Epoxy Bass Bridge Repair

[AlliedPianoCraft]

Terry, is this the same material you use to fit the pinblock?

Al Guecia


From: Farrell 
Sent: Friday, May 09, 2008 8:57 AM
To: Pianotech List 
Subject: Re: Epoxy Bass Bridge Repair


Epoxy repairs for a situation as you describe can yield very good results. Sometimes the crack opens up a fair bit - you'll want to clamp it back into position - not to clamp in the traditional sense, but rather to simply position the parts in their original orientation - you need to leave some epoxy in the gap. You don't want to epoxy-starve the joint.



I use West System epoxy resin, hardeners and fillers:

www.westsystem.com My favorite for a cracked bridge is #404 High-Density Filler and using the West System two-step bonding procedure described on the West System web site. The following is from the West System web site:



404 High-Density Filler

404 High-Density filler is a thickening additive developed for maximum

physical properties in hardware bonding where high-cyclic loads are

anticipated. It can also be used for filleting and gap filling where maximum

strength is necessary. Color: off-white.



You can either push the bridge pins into the uncured epoxy, tidy up and be done with it, or, for a neater, more exacting job, you can epoxy the gap and then drill bridge pin holes after the epoxy hardens. I have found that if cosmetic considerations are not paramount, I apply the epoxy, clamp together until the wood is close to original dimension, clean off epoxy squeeze out (acetone) - at that point you will be able to see the outline of the original pin holes - push pins in place - the wood will have been drawn together enough to hold the pin in its original position - and then level off and clean up the little bit of epoxy that squeezes out of the holes as you push the pin in place. Wait a day or two for the epoxy to completely cure, go back and install bass strings.



I've done this repair numerous times with great success.



And of course, on a nicer piano where the budget allows, new bridge and/or new cap is preferred.



Terry Farrell

  ----- Original Message ----- 
  From: Gregor _ 
  To: pianotech at ptg.org 
  Sent: Friday, May 09, 2008 5:13 AM
  Subject: Epoxy Bass Bridge Repair


  I crawled the archieves but I did not really find what I was looking for: does Epoxy work even for bigger gaps?

  I wanted to tune a Kawai CE-11 upright yesterday but the bass bridge looked horrible: a long gap which affected 9 notes. The gap started at the upper pin row and the pins were vertical. Some strings rattled at the pins. The gap expanded up to 4 mm above the upper pin row. I did not try but I could imagine that I could have pulled out some pins without using pliers.

  First at all: I never worked with Epoxy. My first thought was to pull out the pins, fill the gap with epoxy and drill new holes for new pins. Could that work or is such a gap too much for Epoxy? The bridge is made of one piece of wood, no cap.

  I was shocked about such a gap in a Kawai from 1992 (no grey market import): no floor heating, no air con and no heater near by the piano. And I don´t live in an area with huge differences in the climate. Very strange. That damage is a pitty because everything else in this piano was in a pretty good condition. But making a new bridge would be definitely too expensive including transports from the second floor into a workshop and back to the customer.

  Gregor


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