Bad heat treatment

BOK

BOK

Joined
Apr 16, 2002
Messages
2,413
How can you tell if a knife has received a bad heat treatment?

Edge retention?? Resistance to rust?? Visible flaws in the blade??

Was just wondering because I've read about batches of Ontario knives that received a bad heat treatment. How would you know?
 
If it doesn't perform as it is expected to behave then one of the reasons could be problems with the heat treatment and this can effect pretty much all aspects of the properties of the steel. A RC test is a decent guage, if this is off then obviously something went wrong (however it can be where it should be and there could still be something wrong).

-Cliff
 
If you have one of the knives in question it might be a good idea to contact Ontario and find out what kind of problems these knives are having. They could probably tell you what to look for.
 
I wish that I had access to a Rockwell tester, but I don't. I gage the hardness of a blade a bit by how it feels when I hone it on a bench. If I was suspicious I would test a blade with a file. I would take a new 6 to 8 inch mill bastard file and file sharpen the edge a little. For a simple carbon steel knife like the Ontarios I would expect to be able to file sharpen the blade. I would not expect the file to dig into the metal like it does on mild steel. If the blade is on the hard side (58 Rc and up) the file will feel more like it is skating across the metal with minimal cutting (low drag and sort of skipping). If the file cuts the metal without skating, but doesn't cut very deep it is about normal (about 56 Rc I would guess). If the file won't cut at all the blade may be too hard and at risk of breaking.

It may be a sign of a bad heat treatment if the blade is harder in some sections of the edge than others.
 
Thanks for the replies. I don't have any Ontario knives or any badly heat treated knives (I don't think).

I was just interested to know what the tell tale signs would be if it were to happen.
 
General telltales are: If blade is too soft you get dents in the edge or the point is easily bent. If the blade is too hard you can get significant chips out of the edge or the point breaks off. You notice these mostly when you chop or pry with the blade. If you sharpen the blade to a thin edge you may notice it getting dull really fast if the blade is too soft.
 
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