Adjusting Action Centers

Clark caccola@net1plus.com
Tue, 18 Sep 2001 10:24:43 -0100


>> Old Chickerings show signs of this having been done, consistently 
>> with four dimples in the wood around the holes.

> I wonder if they had a four prong dimpling tool?

Yes, probably something like that, maybe mounted like a pinning vise
with a stop.

Ch. sometimes omitted forming birds eye bearing surfaces and instead cut
the bushings proud so this may have been thought as a sort of thrust
bearing for the bushing. In many instances, I've seen these on wooden
flanges which are engineered to fit rails more appropriate to brass
flanges (tapped steel bar inlaid, very small vertical offset between
rail and action center) - I don't think the little brass flanges showed
these dimples but might need them, while their wooden versions have so
little material around the bushings the procedure may have harmed them.

> The voicing needle works up to a point for key bushings.

The tool sold for this purpose looks like a front mortise caul, angled
to form wedges to either side of the insert (used to cut the cloth when
bushing). The wedge angles aren't very far from perpendicular, though,
so pressure meant to squeeze the mortise smaller very easily could
squash or break it instead. At least in modern harpsichords sometimes a
slit is made next to the mortise and a thin slip of something inserted
to adjust its width, a more permanent and elegant fix. But with
bushings, why not just rebush.


Clark


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