Ron, If you are going to do this stuff, you should at least attempt to be a scientific as the marketing folks were. I see no mention of the silk scarf test in all that you've written below. Consequently, I must assume that your tests are, at the very least, incomplete! On pins and needles, we still await the true test of tuning pin functionality... Regards, Del --------------------------------------- ----- Original Message ----- From: Ron Nossaman <RNossaman@KSCABLE.com> To: <pianotech@ptg.org> Sent: February 28, 2000 4:22 PM Subject: Tuning pins with teeth > I just tried a little experiment out in the shop. I took four new cut > thread tuning pins and a scrap of Baldwin's pinblock. I figured that if > anything would strip the thread burrs off when the pins were driven in, > it's that block. > > Drilled four "I" holes and drove in the pins to the same height, and about > as deep as they would be in a real piano. Two of the pins, I took counter > clockwise torque readings, followed by clockwise readings. On the other > two, I took clockwise readings, followed by counter clockwise. The idea was > to see if there was more initial resistant to movement in one direction, > than in the other. The torque peaked around 25 foot pounds either > direction, and settled immediately to around 20 after the initial movement. > There was no discernable difference in torque values between clockwise, and > counter clockwise movement of any of the four pins. > > Next, I turned two pins clockwise 180°, then back to their starting point. > The other two, I turned counter clockwise 180°, then back. Torque readings > were similar coming and going on each of the four pins. > > At the bandsaw, I cut to within a millimeter of each pin from both > directions and broke the block apart to get a look at the pins without > further twisting them. About half of the threads ( those that protruded a > little further, I suppose) were filled with sawdust. > > current conclusions: > 1: The "one way" nature of the thread burrs is, as suspected, nonsense. > Rebuilders have always known this to be the case, so why hasn't every piano > tech with this question tried this experiment for themselves? > 2: The thread burrs are not taken off during driving, and survive enough to > provide some initial resistance to turning as they bite into the block and > fill with sawdust. > 3: The thread burrs don't continue to chew up the block because they are > immediately filled with sawdust with the first turn, clogging the burr > "tooth", and the sawdust has nowhere to go to clear the burr for another bite. > 4: The sawdust between the pin and the block, trapped in the threads, > lowers the static friction, and raises the sliding friction, so the > transition is smoother when the pin is turned. It slides smoothly instead > of jumping. > > > In the interest of symmetry, I cut apart a block in which a pin had been > driven, but not turned. There was not nearly as much sawdust in the threads > as those which had been turned. So far so good. I then put the block halves > back together, clamping the halves in a vise, and cranking the pin back and > forth. When I took the block apart again, the pin hadn't picked up any > additional sawdust that I could tell, but there didn't seem to be that > initial resistance to turning at the first movement either. This one was a > tad on the inconclusive side, and just serves to supply some contradictory > evidence to the above experiment, lest anyone be too easily convinced. > > That ought to get you started. Go forth and ponder. > > > Ron N
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