[chadr03]

If you are buying gears they usually sold by the tooth size, or Diametral Pitch, and the Pressure Angle.

The Pitch Diameter of the gear is measured roughly the middle of the tooth when you look at it from root to tip.

Here are some handy gearbox design formulas for spur gears.

Diametral Pitch=(Number of Teeth)/(Pitch Diameter)

Center Distance= ((Number of Teeth in Pinion)+(Number of Teeth in Gear))/(2*Diametral Pitch)

The tolerance of this center distance usually is pretty important and needs to be held at around +.003/+.010 for FIRST applications.

Make sure you purchase gear of the same pitch and pressure angle to mesh with each other. It does not work to mix and match.

AndyMark sells 20dp (or Diametral Pitch) gears with 14-1/2° Pressure angles and 32dp gears with 20° pressure angles.