Hand Tools

Subject:
Confirmation of our Iron Testing

David Weaver
https://knifesteelnerds.com/2021/05/10/edge-retention-testing-of-seven-more-steels-xhp-spy27-maxamet-rex-45-420-t15-rex-76/

Larrin thomas has a catra tester (it pushes edges through abrasive cards). Toughness aside, this turns out to be a pretty good proxy for plane blade life in clean wood. At one point last year, he tested 48 steels, but XHP wasn't in it, which was annoying.

He also cleared up with these results and micrographs that he was seeing the same thing I saw from blue steel - that the wear potential really isn't there. In super blue, it's not really that great either, but experience with both from makers in plane irons (both traditional style and western plane replacement type) led to edge uniformity issues and the bargain of just what you're getting with either in a plane didn't pan out (the western plane replacement blade works well, but it wears with O1 and doesn't provide an advantage in edge life over light straw temper O1).

He recently released an article with XHP included. This chart also has 3v, 4v, cpm M4, etc, that we tested.

3V was similar in relative performance to the V11 iron (this is a direct link to the chart with steels and card length cut):

https://i2.wp.com/knifesteelnerds.com/wp-content/uploads/2021/05/CATRA-5-7-2021.jpg?w=754&ssl=1

Note that we found M4 to last slightly longer than the V11 iron, and the results are flip flopped on this chart, in about the same magnitude. But the reason for that is likely that the hardness results are flip flopped on this chart, too. I never did use M4 in regular work, but wouldn't be surprised if it tolerated regular work in rougher wood better than V11 does.

Toughness is hard to gauge in terms of plane irons - when hitting silica, 3V is multiples tougher than XHP, but the damage looked the same. The Japanese iron is almost certainly lowest toughness in the group, but it fared best. All required resharpening, and at that point, the one that abrades less slowly becomes the favorite.

Just how close these results are to our hand plane tests is interesting. If I take the V11 results and predict 3V from them, I'd expect the catra test to provide about 475mm TCC. The chart shows about 465 or so.

I would expect O1 to chart at 290. It charts around 285 or so (it should actually show a little better vs. 1095, but larrin said he thought there may have been some issues with his O1 sample). based on testing a 52100 and my favorite O1 iron planing, they are about the same. One of the 1.2## steels at the bottom is blue one or a german equivalent - around 52100, and where O1 should probably be.

These numbers reinforce just how accurately you can test steels in a tool if you come up with a good testing regime.

You can see my pet-suspicion for stainless (AEB-L), which has ultra fine grain and good wear resistance. I can't heat treat it quite right, but did get slightly better results than this in wood (the edge has to wear some before it settles in, and I can't temper it hard and have it hold up - it's an ingot steel and needs a high temperature soak in an inert atmosphere, something I'm not able to do and at a cost of $2000 in furnace to do it, I'm just not going there). The virtue of AEB-L? It sharpens like a carbon steel - if you didn't know it was stainless and sharpened it on an oilstone, you probably wouldn't notice. It grinds nicely, and it costs a pittance - it's manufactured as a strip steel and not a gauging steel, so the strips are just made inexpensively (about half the cost of O1 ground stock).

Years ago (and maybe I still have some), I got a couple of early 1900s razors with tungsten additive in them. It was sort of popular at that time (probably due to the use of tungsten in HSS). There may be some potential to get tungsten carbides uniformly distributed in lower carbide % steels, but I haven't seen it. The razors showed the same behavior - they were high hardness, but the edge just would not match carbon steel, no matter what the abrasive was (even synthetic submicron abrasives). I don't know where it was lost - it could've been on the strop - steels that take a brisk stropping at a low angle generally end up being great razor steels.

XHP toughness is also shown here - 10 - but the toughness numbers don't quite nail what happens with plane and chisel irons as I'm sure the Ward irons that I have would be low toughness, but they are the last to lose an edge on same-wood planing. And it's uncanny how different - this isn't an issue of perceiving something not there - but rather planing the same piece of wood with several planes and having some irons take varying levels of damage and the wards take none (With O1 slightly behind, even though O1 shows poor toughness levels above 60 hardness). This is observed over and over planing pine with knots. Everything else chips, and a softer iron unicorned fares better, but the ward iron seems indifferent about the knots and the sharpening interval is pretty much unchanged without much geometric modification.

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