Setting the Tailstock Center with a Square.—Still another method of adjusting the tailstock for taper turning, which is very simple and eliminates all figuring, is as follows: The part to be made tapering is first turned cylindrical or straight for 3 or 4 inches of its length, after the ends have been properly centered and faced square. The work is then removed and the tailstock is shifted along the bed until the distance a—b between the extreme points of the centers is exactly 1 foot. The center is next offset a distance b—c equal to one-half the required taper per foot, after which a parallel strip D, having true sides, is clamped in the toolpost. Part D is then set at right angles to a line passing from one center point to the other. This can be done conveniently by holding a 1-foot square (preferably with a sliding head) against one side of D and adjusting the latter in the toolpost until edge E of the square blade is exactly in line with both center points. After part D is set, it should be clamped carefully to prevent changing the position. The angle between the side of D and an imaginary line which is perpendicular to axis a—b is now equal to one-half the angle of the required taper.
Fig. 8. Second Step in Adjusting Tailstock Center by use of Square
The axis of the part to be turned should be set parallel with line E, which can be done by setting the cylindrical surface which was previously finished, at right angles to the side of D. In order to do this the work is first placed between centers, the tailstock being shifted along the bed if necessary; the tail-center is then adjusted laterally until the finished cylindrical surface is square with the side of D. A small try-square can be used for testing the position of the work, as indicated in [Fig. 8]. If the length of the work is less than 1 foot, it will be necessary to move the center toward the rear of the machine, and if the length is greater than 1 foot, the adjustment is, of course, in the opposite direction.
The Taper Attachment.—Turning tapers by setting over the tailstock center has some objectionable features. When the lathe centers are not in alignment, as when set for taper turning, they bear unevenly in the work centers because the axis of the work is at an angle with them; this causes the work centers to wear unevenly and results in inaccuracy. Furthermore, the adjustment of the tailstock center must be changed when turning duplicate tapers, unless the length of each piece and the depth of the center holes are the same. To overcome these objections, many modern lathes are equipped with a special device for turning tapers, known as a taper attachment, which permits the lathe centers to be kept in alignment, as for cylindrical turning, and enables more accurate work to be done.
Fig. 9. A Lathe Taper Attachment