. 1, is composed of wrought sheet
iron, which may be of any thickness so that, when several pieces
are placed together, they will make a frame 3/4 in. thick. It is
necessary to layout a template of the frame as shown, making it
1/16 in. larger than the dimensions given, to allow for filing to
shape after the parts are fastened together. After the template is
marked out, drill the four rivet holes, clamp the template, or
pattern, to the sheet iron and mark carefully with a scriber. The
bore can be marked with a pair of dividers, set at 1/8 in. This
will mark a line for the center of the holes to be drilled with a
1/4-in. drill for removing the unnecessary metal. The points
formed by drilling the holes can be filed to the pattern size. Be
sure to mark and cut out a sufficient number of plates to make a
frame 3/4 in. thick, or even 1/16 in. thicker, to allow for
finishing.

After the plates are cut out and the rivet holes drilled, assemble
and rivet them solidly, then bore it out to a diameter of 2-3/4
in. on a lathe. If the thickness is sufficient, a slight finishing
cut can be taken on the face. Before removing the field from the
lathe, mark off a space, 3-3/8 in. in diameter, for the field core
with a sharp-pointed tool, and for the outside of the frame, 4-1/2
in. in diameter, by turning the lathe with the hand. Then the
field can be finished to these marks, which will make it uniform
in size. When the frame is finished so far, two holes, 3-3/8 in.
between centers, are drilled and tapped with a 3/8-in. tap. These
holes are for the bearing studs. Two holes are also drilled and
tapped for 1/4-in. screws, which fasten the holding-down lugs or
feet to the frame. These lugs are made of a piece of 1/8-in. brass
or iron, bent at right angles as shown.

The bearing studs are now made, as shown in Fig. 2, and turned
into the threaded holes in the frame. The bearing supports are
made of two pieces of 1/8-in. brass, as shown in the left-hand
sketch, Fig. 3, which are fitted on the studs in the frame. A
5/8-in. hole is

[Illustration: The Field-Coil Core is Built Up of Laminated
Wrought Iron Riveted Together]

drilled in the center of each of these supports, into which a
piece of 5/8-in. brass rod is inserted, soldered into place, and
drilled to receive the armature shaft. These bearings should be
fitted and soldered in place after the armature is constructed.
The manner of doing this is to wrap a piece of paper on the
outs