Just to clarify this Kevin, do you simply chop downwards into the 1/2" brass rod, or is there some subtelty I'm missing? Also, I'm assuming that any dulling or rolling of the edge amounts to failure. Is there any other output of this test one should pay attention to?
Thanks,
-d
My purpose was to point out the differences between the popular brass rod test and the use of another test that measures an entirely different property. Just because the majority of folks do something in this business does not mean that it measures what they and we think it does. Take the 90 degree bend for example, it is the benchmark in our trade and yet it really tells us very little at all about our heat treatment or how a knife should work in performance as a knife, and has in fact not only allowed sub par blades to be held up as superior but also steered a large number of bladesmiths into intentionally doing things that compromise proper heat treating for true edge retention.
Bladesmiths seem to have an obsession for being at odds with or totally ignoring the existence of Youngs modulus. Test after test we come up with ones that measure properties that gives us the least amount of information about our heat treatment and is heavily affected by features that are the same for steel that is dead soft or fully hardened. But the real puzzler for me is how so many of our tests are not even geared to measure properties that will be called on in the use of a knife. Actually it is not a real puzzler if one realizes that it is all about slick marketing and grabbing the spotlight with hype.
If you need to demonstrate that your knives can do something that nobody elses can do, you have two choices. You can do it the hard way and really come up with something that is greater than all the other cutting instruments made in the last 2000 years, or you could simply make your knives to do things that have nothing to do with knives- it is then quite easy to have your knives do something that everybody elses does not, since everybody else is still trying to make good knives. If all the other pogo stick makers are trying to get the maximum bounce and you cant keep up, you may be able to stay in business by putting wheels on the bottom of yours and marketing it as a pogo stick that can do something none of the others can do- roll. Of course it wont bounce worth a damn but if you can convince the public that the proper roll is essential to pogo sticking it will all work.
But I digress, I like impact, because that is what large knives will be asked to do and it tells me things about my heat treatment. At the ABS Midwest Expo last summer I demonstrated how I tested my competition blades (in competition the thinnest edge possible that will not blow out can be an advantage) I used a sharpened knife and held it edge up in one hand and impacted the edge with a ½ brass rod in the other. I was making around 1/8 penetration into the brass and you are correct, if there would have been any visible damage to the edge I would have known something about my edge geometry vs. heat treatment instantly. I do straight on blows, as in a perfect cut, but also push the envelope by whacking the edge at an angle- this is much more destructive than the straight on hit and much more likely to result in rolls or chips. Hitting other metals is extreme but one should be able to chop up things like deer antler with their knives or they may have to be concerned about customers who think every knife should be a cleaver.
I came up with this in answer to all the folks who would ask me about my brass rod test. I dont use the popular brass rod test because I already know what the modulus of elasticity is of my steel, it is 30 PSI x 10
6 dead soft or fully hard that is what it is, so I came up with my own brass rod test to demonstrate, in stark terms, a different perspective on edge testing.
