Heat treat question

[Rock Crusher]

I've read that to get the temper back to the right hardness after quenching it that you should put it in the oven for 45min at 450 degrees and then let it cool. My question is do shut the oven off and let it all cool together or take it out of the oven and let it cool at room temperature or doesn't it make much difference?

[kbaknife]

Assuming you achieved full hardness when quenched, and you are working with some of the more commonly used simple carbon steels, I would give it no less than 2 one hour tempers at 400+ degrees, depending on knife usage.
Wait until oven has been up to heat for about 20 minutes before placing the knife in, and then shut oven off and let cool with knife inside.

[gables]

You should learn to test your blades with a few common tests like using a brass rod, chopping wood, cutting rope, etc. After tempering you test the knife to see how to adjust temper. You should be able to find the info by searching this forum. If you keep using the same steel you will soon develop a recipe for hardening and tempering. The more you research this topic the more lost you can get. Keep it simple and control your variables.

[GabeO]

im always learing from you guys thanks

[mulie]

The knives I've made have either been out of Save Edge or Diamond farrier rasps or from an old set of leaf springs that are probably 50 yrs old.  I shaped the knives by preheating the metal to soften, stock removal, quenced in oil, and then tempered in a preheated oven set at 400 degrees for an hour.  I know that the knives were very brittle after quenching as I was able to snap a practice one in half without it bending at all.  Any suggestions as the the hardness I achieved?  Is there a better way to temper and why?
Thanks

[Rock Crusher]

I appreciate all the info guys.