Hand Tools Archive

Hardness Data for Chisels *PIC*

david weaver
(this is long, and if you're the type who boasts about minimal time thinking about tools, and maximum with tools in wood - it's not for you. Fair warning)

(Also, picture is at the bottom)

Attached is a summary of hardness data that I have copied over from Rob Streeper's efforts. I don't think you can view the pictures on the forum that he posted them on without registering, so I have put the picture here. I have a lot of opinions about how hard I think tools are due to switching over to using a washita stone on a regular (majority of the time) basis, and correlating how the chisels on that stone behave (from time to time looking at the edges under a microscope, but not often - it just confirms what I feel).

I was pleased that rob got a hold of some sets of chisels, and in some cases, single chisels, and tested them (none of the tests are single strikes).

These results are for individual chisels and not sets, but they generally correspond with what I've been able to gather from stones.

I purchased three sets of sorby chisels that I found for a steal (different styles) because I like the style so much, and they were just a touch soft (something you can work with, but disappointing) and I didn't know if they were 56 or 58 or what, and Rob has confirmed with multiples of them that they are about 57/58. I knew from a previous versitron test on a defective witherby that they were a lot harder than 53 - 53 is unusable.

This is the basis for my comment the other day about hardness.

I can't recall if Rob tested more than these chisels (I encouraged him to test some older chisels, but didn't want to be the donor as I don't have many that are in a condition that I'd just send them on a one-way trip - I have in the past, but have gotten rid of most of them, as well as two sets of the sorby chisels).

I see some interesting take aways from this data that I am afforded comparing only due to excessive buying and screwing around.

1) the softest japanese chisels to me, even when they are criticized (iyoroi mokume come to mind, I guessed them at 62 or so, maybe 63 - they were wonderful, but I sold them as I got a set of chisels that have geometry more to my liking) are harder than most western chisels, almost all. The off name chisels in this test (as someone who has ever had a lot of j-chisels go through their hands) show 63.5 hardness. You can easily feel this difference vs. a chisel that's 65 - it's stark if you have access to natural stones. 63 sharpens easily on a decent japanese natural stone, 65+ does not.

2) I would've pegged narex (the ones I've had, I have none now) around the same as sorby. That's about where they are. They feel like they have potential but they're two points shy of it. In my opinion, there are much better options for geometry, but they fit a price point. Sorby chisels on the other hand can be $225 for a set of five or six, as much or more than ashley iles.

3) the funmatsu chisel, I sent to Rob. I don't think he managed to flatten the back of it, but that doesn't really affect the hardness. I'd had the last 1/2 inch or so flat and sharp, which is not unusual with japanese chisels (a slightly convex back) but didn't convey that the entire back shouldn't be ground flat. The reason I sent it is because it's one of the super hard powder metal chisels that I'd gotten from stu in the past to try one. I think they would chisel a nail, but in the cycle of regular work, I preferred the less impressive iyorois mentioned above.

4) the comment at the bottom of the picture should've said "tasai". The tasai chisel had varying spots of hardness on it, thus the large SD. (I cut the comment out to save size of the picture after posting this, but the large SD is still there. I wonder if these chisels may actually be hand hardened in the open atmosphere by tasai)

It's interesting that all of the western chisels that we tend to view favorably are pretty much right at 60. Pfeil, Blue Spruce (twice), berg, ... I'm sure I could've provided a half dozen other chisels that were 60-61, and easily picked chisels that were on average 2 clicks less hard (many of the early-mid century american chisels like stanley 750s, witherbys, etc. chisels that were all the rage about a decade ago, but I never liked as much as other folks did - I think that was just a socket chisel craze that seems to have subsided because nobody is releasing new socket chisels right now and the stanley sweetheart type collectors that existed pre-internet don't really have much presence on woodworking forums).

Curious in this group is the PM V11. I would have guessed the V11 that I have is slightly less than 63 (which is the top of LV's spec, IIRC), but it has a lot of chromium in it, so it is a little less easy to tell with the washita test. I can sharpen it on a washita, but the chromium grades the stone a little bit. It was common in razors to back off hardness a little bit on stainless razors to make them more sharpenable. There's plenty of possibilities (maybe the data is incorrect here, maybe the step down in hardness is intentional for user benefit, whatever it may be). I'd love to see a couple more struck by calibrated testers (rob's using a portable tester, but it's got a calibration kit and he provides the data from the tests blocks at the beginning of each experiment that he does).

Separate and aside last comment - the marples chisel discussed is a chinese marples chisel. I was surprised to see it get some strikes around 60 and wondered if it might hold up well, but Rob did run some tests with these in soft and hard wood - paring. The tests were difficult to decipher because the chisels didn't all have the same bevel angle, so they didn't provide much information except the let down for the marples -which was that it seems to be subpar steel driven up in hardness (medium carbon? who knows), and it flaked out quickly once rob started paring hardwood.

I cannot recall the original point of the study - I think it had something to do with hardness and sharpness, but Rob is a tinkerer, and by the time he was done, there were about 140 different data summaries and he had spent huge amounts of time working various chisels full bevel in honing guides. I didn't want to bother him to try to make everything identical. The hardness data ended up being the most interesting. If I never knew it for sure, it wouldn't matter that much, but it's always nice to see numbers agreeing with your information.

I've got a huge amount of experience with older sets of chisels and plane irons and can make generalizations about those far enough to dispell the long-time myth that quality was bad and hardness was inconsistent. I can only guess that because certain makers uniformly made their chisels less hard that people with mixed sets of old chisels sometimes don't discern that if they sort them into makes, that within make, they are very consistent. I'd guess old bucks at 58/59, and old ward chisels at 61, perhaps 62 - some with some other makers like i. sorby. It sounds like a small difference, but they behave differently in use, and I've never had one from either make that crossed into the others' territory.

I can also conclude that if I were lucky enough to come up with a shop to make chisels with dies and a hydraulic press (which will never happen), I'd make them with the plainest steel I could find - 61 hardness for western chisels and two versions of japanese - 63 and 65 hardness.

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