how long is to long before tempering a hardend blade

H

HarleyMech.

Joined
Nov 13, 2014
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Hey guys, New to site, and knife making. I was wondering if I could get some direction on how soon the blade needs to be tempered after quenching. Using 1095. Thanks any info would help:confused:
 
Thanks, I have read that before. I gguessing asking if there are any other problems than the cracking. My buddy heat treated it at his factories heat treating plant. The problem is that he has no way of bringing it down for me. When it leaves his place after there temper cycle it is 63. Thus when I get it I would like to bring it closer to 60.
 
Coming out of the quench, we need to temper it very soon. But not TOO soon! Steel needs to reach its Mf point before tempering. The Mf for 1095 is a few hundred degrees or so, so like Utican mentioned, let it cool down to about room temp.....or to where you can hold it in your hand without much discomfort. Don't wait overnight, for sure! Usually 15 minutes or so after the quench, the steel is cool enough to temper.

One thing you mentioned tho has me confused. Your buddy heat treated your blade for you, but you need to temper it further? You said he tempered the blade to 63HRC, but you want to bring it down to 60HRC, correct? I suppose I am lost as to why he could temper the quenched knife to 63, but he can't temper it to 60? You can certainly temper it further in your kitchen oven once you receive the knife. No problems at all.....if it has already been tempered once already. Around 400F or 410F should get around 60.
 
Thanks samuraistuart. The system is automated at his facility. He doesn't have access to a small batch oven to control the temperature and time of temper. I just wanted to make sure I'm not doing any damage if I try to bring it down a bit more at hom.
 
There's a good chance that a 1095 blade will crack if you don't temper it soon after quenching.
 
Thanks samuraistuart. The system is automated at his facility. He doesn't have access to a small batch oven to control the temperature and time of temper. I just wanted to make sure I'm not doing any damage if I try to bring it down a bit more at hom.
 
Absolutely you won't damage anything by tempering it lower. And since he has already tempered it once.....time is not an issue any longer. You probably don't have a Rockwell testing machine (I wish I had one!), but if everything went correctly during austenitizing and quenching, 400F should be in the 60 ballpark...you may need to go to 410 or so. And if using the kitchen oven....again...just make sure the reading is correct, and put something in there to act as a heat sink. I use my kitchen oven with the wife's large baking stone, and temperature stays right where I put it (takes longer to come up to temp, tho!). Make sure about that reading....many of those oven thermometers are way off. I use three thermos to verify temps. You're good to go, Harley Mechanic!
 
Stuart is correct, re-tempering wont hurt a thing. I suggest doing like Stuart said and start at 400 and test the blade. You can test with a tester or actual testing. If the hardness is not where it needs to be just increase the temp by 25 degrees and test it again. This way you can "walk" it in to the hardness that you like best. Once you find the proper temp. or "sweet spot" you can just re-temper them all at that temp. and you'll be good to go.
 
On high alloy steels, such as D2 or stainless, I tested tempering the next day without problems, is the alloys isn't it?


Pablo
 
A clarification requested here. Once the blade is quenched, is it critical how quickly you temper - other than the dreaded "ping"? If a blade is quenched today to 65Rc, normally as soon as it cools enough to hold in hand, I'll pop into tempering oven. BUT - other than the dreaded "ping", would it matter if it was the next day or two before tempering?

Thanks to all for such a great place to learn.

Ken H>
 
Yes it is critical. The longer you wait to temper the RA in the blade will stabilize and not convert when you temper.
Personally I don't like to let my blades rest at any time during the H/T cycle. They are either going up or down in temp until they are done.
 
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