The button e, Fig. 18, is next made on centers and the thread chased. Then the plunger d is made; being roughly turned on centers to say, within 1/16 inch of finish size. The long hole in the plunger is now drilled, bored, and threaded, by holding one end in the steady rest and the other end on the live center, a lacing in connection with a lathe dog being used to hold the plunger against the live center. When using a lacing, the faceplate should be loosened several threads, and, after the dog on the end of the plunger is securely tied to the faceplate, the plate is screwed against the shoulder of the spindle, which tightens the lacing and securely holds the plunger against the live center. After the hole is bored and threaded the button is screwed into the end of the plunger, and, placing the dog on the button, the plunger is turned perfectly straight and smooth and so it fits the hole in the cap. The end of the plunger is turned J inch smaller in diameter for a distance of 1 inch as in d, Fig. 17, and also in Fig. 18.
The lathe spindle is now locked and four unequally spaced grooves/ are cut in the plunger the entire length but not deep enough to touch the reduced diameter at the end of the plunger. The grooves are to act as guides when babbitt is poured around the plunger, and the object of unequally spacing is to prevent returning the plunger in the babbitt bearing in any position but that in which the punch and the die line up.
The steady rest is now brought to bear on the reduced diameter, the recess g is bored for the punch holder h, and the shoulder i is turned to the desired diameter to act as a centrally locating member for the blanking diej. The diameter of the plunger is of course governed by the outside diameter of the blanking die which is attached to plunger, for it is obvious that a die larger than the plunger could not be withdrawn from the frame after the babbitt surrounds the plunger.
The points to be observed in making the plunger are: absolute straightness; grooves perfectly straight and free from chatter marks, and each one of a uniform depth its entire length; and the finished plunger absolutely free from blowholes caused by casting.
It is immaterial in which order the remaining parts are made, as they will be only partly finished when turned to size in the lathe. The blanking die j, Fig. 17, should be made from the end of a bar gripped in a chuck and the large diameter of the die should be on the outer end, as in Fig. 19a, so that the recess can be fitted to the step on the plunger. The hole k, Fig. 17, should be bored at the same setting, and the diameter of the hole must be smooth and of the exact diameter desired at a, Fig. 15. The die is cut from the rod with a cutting-oflf tool in the lathe.
The piercing-punch holder A, Fig. 17, is also turned on the end of the rod, and the step L fitted to the recess in the end of the plunger. The upper stripper M, Fig. 17, should be turned on centers as at b, Fig. 19, and left on the piece of rod, for the next operation on the stripper is to mill to form the projections on the balance wheel, as shown at M, Fig. 17.
Instead of making the blanking punch a, Fig. 17, solid, then filing out the recess at each side of the crossbar, which would be a difficult job, the blanking punch is turned in the manner shown in a, Fig. 19. The hole N is bored smooth to the exact diameter of b, Fig. 15, and the outside of the punch is turned to exactly the same diameter as c, Fig. 15. The large diameter of the blanking punch is turned to fit the recess a in the base. Fig. 16, after which the punch is cut from the rod.
A die to produce the balance wheel cannot be readily ground to shape after hardening, therefore, an oil-hardening make of steel should be used, which will eliminate many chances of the die changing shape and will permit of machining the parts to exact size while soft.
The piece o, Fig. 17, which is milled to the shape of the crossbar and when completed is inserted inside of the blanking punch, is turned on the end of the rod with the small diameter on the end of the rod. The diameter of the small end must be left 1/16 inch larger than the hole through the blanking punch, for the blanking punch is splined to a depth of 1/32 inch on each side, as in the enlarged section at P, Fig. 17, to position the ends of the crossbar as shown in the assembled sketch Q of the end view of the blanking punch.