[pianotech] Pinblock Separation

[Terry Farrell]

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