en bolt
and yoke. Several ways of fastening the bolts and yokes are shown; but
it will be found best to cut holes in the base for the lower nuts, and
to screw the yoke directly to the base. This makes a solid and pleasing
arrangement. For the experimental magnets (App. 89) make the yoke 3-1/4
in. long, and place the magnets 2 in. apart center to center.

[Illustration: Fig. 67.]

CHAPTER X.

WIRE WINDING APPARATUS.

APPARATUS 91.

_127. Winder._ Fig. 68. In case you do not have any means of making a
smooth hole for the "bearings" of the winders of App. 93 and 94, you can
use a spool for the purpose. B is the end of a piece of board about 1
in. thick, 3 in. wide, and 6 in. long. The spool, A, is laid upon this,
a band of tin, T, being used to hold it down firmly upon the end of B.
Screws, S, hold T down. A stove-bolt axle (See App. 93) is shown, and by
using a nut, as explained, bolt magnets may be wound. By using the
handle of App. 92, this arrangement can be used to wind almost anything,
when used together with the attachment of App. 95.

[Illustration: Fig. 68.]

[Illustration: Fig. 69.]

APPARATUS 92.

_128. Crank for Winders, etc._ Fig. 69. This form of crank or handle
will be found easier to make than the one in which a wire is expanded in
the slot of a stove bolt, and it can be used for many purposes,
especially where dowels serve as axles. Wrap a little paper around the
end of the 1/4 in. dowel, D, and push it part way into the spool, A,
then put in a set-screw, S, to keep A from twisting upon D. The straight
end of the wire, H, should be put into a hole, B, and another set-screw
used to fasten it into the spool.

APPARATUS 93.

_129. Winder._ Fig. 70. For winding bolt magnets, this form of winder is
very useful. It consists of a "stove bolt," S B, 2 in. long (total
length) and 5/16 in. in diameter.

[Illustration: Fig. 70.]

130. Handle or Crank, H, is made of a stout wire, 4 in. long, bent at
the lower end as shown. H is fastened into the slot of S B. To do this
the end of H is hammered flat until it will just slip into the slot. It
may be soldered there, or be made to fit by expanding it so that it will
press out against the sides of the slot. To do this, place S B into a
hole in an anvil, or hold it in a vise, being careful not to injure the
thread. Place the flattened end of H in the slot, and strike it on top
so that it will expand and be pinched in the slot; but do not pound i