Plate Bolts

[Delwin D Fandrich]

Jon Page wrote:

> Make sure the rim bolts are screwed down. I've had uprights where I found
> the bottom of the  plate
> lifted 1/4".  Be careful for new Baldwin grands. They claim that they do not
> need tightening. But if the
> bolts rattle loose (figuratively speaking), why not.   The double thread
> should still need tightening.
> Shouldn't it?  (Any replies to these last few sentences, please change
> <subject> to: rim bolts).


Jon,

You don't tighten plate bolts on Baldwin grands for good reason. The
bolt holes in the plate are threaded to accept a 3/8" x 16 NC machine
bolt. A machine bolt is run through this threaded hole and into the rim
of the piano. The plate is not actually in contact with the rim or the
soundboard in any way. There are no plate dowels or spacers. The plate
is actually suspended above the soundboard surface by the bolts.

The head of the bolt actually doesn't have to even be there. I once
assembled one of these pianos using headless socket bolt just to
illustrate this point. "Look, ma, no heads!" Looked a little strange,
but it worked great. I liked it, but then...

There is usually a machine washer and a lock washer under the bolt head.
As long as these are snug, no further tightening is needed or desirable.
To tighten these bolts repeatedly puts excessive strain on the bolt head
that can, in time, lead to a failure--the bolt head pops off. And you
ain't had fun yet until you try to drill one of those babies out without
damaging the plate.

Other "normal" plate bolts and screws become loose primarily because of
the continuous working of the swelling and shrinking of the wood they
are brutally forced into. Secondarily, the bolt or screw threads tend to
crush the wood fiber just by the very act of holding things tight. So,
yes, here a periodic check might be in order. I tend to think, though,
that the practice of continually tightening these bolts and screws often
does as much damage as it does good. Like everything else, it has to be
done thoughtfully and with at least some level of finesse.

 ddf