Bushing Pivot Holes

American Watchmaker and Jeweler (1892)

The bush may be either a turned or tapped one. A bush is selected as small as the pivot will admit. Open the hole in the plate or cock and finish with a rat-tail file. Slightly taper the end of the bush with a fine file until it will fit the hole. With a knife score the bush just above the edge of the plate and press it firmly into the hole. Break off the bush at the point scored and drive it firmly into place by means of the bushing punch shown at Fig. 45, and you will find your bush is riveted firmly into the plate. Observe the endshake your pinion requires and make due allowance when finishing off your bushing. In bushing a plate, particularly where the bushing must be large, some watchmakers prefer to use a solid wire and drill the hole after fitting. If this method is followed be careful to see that you accurately center the work before drilling, and drill first with a small drill, subsequently passing through a larger one, or open up the hole by means of a small broach. It is always well to use bushing wire with a hole smaller than is ultimately required, and enlarging afterwards while the work is centered in the lathe. A tapped bushing is very firm, but unless the threads are well made is apt to be out of center. The closing hole punch shown in Fig. 45 often obviates the use of a bushing, if skillfully used. To Bush a Wheel. A watch will frequently stop because a wheel is improperly centered in itself, whereby one side will gear too deep, the other too shallow, into the pinion driven by it. Such a wheel likely is of the proper size and has good teeth, but the difficulty is its proper centering, when fitted to its pinion. The following will be found to be an easy way of correction. Take a piece of lead of about the thickness of a silver half dollar, and clip and file it round so that it will fit into one of the larger steps in a step chuck of an American lathe. Screw it fast into the lathe, and while revolving, center and drill a hole of about the size of a winding arbor. Then, with a graver, turn out a recess, the size and a trifle more than the thickness of the wheel, so that it will fit in exact, with its teeth touching the outside of the cut. Drive the wheel from its pinion, and broach out the center, so as to take a bush of sufficient length, which should be firmly riveted in and filed smooth on the lower side. Turn a small groove around the outside of the cut in the lead, crowd in the wheel, with a burnisher set as a gavel. This fixes the wheel perfectly true on the outside. Now center and drill, leaving a little to be turned with a fine polished graver, to fit the same pinion. Rivet on, and your wheel is all right.