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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
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
position on the completed field by springing the cut portions apart sufficient to force them over the neck of the field. In Figures 1, 2, 3, and 4 these washers are shown in proper position. When in place the washers are supported by the projections on the field punchings.
The field is now ready for winding but it is preferable to finish all of the machine work and assemble the parts to see that all are correct before the winding is attempted. CHAPTER IV
The bearings are cast from a composition which makes a very smooth-running bearing for the armature shaft.
On one side of these castings is a projecting hub which we shall utilize in chucking the parts in the lathe.
Place this hub in the chuck so that the piece is held in the chuck jaws as shown in Fig. 12, but, before the jaws are screwed down very tight set the slide rest with a tool standing parallel with the lathe bed and bring the point of the tool up to the side of the casting at the boss, where one of the holes for the side-bearing rod is to be drilled. Let the point of the tool just touch the casting, then revolve the lathe with the hand until the boss on the opposite end of the casting comes over to the tool. If both bosses touch the tool equally, all right; if not, then the casting should be tapped very lightly and again tested. When both ends of the casting touch the point of the tool equally the jaws of the chuck should be tightened, after which it is well to make another test to see that the casting has not shifted its position.
Now be sure that your slide rest sets true with the lathe and, using a tool with a .small rounded point, placed at the proper height, take a light cut across the outer end of the hub of the casting and also across the two projecting bosses for the side-bearing rods. These two last surfaces should stand lower than the end of the hub as shown in the top view of the bearing, Fig. II.
Next use a centering tool or a pointed hand tool, and, with the work revolving at a good speed, carefully locate
the center of the hub. In this case the center must be marked very accurately that the drill to be used may start true.
The hole in this bearing is of small diameter and a proportionally great length, and there is danger of the hole being so far out of line, when the drill reaches the inner end of the hub, that it cannot be trued up with a boring tool. In drilling a piece of work held in the