Temper temp questions

[cckw]

Can I get some rules of thumb on the temp you can ruin heat treat with different steels?

What are the actual temperatures that affect it?

What is the temp range the heat discolor appears?

Any anything else..?

I use power tools on blades with extreme caution, but see others going at it more aggressively.

 

[Ed Caffrey]

In general, for carbon/alloy steels, "tempering" starts at 350F, and for every 25F above that, it produces a change in the steel's matrix. At the 350F temp, the color will be a light "straw" color, with the shades and colors changing with ever 25F.

The best rule of thumb to follow is that if you are grinding, cutting, drilling, etc. on a hardened/tempered piece of steel, and you get it hot enough to cause a color change, you've likely wrecked the heat treat.

I can't give you any info on stainless steels....because I rarely work with them.

 

[Atlas Knife Company]

The best rule of thumb to follow is that if you are grinding, cutting, drilling, etc. on a hardened/tempered piece of steel, and you get it hot enough to cause a color change, you've likely wrecked the heat treat.

I don't want to hijack, but maybe we can both learn from this: If just a bit at the edge discolors, like 1/16", is just the discolored part ruined? If you grind the edge [or tip] off past the discoloration is it still good?

 

[Ed Caffrey]

Yes, the areas that where not discolored by overheating are still good....but you won't end up with the same blade/knife that you set out to create.

1/16" may not sound like much....until you actually grind it away. Then that issue begats another, and so on, and so on. I suppose that if a person is not concerned that the end product will usually differ greatly from what was intended, then that is an acceptable way to deal with it.

 

[Remyrw]

Ed, that sounds very much like one of my early knives. It wasn't meant to look like that, sure didn't when I did the HT, but a couple goofs while doing cleanup and then smoothing out the fixes from those goofs....

I've learned though. I stick to sharp belts after HT, if in doubt, get a new(er) belt before touching steel. That and no more than one light pass at a time, cooling the blade between each. If it's not room temp or below it gets dunked. Since my shop is pretty cold the water container stays pretty cold no matter what so it works well. Lol, until my fingers wind up too cold to work safely and I have to take a break to warm them up.

 

[Atlas Knife Company]

1/16" may not sound like much....until you actually grind it away. Then that issue begats another, and so on, and so on. I suppose that if a person is not concerned that the end product will usually differ greatly from what was intended, then that is an acceptable way to deal with it.

In my case, the knife would turn out the way I intended. Since I usually grind my edge too thin, I design the blade and usually add a bit to the edge when cutting it out. 1/8" or more depending on how thin the blade is. That way, I can grind of the extra at the last step and end up with the blade exactly how I intended. Someday I'd like to be able to prevent this mistake, but until then I can plan for it so the knife does turn out the way I intended.

 

[mete]

Remember the color is just a surface thing. It's possible to damage [even seriously] the steel by overheating , then grind off the surface color so it looks fine but isn't.

 

[Carl_First_Timer]

Remember the color is just a surface thing. It's possible to damage [even seriously] the steel by overheating , then grind off the surface color so it looks fine but isn't.

One of the biggest mistakes rookie tool & die guys make.