Version 1.05 March 2020
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2.1.5 THE PLATEN
The Platen is permanently attached to the Spindle
—a sub-assembly that rides in permanently lubricated ball
bearings. When a lap is placed onto the Platen, take care that the undersurface of the lap is clean and is held
down by the Safety Nut.
2.1.6 THE LAP HOLD-DOWN NUT
(Safety Nut)
The Lap Hold-Down Nut is cinched down to hold the lap in place. It is machined of Delrin, which is soft enough
to prevent damage to a gem which is accidentally bumped
(the reason it is called a “Safety Nut”). It should be
adjusted firmly to hold the Lap in place
—the resilience of the Delrin Material will snug into firm position.
2.1.7 THE SPEED CONTROL
The variable electronic speed control converts AC current to DC, which the motor requires, and of course sets
the speed.
The left-side Switch is a toggle for ON-OFF. The right-side switch is for selecting clockwise (CW) or counter-
clockwise (CCW) lap rotation -- it has a central off position and two directional positions.
The central knob is a speed selector. The incremental positions of the speed selector are not exactly linear but
may be considered as each increment providing an added 100 RPM up to number 7 (700 RPM at that point),
and approximately 50 RPM per increment on the remainder of the dial. The top speed is approximately 1850
RPM. When using the directional switch, set the rotation so that the lap direction is not running into the gem.
When changing the lap direction, the motor should be off or running at a low speed. Repeated changing of
direction at high speed tends to demagnetize the motor, which results in higher speeds, but lower torques.
Don't worry about the occasional forgetting of this rule--just don't flick the switch back and forth for fun. The
speed selector can be at any setting when turning the motor on or off.
