The tree will be burnt along the pencil marks, and if the
glass is not held in one spot too long, the inscription will be
burnt in as evenly as if it had been written.
--Contributed by Stewart H. Leland, Lexington, Ill.
** How to Make Small Gearwheels Without a Lathe [46]
To make small models sundry small gears and racks are required,
either cut for the place or by using the parts from an old clock.
With no other tools than a hacksaw, some files, a compass,
[Illustration: Making Model Wheels]
and with the exercise of a little patience and moderate skill,
very good teeth may be cut on blank wheels.
First take the case of a small gearwheel, say 1 in. outside
diameter and 1/16 in. thick, with twenty-four teeth. Draw a circle
on paper, the same diameter as the wheel. Divide the circumference
into the number of parts desired, by drawing diameters, Fig. 1.
The distance AB will be approximately the pitch. Now describe a
smaller circle for the base of the teeth and halfway between these
circles may be taken as the pitch circle.
Now describe a circle the same size as the largest circle on a
piece of 1/16-in.
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