Gear rack is a particular gear whose teeth are distributed in the strip.
1. The basic concept:
The rack is also split into a spur gear rack and a helical gear rack, which are paired with a spur gear and a helical gear, respectively; the tooth profile of the rack can be a straight line instead of an involute (planar for the tooth surface) , equal to the indexing circle radius is normally infinite cylindrical gear.
2. The main features:
(1) Because the tooth profile of the rack is direct, each point on the tooth profile gets the same pressure position and is add up to the inclination angle of the tooth profile. This angle is called the tooth position and the typical value is 20°.
(2) The same pitch and modulus are provided on the right lines parallel to the very best line.
(3) A series parallel to the top line of the tooth and having a tooth thickness equal to the 
width of the tooth groove is named a dividing series (middle line), which really is a reference collection for calculating how big is the rack.
3. The main parameters:
Groove width, high tooth suggestion, high root height, tooth elevation, tooth thickness, root radius, etc.
4. The decision of parameters:
(1) Whether the gear is beating, the full tooth depth, the common normal line, the tooth direction is qualified, the tooth pitch is poor, and the circumferential section error has gone out of tolerance.
(2) If the installation distance after the gears and racks are installed is suitable.
(3) The rack and gear meshing clearance ought to be 0.25* modulus.
(4) Whether the complete tooth depth, runout, and common normal line of the rack are competent.
5. Processing methods:
Gear rack and pinion machining method:
(1) hobbing
(2) gear shaping
(3) shaving
(4) grinding teeth
(5) molars
