In making a worm wheel the cuts must be taken in a sloping
direction, the slope and pitch depending on the slope and pitch of
the worm thread, which, though more difficult, may also be cut
with a hacksaw and file.
A bevel wheel should be cut in the same manner as the spur wheel,
but the cut should be deeper on the side which has the larger
diameter. To cut a rack the pitch should be marked along the side,
and the guide and saw used as before (Fig. 4).
** How to Make Four Pictures on One Plate [46]
Secure two extra slides for the plate holders and cut one corner
out on one
[Illustration: Four Photos on One Plate]
of them, as shown in Fig. 1. Make a hole in the other, as shown in
Fig. 2. With a lead pencil draw on the ground glass one line
vertical and one horizontal, each in the center. This will divide
the ground glass into four equal parts.
Focus the camera in the usual manner, but get the picture desired
to fill only one of the parts on the ground glass. Place the
plate-holder in position and draw the regular slide; substitute
one of the slides prepared and expose in the usual way.
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