Chisel Blade Testing - 5 Steels

[Derek Cohen]

There has been considerable discussion about the merits of the "new" powdered metal super steels over the past year. Of course these are not new steels - they have been around quite a while and "old hat" to knife makers. However they represent new possibilities for woodworkers in the form of longer-lasting edges.



Longer lasting edges reflect high abrasion resistance, and the challenge with these super steels is to find an efficient and economical sharpening regime. Put away the Japanese waterstones, even the ceramic variety. Hide the sandpaper, and don't even admit to thinking that you may try oil stones .... none of these are effective. Yes, my Professional Shaptons do work, but ever so slowly, and you will be fooled (as I was) into believing that you have a working edge. The only medium that works effectively is diamond. I used diamond paste on a cast iron substrate with 40, 10, and 0.5 micron grits. With diamond, these steels were sharpened as easily as my A2 and laminated Japanese blades are on Pro Shaptons.

Using the above regime, all chisels easily pared Radiata Pine end grain as a pre-assessment screening.

The Steels

There are three powdered metal chisels, CPM 3V, CPM 10V and CPM M4. These blades were supplied by John Payne, who arranged for their heat treating. Hopefully John will join the thread and provide some details about their hardness and heat treating.

As a measure of control, I added a vintage Stanley 750 chisel, which is likely to be W1 steel. I also added a 30-year old Koyamaichi dovetail chisel, which I believe to be white steel. Stu Tierney will no doubt challenge me if I am incorrect

Five 3/4" chisels: 3V, 10V, M4, W1 (Stanley), and Laminated White (Koyamaichi)




The Test

I wanted a Real World evaluation, and so took the opportunity to chop out the dovetail pins in a 3/4" thick Jarrah carcase for a cabinet I am constructing. Each pin was 45mm in length.



The method involved chopping out one half of a pin waste with each chisel in approximately 1/16" - 1/32" slices, checking the blade subjectively for a wire edge (by touch), testing the edge for sharpness by paring end grain Radiata Pine, turning the Jarrah board over and completing the removal of waste, and repeating the checks. At the conclusion, the blade edges were photographed at 200 magnification.

Half way ...

The Results

All the chisels were able to chop Jarrah waste even when the edges were dull. Few could pare end grain Pine comfortably after chopping the first half of the Pin waste, and only one chisel stood out as a tool of significant worth, the Koyamaichi. In second place was the M4 chisel, with the 3V coming in after this. The Stanley and 10V came in at the tail, with the Stanley just shading the 10V.

The Koyamaichi was outstanding. Not only did it fail to evidence signs of a wire edge (i.e. steel edge folding) at the half-way stage, but it was still paring end grain after 9 full dovetails. By contrast, only the M4 and 3V chisels were able to pare end grain at the end of a single dovetail, and at this stage they performed less well than the Koyamaichi did at the end of 9!

What of the Stanley? Well it did not disgrace itself and, in fact, did a very decent job. The 3V was tested initially with a 25 degree bevel (as this was the angle recommended). The Stanley (also with a 25 degree bevel) was better than the 3V in all departments (edge holding and performance) at this stage. However the 3V improved significantly when the bevel angle was increased to 30 degrees.

The Koyamaichi, M4 and 10V were given 30 degree bevels at the start (all recommended angles). This appears to be a good choice as the latter two blades developed only a fine wire edge. The wire edge on the Koyamachi was difficult to find.


Images

The images are in a set of two, with the first a magnification of 10X of the back of the blade, and the second image a magnification at 200x.

Koyamaichi ...



M4 ...



3V - note that the top images are with a 25 degree bevel, and the lower at 30 degrees ...



Stanley 750 ...



10V ...




In Summary

Relatively better performances from 3V and M4, and superlative performances from Koyamaichi laminated white steel.

Will there be a different presentation when the test is repeated, and will these results differ from blades used for planing?


Regards from Perth

Derek

[Tony Shea]

Very interesting stuff Derek. Proof that good old laminated white steel is hard to improve upon as a chisel. I'd be interested in seeing how blue steel compares as I've had great success in the couple chisels of blue steel I use. I'm just now starting to build a collection of Japanese chisels, most coming from Koyamaichi but have a couple cheaper Ioyori's in the mix that perform admirably as far as edge retention is concerned. Not as nice a fit and finish but is not what this thread is about. Great thread and very reassuring that my new found interest in japanese steel is worth its while.

