This is a general overview of the process
of setting proper down bearing, and is
not an exhaustive set of instructions..
This is only for example purposes, and
should not be followed as directions,
without proper guidance by someone
familiar with the process.
Setting up bearing
specs for a rebuild…
1- First , Measurements must be taken to
document speaking lengths etc.
2- Bridge patterns need to be made of the pin
3- Then with the strings removed, you will
need to measure the amount of crown existing
in the piano at different stations on the
soundboard… This is done by creating a
straight line from each end of the underside
of the board next to the specified ribs on the
chart… The mid point of that line is then
measured up to the crowned point on the
board at the rib center and then documented.
4- The new bridge or cap is then set at a
higher plane than the original height, so as to
leave material to remove for setting the proper
5- Using the crown measurements, a new set
of down bearing specs are created, using
the Bearing spec chart.
Setting down bearing on
a new bridge…
1- With Bearing String secured to the Tuning area
or Agraff, of each specified note on the chart. The
bridge is then cut using a Wide kerf saw , to the
specified heights at different points along the
bridge. For example…. If you measured .100 crown
on the middle or longest rib, you would set the
bearing above on the bridge with the .080 gage, and
by the chart, note 88 would be set to 2/3 rds of that
figure, which would be approximately the .060
gage……. And so on…..
Gages are placed on top of the aliquot for each note
corresponding with the chart, for the correct down
bearing. The depth of each cut is finished, when the
tightened bearing string just makes contact with the
gage top, as it runs thru the new channel in the
Back bearing, is measured to about half of that of
the front specs…
2- More cuts are then made every 6" or so between
the original cuts, interpolating as you go.
3- The cap is then planed to meet all of the cuts,
blending them together, creating a smooth
tapered bridge cap, that can then be marked and
drilled for new pins, and restringing.
4- The cap is then Marked with punches and drilled
at the proper angles for the bridge pins.
5- The top of the bridge is then coated with black
graphite paint, Sawn , Cut and Notched.
6- Pins are then Inserted to the proper height.
7- The pins are now Filed flat and even.