t, informed and uninformed opinions, bloviating and the on-line compost of useful tidbits floating in a Sargasso Sea of ephemera I'm trying to build a database of reproducible numerical measurements and analyses.

If there's anything pertinent that I've overlooked including here please let me know and if I can I'll post it. I'm up to 153 slides now and the combined tool (saws, chisels, hammers and anvils) dataset is just a hair under 2MB with a long way yet to go.

Originally Posted by D.W.

(not surprised that hardness and cutting angle are the two biggest factors on a regression when other items are generally unknown. I am surprised that a couple of japanese chisels held up poorly at 30 degrees, but one never knows why that is. there *are* duds from every maker. I've got three kiyotada chisels, and one of the three is ....meh. It happens.)

So far the Japanese chisels lead the way. Surprising that the rest of the world hasn't been able to equal them. Even more surprising that so many of the vaunted names in European chisels are so poor.

Sharpness testing results 042018a_Page_119.jpg