Fig. 6. Side View showing Relative Positions of Gage and Work
Setting the Tailstock Center with a Caliper Tool.—Another method of setting the tailstock center for taper turning is illustrated in [Fig. 5]. The end of an engine piston-rod is to be made tapering as at A and to dimensions a, b, c and d. It is first turned with the centers in line as at B. The end d is reduced to diameter b up to the beginning of the taper and it is then turned to diameter a as far as the taper part c extends. The tailstock center is next set over by guess and a caliper tool is clamped in the toolpost. This tool, a side view of which is shown in [Fig. 6], has a pointer p that is free to swing about pivot r, which should be set to about the same height as the center of the work. The tailstock center is adjusted until this pointer just touches the work when in the positions shown by the full and dotted lines at C, [Fig. 5]; that is, until the pointer makes contact at the beginning and end of the taper part. The travel of the carriage will then be parallel to a line x—x, representing the taper; consequently, if a tool is started at the small end, as shown by the dotted lines at D, with the nose just grazing the work, it will also just graze it when fed to the extreme left as shown. Of course, if the taper were at all steep, more than one cut would be taken.
Fig. 7. Obtaining Tailstock Center Adjustment by use of Square
If these various operations are carefully performed, a fairly accurate taper can be produced. The straight end d is reduced to size after the tail-center is set back to the central position. Some mechanics turn notches or grooves at the beginning and end of the tapering part, having diameters equal to the largest and smallest part of the taper; the work is then set by these grooves with a caliper tool. The advantage of the first method is that most of the metal is removed while the centers are in alignment.