Tightening the plate...

BobDavis88@AOL.COM BobDavis88@AOL.COM
Fri, 25 Feb 2000 18:06:14 EST


Terry,

No torque measurements are necessary. I've always thought of fastener 
tightening this way: The purpose of the plate screws and rim bolts is to 
restrain the movement of the plate. If you're tightening one, the torque 
remains low until the fastener head has made contact with the plate, and the 
threads of the fastener have begun pulling upward on the threads in the rim 
or block. At that point, the torque begins to rise quickly. That's easy to 
feel. What does going much beyond that point accomplish? If they're all that 
tight, where is the plate going to go? Well, a tiny more can assure you it's 
truly seated, that you've used up the elasticity of the wood threads, and 
that it's not stripped; beyond that it's only the crushing of the wood 
fibers. If it strips with that little torque, it needed fixing anyway, and 
you can feel confident that wasn't your own, shall we say, excessive 
enthusiasm. 

Suppose ALL the fasteners were an eighth turn loose, due to seasonal 
movement. At, say, six threads per inch, that's between 0.010 and 0.020", 
depending upon elasticity. That just doesn't worry me too much.  So, when you 
feel the torque just begin to rise, go just a little farther and that's 
enough!

Bob Davis


This PTG archive page provided courtesy of Moy Piano Service, LLC