Tempering Question

[tgw914]

I am new to knifemaking and I have a question on tempering. The knife I am working on is ground from an old file and when I tempered it in a toaster-oven at 425 for 35min it turned blue/purple. I now fear that it has been softened too much and will be unuseable. Can anyone give me some advice?

 

[B Finnigan]

That is normal for that heat. The color comes off real easy and most people still sand/finish quite a bit after HT anyway. It is not softened.

 

[Jared Stenoien]

what are you going to use it for? depending on the application you probably just need to ht it again, then again you might be fine

 

[son_of_bluegrass]

The tempering colors tend to be accurate. At 425 F the color should be in the yellow range. Blue/purple is closer to 500 - 550 F. That is not necessarily bad depending on what you want in a knife.