Heat treat question

CRAIG1952

CRAIG1952

Well-Known Member
I was just heat treating a neck knife that is a WIP. I am making this from an old Nickleson file. When I reached critical temp (Non Magnetic) I was pulling it from my home made furnace, I heard a crack sound:s12108:. I went ahead and did a quench. After it cooled off I noticed that it hadn't cracked, but a chunk of file had broken off. I looked it over and found no more problem :les: I should have taken a picture of it ! I cleaned up the area with my belt sander. It still looked good so I put it in the oven for a soak :chef:
I guess my question is it ok to go ahead with my grind ?
 
A chunk breaking off just out of the fire and before quench shows it was under some stress. Do you do normalize before final heat and quench? I'm curious, Do you have a pic of the broken piece. The size and shape of the grain may give you some answers.
 
I do normalize before cutting and shaping the knife blank. I had made one other knife from the same file and had no problem. I ground down the area prior to soaking @ 420 degrees. The area were it broke off was very dull in color, no grain, that I could see.
 
CRAIG1952 said:
I do normalize before cutting and shaping the knife blank. I had made one other knife from the same file and had no problem. I ground down the area prior to soaking @ 420 degrees. The area were it broke off was very dull in color, no grain, that I could see.
Click to expand...

no grain that you could see is probably a good thing. Files usually have a very fine grain and it is hard to see. I'm going to put a guess out that it had an inclusion of some sort that created a weak spot. Most likely the rest of your blade will be unaffected.

Here is a handy pic. The bottom piece is what file steel usually looks like because it is usually very well heat treated. If the piece that came off your file looked like that bottom piece you had everything right.

grain in steel.jpg
 
Last edited:
Thanks for the picture, it did look like the bottom picture (factory Heat treat). That picture is a great tool for understanding what we see, when something, like this happens. Going to save that picture!
 
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