Hand Tools Archive

Re: Another iron provided - CPM M4

david weaver
For a guy like me who isn't afraid to make an ugly iron and do minimal work (as in, it's pitiful looking stuff that nobody would dare sell), I'm curious as to the ability to drill the stuff at low speed and then saw and file it.

Everything will harden with air - I found that out the hard way with the files that I made into rudimentary chisels recently. They won't harden into what you want, but if you don't make an effort to allow them to cool slowly, or do something like lay them on an anvil (which will suck the heat out of them), all of the sudden you can't shape them like you'd like to.

I'm a little gunshy about what might happen on the micro level.

The tinkering habit makes me want to buy stock for a single iron (about $35), heat it to bright yellow (completely ignoring the soak schedule and rules about gradual temperature increase) and give it an interrupted quench in oil and then finagle something with the can forge and a paint stripping gun to see if I can get it to a nice dark gray tempering temperature.

But I know that's likely to produce garbage. And if you can't drill and file it easily (figure 1/2 or 1/3rd of the metal removal rate with files being "easily"), then it's a bust all the way around.

Making an iron with lots of screwing around (foil wrapping, etc, all of that stuff) that doesn't perform better than the $7 chinese iron due to suboptimal process...that would also be dumb. I've done plenty of dumb things experimenting with tools, though.

The sound of the properties of M4 (its ability to be more fine seeming than 3V, and the attestation of quality of carbide dispersion in the PM version, leading to good sharpenability - and not to forget, its ability to work at high hardness and also be relatively immune to grinding heat after its made....all very tempting, even if it really means making the irons and sending them out for the rest.

Out of sharpening laziness, I'd probably go back to ward and O1 irons, though. I get off track from what I would normally do when I experiment with stuff like this test, because I'm doing something different than what I'd do day to day.

Last year or two years ago, I used the hardest purpleheart I've ever found to make a skew shooting infill plane. I sized the blank with one of my softest irons, and thanks to the cap iron presence, it wasn't as big of a failure as I thought it would be. I think I sharpened once while doing it, and once before.

(but the tinkering with stuff like PM M4 is still a draw. I have bar stock in another PM stainless that has a more household attainable tempering temperature and a very wide range for heat before quench).

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