Brief introduction of rack and pinion
The rack is also divided into straight and helical gears, which are paired with straight and helical cylindrical gears respectively; the tooth profile of the rack is straight rather than involute (flat for the tooth surface), which is equivalent to an infinite radius of indexing circle cylindrical gear.
The main characteristics of rack and pinion
(1) Because the tooth profile of the rack is straight, so all points on the tooth profile have the same pressure angle, and equal to the dip angle of the tooth profile, this angle is called tooth angle, the standard value of 20 °.
(2) parallel to the top of the tooth angle line on any line has the same tooth pitch and modulus.
(3) The line parallel to the top angle line and the tooth thickness is equal to the width of the tooth groove is called the indexing line (center line), which is the reference line for calculating the size of the rack.