[Salem Ganzhorn]

Quite an interesting result. When I was looking at chisels I read quite a few accounts of Japanese chisels faring poorly for chopping. Especially in hardwood and at 25 degrees. I read many suggestions to increase the angle when chopping hardwood.

Thanks for the comparison. It is the first I have seen with these steels and chisels.
Salem

[Chris Vandiver]

Thank God for those results, because those chisels made from powdered steels sure are ugly and clunky looking!

[Derek Cohen]

Chris, those PM chisels were shopmade for this test.

What these results are indicating is that PM steel is probably better suited to plane blades or paring chisels than chisels used for chopping. They have great wear resistance, but are not significantly different with regard impact resistance.

Note this this is only the first round. I would have liked to have included an A2 blade but did not have one (the testing was something of a spur-of-the-moment). Also, I need to try higher bevel angles on all (except the Koyamaichi) and see what difference this makes).

Any other ideas to include?

Regards from Perth

Derek

[Johnny Kleso]

What was the hardness of the blades?
Also did the edges fracture or roll over?
Its hard to tell from pics..

[David Wong]

Derek, Your evaluations and reviews are always so well written and informative. I am awed by the sheer output of information you can generate. You are very generous to share with everyone.

It amazes me that the Koyamaichi chisel that performed so well, is a dovetail style chisel. I wonder if a bench style Koyamaichi with more support for the hard steel would perform any differently.

[Jim Foster]

Interesting results, In the pictures, the blade backs do not look to be equivalent in finish and some grinding swirls look present on several bades. (It might just be the pictures) Do you think there is enough difference in the state of the flat side finish on the various blades to affect the results?

[Derek Cohen]

What was the hardness of the blades?
Also did the edges fracture or roll over?
Its hard to tell from pics..

Hi Johnny

Good question. I don't know the hardness of the PM steels. They seem softer than they should be since the edges roll rather than chip.

Regards from Perth

Derek

[Derek Cohen]

..It amazes me that the Koyamaichi chisel that performed so well, is a dovetail style chisel. I wonder if a bench style Koyamaichi with more support for the hard steel would perform any differently.

Hi David

Thanks for your kind words.

Japanese "dovetail" chisels are bench chisels. The term is merely descriptive of the triangular shape. My smaller Koyamaichi are custom ground to a minimal shoulder. The larger ones are standard.

Regards from Perth

Derek

[Derek Cohen]

Interesting results, In the pictures, the blade backs do not look to be equivalent in finish and some grinding swirls look present on several bades. (It might just be the pictures) Do you think there is enough difference in the state of the flat side finish on the various blades to affect the results?

H Jim

It is just the picture - difficult to take handheld. The important area at the back of each blade is honed to .5 micron on each chisel.

Regards from Perth

Derek

[Tony Shea]

Thank God for those results, because those chisels made from powdered steels sure are ugly and clunky looking!

I couldn't disagree more. I think they look to be a very comfortable style chisel to use. Considering the tools at hand to make such chisels I think you've done a superb job.

When I was looking at chisels I read quite a few accounts of Japanese chisels faring poorly for chopping. Especially in hardwood and at 25 degrees.

This angle seems far too low for any kind of chopping for any style of chisel IMO. Maybe for soft woods such as pine but def not any type of hardwood.

[Pam Niedermayer]

Quite an interesting result. When I was looking at chisels I read quite a few accounts of Japanese chisels faring poorly for chopping. Especially in hardwood and at 25 degrees. I read many suggestions to increase the angle when chopping hardwood....

And that's why these forums are so needed, to combat misinformation published in respected journals, which, of course, shouldn't be all that respected. After all, they do it for the advertising money.

Pam

[David Weaver]

What was the hardness of the blades?
Also did the edges fracture or roll over?
Its hard to tell from pics..

If derek's KI dovetail chisels are like mine, they are probably accurate to their spec of 65/66 hardness.

I seem to recall the makers of the powder metal chisels saying 58-60 or so. there's a huge difference between those two in hardness to my feel on the stones.

I'll bet the stanley chisel is close to the powder metal chisels in hardness.

This test is interesting to me, because I had assumed that the results would follow the toughness ratings on the charts, and though I don't have any "exotic" steel tools, i really like M2 plane blades and have been an advocate of trying to find better metals for chisels.

