Hi Jim, It's GREAT to see you back on the list. Just drop in or are you here to stay? :-) Avery At 09:02 AM 08/31/00 -0700, you wrote: >Hi to all: > >I was reading in the last digest about drying tongues and flanges before >pinning. > >Here's the scoop, plain and simple. > >Humidity causes wood to swell, Drying causes wood to shrink. In the case >of tongues and flanges, the holes in the wood shrink when dried. This makes >the teflon bushing setup tighter, Humidity makes them looser. But when >applied to felt bushings, both the wood and the felt go the same way, so >that there is a minimum interruption from the norm. > >Now, every technician knows that when humidity is applied to pinblocks, >the tuning pins get tighter. This at first glance seems counter to what >was just said above. But here's how it works. > >Above, we were dealing with one hole in an unrestricted piece of wood. >In other words the entire piece of wood was free to widen. >In pinblocks we are dealing with multiple holes in a restricted piece of >wood. In other words, the pinblock is fitted to the plate flange and is >screwed to the plate with many screws. Any added humidity will cause the >wood between the holes to expand, therefore causing a tightening of the pin. >I have done experiments where a 1" hole was carefully drilled through a >1/2" piece of hard maple. After heating and drying, the hole became smaller, >in the cross-grain direction mainly (W=1.437", L=1.498). >When the wood was subjected to humidity (70% rel; W=1.505, L=1.502), the >hole was enlarged crossgrain mostly. The original hole was drilled >probably at around 60% rel hum in Apr.'67, so there was less variation >seen in the humidity test above, Since pinblock material is laminated, >you can see how that the crossgrain is held more captive than is a plain >piece of wood such as a tongue or flange. Any swelling of the side grain >applies pressure to the tuning pin between the longitudinal grains. > >In summation, it would not be a good idea to heat or dry a tongue or >flange before pinning since the hole would enlarge with humidity and >hence the hole would be larger and the pin looser. The pin in the >birdseye must be tight at all times. > >Jim Coleman, Sr.
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