Deep hardening steels

[Forest Xavier 0]

My question is this, with a deep hardening steel (1084,5160,etc) could one just cut out a blank profile, harden, temper, then grind the bevels in? I know this is a bit backward but with a thinner knife (say under .25”) shouldn’t the hardness be the same through the entire blade and wouldn’t matter?  Or am I just an inexperienced noob...also I’m sure there is the short yes/no answer but also why it would or would not be advantageous to do it this way? Thanks in advance! 

[Jeremy Blohm 573]

Yes you can do that. You need to keep the blade cool while grinding though or you will lose the hardness. 

[Jeremy Blohm 573]

Another thing to consider is what you are going to use to grind the bevels in. Your going to need some horse power and ceramic belts to cut the hardened steel.

[Alan Longmire 3,675]

What Jeremy said, but 1/4" is a thick blade. Anything thinner than, say, 3/32" / 0.093" /1.5mm is better to grinder after HT, only because steel that thin tends to warp in the quench if it's bevelled. Think filet knife or thin kitchen blade.

With most blades over 3/32" you'd just be wasting belts to do heavy grinding after HT in my opinion.  But that's just me.

[Forest Xavier 0]

Thank you Jeremy and Alan all your guys help is always appreciated.  One more question related to this topic, what is the depth that the steel hardens to? I do know it is proportional to the time it is kept at critical temp and thickness of the steel, which I’m sure has to do with the heat being consistent through the entire piece, but as a general rule of thumb if one were to heat treat a deep hardening steel, soak 15 min @ critical  what would be the depth that it would harden to? 

[Alan Longmire 3,675]

1084 and 5160 do not require a soak at all. Get them to critical, quench, and you're fully hardened all the way through, assuming a blade-shaped section.

Depth of hardening is dependent on alloy, and has nothing (or very little) to do with thickness or soak times.  The textbook example is a 1" round bar of W1 versus a 1" round bar of O1. W1 is a shallow hardening steel because it's just iron and carbon with a trace of manganese. It will harden to a depth of around 1/16" from every surface. O1 is deep hardening because it has a lot more manganese, plus chromium and tungsten for carbide formation. It will harden all the way through as 1" round.  

Those carbide formers are what require a soak to get evenly distributed. 1084 and 5160 don't have enough of anything that forms carbides to require a soak.

[jake cleland 702]

Any deep hardening steel will harden up to 1" thickness with no problem, so it's really not an issue in the sections we deal with. The problem we generally encounter with deep hardening steels is preventing through-hardening, which can only be done by either edge quenching or selective heating. Soak time isn't really an issue in terms of depth of hardening with most steels either - that's more a matter of carbide formation and distribution (though this is obviously still important).