Thread: Chisel Hardness Study, the first step.

One aside - years ago, I was building a cabinet - dimensioning by hand. I had a hock O1 iron and A2 iron and tested the two. At the time, I concluded that A2 is much better suited to planing than O1 because Hock's A2 iron lasted noticeably longer (no stroke counting required - it actually planed more panel territory between sharpenings - at least 1 1/2 times as much, consistently).

What I didn't know was that Hock's carbon steel irons tend to be a little bit chippy, and that was the problem. If I had used a ward iron, the contest would've been a draw. If I'd have used a too soft freres iron, then the A2 would've also lasted a lot longer, but for a different reason (fast wear on a soft iron - even though the wear is uniform, it occurs quickly).

I think freres irons are french, and they have been uniformly a bit soft. The market there must've preferred that, perhaps due to sharpening stones. Don't know. that's in line with my comments earlier, that if you buy a mixed bag of old irons and chisels, you'll conclude that they're inconsistent in hardness. If you buy a set of old irons or chisels of the same maker, you'll start to find that each maker shot at a different target, but they were very consistent in that target.

Dwight and French stick out to me (I think an American maker) as another maker who made very soft irons. They work great in try planes, but you have to keep shavings on the thicker side of things to get the best from them - which means they're not going to be great for planing very hard wood for a long time. In a smoother, the several that I've had would be pretty gross. Again, goes back to finding what something likes and using it that way.

Hi rob

all this talk about carbides and their plucking from an edge as it is sharpened, could have a major bearing on your quest.
I suspect that the size and distribution of carbide particles may have a correlation with hardness and if it does their orientation in respect to the cutting edge could be substantially distorting your results.

Rob, I have more stones than debeers, and a giant array of various steels (old and new - except nothing funny). If you're curious about the edges on anything and a picture is useful, let me know.

Separate comment (already obvious, but I think I'll make it). A2 isn't an ideal steel for chisels. It's pretty good for planes, depending on what you're doing (relatively wear resistant, but not a good choice for finish planing if absolute appearance counts - which is why you see a lot of japanese, et. al (think warren mickley on the US side) completely disregarding it and its types).

If you use anything other than the washita (al-ox based stones, diamonds, etc), no problems with the carbides being plucked, but it remains to be seen (other than beach's confirmatory pictures) whether or not those get plucked during use. I suspect they do, which is why people will make statements like "I can see the edge on this carbon steel iron, but it's still planing well" (story at the end).

A2 is more resistant to Al-ox stones than carbon steel, but the difference is partially due to the hardness of al-ox marketed tools. If you sharpen 62 hardness O1 and 62 hardness A2 on anything other than diamonds, then all of the sudden, the difference doesn't seem as large (except that the O1 will have less hold on the finished wire edge).

that causes what Rob is referring to - conflicting reports: "I find A2 easy to sharpen and it holds its edge really well", then the next person will grouse about its sharpenability all the way down to someone like charlie stanford on another forum talking about it being a lost cause to flatten when he tried to flatten a block plane iron made of A2.

I don't grind my irons and stuff them in a jig (no shot, again at this test, you have to use a jig to standardize the process or it is the first thing people will criticize), so I notice if A2 takes twice as many swipes to get all of the wear removed on a washita, less so on diamonds. It's an appreciable part of my sharpening routine, where as a jig-based routine that involves flattening the stones used and then time setting the jig, it doesn't seem like much.

That's why I made the comment on perhaps rikizai chisels (made from two layer white 2) perhaps being an excellent place to go if thinking of making a chisel (presumably it would cost about $70-$80). It sharpens with anything (unless it's driven to 65/66 hardness, and then it's a pain - same with white 1), takes reasonably high hardness well, has a little bit of that exotic factor that makes people open their wallets, and because it's laminated, its behavior in heat treat should be pretty good. It's got good lower-angle toughness. The only real knock is that it has a fairly low temper point and could be burned easily, but minor burning would just knock the hardness down a little bit (and it would be still quite pleasant to use).

If it could be shaped something like the older chisels in bench and butt style, I think you have a winner. The question then becomes whether or not you can tolerate $15 or $20 worth of steel material in each chisel, and whether or not you can source it.

On the slightly less high-tech front, the ashley iles bench chisels are lovely. 61 hardness, O1, reasonably well finished and relatively cheap (here in the states, cheapest if you buy them directly from england).

