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11-23-2013, 10:43 AM
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Steel Addict
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Join Date: Sep 2013
Location: Southwest GA
Posts: 275
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Testing a blade
Searched the previous forums for this topic, but couldn't find. Maybe due to the keywords, I dunno. Regardless, what are some good ways to test a blade you have heat treated? Not looking to Rockwell grade the blade, just something simple to see if my HT is working by doing a little more to it than scraping a file on it.
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11-23-2013, 11:05 AM
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Founding Member / Moderator
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Join Date: Jun 2002
Location: Wauconda, WA
Posts: 9,840
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One popular test is the brass rod test. Roll the edge on a brass rod on a table with the edge laying a little bit on its side. You should see the edge bend around the curve of the rod (might need magnification to see this). If the edge recovers its just about perfect. If it stays bent its too soft and if it chips out its too hard.
After that, chopping 2x4's, slicing cardboard, and slicing rope are popular tests. Count the cuts and compare to the results you got from some other blade you have that seems really good to you. Finally, break the blade and observe how it behaves when you try to break it and how the grain looks after it is broken. This step is especially necessary when working with a new steel OR a new batch of steel. It is not necessary for the blade to bend 90 degrees before breaking but you don't want it to snap off at the first sign of lateral pressure either. Put the first 25% of the blade between two pieces of hardwood in the jaws of a vise, then use a pipe over the tang to slowly and steadily bend the knife over until it breaks (don't jerk it). Wear eye protection AND a face shield and stay off to the side as you do this to avoid being hit by flying pieces. If the blade is tough there should only be two pieces, if the blade is too hard there could be several pieces...
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11-23-2013, 11:16 AM
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Skilled
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Join Date: Mar 2012
Location: Alabama
Posts: 554
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All those + my favorite; holding the blade out and dropping it point first into the concrete floor. If the tip rolls it's too soft, breaks it's to hard; a nice divot and everything is perfect. This test is not for the faint of heart. Take safety precautions if you do this.
It should be noted, I only do this to differentially hardened blades.
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11-23-2013, 02:20 PM
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Steel Addict
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Join Date: Sep 2013
Location: Southwest GA
Posts: 275
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by differentially hardened I take it you mean just the blade is hardened and not really the tang?
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11-23-2013, 02:24 PM
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Founding Member / Moderator
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Join Date: Jun 2002
Location: Wauconda, WA
Posts: 9,840
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No, he means the lower part (the edge) is hardened and the spine is left soft (or, at least, softer). This is accomplished by either edge quenching, clay hardening, or drawing the temper of the spine with a torch . Incidentally, all of these methods usually result in the tang also being left soft but that isn't the main aim of the process ...
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Tags
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blade, blades, brass, edge, file, heat, knife, rod, simple, steel, tang, temper, vise |
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