Gatan 656, User Manual, Page: 34 / 49

Performance Check
24 Dimple Grinder User’s Guide
Unscrew the Counterweight sufficiently to balance the Platform at this
point.
5. Screw the Counterweight in two full turns.
This applies the necessary load to overcome the stylus spring and the weight
of the wheel.
6. Lower the Platform onto the Micrometer end face.
The Dial Indicator needle will rotate clockwise and creep towards zero
when the dimple grinder base is gently tapped. If the needle does not reach
zero, increase the load by 1-g increments until the needle slowly and
smoothly reaches zero. If the needle rotates hard towards zero, reduce the
load until the needle settles within one division of zero.
7. Raise the Platform.
Firmly hold the Counterweight and rotate and slide the black load scale to
align the zeros.
It should be possible to position the Dial Indicator needle within one divi-
sion of zero by adjusting the Counterweight no more than ± 2g from the
load scale zero.
5.3 Eccentricity (Run-Out)
Excessive vertical movement of the Platform makes it impossible to accurately
monitor the progress of dimpling and to determine the final thickness. This ver-
tical movement is due to run-out (play in the wheel), which can be attributed to
either the axle, a specific wheel, or a combination of both. The axle must first be
tested without a wheel since any axle run-out would be added to any wheel run-
out, thus compounding the problem.
To check run-out of axle assembly
1. Remove any wheel that may be mounted to the axle.
Carefully clean the axle surface with a tissue.
Caution
:
Do not flood the axle with solvent, as this may wash grit into the axle
bearings.
2. Place the axle calibration post (Accessories Kit) into the centering ring
and place both on the Magnetic Table.
Use the cross hair of the microscope to center the post.
3. Set a Counterweight load of 20 g.