d along the
mounting strip, the purpose of which will be shown later.

Next cut another piece of 1/8-in. brass, 2-3/4 in. long and 5/8
in. wide. In this piece drill two 1/8-in. holes, as indicated in
Fig. 7, and then bend it at the dotted lines into the form shown
in Fig. 8. Mount this strip upon the main mounting strip by means
of two brass machine screws placed in the holes C, so that the
upper part is over the center-punch mark for the hole A in the
main mounting strip.

You are now ready to drill the hole A, which should be done as
follows: Remove the piece you last mounted and then clamp the main
mounting strip in the drill press so that the center-punch mark
for the hole A is directly under the point of the drill. Then
remount the piece you just removed, without disturbing the piece
you clamped in the drill press, and drill a small hole through
both pieces. This hole should be about 3/64 in. in diameter. After
this small hole has been drilled through both pieces, a
countersink should be placed in the drill chuck and the hole in
the upper piece countersunk to a depth equal to half the thickness
of the metal in which it is drilled. Unclamp the pieces from the
drill press, turn them over, and countersink the small hole in
what was originally the lower piece. The object of countersinking
these holes is to reduce the bearing surface of a small shaft that
is to be supported in the holes and must be as free from friction
as possible.

We may now construct the needle, or moving portion of the
thermostat, which should be done as follows: The shaft that is to
carry the moving system must be made from a piece of steel rod,
about 3/32 in. in diameter. Its dimensions should correspond to
those given in Fig. 9. Considerable care should be used in turning
this shaft down, to make sure that it fits perfectly in the small
holes in the supporting pieces. The shaft should turn freely, but
it must not be loose in the holes, nor should it have but a very
small end play.

Cut from some 1/32-in. sheet brass a piece whose dimensions
correspond to those given in Fig. 10. Drill a 1/8-in. hole, A, in
this piece, and cut a slot, B, from one side of the piece into
this hole, and a second slot, C, along the center of the piece as
indicated in the figure. Considerable care should be exercised in
cutting the slot C, so that its breadth is exactly equal to the
diameter of the piece of steel wire fastened on the end of the
couple. Also mak