Ditch the tuning pin bushings

[Overs Pianos]

>Would you assume that a new or newly rebuilt instrument without bushings
>in which tuning pins already contacting plate is starting out with 
>an acceptable alteration in its design parameters?

Ron N

>Absolutely not. It's starting out with sloppy workmanship.

Del

>I wonder about this....
>
>If you'll make a drawing of the S&S tuning pin arrangement . . 
>.you'll find that there is just about no way to keep the pins from 
>contacting the plate. Given the thickness of the plate panel over 
>the pinblock, the diameter of the holes, the diameter of
>the pins and the . .  pin back angle the pin is going to contact the
>plate no matter how careful you are at drilling. Indeed, it begins to look
>like this contact was intentional from the start. I suspect this is how they
>managed to keep their three-ply pinblocks from self-destructing. It is also
>the only explanation I can think of for their long-term practice of drilling
>at such an extreme back angle -- the pins can contact the plate at the
>bottom edge and still look reasonably centered out where folks can see
>them..

An interesting suggestion Del, so you suspect that there's a bit of 
'getting away with it but don't tell anyone' coming from the S&S 
camp. I also agree with Ron N about the sloppy workmanship, and 
there's no doubt about the excessive pin back angle S&S use. We drill 
the new pin holes to 3 degrees using a hardened bush with a tapered 
center hole, to align the pin to the center of the plate clearance 
hole, which is also slightly enlarged as a further precaution. If the 
plank is well fitted all along the flange, at 3 degrees the pins will 
continue to clear the plate when the piano is at pitch. When fitting 
blocks we chalk fit it for its entire length of contact with the 
plate flange (while out of the piano). Once the fitup is complete, 
the block is bolted to the plate (also out of the case) for the datum 
holes to be drilled into the new block. The datum holes are drilled 
through the plate and pin block together before the plate is taken 
out of the case. I understand that Newton Hunt has been using this 
technique also for many years. The new block can then be trimmed to 
the correct dimensions (and to the correct angle of cut along the 
back where the block meets the stretcher rail) to ensure that the 
plate ends up back in its original position (using datum to case 
measurements which were taken from the original block before it is 
removal from the case).

The treble end datum hole in a rebuilt D can be viewed at;

http://www.overspianos.com.au/testa.html

The piano shown in the image (rebuilt in 1996) is currently for sale.

Ron O.
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Website:  http://www.overspianos.com.au
Email:        mailto:ron@overspianos.com.au
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