Practical differences between four common steels

[james terrio]

What are you leaving for edge width on O1 and A2 prior to heat treat?

I haven't used A2 at all. But with O1, CPM-154, 440C, CTS-XHP, CPM-3V and 1084 I've sent blades in with edges as thin as .015" with no wiggly-edge warping issues. I'm reasonably certain that keeping the grinds even and symmetrical on both sides plays a big part in helping prevent warping*, but I'm equally sure that an experienced heat-treater is also important. I am not an experienced HT'er, so for the time being I leave it to the pros

*The only blade of mine that Brad reported having some trouble with was a 9" bowie of 3/16" O1. Full distal taper, keen bevels, and an equally keen clip edge. The tip wanted to warp on him; as I recall, he had to bring it back up to tempering temperature once or twice and straighten it while it was still malleable. He explained it to me as something that just happens sometimes, from grinding stresses. "You guys can only grind one side at a time," as he told me. In any case, it was a fixable issue. My friend Rick Marchand has written a good deal about his experiences in dealing with warpage, it's interesting reading. :thumbup:

Unless a coffee can forge is all you have or want. The steel you choose should always match your process and equipment.

Good point! I certainly wouldn't advise HT'ing powder steel in a barbeque grill, yet I have no doubt that damn good knives can be made with simple steels and barely any equipment. I've just chosen to approach the issue from the other end - final performance - and work my way backwards to determine what materials and processes are appropriate.

 

[Brian.Evans]

Thanks. I need to get a set of calipers just to be sure. One that I have done in A2 will be fine, but two in O1 and one in A2 might be too thin.

I think what I should do, is just for kicks and grins, is get a piece of O1, 1084, and A2 all the same dimensions, grind identical knives and then HT all the same. Then test and destruction test them all. I'm just making some small EDCs (3" cutting edge) so I suspect the difference to be negligible.

Is there a difference on Hardness I should be looking for on these steels? One does better for small stuff at 58, another at 60, etc.

 

[Matthew Gregory]

Not that there's anything wrong with using any of the chosen steels, but there have been MANY new steels that will surpass every one of these listed in regard to performance. Granted, these are certainly at the top of the list for ease of workability and heat treat process, but if the end goal is to provide a superior product consider one of the modern steels from Carpenter or Crucible, to name a couple.

Instead of trying O1 or A2, perhaps consider CPM-3v. Toughness and wear resistance are vastly improved, with similar stain and rust resistance. A pet steel of mine to use is CruForgeV - I'd place it just above CPM-3v for wear resistance, but with a slight tradeoff in toughness (I differentially temper the spine to improve its odds, here). Regardless, it's a step above both O1 and A2 in my experience.

Haven't mentioned any of the higher alloy steels, but there's a world of them out there - give em a shot!

I use 1084 and 1095 for a lot of my knives, but I'll be the first to admit that they offer NO wear resistance in comparison to most other steels. It's not to say that this is a terrible thing, some people prefer the ease of sharpening this offers. Others don't want to have to sharpen as often - make sure you know who you're dealing with!