Sharp SH-920 Instruction Manual page 34

3.3.3 The spindle cartridge assembly are designed to have a life of
operation more than 10 years under normal operation, please should
not disassemble it without our advice.
3.3.4 Because of the very high spindle running speed, the wheel must be
well balanced. Otherwise spindle vibration will be resulted and
unable to get good surface finish. A balanced wheel assembly will
lose its balance during grinding operation owing to its wear. It is
advisable to rebalance the wheel assembly periodically.
Grinding wheel is intended to absorb humidity and coolant, it is advisable
not to start coolant supply when the wheel is not running. Otherwise the
wheel will absorb liquid on its bottom side only and make it out of balance. If
the wheel is allowed to stand for any length of time coolant will be collected
at its lowest side. Unbalance will also be resulted, if the wheel is not allowed
to idle running some length of time after the completion of grinding
operation. The purpose of idle running is essential to throw-off coolant by
centrifugal force.
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