Making bridges

Ron Overs sec@overspianos.com.au
Fri, 9 May 2003 00:40:00 +1000


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>What's a scarf joint?
>
>David Love
>davidlovepianos@earthlink.net

A scarf joint is a variation on a butt joint, which instead of being 
vertical, is leaned over at an angle to present a longer and stronger 
gluing surface between the pieces being glued. A good scarf joint can 
be approximately 90% of the strength of the wood. We use Titebond 
Extend for all scarfs since it has a tensile strength of around 3,600 
psi.

However, a standard scarf joint will result in the two pieces being 
in a line, which is not satisfactory for the manufacture of a bridge. 
The joint required for bridge manufacture is the compound scarf 
joint, which has the standard angled scarf joint (typically angled at 
a slope of 1 in 5) with an added angle to cause the two pieces to be 
joined at an angle. This is necessary to allow all of the bridge 
stock to follow the outline of the bridge. Once all scarfs are joined 
(usually there are two per long bridge), the bridge outer profiles 
are then cut out with the band saw.

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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