Rack gears come in straight and helical types, respectively pairing with straight and helical cylindrical gears; the teeth of the rack gears are linear rather than involute (flat for the mating gear surface), which is a key feature of rack gears on cylindrical gears with an infinite pitch diameter.

The rack tooth profile is linear, resulting in all points on the tooth profile having the same pressure angle, which is equal to the tooth profile's inclination angle. This angle is known as the tooth form angle, with a standard value of 20°.

2. Any straight line parallel to the top land has the same pitch and module.

3. A straight line parallel to the top of the gear teeth and equal in thickness to the gear slot width is called the pitch line (midline). The rack serves as the reference line for calculating the dimensions of the rack.

Main Parameters of the Rack Gear:

Tooth slot width, tooth top height, root height, tooth height, tooth thickness, root radius, etc.