Fig. 752.
Another method is shown in [Fig. 751], in which a clamp in two parts is employed, the driving-pins p fitting into two holes equidistant from the lathe centre, while loosening one bolt, j or k, and tightening the other is resorted to, to equalize the driving contact on the two arms, but in this case again there is no certainty that the two pins will drive equally, and there is danger of drawing the work somewhat out of true. Another form is shown in [Fig. 752], the idea being to equalize the pressure of the driving pins, by means of the four screws, but here again, there is no means of knowing whether the driving pressure is equalized.
Fig. 753.
The best form of driver is shown in [Fig. 753], which represents a Clement’s driver. The driving-plate f has four slots; two of them, a and b, pass entirely through this plate to admit bolts c d, which have a shoulder, so that they may be secured firmly to the lathe face plate, but which are an easy fit in the plate f, so as to permit it to move upon the lathe face plate. The other two are T-shaped slots to receive nuts, into which the pins p p are to be screwed. The bolts c d drive f, and the pins p drive the work, the freedom of the plate e to move upon the lathe face plate permitting this strain-equalizing action of the driving-plate and driving-pins.
