Gears

As promised, I've uploaded a couple of photos of the custom gears I
made on the CNC machine. They can be found in the "Smoke Works" file
of the photo section. One image is a photo of the gears and the
other shows how the gear was designed.

The gear was designed as follows:
I started with a known desired pitch diameter plus a desire to have a
tooth profile that coould be cut usi g a 1/4" end mill. First I
divided the pitch circle equally into a number of segments. I then
constructed a circle tangent to two adjacent lines with it's ceter
lying on the pitch circle.

The diameter of this circle indicated my first guess (as to number of
teeth) was OK as the diameter was approxiiately 5/16". I then
divided one of the segments in half (shown by the red radial line)
and constructed a line perpendicular from this dividing line to the
center of the tooth profile. This distance gave me the radius of
both the teeth and the spaces between them. The construction circles
for one tooth and one space are shown in red.

For gears having a different number of teeth, the pitch diameter can
be found as follows:
First divide 90 by the number of desired teeth.
Next, divide the tooth diameter of the tooth profile found for the
first gear by the sin of the angle found in the first step.

Does it work? Yep!