[pianotech] Pinblock Separation

[paul bruesch]

The one P/B separation repair I've done had to compensate for a couple of
P/Rs done by yers trooly, so I absolutely had to let tension down. I still
found it to be very hard to tighten my pipe clamps, and even bent one. I
wound up letting it WAY down, at which point the clamps pulled it closed
quite nicely.

I used large washers in the back, but found the wood still crushed fairly
considerably. It occurred to me at the time that I may want to glue on a
1/4" strip of maple or a hardwood plywood next time.  Thoughts?

Paul Bruesch
Stillwater, MN


On Sat, Jan 12, 2013 at 10:42 AM, Terry Farrell <mfarrel2 at tampabay.rr.com>wrote:

> Theoretically, the tension does not have to be let down. However, it is
> possible that the piano has been getting pitch raises every time it's been
> tuned since the crack has been developing. IMHO, it is best to let the
> pitch down - unless perhaps the crack is small and the pitch is already a
> bit low. Just be careful!
>
> Also, if possible, sink all or most through bolts into a backpost for the
> most effective repair.
>
> Terry Farrell
>
> On Jan 11, 2013, at 8:26 AM, Jon Page wrote:
>
> > I've done this many times. The tension does not need to be let down. You
> do need many industrial strength clamps. I use hand screws and pipe clamps.
> > Draw the crack closed with the clamps. Remove a screw and drill thru for
> a 5/16" bolt. A carriage bolt could be used but I have found the the soft
> face board on the back allows the bolt head to crush into the wood too
> much, so I use hex head bolts with washers. 3/8" bolts if more force is
> required.
> > You could use T-nuts but they are pricey and chances are that your local
> hardware store does not supply enough.
> >
> > The reason to close the gap first is two fold. First, to prevent
> drilling debris from impacting into the gap, thus preventing its closure.
> Secondly, if the bolt hole were drilled prior to closing the gap then the
> holes on either side of the separation will no longer be in straight
> alignment once closed and the bolt itself will restrict closure.
> >
> > Many times glue is not needed for shallow separations. If glued, leave
> the clamps on overnight after all the bolts have been installed.
> > Also, if the top is loose, bet that it is separated along the bottom as
> well. Check the bridge apron/body glue joints while you're at it. It's also
> good time to check the bridge notch at the treble break strut. Many time
> the bridge is touching the plate. Cut the bridge free with a saw blade
> drawn against the plate to recess the bridge. Might as well lube the
> casters while its on its back....
> >
> > -- Regards,
> >
> > Jon Page
>
>
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