y without special tools or equipment.

As those familiar with this machine know, the longitudinal movements of
the turret as well as the transverse movements of the headstock are
controlled by positive stops. The headstock of this machine has ten
stops which are mounted in a revolving holder and are brought into
position, as required, by manipulating a lever at the front. The stops
for length, or those controlling the turret travel, are divided into two
general groups, known as "A" and "B". Each of these groups has six stops
so that there are two stops for each of the six positions or stations of
the turret, and, in addition, five extra stops are available for any one
tool, by the engagement of a pin at the rear of the turret. The change
from the "A" to the "B" stops is made by adjusting lever _L_, Fig. 26,
which also has a neutral position.

[Illustration: Fig. 25. Third Operation--Turning Recess at Rear End;
Tool is shown withdrawn]

After the box-tool for the roughing cut, shown at work in Fig. 23, has
reached the end of its travel, further movement is arrested by a stop of
the "A" group. The outside turning tool is then withdrawn by operating
lever _E_ and the turret is run back and indexed to the second station,
thus bringing the threading attachment into position. The surface speed
of 130 feet per minute which is used for turning is reduced to about 30
feet per minute for threading by manipulating levers _H_, Fig. 24. After
the turret is located by another stop of the "A" group, the threading
attachment is made operative by depressing a small plunger _I_, which
connects a vertical driving shaft from the spindle with the splined
transmission shaft _J_. A reciprocating movement is then imparted to the
thread chaser _t_ which advances on the cutting stroke and then
automatically retreats to clear the thread on the return. This movement
is repeated until the thread is cut to the proper depth, as determined
by one of the stops for the headstock. While the thread is being cut,
the carriage is locked to the bed by the lever _N_, Fig. 26. It was
found necessary to perform the threading operation before taking the
outside finishing cut, owing to a slight distortion of the shell wall,
caused by the threading operation.

[Illustration: Fig. 26. Fourth Operation--Finishing the Bore and
Outside]

After the thread is finished, the turret is turned to the third station
as shown in Fig. 25, and tool _K_ for the inner recess