The forward movement of the slide for each position of the turret is controlled by stops at F, which are set to suit the work being turned. When parts are being turned from bar stock, the latter passes through the hollow spindle of the headstock and extends just far enough beyond the end of the spindle to permit turning one of the parts. The bar is held while the turning tools are at work, by a chuck of the collet type at G. This chuck is opened or closed around the bar by turning handwheel H. After a finished part has been cut off by a tool held in cross-slide J, the chuck is released and further movement of wheel H causes ratchet feed dog K, and the bar which passes through it, to be drawn forward. This forward movement is continued until the end of the bar comes against a stop gage held in one of the turret holes, to insure feeding the bar out just the right amount for turning the next piece. On some turret lathes, the lever which operates the chuck also controls a power feed for the bar stock, the latter being pushed through the spindle against the stop.
The machine illustrated has a power feed for the cross-slide as well as for the turret. The motion is obtained from the same shaft L which actuates the turret slide, but the feed changes are independent. The cross-slide feed changes are varied by levers M and those for the turret by levers N. For many turret lathe operations, such as turning castings, etc., a jawed chuck is screwed onto the spindle and the work is held the same as when a chuck is used on an engine lathe. Sometimes chucks are used having special jaws for holding castings of irregular shape, or special work-holding fixtures which are bolted to the faceplate. The small handle at O is for moving the cross-slide along the bed when this is necessary in order to feed a tool sidewise.
This particular machine is driven by a motor at the rear of the headstock, connection being made with the spindle through gearing. The necessary speed changes are obtained both by varying the speed of the motor and by shifting gears in the headstock. The motor is controlled by the turnstile P and the gears are shifted by the vertical levers shown.
While many of the features referred to are common to turret lathes in general, it will be understood that the details such as the control levers, arrangement of stops, etc., vary on turret lathes of different make.
Figs. 2 and 3. Diagrams showing Turret Lathe Tool Equipment for Machining Automobile Hub Casting