[Ill.u.s.tration: Fig. 174]
[Ill.u.s.tration: Fig. 175]
[Ill.u.s.tration: Fig. 176]
[Ill.u.s.tration: Fig. 177]
We next provide a sleeve or guard for our gage. To do this we take a piece of hard bra.s.s bushing wire about " long and, placing it in a wire chuck, center and drill it nearly the entire length, leaving, say, 1/10" at one end to be carried through with a small drill. We show at _F_, Fig. 174, a magnified longitudinal section of such a sleeve. The piece _F_ is drilled from the end _l_ up to the line _q_ with a drill of such a size that a female screw can be cut in it to fit the screw on the needle, and _F_ is tapped out to fit such a screw from _l_ up to the dotted line _p_. The sleeve _F_ is run on the screw _t_ and now appears as shown at Fig. 175, with the addition of a handle shown at _G G"_. It is evident that we can allow the pivot _s_ to protrude from the sleeve _F_ any portion of its length, and regulate such protrusion by the screw _t_. To employ this tool for getting the proper length to which to cut the pivot _y_, Fig. 171, we remove the lower cap jewel to the cylinder pivot and, holding, the movement in the left hand, pa.s.s the pivot _s_, Fig. 175, up through the hole jewel, regulate the length by turning the sleeve _F_ until the arm of the escape wheel _I_, Fig. 176, will just turn free over it. Now the length of the pivot _s_, which protrudes beyond the sleeve _F_, coincides with the length to which we must cut the pivot _y_, Fig. 171. To hold a cylinder for reducing the length of the pivot _y_, we hold said pivot in a pair of thin-edged cutting pliers, as shown at Fig. 177, where _N N"_ represent the jaws of a pair of cutting pliers and _y_ the pivot to be cut. The measurement is made by putting the pivot _s_ between the jaws _N N"_ as they hold the pivot.
The cutting is done by simply filing back the pivot until of the right length.
TURNING THE PIVOTS.
We have now the pivot _y_ of the proper length, and what remains to be done is to turn it to the right size. We do not think it advisable to try to use a split chuck, although we have seen workmen drive the sh.e.l.l _A A"""_ out of the collet _D_ and then turn up the pivots _y z_ in said wire chuck. To our judgment there is but one chuck for turning pivots, and this is the cement chuck provided with all American lathes. Many workmen object to a cement chuck, but we think no man should lay claim to the name of watchmaker until he masters the mystery of the cement chuck. It is not such a very difficult matter, and the skill once acquired would not be parted with cheaply. One thing has served to put the wax or cement chuck into disfavor, and that is the abominable stuff sold by some material houses for lathe cement. The original cement, made and patented by James Bottum for his cement chuck, was made up of a rather complicated mixture; but all the substances really demanded in such cement are ultramarine blue and a good quality of sh.e.l.lac. These ingredients are compounded in the proportion of 8 parts of sh.e.l.lac and 1 part of ultramarine--all by weight.
HOW TO USE A CEMENT CHUCK.
The sh.e.l.lac is melted in an iron vessel, and the ultramarine added and stirred to incorporate the parts. Care should be observed not to burn the sh.e.l.lac. While warm, the melted ma.s.s is poured on to a cold slab of iron or stone, and while plastic made into sticks about " in diameter.
[Ill.u.s.tration: Fig. 178]
[Ill.u.s.tration: Fig. 179]
We show at Fig. 178 a side view of the outer end of a cement chuck with a cylinder in position. We commence to turn the lower pivot of a cylinder, allowing the pivot _z_ to rest at the apex of the hollow cone _a_, as shown. There is something of a trick in turning such a hollow cone and leaving no "t.i.t" or protuberance in the center, but it is important it should be done. A little practice will soon enable one to master the job. A graver for this purpose should be cut to rather an oblique point, as shown at _L_, Fig. 179. The slope of the sides to the recess _a_, Fig. 178, should be to about forty-five degrees, making the angle at _a_ about ninety degrees. The only way to insure perfect accuracy of centering of a cylinder in a cement chuck is center by the sh.e.l.l, which is done by cutting a piece of pegwood to a wedge shape and letting it rest on the T-rest; then hold the edge of the pegwood to the cylinder as the lathe revolves and the cement soft and plastic. A cylinder so centered will be absolutely true. The outline curve at _c_, Fig. 178, represents the surface of the cement.
The next operation is turning the pivot to the proper size to fit the jewel. This is usually done by trial, that is, trying the pivot into the hole in the jewel. A quicker way is to gage the hole jewel and then turn the pivot to the right size, as measured by micrometer calipers. In some cylinder watches the end stone stands at some distance from the outer surface of the hole jewel; consequently, if the measurement for the length of the pivot is taken by the tool shown at Fig. 175, the pivot will apparently be too short. When the lower end stone is removed we should take note if any allowance is to be made for such extra s.p.a.ce.
The trouble which would ensue from not providing for such extra end shake would be that the lower edge of the half sh.e.l.l, shown at _e_, Fig.
171, would strike the projection on which the "stalk" of the tooth is planted. After the lower pivot is turned to fit the jewel the cylinder is to be removed from the cement chuck and the upper part turned. The measurements to be looked to now are, first, the entire length of the cylinder, which is understood to be the entire distance between the inner faces of the two end stones, and corresponds to the distance between the lines _v d_, Fig. 171. This measurement can be got by removing both end stones and taking the distance with a Boley gage or a douzieme caliper.
A CONVENIENT TOOL FOR LENGTH MEASUREMENT.
[Ill.u.s.tration: Fig. 180]
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 c.o.c.k 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 s.p.a.ce 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 c.o.c.k, 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 sh.e.l.lac is dissolved away. The balance to most cylinder watches is of red bra.s.s, 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 pota.s.sium 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.
[Ill.u.s.tration: Fig. 181]
In staking on the balance, care should be observed to set the banking pin in the rim so it will come right; this is usually secured by setting said pin so it stands opposite to the opening in the half sh.e.l.l. The seat of the balance on the collet _D_ should be undercut so that there is only an edge to rivet down on the balance. This will be better understood by inspecting Fig. 181, where we show a vertical section of the collet _D_ and cylinder _A_. At _g g_ is shown the undercut edge of the balance seat, which is folded over as the balance is rivetted fast.
About all that remains now to be done is to true up the balance and bring it to poise. The practice frequently adopted to poise a plain balance is to file it with a half-round file on the inside, in order not to show any detraction when looking at the outer edge of the rim. A better and quicker plan is to place the balance in a split chuck, and with a diamond or round-pointed tool scoop out a little piece of metal as the balance revolves. In doing this, the spindle of the lathe is turned by the hand grasping the pulley between the finger and thumb. The so-called diamond and round-pointed tools are shown at _o o"_, Fig. 182.
The idea of this plan of reducing the weight of a balance is, one of the tools _o_ is rested on the T-rest and pressed forward until a chip is started and allowed to enter until sufficient metal is engaged, then, by swinging down on the handle of the tool, the chip is taken out.
[Ill.u.s.tration: Fig. 182]
[Ill.u.s.tration: Fig. 183]
In placing a balance in a step chuck, the banking pin is caused to enter one of the three slots in the chuck, so as not to be bent down on to the rim of the balance. It is seldom the depth between the cylinder and escape wheel will need be changed after putting in a new cylinder; if such is the case, however, move the chariot--we mean the c.o.c.k attached to the lower plate. Do not attempt to change the depth by manipulating the balance c.o.c.k. Fig. 183 shows, at _h h_, the form of chip taken out by the tool _o o"_, Fig. 182.