The power flows from the motor in the base to the cone-pulley by means of a belt. The belt can be adjusted to three or four positions to vary the spindle-speed. Fig. 12.15 gives the idea as to how the different spindle speeds can be obtained.
Various spindle speeds can be obtained by shifting the belt on different steps of the cone-pulley. The various spindle speeds, thus obtained can be further reduced by employing the back gear arrangement. The very much reduced speeds are normally used for cutting threads.
During the normal course, when the gear B is disengaged by shifting the lever F, and the pin is engaged, the cone-pulley, gear A, bull gear and the spindle will rotate as one body. When reduced spindle speeds are required, then pin G is taken out which disengages the bull gear from cone-pulley and engages gear B with gear A through lever F. It will cause the gear C to engage with gear D. Power will now flow from the cone-pulley to gear A, then to B and finally to bull gear D. In this way, the spindle will revolve at lesser speed.