I've never asked LN, but I'd be almost certain that they use A2 for chisels because it's easier to heat treat than O1, and involves less follow-up work. Not because it makes a better chisel. While the switch to plane blades from W1 to A2 was marketed as a better wearing iron, they had documented QC problems with W1 and didn't harden the entire iron up to the slot (only an inch or so). A2 is better post-quench if you resurface everything (less movement) than O1, and if O1 is done right (not chippy) the difference in plane iron life is fairly little. In chisels, it's none, or in favor of the O1 a little bit at the hardness level LN uses. Hock's O1 muddies the water because it's chippy (relatively, it's not a bad iron, it's just not that great).


the story: I make planes, but I only sell them for the cost of materials or give them away (unless someone offers extra as a means to donate the extra to the charity of their choice or mine). I don't make planes for the general public because the type I make requires some skill to use (double iron wood planes) and it's too much of my personal time to try to make planes that people might set aside and not use, or inundate me with questions. Or complain that a later sheffield iron that I put in a try plane isn't hard enough. Or to be more clear, if I see someone doing a lot of dimensioning work with a metal plane, I will offer up a wooden jack and try plane at cost. Early in Brian Holcombe's full time woodworking startup, he was doing nearly all of his work by hand, but using metal planes. I made him a try plane, and used a new but relatively soft simple steel sheffield iron in it. I also told him that it was coming with a softer iron, and if he found issue with it to send it back. I knew he wasn't going to use the plane to smooth, so it didn't need to excel at a contest of the most feet of thinnest shaving. I also told him to resist the urge to sharpen the plane just because you can see an edge, and see how far you can take it before it actually becomes a problem planing.

I would never give an iron like that to an inexperienced user under any condition. Brian wrote back about a month later that he could see the edge (reflecting light back at him, viewable by naked eye), but that even so, the plane kept cutting for a long time. If the steel was soft and failed in a way that wasn't uniform, the part of the edge wouldn't just become worn, but also blunt where it's introduced to the wood. It would be a pain to use.

I also figured that at some point, Brian would request to change the iron, because even though it works fine, in the back of your head is always "I wonder how well it would work if it was harder, given how well it works now". (I have that same mentality, and I know other people do, too). This past year, Brian's order list got too large to keep up with doing all of the work by hand, and he bought some good machines. So my plane is mostly out of commission (which is fine with me), and he never felt the need to change the iron.

Is there any chance that the general public would understand the sentiment that I was conveying about sharpenability and usability? I know Chris Schwarz wouldn't, and neither would most other people who pretty much buy or do what he says. But, at any rate, the uniformity of failure of the edge allows a plane like that to continue to work in a condition that would look like extreme wear on Brent Beach's page (brent is obsessed with the length of the wear bevel, but he doesn't tie in the wear bevel to the condition of the edge, so an O1 iron on his page with a similar length wear bevel to A2 is the same to him.

Plane Iron Tests

The avid user wouldn't agree, though - the knight blade would probably leave a surface with little evidence of planing.

Rob,

an interesting thing to test out would be the working of a chisel as the steel gets progressively softer.

I could harden up the last 1" or so of a new Buck Brothers chisel and temper it to 325-350F or so... Which will be really hard.. Then - you could test it and then progressively temper it softer 25F at a time... I personally like them on the hard side for the work I do..

At worst, we ruin a $12 chisel "For Science"......

Sure, why not. I'd like to know if they can be improved.

Originally Posted by truckjohn

Very interesting... I was not expecting to see a steel grain quite so coarse or carbide particles quite so large...

I could be quite wrong about those being carbide (or some other type of steel) particles. But if they are not, I don't have an explanation for what they are.

In relation to DW observation about carbide particles being pulled out of the steel matrix by some abrasives, I have observed pitting in the surface of some steels which I have assumed were gas entrapment created during the steel making and/or forging process.

The following image is an example at x80 magnification. These definitely look to be too large to be carbide particles at that magnification, but I could be wrong there again. The steel is Blue Hitachi and the abrasive was Nakayama.

Wantanabe santoku off Nakayama stone - higane - after use - magx80.jpg

It sure looks like DW's carbide particles... The other possibility would be slag inclusions in the wrought iron backing. But it looks very close to the bevel - probably not that...

A 7 grain "Fine" crystal structure means an average grain size at 0.0012"... Average means that for every 1 grain at 0.003", 2 others are at 0.0003". I would bet you can see 0.001" stuff. At 80x optical magnification...

Here's something to think about... If it's not pulling grains up at the actual sharp end - is it going to hurt your cut?

To confirm - you could sharpen the primary bevel on diamond and see if it goes away..

I saw similar in a new powder metal knife (one that wasn't cheap), and then saw the same thing again with various sharpening media - that is, the knife came like that more or less (the pits looked a little bit different), and can be made to look like it again with various sharpening media. I'll dig up the picture tonight. It's only a problem if those pits get to the center of the cutting layer, but when they do, the effect is obvious (the edge never feels fully sharpened).

I never saw these pits before getting a microscope, but every edge that has failed to feel sharp has failed due to damage at the edge rather than some imaginary bugaboo (like stating that an abrasive sharpens the matrix but leaves bulbous carbides unaffected or unsharpened).

