----- Original Message ----- From: "Clyde Hollinger" <cedel@supernet.com> To: <pianotech@ptg.org> Sent: December 03, 2002 4:16 AM Subject: Pressure bar screw variation? > Friends, > > Yesterday as I was inserting the strip mute in the treble section of a > one-year old Charles Walter studio piano, my hand brushed against a > pressure bar screw which was loose. I assumed it had broken off, so I > took it out to look at it. I was surprised by what I found. It > appeared to be threaded like a bolt, with the threads much closer > together than wood screw threads, and there was a notch in the end as if > it were designed to be tapping its own threads. It is a self-tapping screw. > > Now my limited understanding of piano construction is that pressure bar > screws go through holes in the plate to anchor into the wood behind it. > In this case, however, it appears that there is a threaded hole in the > plate itself for each of the pressure bar screws. > > Am I understanding the construction correctly? Are any other pianos > made this way, or are they all made this way and this is the first time > my meager powers of observation are kicking in? It can be done either way. It is more common to find a large hole in the plate and a wood screw (or, now more common, a sheet metal screw) driven down into the wood pinblock. This system allows a considerable amount of slop during assembly. It is considerably more difficult to space and align the holes in the pressure bar and the plate accurately enough to use either a machine screw or (as is used in this case) a self-tapping screw and anchoring them to the plate itself. Arguments can be made for the superiority of either system. In theory I think I prefer anchoring the V-bar to the plate as has been done in this case but, in the end, it probably doesn't really matter which method is used. > > On this piano I just snugged up this one screw, but the pressure bar at > that place is out of line with the rest of the bar. In my opinion there > is still enough downbearing, but I could drop the tension on the strings > in that area and tighten the loose screw down further to bring things > into better alignment. What think ye? When you say "out of line" do you mean in terms of height (or, more properly, distance from the plate)? If so, it is a simple matter to do just as you say, tightening the screws evenly until the bar is uniformly spaced from the plate and the strings are at a uniform deflection angle. Regards, Del
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