Rack Explained

A rack is a special gear in which teeth are distributed on a strip.


The main features

(1) Since the rack profile is a straight line, each point on the tooth profile has the same pressure angle and is equal to the inclination angle of the tooth profile.

This angle is called the tooth angle and the standard value is 20°.

(2) The same pitch and modulus are available on any line parallel to the top line.

(3) A line parallel to the top line of the tooth and having a tooth thickness equal to the width of the tooth groove is called a dividing line (middle line).

It is the baseline for calculating the rack size.

The main parameters

  • Cogging width
  • High tip
  • Root height
  • Tooth height
  • Tooth thickness
  • Root radius

The choice of parameters

(1) Whether the gear beating, the full tooth depth, the common normal line, the tooth direction is qualified;

Whether the cycloid and the circumferential section error is out of tolerance.

(2) Whether the installation distance after the gears and racks are installed appropriately.

(3) The rack and gear meshing clearance should be 0.25* modulus.

(4) Whether the full tooth depth of the rack, the runout, and the common normal line, especially the tooth direction, are acceptable.

The processing methods

Gear rack processing method:

(1) gear hobbing

(2) gear shaping

(3) gear shaving

(4) gear grinding

(5) gear honing

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