The gear train, shown in Fig. See right picture, transmits drive to
the Lead screw. The lead Screw acts as a worm and by
Operating the Auto Feed lever, which engages a nut with the lead
screw, drive is transmitted to the carriage/saddle and
consequently the cutting tool. Thereby providing a power feed
for thread cutting or general turning operations. The rotational
speed of the lead screw, and hence the rate of feed of the cutting
tool, is determined by the gear configuration. This is explained in
greater detail under "Screw cutting".