With the double-spindle flat turret lathe, each operation is a double operation, and the speeds are varied according to the nature of the cut; thus, if at one position of the turret, the tools are required to rough out the work, this may be done rapidly, for it has no bearing on the other operations that are subsequently performed. Furthermore, if the following operation has to be performed with great care, this may be done without reducing the speed of the less exacting operations.
Fig. 32. Potter & Johnston Automatic Chucking and Turning Machine
Automatic Chucking and Turning Machine.—The chucking and turning machine shown in [Fig. 32] is automatic in its operation, the feeding of the tools, indexing of the turret, etc., being done automatically after the machine is properly arranged, and the work is placed in the chuck. This machine is adapted to turning and boring a great variety of castings, forgings or parts from bar stock, and it is often used in preference to the hand-operated turret lathe, especially when a great many duplicate parts are required. It is provided with mechanism for operating the cross-slide, feeding the turret slide forward, returning it rapidly, rotating the turret to a new position, and feeding it forward quickly for taking a new cut. The cross-slide and turret-slide movements are effected by cams mounted on the large drum E seen beneath the turret, while the various speed and feed changes are effected by dogs and pins carried on disk D which is keyed to the same shaft that the cam drum is mounted upon. This shaft with the cam drum and governing disk D, makes one revolution for each piece of work completed. The cams for operating the turret slide are mounted upon the periphery of drum E. The roll which engages the angular faces of these cams and imparts movement to the turret is carried by an intermediate slide which has rack teeth engaging a pinion on the square shaft C. By turning this shaft with a crank, the position of the turret-slide, with relation to the cam, may be adjusted for long or short work and long or short tools, as may be required.
Fig. 33. Rear View of Machine showing the Cross-slide Mechanism, Driving Gearing, etc.