When tempering a blade do you...

M

Matt Lucas

Joined
May 11, 2020
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Do you take it out of the oven to air cool or turn the oven off and leave the blade in to cool slowly? Does it matter which way you do it?
 
Take it out. Probably wouldn't matter. But when I'm done tempering, I'm either getting ready for another temper, or getting ready to clean it up. Either way, I want it to cool off now.
 
Take out of the oven and cool off in water ( running tap works fine), then put right back in for the second temper. Cool in water again after the second temper.

You could let it air cool, but it takes time and the oven is running all that time.
 
I’ve let it air cool and left it in the oven while is cooled, but the results are the same.
 
Thanks for the replies. I have seen guys on YouTube cooling the blade with water between temper cycles. I may give that a try to speed up the process.
 
When dropping from the first temper you are creating new martensite from retained austenite. A very slow cool may not convert quite as much as a faster cool. The difference would take a laboratory to test, and the practical difference in a knife blade would be insignificant. I would not slow cool in the oven, but room temperature air cooling is fine. A 10 second dip in water just saves about ten minutes time.
 
I did what he suggested. Ran sink water over it and threw it back in the oven. I let it air cool after second cycle.

On a side note I bought an oven thermometer to use for this knife’s temper. Turns out my toaster oven gets to almost 500 when set at 400. That explains why the edge rolled over very easily on my last knife. I’m glad I got the thermometer.
 
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