What does a burnt overheated edge look like?

[zzzspik]

What does it look like when you grind a hardened axe and you overheat it? Do you guys have some pictures?

 

[FortyTwoBlades]

You would see colored oxidation ranging somewhere from straw-colored to blue-purple. Typically this will only be seen right at the edge. Here's a razor blade that someone presumably hit with a torch to produce the discoloration of overheating. Note that all the way to the left it's a dead, ashy blue-grey color. That's what you get when the heat goes above the temps that produce the rainbow discoloration.

 

[zzzspik]

You would see colored oxidation ranging somewhere from straw-colored to blue-purple. Typically this will only be seen right at the edge. Here's a razor blade that someone presumably hit with a torch to produce the discoloration of overheating. Note that all the way to the left it's a dead, ashy blue-grey color. That's what you get when the heat goes above the temps that produce the rainbow discoloration.

So if this where to happen to an axe, knife or any other tool what should you do?

 

[3fifty7]

Depending on the severity in most cases you could file/grind past it to hard steel that hasn’t been effected. In the worst cases it would have to be re heat treated.

 

[Square_peg]

If they ground off the oxidation colors you wouldn't see a thing. But when put to use the edge would roll. If the damage is shallow you can grind past it. If you annealed it deep it will need to be re-heat treated.

 

[FortyTwoBlades]

So if this where to happen to an axe, knife or any other tool what should you do?

It's merely a sign that the damage has been done. Either you would need to remove the overheated steel to get to material with the proper temper intact, or else re-heat-treat the head. Merely buffing off the oxidation does nothing except conceal the signs that the damage occurred--it does not undo it. The steel in that zone has been heated to the point where its temper has been affected, and so only redoing the heat treatment from scratch or removing the affected steel will restore a proper hardness to the edge. That's why it's bad for that to happen. Dunking or spraying with water after the damage has occurred will also do nothing. When coolant is used in grinding it is to absorb and dissipate heat to prevent it from ever reaching temperatures that affect the temper in the first place.