View Full Version : Time between heat treat and temper


canyonman
07-31-2003, 06:44 AM
In everything that I've heard and read says that after HT you should Temper right away. What is considered right away? Out of the oil and into the oven, within an hour, sometime that day?
Also could someone explain the whyfores of this time thing?
Thanks Larry

Don Cowles
07-31-2003, 12:15 PM
As soon as the steel is cool enough to pick up bare-handed.

canyonman
08-01-2003, 05:54 AM
Thanks Don,

What would happen if you waited for 1/2 hour or an hour, or even a day? Why is it better to temper right away?

Don Cowles
08-01-2003, 07:30 AM
For a detailed technical explanation, I suggest that you read Heat Treatment, Selection, and Application of Tool Steels by Bill Bryson. Here's a link to Amazon.[URL=http://www.amazon.com/exec/obidos/ASIN/1569902380/qid=1059740731/sr=2-3/ref=sr_2_3/002-8723999-5332842[/URL]

His position is that if you wait overnight, you might as well throw it away.

Coutel
08-08-2003, 05:37 AM
This is a very good link to a previous thread started by Tim Lively and discussed at length by Ed Caffrey which concerns multiple quenching of 5160 and leaving the steel cool down overnight between each quench...................

http://www.ckdforums.com/showthread.php?s=&threadid=3277&highlight=5160+heat+treatment


I now follow this advice when using 5160 for the reasons suggested.

When using 10xx I usualy remove from the quenching oil when it is warm enough to handle, but I have also let it stay in the oil overnite till it was completely cool before tempering. I couldnt see any difference in performance (after testing) between removing it warm or letting it cool and I have not experienced any cracks forming because I let it cool to room temperature.

I have heard that leaving carbon steels completely cool down runs a risk of the steel fracturing....but this has not been my experience. Living in Florida may be in my favor....if I lived further north and experienced freezing winters then that may have a different effect.

Hope this helps
Kevin.

Gary Mulkey
08-08-2003, 07:49 AM
I have never done a snap temper and primarily because my Evenheat won't cool down that fast to allow it.

Don-- Are you tempering in a different oven than you H/T in?

Gary

Don Robinson
08-08-2003, 08:24 AM
The quench sets up tremendous stresses in the steel. The primary reason for tempering is to relieve some of that stress. A side affect which we knifemakers like is to reduce the working hardness of the blade.

If a blade is kept for any length of time after the quench before tempering, there is a real risk that the blade will crack or shatter. Imagine dropping a piece of glass on the floor. A shock could break the blade.

If you have only one furnace like me, simply put the as-quenched blade into your kitchen oven set at a temperature around 50 degrees less than your desired tempering temperature, let the furnace cool down, then go thru your regular tempering cycles.

The kitchen oven cycle is beneficial to the steel, adding another tempering cycle, but won't reduce the working hardness you desire.

You can remove the blade after 2 hrs. in the oven, then use your furnace the next day to finish the tempering.

Don Cowles
08-08-2003, 10:20 AM
Gary, I bought a $20 toaster oven to use for tempering. That way I don't have to wait for my Evenheat to cool down. I also equipped it with a good oven thermometer.