Part 18 (1/2)

[Illustration: Fig 174]

[Illustration: Fig 175]

[Illustration: Fig 176]

[Illustration: Fig 177]

We next provide a sleeve or guard for our gage To do this we take a piece of hard brass bushi+ng 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 situdinal 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 froulate such protrusion by the screw _t_ To eth to which to cut the pivot _y_, Fig 171, we re, the175, up through the hole jewel, regulate the length by turning the sleeve _F_ until the ar 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 we171 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 Thethe pivot _s_ between the jaws _N N'_ as they hold the pivot

The cutting is done by sith

TURNING THE PIVOTS

We have now the pivot _y_ of the proper length, and what reht size We do not think it advisable to try to use a split chuck, although we have seen workmen drive the shell _A A'''_ out of the collet _D_ and then turn up the pivots _y z_ in said wire chuck To our judg 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 soinal cement, made and patented by James Bottum for his cement chuck, was made up of a rather complicated mixture; but all the substances really deood quality of shellac These ingredients are compounded in the proportion of 8 parts of shellac and 1 part of ultraht

HOW TO USE A CEMENT CHUCK

The shellac is melted in an iron vessel, and the ultramarine added and stirred to incorporate the parts Care should be observed not to burn the shellac While warm, the melted mass is poured on to a cold slab of iron or stone, and while plastic made into sticks about ” in dia 178]

[Illustration: Fig 179]

We show at Fig 178 a side view of the outer end of a cement chuck with a cylinder in position We co the pivot _z_ to rest at the apex of the hollow cone _a_, as shown There is so no ”tit” or protuberance in the center, but it is important it should be done A little practice will soon enable one to raver 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, rees The only way to insure perfect accuracy of centering of a cylinder in a ce 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 ce 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 th 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 space

The trouble which would ensue fro for such extra end shake would be that the lower edge of the half shell, 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 th 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 Thisthe distance with a Boley gage or a douzieme caliper