Page 299 - Machinery Component Maintenance

Balancing of Machinery Components 281
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Figure 6-24. Rotor in center of arbor.

Figure 6-25. Rotor mounted outboard

eration. To prevent this, a hydraulically or mechanically expanding arbor
is ideal. If none is available, a set screw may do. A small, flat area
should be provided on the shaft for set screw seating.
If the rotor has a keyway, the arbor should be provided with a mating
key of the same length as the final assembly key. If the arbor has no key-
way, the void of the rotor keyway should be filled with a half-key having
the same length as the final assembly key, even if it differs from the
length of the keyway.
Threads are not a good locating or piloting surface. Sometimes a nut is
used to hold the rotor on the arbor (see Figure 6-26). The nut should be
balanced in itself and have a piloting surface to keep it concentric with
the arbor axis.

Error Analysis

The tighter the balance tolerance, the more important it is to keep all
working surfaces of the arbor as square and concentric as possible. Any