On Jun 11, 2010, at 8:39 PM, Jim Busby wrote: > Remember Wally's class where he said an electron microscope showed > that the very tip of a needle is about 30 times the size of a wool > fiber diameter? This means simply that felt is cut whether you stab > or push. Mute point either way. Is that right? Yes, felt fibers will be cut or torn either way. The variable is speed. Take a not too sharp grass whip and vary how fast you swing it. At fast speeds, you mow down the grass, even if the whip is rather dull. I don't think there is much actual "cutting" going on with needles in felt, more tearing, but again it is speed, and whether the fiber has a chance to slide out of the way, or the impact is so fast it simply breaks.. Regards, Fred Sturm fssturm at unm.edu http://www.cdbaby.com/Artist/FredSturm
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