At 12:24 -0700 02/09/2010, Patrick C. Poulson wrote: >I am restringing the Wegman upright that I spoke about in an earlier >email. The problem is that I am finding that some of the tuning pins >no longer have enough friction to hold to pitch. The piano uses .284 >diameter 1 1/2" unthreaded pins that go in to a slighter oval hole >in the plate (there is no pinblock), and create sufficient friction >by the pressure against the narrow end of the oval hole. Usually, >that is. Many pins in the tenor and bass sections slip. These are >the options that I can think of this point: >1. Use epoxy or CA to tighten the hole, as in a wooden pinblock. >2. Use a shortened standard, i.e. threaded, 3/0 tuning pin . This >would require cutting or grinding a number of these down to the >correct length. Hello Patrick, You will remember from the previous thread that I mentioned the Papps upright made in England the has a similar but not identical system. I posted a description and a picture. I now have two of these -- a vertical and an overstrung -- and have been experimenting with them. I got the vertical simply to investigate the system but I intend to rebuild the overstrung because it has great potential. First of all I'd say DON'T PANIC! It's simply a question of friction and can easily be solved, I'm sure. With the Papps I have had no problem whatever pins I use -- threaded, not threaded, oversize, undersize, same size -- though the cleaner things are the smoother the feel in tuning. I got the 1924 overstrung on eBay a few weeks ago and it arrived at pitch and pretty well in tune, and there it has stayed. The vertical has smooth pins and the overstrung has file-roughed pins. It seems to make very little difference and simple laws of physics dictate that the friction will be the same in either case. My guess is that you simply need to make sure that the sides of the hole are clean and that the pin is clean. You could also roughen the pin with a file to speed up the process of settling in. But I think that if you pull the string up to a few semitones below pitch, then up and down a bit, applying a slight downward pressure on the pin all the time, you will find that it holds and will continue to hold. Using CA glue would almost certainly be worse than useless because you would reduce the coefficient of friction and give yourself a lot of work cleaning it off. You can (at least on the Papps) use a larger or a smaller pin to bite at a slightly higher or lower point in the tapering hole. If the sides of the hole in the cast iron have been eroded by the wear of the previous pins, in other words the sides are not giving a straight taper, then you must use a larger or a smaller pin because the whole system relies on a certain angle of taper. I have not come across this problem on the Papps, since if anything wears it is the pin and not the hole, but in theory it is possible. In any case I am sure you will find you had nothing to worry about. JD
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