Bridge cap materials

[Ron Overs]

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At 11:33 AM -0400 19/10/02, Erwinspiano@aol.com wrote:
>A last thought as to your bridge cap material. Although it's 
>important to have a tight bridge pin fit throughout the bridge the 
>tightest hardest grain is most desireable in the top two sections. 
>I save the tightest grain  for this area. I replaced a cap on a 
>1920s baldwin this week that had  a decent grain  (12 14) 
>throughtout) and they were as badly split up as the rest of the 
>belly and I don't think it was a reflection on the grain just age 
>and abuse.

As I wrote in a post last week, I suspect that some highly suitable 
wood for caps might fail in service as a result of poor seasoning. 
This is the primary reason why we now laminate the capping material 
in 1 mm thick laminations, since any invisible checks in the wood 
will be glued together with the West System epoxy at the time of 
gluing the cap laminations together.

While European boxwood is very suitable as a bridge capping material 
(with an air dry density of around 0.9 gr/cc), much of it fails in 
service since it is so dense that it very difficult to season without 
small splits developing. Steinway Hamburg had a lot of trouble with 
Boxwood caps until they stopped using it sometime around 1987 (but 
they also encouraged problems since they weren't ensuring the 
material was strictly quarter cut). They now use maple caps (which 
are properly quarter cut). Yamaha are now using Boxwood but they seem 
to be having less trouble with splitting. But then again, Yamaha have 
always been careful about insuring that they use only quarter cut 
material.

Ron O.
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OVERS PIANOS - SYDNEY
Grand Piano Manufacturers

Web: http://overspianos.com.au
mailto:info@overspianos.com.au
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