Robert D. Posted July 7, 2015 Share Posted July 7, 2015 So today, I was cleaning up a blade that is part of a matched set for a friend of mine and his wife. They are avid bowhunters, and wanted some hunting knives made. Did the heat treating and tempering at the same time for each knife, cleaned up the first one yesterday pretty much entirely by hand using just a flat board and sand paper as I wanted to see how long it would take. Thank GOODNESS that is not the blade that broke. Today I am cleaning up blade #2 and I notice this line in the blade. Then I notice the much darker thicker line at the spine, which appears MUCH more like a crack then the first one does. So I stop cleaning up, clamp it in the vice, and give it a couple sharp tugs, nothing, not even a slight " tink " sound. So I grab it with both hands. prop my feat up on the bench, and lay back. after a couple seconds at most, it snaps clean off. ( I weigh 145 lbs, so its not shocking just adding my weight did not break it without trying. ) and low and behold it snapped right at the end of the spine crack, and shows the extent of cracking in the horizontal crack. There is the grain and the cracks in all their failed glory, the spine was FOR SURE cracked to heck and there was no fixing it, the horizontal one, had the blade been thicker its possible it could have been ground out, but while the picture is not that great, by my guess my normalization falls into the " 1 - 2 normalization " range on that file normalization pic that has been floating around. I did triple normalize these, however in hindsight I expect that laying red hot metal on a cold concrete floor probably didnt help the cool down process as much, and next time I will be trying to use more space in my forge for the normalization process. I also expect with the relative " ease " I experienced breaking these, that my tempering process is not working to the extent it needs to and needs to be addressed. Here is the grain after I broke the blade at the half way point. I did get my grubby fingers on the grains, so I expect that is why the grain looks a bit larger then it really is close up, that and I dont take good pictures, and my digital camera is the special ed model that takes blurry pics when mounted to a tripod even. The steel is " Mystery Steel " in a sense, old Leaf Spring, I suspect / treated it as 5160 based on the info I could gather about 1976 Camaro leaf springs, After this testing, I am going to bump my Tempering temps up a bit, from 400 to around 475 - 500 in my crappy toaster oven, and perhaps temper for more then 3x1 hour sessions. But there you have it, my first " Destructive test " of a blade http://robertjamescustoms.tumblr.com/ Link to comment Share on other sites More sharing options...
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