A flat or straight bar with a series of evenly spaced teeth.

Rack gears come in straight and helical varieties, respectively pairing with straight and helical cylindrical gears; the teeth of the rack gears are linear rather than involute (flat for the mating surface), equivalent to a cylinder gear with an infinite pitch circle radius.

The main features of the rack

Due to the linear nature of the rack tooth profile, each point on the profile has the same pressure angle, which is equal to the tooth profile's inclination angle. This angle is referred to 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 line parallel to the top of the teeth and equal in thickness to the width of the tooth space is called the pitch line (midline), which serves as the reference line for calculating the dimensions of the rack.

Main Parameters of the Rack

Slot width, tooth height, root height, tooth height, tooth thickness, root radius, etc.