Thread: How to heat treat a file?

Had the opportunity today to take a pic of the oven I am using. Does the trick







Oven is calibrated couple of times a year to very high tolerance.

That's fancy, should be able to get the exact HT you want...almost as absolute as salts.

Originally Posted by shooter74743

That's fancy, should be able to get the exact HT you want...almost as absolute as salts.

Atmosphere requires some sore of scale prevention barrier like foil or paint-on refractory coating. The oven gets hot, you quench, remove said scale preventer and you're done.
Salts require playing with a very small scale volcano. A much higher danger/fun factor and no fiddling with foils and paint-on wait for it to dry crap.

Thats why when i grow up i want to be like you mike! I am all guy &a the danger factor is like a bug to a bug zapper!

I'm so jelous. I used to operate ovens like that, but don't have access to them anymore. I have to resort to more primitive methods.

+1 to what mike has said about foil or another oxidisation barrier for use when heat treating. It saves a lot of work later cleaning up the material once hardened, and it will also reduce decarburisation during heating to a degree.

It's a small privilege I have in the work that I do. Having good ovens and small machines to help with the end result.

""Hi Shaggy, The best method to establish the temperature to reharden at is by using a magnet. The steel will become non magnetic once the bottom end of the critical temperature zone is reached. If you go above this by around 200 degrees you will obtain the full hardness without the guess work""

Reminds me of being at the Farmers Museum in Cooperstown NY ~30 years ago. Watching a blacksmith working on an old forge. I asked him how he knew when the metal was hot enough. Showed me using an old Cow Magnet. But then said: 'or you can do it the way the 'old timers' did': ...and ran the piece of hot orange bar across his palm!!! Said ' just about right'. I said 'What' and he did it again. Asked if it didn't hurt?? He said: 'No, you get use to it!!'
Still one of the darnedest thing I've seen!

Well, I know some of the old timers, and seen some others in action on youtube. They use the color as an indication. Not a single one ran the steel across his hands. That is a good way to need a rush trip to the ER with 3d degree burns.

Agree with you... But... that why I can still see him sitting there doing it. Twice. He said that the piece he was working on was a chisel and he was placing a piece of steel for the edge onto the iron bar.
Only thing I could think of is that he came close but never touch his skin.

The sticker says 3000 Celsius? Does that oven really get that hot? That is about Double the melting temp of steel.