Profile question

B

BD Blades

Well-Known Member
I had a blade I forged and HT and it would only get 5-6 cuts on 5/8" rope. I figured the HT was bad so I Ht'd again. Still only 5-6 cuts. I looked at it closely and determined I may have had it a little too thick. I am new to this and that is my tendancie to get them a little thick some times. I slimmed it down and sharpen and got 35 cuts before I ran out of rope. It was still cutting. I can't believe what a difference a little in the profile made.

what is driving me crazy is the fact that it would cut the rope 5-6 times and quit. Seems like to me if the profile was that bad it would not have cut at all. Can any help me get a better grip on this please. Steel is 5160, triple quenched and tempered 3 times at about 350.

Thanks for your help.
 
I had to think on this myself. I doubt that the blade actually dulled any faster beefore regrinding. I think that the poor blade geometry added reisistance that only a fresh sharp edge would overcome. After making a half dozen cuts the sharpness of the blade was no longer enough to overcome it. When you improved the geometry of the blade you removed this resistance and allowed the sharp edge to work. I made a blade with very good geometry for cutting, mostly by chance. It cut through two free standing water bottles and left the bottoms standing with water in them. I made another knife with not so good, or at least a different geometry, and it would only cut through the first bottle and knock both halves of it and the uncut second bottle across the yard. Both were sharp enough to pop hairs off my arm.

Doug
 
I have to agree with Doug. My guess would be that it was the geometry. Geometry is just as critical as HT for a well performing blade.
 
Thanks for the info. That makes sense. It seems like the more I learn about blade geometry, the less I know. Suprising how much difference a little off the profile can make.

Thanks again guys.
 
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