As it stands after this test, and from my experience with the KI chisels, i'm starting to wish that more attention would be given to what's done with the metal rather than what the metal is.

I couldn't tolerate a chisel that can't stand up to general use reasonably well at 25 degrees.

It'll be interesting to see what more iterations of the tests with the chisels show.

[John Payne01]

Derek

You've been busy! I saw your post Saturday evening but was down in Santiago, Chile and only had my iPhone with me then. No way was I going to try to write a response using just that. I'm back home now and got a little sleep so here goes.

The heat treating of all the CPM steels was done by Mid-South Metallurgical. They specialize in these types of steels and were recommended by Crucible Metals and numerous custom knife makers. The RC hardness for each steel was based on recommendations from Crucible and from custom knife makers who have been using these steels for many years. Neither of these sources had experience in making wood working tools so I made an educated guess based on their inputs. For the CPM-3V I had it hardened to RC61. It's above the upper end of the recommended hardness range for it (58-60), but even at this hardness it's more impact resistant than A2, and both groups said it was noticeably more wear resistant at RC61 than RC60. The knife makers said they have had no problems with chipping at that hardness and it would still pass the ABS Bladesmith test of being bent 90° in both directions without cracking or breaking. It is used in knives and tools for special forces at RC59 and the guys that make these say that at that hardness, "you cannot break it". The CPM-M4 was heat treated to RC64, higher than I had asked for. It's working range is 61 - 65, I think RC 62-63 would be about optimal for it. At RC64 it is more impact resistant than D2, and many times more wear resistant but the edge may be more prone to chipping. The CPM -10V was hardened to RC60, it's working hardness range is 60 - 63, but at each point of additional harness, impact resistance drops and it's not high to begin with. At RC60, it's about the same as D2 and it's wear resistance it higher than any of the other steels in the test. I didn't think it would make a good chisel for chopping, but included it for testing purposes.

As for the results of the test, I was a little surprised in 3V's performance, but not M4 or the 10V. I'm not familiar with Jarrah but a little research showed that it's harder than Purpleheart which I find as pretty tough stuff. 3V will bend or fold before it breaks, and will develop the small microscopic chips in the edge as it wears. With a 25° bevel it handles cherry, walnut, and curly maple without any problems. I think Chuck Bender or EODdave could shine some light in this area as they have had 3V chisels in their hands longer than any others. I believe Chuck uses his with a 25° hollow ground bevel and Dave at 35°. I don't think either has had an edge failure and use these constantly. It does very well as a plane blade, even when used on knots, glue lines, etc. Could there be a heat treating problem with this chisel? It's always a possibility but this one was out of the original batch and was heat treated at the same time as the ones used by Chuck and Dave. I agree with one of the comments that griding off 1/8" and trying it again may remove that possibility.

M4 was steel that I thought could be a surprise. It does make a great plane blade and at the proper hardness may also do very well in chisels. Again, I have people using them in our domestic hardwoods and have not heard of a failure yet.

10V was an experiment. Our Friar(on Woodnet) has 3 of them, 2 paring chisels and one for chopping. As a paring chisel with a 25° bevel it does very well and holds its edge for a very long time. As Peter mentioned he has the chopping chisel at 30° with a 35° micro bevel. He recently cut dovetails in Purpleheart without an edge failure. Honestly I doubt if I'll make any more chisels out of it. I think there's better stuff out there and it is extremely difficult to work. Much more so than other steels. However, it makes an incredible turning tool. I have a couple tools made out of it and I honestly can't remember when I last sharpened them.

For future tests try using them for paring in several woods, including Jarrah, and chopping in not such a hard wood, I think the results may be quite different. Because Jarrah is so hard it may be testing the impact resistance of the steel more than it's edge holding ability. If I new I'd be working in such a hard wood with one of these steels I'd change the bevel angle definitely higher than 25°. Even with that said, the Japanese chisel did out performed these it in chopping this wood. So if I worked stuff like this regularly, I'd definitely go with them. But in the case of Dave who chops a ton of dovetails per weekend in curly maple, the 3V held it's edge longer in this less tough wood than his laminated Japanese chisels. So it may just depend on what you will be using these for. That's what testing is all about and I know you will run them through very thorough tests and present an unbiased review.

Another note on these steels. I'd love to test them all at several different hardnesses, but each change is $75 a pop so you see how that could add up, my pockets aren't that deep.

John