How much heat can a knife take before it'ruined?

[TorzJohnson]

My dad told me about an old Marbles his brother had which was in a cabin that burned down. When they found it, the stacked leather handle had burned off. My dad took it and polished it back up and replaced the leather washers. He says the knife is as good as ever. I'm thinking the heat treat is long gone now. What are the odds that it's useable? I haven't actually seen the knife myself because they live on the opposite coast.

 

[Mike Hull]

The house burning down will not make the knife disappear, but it no doubt, took the temper out of it. You can repolish and rehandle a blade like this, but it wont hold an edge like before the fire, unless you have it retempered.
The thing is, most people don't use a knife that much to notice the difference.

 

[Mike Hull]

Forgot your original question.
On an old knife like that, once the temperature exceeded 350-400 degrees F, the temper went.