John: thanks for the information. I will try these techniques, and hopefully one will be the cure. BTW, when you used new pins, did you have to cut them to a shorter length, and if so, how did you cut them? Thanks, Patrick C. Poulson Registered Piano Technician 530-265-1983 ----- Original Message ----- From: "John Delacour" <JD at Pianomaker.co.uk> To: <pianotech at ptg.org> Sent: Thursday, September 02, 2010 2:42 PM Subject: Re: [pianotech] Wegman, we have a problem > 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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