On 10/5/2010 5:48 AM, Ed Foote wrote: > Not an alignment problem, a strength problem, as in an agraffe that > jumps up a thread when the strings are pulled up to pitch. Upon > measuring, the threads were too small for the hole. I finally put an old > one back in and it held just fine. The differences between them were > something like .008" at the thread. It may have been a slightly > oversized hole and the combo just didn't work, but all new agraffes seem > to be considerably undersize. They are undersize, both the 7/32" and the 1/4", and somewhere around 0.008", or 0.004" of thread overlap. Agraffe threads, determined by filing a couple down, look to be about 0.016" deep. Given that the tapped hole will be slightly oversize, that doesn't leave a whole lot of overlap when you've already lost 0.004" to undersize stems. Still, when the plate hole is made to accommodate stems as pictured in the photo, you're going to lose more thread bite. When I find 7/32" threads that are a sloppy fit with new agraffes, I tap them to 1/4" and get a fresh start. That's the whole set, not individual agraffes. > > When the agraffe comes to its final position, it needs to be as tight as > > possible without damaging the stem. > > There may be reasons for tightness beyond noise. I can't see the benefit > of an agraffe that can move during the stringing process, so there is an > argument there for tight. I have seen pianos with agraffes that were > crooked, and upon unstringing, found them to be loose. Did they turn by > themselves, over the years? The offset string angles to them may have > had enough force, I don't know, but I am not going to make a case for > anything loose in the terminations. That's the point. They don't *need* to be as tight as possible without damaging the stem. Just tight enough to stay put, at a minimum, but not tight enough, at a maximum, to damage the stem. It's a range, not a point. Ron N -------------- next part -------------- A non-text attachment was scrubbed... Name: agraffes.jpg Type: image/jpeg Size: 185538 bytes Desc: not available URL: <http://ptg.org/pipermail/pianotech.php/attachments/20101005/03967275/attachment-0001.jpg>
This PTG archive page provided courtesy of Moy Piano Service, LLC