Introduction to the characteristics and parameters of precision racks

The precision rack can be regarded as a part of a gear with an infinite number of teeth. At this time, each circle of the gear becomes a straight line, and the involute as a tooth profile also becomes a straight line. The rack is also divided into a straight rack and a helical rack, which are paired with a spur gear and a helical gear, respectively; the tooth profile of the rack is a straight line rather than an involute (planar for the tooth surface) The main characteristic of the cylindrical gear rack with the radius of the index circle is infinite (1) Since the tooth profile of the rack is straight, each point on the tooth profile has the same pressure angle and is equal to the inclination angle of the tooth profile. For the tooth angle, 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), which is a reference line for calculating the size of the rack. The main parameters of the precision rack are the groove width, the top of the tooth, the height of the root, the height of the tooth, the thickness of the tooth, and the radius of the root of the tooth.