Fig. 762.
[Fig. 762] represents a driver of this kind having a sliding jaw so that it may be set for different sizes of bolt heads. When the driving end of the work is threaded an ordinary dog or driver cannot be used because its screw would damage the thread on the work. A common method of overcoming this difficulty is to place over the ring a split ring of copper, or to place on it two nuts, putting a common dog on the end nut. It is better, however, to use a driver, threaded part of the way through, as in [figure 762] (from The American Machinist) and to screw it upon the work.
Fig. 763.
[Fig. 763] represents a very useful form of work driver designed by Mr. William A. Lorenz. It consists of two jaws a, a held together by two screws, and threaded to receive two driving screws d, e in the figure, which enable it to be used to hold work to the live centre as is necessary when using the steady rest, as is shown in the figure, in which b represents the work and c the jaws of the steady rest. It is obvious that the dog may be thus employed to chuck work independently of the steady rest, because the live centre may be removed, and the face of the work held against the face of the chuck, the short screws h being used instead of the long ones d, e.
If the carrier is used to simply drive the work without clamping it to the live centre or face plate, one or both of the screw pins j, k may be used in place of bolts d, e, the carrier being balanced when both are used.