One more aside comment - when I brought up the SGPS knife on another forum, I was getting frustrated with its inability to agree with sharpening media, even that which sharpened it easily (it still pulled out carbides). I made the comment that on plain carbon steels, it's never an issue, which was challenged ("take pictures of those and see what they look like"). On the plainest of steels, I have never seen anything pulled free or any lack of organization at the edge of a blade or razor. the first picture that I took was a butcher iron from approximately 1830. The structure was beautiful and uniform off of the sharpening media (the iron itself is a bit soft, but very plain and very sharp no matter the abrasive - softness would've been the choice of the maker, as leaving it harder would've been easy). It's possible that the butcher iron is closer to being eutectoid, but steel that's not above the eutectoid limit is discoverable in use (it holds a fine edge less long). I'm fairly certain that wards and I. Sorby's old make is higher carbon than that, possibly by a fair amount (could be low 1s like white 2).

And for certain, white 2 is comfortably above that 0.8-0.83% carbon limit, but still exhibits that excellent uniformity, regardless of sharpening media. The consequence, though, is that it's poorly behaved when hardening, especially if it's not laminated to something that stabilizes it. The stabilizing backer wasn't an issue in the era of the 1830s butcher iron - it was probably much cheaper to deal with a bitted iron that had not too much money tied up in steel, and that would've been much easier to smith with the rest of the iron being wrought (which would've milled and drilled much easier, too, and had less chance of breakage).

I would guess that the modern japanese tooling is generally laminated for behavior reasons, too. White 1 and 2 would crack in an instant in a water quench if it was wasn't laminated to something.

The flip side of laminating is that wrought will bend more but it takes less to force to get it there. On a laminated tool, that amounts to a lot of breaks at the back of the lamination (plenty of very old bitted chisels that were abused by levering that broke at the back of the weld). I broke a newer japanese mortise chisel that had bad geometry the same way (it would stick in the cut, and working it out of a mortise eventually caused it to give up the ghost and break at the weld. It was an expensive chisel and I didn't want to grind the sides to give it some relief (because you can't re-sell an adulterated $100 chisel). I should've done that, though, and sold the other three chisels that came with it after that (they weren't as bad, but how many $100 chisels do you have to break before you unload them?). Point being with this, if you make a western style chisel that isn't overly bulky and is laminated, it won't be as bend resistant as a solid steel chisel, and selling tools to the open market is the easiest way to find the most abusive users.

You guys going back and forth on the carbides issue got me interested so I looked up the subject of carbides in this.

Metallography volume cover.JPG


It has a chapter of micrographs on tool steels, and other kinds too.

Metallography volume Tool Steels opening page.JPG

I didn't find a specific size or size range for carbides in tool steels. However, looking at the 122 included micrographs that make up the bulk of the chapter, I see that the majority were taken at 1000X with only a few showing any visible carbide structures at 400-500X. The text states that carbides are really only made visible by etching.

In an earlier chapter on mild steels the authors point out that very large carbides, i.e. those visible at low magnification, are indicative of damage to the steel or steel of poor quality.

Originally Posted by rob streeper

You guys going back and forth on the carbides issue got me interested so I looked up the subject of carbides in this.

Metallography volume cover.JPG


It has a chapter of micrographs on tool steels, and other kinds too.

Metallography volume Tool Steels opening page.JPG

I didn't find a specific size or size range for carbides in tool steels. However, looking at the 122 included micrographs that make up the bulk of the chapter, I see that the majority were taken at 1000X with only a few showing any visible carbide structures at 400-500X. The text states that carbides are really only made visible by etching.

In an earlier chapter on mild steels the authors point out that very large carbides, i.e. those visible at low magnification, are indicative of damage to the steel or steel of poor quality.

I've never read anything about actual size. I'm assuming that the hole isn't left from a carbide coming out like a golf ball, but rather a clump of stuff. I could be wrong, though. If the surface of the steel is polished or sharpened well (for example, after the translucent ark or after any synthetic polish stone), you can't see anything that you could identify as carbides. As you say, they have to be etched so that you can see the softer matrix etching faster than the carbides.

I have no trouble believing, though, that they could come out and take some extra with them (or come out as several and take extra with them).

It is absolutely true in mild steels that large carbides are caused by some problem... All the carbon can be dissolved into the iron matrix under 0.86% C or so....

In high carbon and high speed steels - this is not the case.. Above 0.86% C - you get 0.86% dissolved in the steel grains and then Fe, Cr, M, V, and W carbides grow in between the steel grains... And the more of these alloying elements - the more of those carbides you get... And that's what the Tool and Die guys find so awesome about good HSS..

The interesting thing is that I have heard of this from numerous sources - just never saw good pix...

I poked around a bit with white papers and found quite a few mentions of average carbide sizes in well prepared non-PM HSS could be around 15 microns... This is well within the criteria for "Fine grained.." A2 and D2 are reputed for "large" carbides (whatever that means)... PM varieties pushed that down to averages at or below 1 micron...

Dredging the memory from the metallurgy I studied as a student 40 something years ago, carbide structures in steel take two forms (Austenite and martensite) and the purpose of heat treatment, quenching and tempering (and also I assume cryogenic treatment) is to have some influence on the grain size and to turn one type of carbide into the other.

I do remember that for some purposes, of the two martensite and austenite, one was "desirable" and the other less so, but I can't recall which was which.

The surface effects you are seeing could be related to martensite / austenite grain structure