OPERATION DRIVE The headstock gear train is driven from a two speed electric motor through standard vee belts and pulley drives. STARTING When correctly tensioned, belts can be deflected I in. when pressed at a point midlength between the motor and headstock pulleys, After an initial period of service (between 150 and 200 hours of operation) it may become necessary to re- adjust the tension of the driving belt to eliminate slap, vrbration or slip due to belt stretching. Tension adjustment can be made any time by screwing down the two bolts retaining the front of the motor platform.
Rotation of the main spindle is controlled from the front of the headstock by means of the starting lever(1), Pull the startirtg lever upward. This action will start the motor through an air brake starter;the starting lever will remain in this position until it is moved downward to stop spindle rotation. The starting mechanism incorporates a no-volt re- lease. In the event of an electrical supply failure, the machine can only be restarted by first moving the control lever to the OFF position and then starting in the normal manner. Correct operation of the no-volt release should be checked from time to tirrrb, as described in Section ELECTRICAL WlRlNG.
Access to these two bolts is gained from the back of the motor compartment at the headstock end of the machine after removal of the louvred cover panel. The drive is completely enclosed in an end guard to avoid the possibility of motor failure due to chips or coolant splashing, STOPPING To stop the spindle, return the starting lever to the original or OFF position. On direct start machines, downward pressure on the starting lever operates a two-shoe Ferodo lined brake inside the driving pulley which causes the spindle to stop instantly. REVERSE On machines supplied for operafion on 3-phase A.C.
supply (only) rotation of the main spindle is readily reversed by means of the finger-tip reversing switch (4) which is inset in the starting lever. Because of the use of the American long taper spindle nose there is no possibility of the chuck or faceplate running off when the spindle is rapidly reversed or stopped ; prov- iding, of course, that these have been correctly fitted. HEADSTOCK SPEED SELECTION Spedd selection is by means of two levers on the top of the headstock (2) and one lever on the front (3). Each lever has two positions, providing eight spindle speeds as shown on the data plate; but this range is increased to sixteen speeds by the use of a two-speed motor.
The two-speed control switch for the motor is incorporated into the headstock controls (4). Lever n o s i f i o n s a n d a c h a r f o f f h e s n p c d s a r p s h n w n i n f h e