When a gear is needed to drive a small pinion and there is none of the right size at hand, one can be made in the following manner: Turn up a wood disk to the proper diameter and 1/4 in. thicker than the pinion, and cut a flat bottom groove 3/16 in. deep in its face. The edges should be about 1/8 in. or more thick on each side. Measure the distance between centers of two adjacent teeth in the pinion and step this off around the periphery in the bottom of the groove. Drill holes into the wood on each point stepped off and insert steel pins made of wire, allowing the end of each to protrude just far enough to act as a tooth. In this way a good gear for light work can be quickly and cheaply constructed. --Contributed by Henry Schaefer, New York City.
Illustration: Steel Pins in Wood