Doweled and Fully Fit Pinblocks

[Michael Spreeman]

Hi Fenton,  When doing full fit blocks, we would fit the block so the fatter treble end would butt up against the outer rim perfectly. (This being after the block has been located, height has been established, height/angle shims fit if necessary, stretcher rail/block joint fit, dry clamped in and 3 screw holes in the treble and 1 in the bass drilled through the block and into the inner rim). The bass end would be cut so that it was approximately 4mm from the rim. A piece of the pinblock scrap that was cut-off during the initial rough fit would then be dry fit into the gap. (When laying out the new block, one can plan ahead to allow a little extra material on the bass end and the end cut off piece will mate almost perfect when fit as the shim.) When dry fitting the assembly, make sure the shim isn't too tight in order to allow for slight expansion when the glue is applied (providing you're not using epoxy or other non-water based glue). The block is removed and the pilot screw holes are opened up for the screw body and countersunk.   At glue up time, we would lay out the clamps and have the plate suspended above the case. All glue surfaces are coated, including the bass shim on both sides,  and the block is set into the case and  pulled toward the treble side. The screws are installed and the bass shim is pounded in with a larger wooden block and mallet.
 
Drop the plate in and put random screws to pull the block up tight. Clamp the stretcher to the block and clean things up. Let the glue set and pull the plate. Finish by installing half inch dowels through the block into the rim in between the screws (this will insure your ring of fire ). Sand the bass end shim and the job will look (better than) factory fresh.
                Michael Spreeman http://www.spreemanpianoinnovations.com

From: fmurray at cruzio.comTo: pianotech at ptg.orgSubject: Re: Doweled and Fully Fit PinblocksDate: Sun, 3 Aug 2008 14:34:14 -0700



List,
Of all the contact and glue surfaces of the full fit block certainly the ones with the least structural significance must be the end grain glue joint at the rim. In many woodworking aplications this is left to float, but not in the wooden fortress circle of sound. I enjoy attempting to fit all of these joints as well as I can if for no other reason than to be able to look under the plate and see something that looks like it did 100 years ago. But this end joint is about the hardest to nail, even when attained it's impossible to get into the piano. So, I inevetably slip in the veneer at the end which always seems difficult and messy to do and never looks quite right. I do under cut the ends slightly.
I would love to read procedures for nailing this left, right, tight at both ends fit. It is, after all one that can be seen by every one.
Fenton
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