A pair of common pinion calipers slightly modified makes as good a pair of calipers for length measurement as one can desire.  This instrument is made by inserting a small screw in one of the blades—­the head on the inner side, as shown at f, Fig. 180.  The idea of the tool is, the screw head f rests in the sink of the cap jewel or end stone, while the other blade rests on the cock over the balance.  After the adjusting screw to the caliper is set, the spring of the blades allows of their removal.  The top pivot z of the cylinder is next cut to the proper length, as indicated by the space between the screwhead f and the other blade of the pinion caliper.  The upper pinion z is held in the jaws of the cutting pliers, as shown in Fig. 177, the same as the lower one was held, until the proper length between the lines d v, Fig. 171, is secured, after which the cylinder is put back into the cement chuck, as shown at Fig. 178, except this time the top portion of the cylinder is allowed to protrude so that we can turn the top pivot and the balance collet D, Fig. 171.

The sizes we have now to look to is to fit the pivot z to the top hole jewel in the cock, also the hairspring seat D and balance seat D’.  These are turned to diameters, and are the most readily secured by the use of the micrometer calipers to be had of any large watchmakers’ tool and supply house.  In addition to the diameters named, we must get the proper height for the balance, which is represented by the dotted line b.  The measurement for this can usually be obtained from the old cylinder by simply comparing it with the new one as it rests in the cement chuck.  The true tool for such measurements is a height gage.  We have made no mention of finishing and polishing the pivots, as these points are generally well understood by the trade.

REMOVING THE LATHE CEMENT.

One point perhaps we might well say a few words on, and this is in regard to removing the lathe cement.  Such cement is usually removed by boiling in a copper dish with alcohol.  But there are several objections to the practice.  In the first place, it wastes a good deal of alcohol, and also leaves the work stained.  We can accomplish this operation quicker, and save alcohol, by putting the cylinder with the wax on it in a very small homeopathic bottle and corking it tight.  The bottle is then boiled in water, and in a few seconds the shellac is dissolved away.  The balance to most cylinder watches is of red brass, and in some instances of low karat gold; in either case the balance should be repolished.  To do this dip in a strong solution of cyanide of potassium dissolved in water; one-fourth ounce of cyanide in half pint of water is about the proper strength.  Dip and rinse, then polish with a chamois buff and rouge.

[Illustration:  Fig. 181]