Page 297 - Machinery Component Maintenance

Balancing of Machinery Components 279

1. Mount the adapter to the workpiece shaft using a full key in the
shaft keyway and fill the half-key void in the opposite side of the
adapter with a half-key (see Figure 6-22B). Balance the assembly
by adding balancing clay to the workpiece.
2. Index the adapter 180” on rotor shaft (see Figure 6-22C). If the
adapter is out of balance, it will register on the balancing machine
instrumentation. Note the gram-inch unbalance value in the plane
closest to the adapter. Eliminate half of the indicated unbalance by
adding clay to the adapter, the other half by adding clay to the work-
piece.
3. Index the adapter 180” once again, back to the position shown in
Figure 6-22, and check unbalance indication. Repeat correction
method outlined above. Then replace clay on adapter with perma-
nent unbalance correction, such as drilling, grinding, etc., on oppo-
site side.

If it is not possible to reduce the unbalance in the adapter to a satisfac-
tory level by this method, it is an indication that the tolerances on fit di-
mensions are not adequate.
This is the method most commonly used in European industry. Shafts
are balanced with full keys and mating components without a key. To bal-
ance the end-drive adapter using this method, proceed as follows:

1. Place a full key into the keyway of the workpiece shaft (see Figure
6-23A). Mount adapter to the workpiece shaft, leaving the opposite
half-key void in the adapter empty (see Figure 6-23B). Balance the
assembly using balancing clay.
2. Follow the index balancing procedure outlined in paragraphs 2 and
3 of the half-key method.

Balancing Arbors

Definition

A balancing arbor (or mandrel) generally is an accurately machined
piece of shafting on which rotors that do not have journals are mounted
prior to balancing. Flywheels, clutches, pulleys and other disc-shaped
parts fall into this category. Arbors are employed on horizontal as well as
vertical balancing machines. Particularly when used on the latter, they
are also referred to as “adapters,” “fixtures,” or “tooling.”
Since an arbor becomes part of the rotating mass being balanced, sev-
eral criteria must be carefully observed during its design, manufacture,
and use.