Fig. 508.
In [Fig. 508] is shown a back view of a Pratt and Whitney weighted lathe having a Slate’s taper turning attachment, the construction of which is as follows:—Upon the back of the lathe shears are three brackets having their upper surfaces parallel with and in the same plane as the surface of the lathe shears. Pivoted to the middle bracket is a bar which has at each end a projection or lug fitting into grooves provided in the end brackets, these grooves being arcs of a circle whose centre is the axis of the pivot in the middle bracket.
The end brackets are provided with handled nuts upon bolts, by which means the bar may be fixed at any adjusted angle to the lathe shears. Upon the upper surface of the bar is a groove or way in which slides a sliding block or die, so that this die in traversing the groove will move in a straight line but at an angle to the lathe bed corresponding to the angle at which the bar may be adjusted. The slide rest upon being connected by a bar or rod to the die or sliding block is therefore made to travel at the same angle to the lathe bed or line of centres as that to which the bar is set. The method of accomplishing this in the lathe, shown in [Fig. 508], is as follows:—
Fig. 509.
In [Fig. 509] a is the bar pivoted at c upon the centre bracket b; e is the sliding block pivoted to the nut bar f. This nut bar carries the cross-feed nut, which in turn carries the feed screw and hence the tool rest. When the nut bar is attached to the sliding block to turn a taper it is free to move endways upon the lower part of the carriage in which it slides, but when the taper attachment is not in use the bar is fastened to the lower part of the carriage by a set screw.
The screw at d is provided to enable an accurate adjustment for the angle of the bar a. g and h are screws simply serving to adjust the diameter to which the tool will turn after the manner shown in [Fig. 588], g being for external and h for internal work.