holder placed against the tail stock, after the back center has been removed. One end of the die-holder rests against the lathe bed. The tail stock should be loosened so that it can slide on the lathe bed. If the tail stock of the lathe is then firmly pressed against the back of the die-holder, with one hand, and the lathe head revolved forward by pulling the belt with the other hand the die will start squarely and the thread will run straight. Of course, the die should be opened so that this cut over the work will be as light as possible. The die can be closed down to size and again run over the work when the result will be a finished thread. The 3-inch thread will probably have to be cut by hand, champing the work in the jaws of the vise for that purpose, and running the die down the proper distance. When these rods are threaded they are ready for use in assembling the field punchings. -nter bed. e on mly _nd, belt the be as in d. _d, se, en 1 CHAPTER III FIELD PUNCHINGS One peculiarity which will be noticed in these punchings is the fact that one-half of them have short yoke pieces and the other half have long yoke pieces. This, however, will be found of immense advantage when the stage of winding the field is reached. The best way to build up the field is to take a piece of board and bore two 3-inch holes in it 1 inches apart. Into these two holes set the two side-bearing rods until the collars thereon rest against the board. Place a field punching with a long yoke piece on one of the side-bearing rods and a punching with a short yoke piece on the other rod. Next place a punching with a short yoke piece in position on top of the punching with the long yoke piece and a punching with a long yoke piece on top of the first punching with the short yoke piece. In this manner the entire field is to be built up with long and short yoke pieces alternating in each half of the field. When several layers of punchings have been built up the 1-inch field magnet key can be placed through the holes in the ends of the long yoke pieces which will hold the two halves of the field together. The field parts will then have the appearance shown in Fig. 8. Continue the building-up of the field punchings until the pile is just 2 inches high, at which time the 3-inch nuts should be screwed onto the side-bearing rods and the punchings thereby clamped up firmly together. If any of the punchings are found to have a "burr" on one side, caused by the operation of punching, it FIG. 7.-Field Punchings Showing Short and Long Yoke Pieces. should be removed carefully with a file in order that the punchings may fit together close and not cause an unevenness in them. After the punchings are all in place the field magnet bolts can be inserted to clamp the upper end of the field. together. If now the field magnet key, which passes through the ends of the long yoke pieces, be removed the two 0 FIG. 8.-Assembling the Field Punchings. halves of the field can be separated as shown in Fig. 10. In this cut one of the four field coil washers is shown. These washers are stamped out of sheet brass and are intended to place on the neck of the field punchings to form a sort of spool on which the field wire is wound. Four of these washers are required. At one end they are sheared apart, as shown, and thereby can be placed in |
