Pivoting Chuck
The Gem patent pivoting chuck, shown in Figs. 79 and 80, is intended as a substitute for wax for pivoting and like work. By the means of the ball b, placed between the two sliding sockets c c, with the several other parts as represented in Fig. 79, a combination of sliding and ball and socket movements in connection with a spring pump center, is obtained. A set of ten or more, supplementary chucks g, with different sizes of center holes, and attachment n, for all sizes of wheels, are furnished with each chuck. The supplementary chuck g, in the form of a small split chuck, is made to fit into a hole with taper mouth in the center of the ball b, and is drawn into place and the work fastened firmly in it by means of the binding nut m, which screws on to a projection extending outward from front side of the ball.
To use this chuck proceed as follows: Remove the nut m, and give freedom to the working parts by loosening the large back nut k. Then to bring the hole through the ball b, into line, spin the ball to center, first at the base of the projecting screw and then at the mouth of the hole through it, and in this position again fasten the parts, by tightening the nut k. Then give freedom to the pump center by slightly loosening the set screw j. When doing this, hold your finger against the front of the chuck, to prevent the center rod from shooting out of its place when freed. Then having placed a supplementary chuck g, of proper size, in its place in the chuck, and your work in it, with its back end resting properly in the countersink in the end of the pump center, fasten it there by screwing the cap m down snugly over it, using a small lever pin when necessary for this purpose, but not with undue force. The again loosen the nut k and spin the work to center at its outer end; and then tighten both the nut k and set screw j. In tightening the set screw j, make sure it is so tightened as to prevent the pump center from slipping from place when working. If from tightening the screw j, it is found that the work has been thrown in any degree away from true center, loosen the nut k, leaving the pump center fast, and again spin to center, and fasten as before. All of which after a little practice may be done, and the work be brought to absolute truth in a few moments.
In using attachment n for wheels, the nut m and chuck g are removed, and n substituted therefor; the work being held on the face of the attachment by flat headed screws that grip the arms of the wheel. For cylinder escape wheels a special attachment n is furnished. The best thing to use when spinning work to enter in the chuck, is a bit of peg wood of wedge shape at one end. The countersinks in the ends of the pump center should in all cases be carefully tested, and if need be trued up in the lathe in which the chuck is to be used. In doing this, use a good, fine-pointed sharp graver, and make sure the countersink is perfectly true. The same rules in regard to truth in the countersink, and having the work rest properly in it, are to be observed in using this chuck as when using wax.