over tempering?

Barry Clodfelter

Barry Clodfelter

Knifemaker / Craftsman / Service Provider
Joined
May 29, 2007
Messages
579
is it possible to over temper a blade? I had a blade in the oven this week when my wife called me in from the shop for something or another. There was about 30 minutes left before cutting off the oven. I forgot to go back out and turn it off for about 45 minutes and that got me wondering. If I had left the blade in a 400 degree oven over night...8 to 10 hours or so what would the ramifications have been? Would the hardness have gone down to the point where I would have had to start the HT over again? Any insight on this?
 
I think that you're OK, but maybe someone else can give you a non-newb answer.:)
 
You don't mention the steel type, but an extra 45 min in probably
not going to do much one way or the other. Two hours is usually
recommended (x2), for most steels.
 
I only tempered it for and hour and fifteen minutes so I know that was alright.

What I was wondering about was what would happen leaving it in the oven for 8-10 hours at 400 degrees. For arguments sake lets say it is 1080-1084.
 
The big issue, from my experience, is the max. temperature, not the time. I believe that 2 hrs. should be the minimum draw time for each cycle to ensure that the blade comes up to temperature fully, and has time to soak at full temp.

Make sure you check your oven to ensure that 400 on the oven setting is really 400. Also, some ovens can have a pretty wide min./max. swing, i.e. you set it for 400, and it may peak at 415, shut off, and not kick back on until it drops to 385. If the oven overshoots the temperature (poorly insulated), that could be a problem.

10XX series is pretty forgiving, but the more alloyed the steel the more finicky they can be to drawing temperatures.
 
You must log in or register to reply here.
Back
Top