Plate Bolts

[Richard Moody]

Wondering if the plate bolts in uprignts are different from grands in
the Baldwin makes. I know they are, but then next year it may have
been different.  


Richard Moody

----------
> From: Delwin D Fandrich <pianobuilders@olynet1.olynet.com>
> To: pianotech@ptg.org
> Subject: Re:  Plate Bolts
> Date: Monday, July 21, 1997 11:43 PM
> 
> 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
>