Fig. 26. Fourth Operation—Finishing the Bore and Outside
Fig. 27. Fifth Operation—Rounding Ends, Scoring Large End, and Cutting Off
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.
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 The outside turning tool is then withdrawn by operating lever E and the turret is run back and indexed to the second station, thus bringing the threading attachment into position.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.
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 B, [Fig. 22], is brought into position and fed to the proper depth, as determined by another cross-stop. The turret is also locked in position for this operation. The finishing cuts for the bore and the outside are next taken by a box-tool which is shown near the end of its cut in [Fig. 26]. This box-tool is similar to the one used for roughing, but it is equipped with differently shaped cutters to obtain the required finish. The outside turning tool has a straight cutting edge set tangent to the cylindrical surface and at an angle, while the boring tool has a cutting edge of large radius. An end view of this box-tool is shown in [Fig. 27]. A reduced feed is employed for the finishing cut, and the speed is increased to 130 feet per minute, which is the same as that used for roughing.
During the next and final operation, the turret, after being indexed to the position shown in [Fig. 27], is first located by a stop of the “A” group so that the cutting-off tool R in front can be used for rounding the corner b, [Fig. 22]. The stop lever L is then shifted and the turret is moved to a second stop of the “B” group. The corner c is then rounded and the shell is scored at d by two inverted tools S and T at the rear, after which the finished work is severed by the cut-off tool at the front. The cross-movement of these three tools is controlled by positive stops on the cross-slide, and the latter is moved to and fro by hand lever O. After the shell is cut off, the stop M, mounted on the turret, [Fig. 26], is swung into position, and the tube is automatically fed forward to the swinging stop by the roll feed, as soon as the chuck is released by operating lever Q. This completes the cycle of operations. A copious supply of lubricant is, of course, furnished to the tools during these operations, and the two boring-tool shanks are hollow so that lubricant can be forced through them and be made to play directly upon the cutters.