Thread: Ruining the temper: How hot is too hot?

Originally Posted by Mike Blue

Too hot to touch is almost too hot. The problem is that heat has a lag time and can still increase before you can move the blade from a hot touch to the cold water. The best thing is to work barehanded touching the steel near where you are working and cool frequently even (and especially) when you don't think you need to.

If you did not change the color of the blade, you are probably still okay.

One smallish correction: tempering is the process of drawing back the hardness of a piece of steel. That is often done for carbon steels at or near 400 Fahrenheit. Stainless tempering can occur at various temperatures even up to about 1000 F. But each specific steel has specific numbers for optimum performance. That's the one good reason to really know what steel you're working with.

Sintering is a welding process and needs at least better than 2350 Fahrenheit to work efficiently. But this can also vary based on the particular industrial process and tooling versus home shop and available tools.

Mike,

+1
Good stuff.
The sintering I was making reference to was the sintering of the PTFE layer
on the surface of almost all the factory tossaway blades.
i.e. a Teflon like plastic compound. You are absolutely correct for
the interesting sintered ceramics and knife steel/compounds.

I should comment to the newcomers to this forum... Mike is one of the
experts on steel here.

Originally Posted by niftyshaving

... The sintering I was making reference to was the sintering of the PTFE layer
on the surface of almost all the factory tossaway blades.

But the sintering you refer to is true as well. Hmm context is everything...
I love learning stuff. Thanks Nifty.