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piece at the point where the cut is to end, and another hole. near the end at right angles to the first one through which the clamp screw is to pass. These holes are all made with a No. 42 twist drill.

The piece is next to be held in the vise and slitted with

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a hack saw until the slit cuts into the hole drilled for the purpose.

After the slitting is completed the hole through the end of the brush holder should be rebored with a No. 32 twist drill as far as the slit, to make a clearance hole for the 4-36 screw. The remaining portion of the hole should be tapped for the screw, using a 4-36 tap.

The brushes of this machine are of hard rolled brush copper and are furnished cut to the proper size.

Carbon brushes are not adapted for a machine of as low voltage as this one.

When the brush holders are assembled they must be

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carefully insulated from the rocker arm. This is done by the rubber bushing and fiber washers as shown in the detail drawing, Fig. 31.

The rubber bushings are forced into the 3-inch holes in the rocker arm. One of the fiber washers is placed on the threaded end of the brush holder and this portion is then pushed through the rubber bushing in the rocker arm. This forces the fiber washer up

against the shoulder of the brush holder.

The second fiber washer is then put on the threaded end and a nut screwed up behind it.

Before these parts are assembled they should be examined very carefully to see that no metal chips or filings are allowed to get in between the parts as they would cause short circuits.

Two brass nuts are supplied for each brush holder. One is to hold the brush holder in the rocker arm and the other is to use in clamping the flexible cord from the connection board.

CONNECTION BOARD

The connection board is made up of two pieces of hard fiber. The main piece is 3/16 inch thick and the other, which is only used as a backing to prevent the binding screws from touching the field punchings and thereby making a short circuit, is only 1/16 inch in thickness.

To lay off the holes in the thick piece of fiber place a short and a long field punching on the top of the piece

FIG. 32.-Detail Drawings of Connection Board.

of fiber and mark the two holes for the field magnet bolts. Draw a line between the centers of these two holes just marked and on this line midway between these two positions locate a point for the center binding screw. On each side of this position locate a point 9/16 inch away for the outer binding screws.

The holes for the field magnet bolts are drilled with a 3/16-inch drill.

The piece of thin fiber and also the brass name plate can be marked out and drilled.

These two 3/16-inch holes are the only ones required in the thin fiber and name plate.

The three holes for the binding screws should be drilled with a No. 42 twist drill and afterwards counter

FIG. 33.-Name Plate.

bored with a drill sufficiently large to give room for the screw heads, as shown in the detail drawing, Fig. 32.

The smaller section of these holes should then be tapped with a No. 4-36 tap and the screws inserted as shown. After the screws are inserted one of the No. 4 brass nuts should be run onto each screw and followed by a No. 4 milled head nut.

The name plate is a punching of sheet brass and gives a finish to the opposite side of the machine from the connection board, and also offers a location for the constructor's name if he desires it.

ARMATURE SHAFT

This piece requires very careful work in turning down to size, because of its small diameter compared with the length.

The work is all plain, straight turning, with the exception of the cutting of the thread for the 5/16-inch brass nuts. This threading of the shaft is best done in an engine lathe, but if care is exercised the thread may be run on

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FIG. 34.-Detail Drawings of Armature Shaft.

with a die, starting it as described for the side-bearing rods. This is to insure the die starting true.

The machine work on this piece is so simple that it is not deemed advisable to show the actual work other than as illustrated in the several diagrams showing the successive operations.

The first operation is to locate the position of the collar, or shoulder, against which the armature punchings are clamped. This is to be left the original diameter of the piece of steel. When this is marked the piece is turned down to a diameter of 5/16 inch from the end to

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