Tempering advice for even color

I am going to temper a frizzen spring and it is always a bit difficult to get a nice even color with the torch. A while back I tried to place a part on a small pile of sand on the oven to even out the heat. But the sand seemed to isolate quite well and the heat did not get through to the part sufficiently for tempering.

Do you have any advice?

 

[chipper]

Reach the critial temperature first to harden it, then temper. My buddy uses 3-mapp gas torches focusing on the part to get it critical. Use a magnet to be sure. A magnet won't stick when the metal is as critical temperature. I personally have a coal forge, that will work too.
The kitchen oven should work nicely for tempering. Most machine tool metals temper between 350 degrees and 650 degrees. By placing the part in a 375 degree oven for an hour and turning off the heat you should be very close. When it cools completly, you should be just right. I wouldn't use any sand in the oven, simply de-grease the part so it won't smoke and throw it on an old cookie tin.
Most folks use sand, vermeculite or ashes to aneal. That's a completly different technique used to soften the metal for working it.
I hope this helps.
Regards
Wounded Knee

 

[rich pierce]

The most reliable way of tempering springs is to sink them in molten lead (just molten, not so hot it would cast frosty balls) using a wire. If you worry about the lead sticking, smoke in a candle first. Soak for 5 minutes, allow to cool, then test.

 

Thanks for the fast replies, I should add that after "technically" tempering I give a high gloss polish and heat again only for a nice blue. My ofen wont go that hot so I normally used the torch with a lot of care (and cussing). The lead method sounds fine.

 

[Vaino]

375 degrees is OK for a frizzen but a frizzen spring should be drawn at 650-700 degrees. The lead pot sounds good, although I temper only by color. I use a 1/4" thick plate and torch it from the bottom and lay the spring on the hot plate until the desired color {gray blue}is achieved. The spring just doesn't lay there but is turned quite often w/ tweezers to even out the color, especially at the bend of a frizzen spring....Fred

 

[barebackjack]

Do you need to temper lock parts from sources such as pecatonica and track of the wolf? Or are these "pre-assembled" locks already taken care of?

Boone

 

[Vaino]

If an assembled lock is purchased, all the parts that need to be hardened and tempered are just that. If individual parts are ordered, springs usually are hardened and tempered, but frizzens would be soft so they can be drilled in assembly and then hardening and tempering would have to be done.....Fred

 

Thank for the help. I previously polished & blued springs from pre-assembled locks. This is a spring from a TRS lock that has been laying around for some years. A friend hardened it for me in a professional tempering oven. This is for looks only. The idea of using a thick iron plate sounds good.