Broken blade

Dennis Morland

Dennis Morland

KNIFE MAKER
I was cruising along on a fillet knife. In process of fitting the guard. And snapped the blade. It twisted a touch when driving the guard on but I did not think much of it. Any of you stainless users see anything as to the “why”??

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Bummer! I haven’t worked with stainless yet so i’m no help in what may have caused it but I’ll be following.
 
Sorry to see that DeMo. I see what looks like a small chip at the bottom of the grind line. Could that have started the stress fracture? To me your design looks OK. But I don't really know what is involved in causing such a break.
 
De Mo, don't know what kind of stainless you are dealing with, lookes to have a lot of grain in it, the only stainless I ever broke was hammering on it after heat treat before draw back, it may be way to hard, have straightened ATS 34 and 440C in the press and it will bend more than you would think, I am thinking it was to hard. Deane
 
oldknife said:
De Mo, don't know what kind of stainless you are dealing with, lookes to have a lot of grain in it, the only stainless I ever broke was hammering on it after heat treat before draw back, it may be way to hard, have straightened ATS 34 and 440C in the press and it will bend more than you would think, I am thinking it was to hard. Deane
Click to expand...

It is 440c.
 
Besides what temper did you put on it before you tried to fit the guard, how did you try to force it down. I assume you had the blade in a padded vice and did you try to use something like a monkey tool to tap it down with.

Doug
 
Yes I tempered it. Twice for an hour at 250 degrees.

Not sure what a monkey tool is...but I use a modified pipe to tap guard into place. The blade is padded and held in a vice.
 
Dennis Morland said:
Yes I tempered it. Twice for an hour at 250 degrees.

Not sure what a monkey tool is...but I use a modified pipe to tap guard into place. The blade is padded and held in a vice.
Click to expand...

250 Fahrenheit? I doubt that’s nearly enough, especially for stainless. You may have also had a stress riser in the middle of your “choil” from its initial shaping, or possible from the plunge.
 
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