Jon writes: > >Place a teflon s/f in a glass of water, it will be loose as a goose within >20 minutes. This was demonstrated by Koe Biscelie (sp?) at a seminar. >The bushing actually is loose in the hole in the shank yoke, go figure. Greetings, I did go figure. I placed four small teflon bushing on a centerpin, and measured their cumlative length. It was .486". I then placed them in water, waited 20 minutes and measured them again. They were .486". Teflon is about as inert, non-absorbtive a material as you are likely to find. It is dimensionally stable. What happens is that the wood's dimensional changes affect the pressure on the teflon bushing, thus changing its I.D. If you drill that hole in the yoke while the wood is damp, when it dries out, that hole will be oblong. If you drill it while the wood is dry, and then wet it, the hole becomes oblong. These changes show up in pinning tightness, but it is not the teflon that is changing, it is the yoke. >Joe's description of the material is as follows (to the best of my memory): > > The plastic is manmade; wood and felt are organic. > With moisture; wood and felt swell, plastic shrinks > With heat; wood and felt shrink, plastic expands. I respectfully suggest that Joe's logic is flawed. Regards, Ed Foote
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