Pressure bar screw variation?

[Delwin D Fandrich]

----- 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