cond, and third operations are on comparatively large
diameters, they should be done at the slow speed, handle _J_, Fig. 34,
being set to give that speed. While the turret slide is being returned
between operations 3 and 4, one of the spindle speed-changing dogs _N_
should be clamped to the rim of disk _D_ so as to change the spindle
speed to the fast movement. This speed is continued until the last
operation is completed, when a second dog is clamped in place to again
throw in the slow movement. The feed knock-off dog should also be
clamped in place on the disk to stop the machine at the completion of
the fifth operation, when the turret is in its rear position. This
completes the setting up of the machine. If the feed is finer than is
necessary, the feed change handle _K_ may now be moved to a position
which will give the maximum feed that can be used.

It has taken considerable time to describe the setting up of the machine
for this simple operation, but in the hands of a competent man it can be
done quite rapidly. While a simple operation has been referred to in the
foregoing, it will be understood that a great variety of work can be
done on a machine of this type. It is not unusual to see as many as ten
cutting tools operating simultaneously on a piece of work, the tools
being carried by the turret, cross-slide and back facing attachment. The
latter is operated from a separate cam applied to the cam-shaft and
acting through levers on a back facing bar which passes through a hole
in the spindle. In this back facing bar may be mounted drills, cutters,
facing tools, etc. for machining the rear face of a casting held in the
chuck jaws. Where extreme accuracy is required, a double back facing
attachment may be used, arranged with cutters for taking both roughing
and finishing cuts. The use of this attachment often saves a second
operation. This automatic chucking and turning machine is also adapted
for bar work, especially in diameters varying from 3 to 6 inches.

=Turning Flywheel in Automatic Chucking and Turning Machine.=--A typical
operation on the Potter & Johnston automatic chucking and turning
machine is illustrated in Fig. 40, which shows the machine arranged for
turning the cast-iron flywheel for the engine of a motor truck. The rim
is turned and faced on both sides and the hub is bored, reamed and faced
on both sides. The flywheel casting is held in a chuck by three special
jaws which grip the inside of the ri