The most critical step in installing the boring bar is making the bar plumb. If the bar
is not installed plumb, there will be gaps between the wicket gate sealing surfaces,
and in severe cases, the top and bottom surfaces of the gates may bind against the
facing plates. There are several procedures for plumbing the boring bar. The best
one for a particular unit will depend on the size and design.
Plumb wires can be used to plumb the bar. Ideally, four wires hung 90 degrees
apart would be used to allow for a check in the accuracy of the readings.
Realistically, there is rarely room for four wires. Normally, a wire hung through the
center of the unit, which is also used for checking the radial position of the bar, and
wires hung in the holes on either side of the hole being bored are used. Readings
should be taken several times to verify their accuracy.
If the bushing diameter is large enough, another method can be used with plumb
wires. This method uses a single wire hung through the bushing bores. The wire is
centered in the intermediate bushing, and reference measurements are taken from the
bushings to the wire. These reference measurements can then be used to position
the boring bar in the same position as the wire. Since the wire hangs plumb, the
boring bar will be plumb.
If the facing plates are within tolerances for parallelism but not levelness, the wicket
gates should be bored perpendicular to the facing plates and not plumb. Some
fixture or jig will have to be fabricated to make the boring bar perpendicular to the
plates. If the facing plate surfaces are smooth, a dial indicator attached to the boring
bar can be used to position the bar.
If it was determined that the top two bushings were within tolerance for plumb and
perpendicularity but the bottom bushing was not, the boring bar can be set up by
centering it in the top two bushings. Plumb, radial position, and distance between
gates still should be checked by plumb wires or other means.
lists tolerances for wicket gate installation. These standards are only
intended to be used as a guide since variables in the construction of the unit may-
make larger or smaller tolerances acceptable.
Units with nonadjustable guide bearings require the precise placement of the bearing
brackets. Bearing brackets and other components that need to be held in an exact position
many times use dowel pins. The boltholes on these components are usually oversized to
allow the parts to be shifted slightly during the alignment process. The dowels have a very
tight fit to prevent the components from shifting once the part is positioned.