Shallow hardening steel and grinding bevels post HT?

woodwrkr221

woodwrkr221

Joined
Jan 28, 2011
Messages
393
First some background info:

So far most of the knives I've been making have been small Wharncliffe style blades for instrumentation workers and electricians, 1095 steel from Aldo at .095" to .100" thick. Blades about 2-3/4" long and either 1/2" or 3/4" from edge to spine, per the customers preference. Micarta scales both with and without bolsters. Thin and hard, final edge thickness .010" to .012" before sharpening. I've tried edges thinner than this but the edge gets even more delicate.

For heat treat I use my propane forge with a ceramic probe and high temp digital thermometer. I use a muffle pipe in the forge with the ceramic probe within the muffle pipe. 1475 degrees to 1525 degrees (it fluctuates as you'd expect) with a ten minute soak. Quench in water and temper twice at 400 degrees for two hours each, quenching after each temper.

Because I don't have any Parks 50 yet, the blades are small and thin and warpage is a common problem I've been grinding the bevels post HT.

I've read here on the forum that 1095 is a shallow hardening steel.

When I grind the bevels post HT am I grinding through the hardened layer and ending up with a blade edge composed of the softer steel underneath?

Would I be better off grinding pre-HT?

If I should be grinding pre-HT what edge thickness should I grind the edge down to pre-HT? .030"? Thicker than .030"?

Should I switch to a different steel that isn't shallow hardening like maybe 1084 or some other alloy?

I prefer to do everything myself but I could send the blades off to be heat treated if I need to switch to a stainless alloy.

What do y'all recommend?
 
From my understanding on stock that thin 1095 will through harden if the heat treat and quench is done properly.


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Those blades will harden with less warpage, if you quench into preheated canola. You can pull them out after a full three seconds, and check for warp, straighten if necessary quite easily in heavily gloved hands. If your steel is in the neighborhood of .100" anyway, it will work at full thickness without bevels too, if you go that way.

I think that .040" is a good thickness to stop at pre-ht, less and edge warp will often crop up, including the dreaded "bacon edge" on chef knives.
 
Shallow hardening and deep hardening are terms for a rod test where a 1" round rod is quenched. The hardness is tested at various depths in the rod. In 1095, the hardened layer may only penetrate 15%, or about an eight of an inch on the round rod. In a 1/4" thick steel knife blade, the penetration goes all the way through.
 
Salem Straub said:
Those blades will harden with less warpage, if you quench into preheated canola. You can pull them out after a full three seconds, and check for warp, straighten if necessary quite easily in heavily gloved hands. If your steel is in the neighborhood of .100" anyway, it will work at full thickness without bevels too, if you go that way.

I think that .040" is a good thickness to stop at pre-ht, less and edge warp will often crop up, including the dreaded "bacon edge" on chef knives.
Click to expand...

So if the blade is straightened after 3 seconds then what? Back in the quench or air cooled? Thank you


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Air cooled is just fine - you're already well past the "Nose" if you're handling it with a gloved hand.
 
Thanks for the replies.

Stacy, your explanation of the 1" diameter bar and the depth of the hardening clears up the shallow hardening description.

Salem, I have some canola I have used with 1084 a couple of times. If I quench 1095 in preheated canola (130 degrees?) will I be giving up any hardness? Maybe it's time to blow the dust out of my wallet and order some Parks 50!
 
It will work great, Parks 50 is the best though and I do recommend taking the plunge if you can afford it!
 
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