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What are the characteristics of gear rack?

Rack and pinion drive is suitable for large stroke, high precision and large torque drive. In CNC machine tools, automation is widely used. Compared with the belt drive and the trapezoid screw drive, what are the advantages? This paper makes a brief analysis. The precision characteristics of Taiwan t-win precision rack are compared with the traditional transmission methods.


(1) As the rack profile is a straight line, each point on the profile has the same pressure angle, which is equal to the inclination angle of the profile. This angle is called the profile angle, and the standard value is 20 °.

(2) Any straight line parallel to the tooth top line has the same pitch and modulus.

(3) A straight line parallel to the tooth top line and with the tooth thickness equal to the width of the tooth slot is called the dividing line (center line), which is the reference line for calculating the rack size.

This paper introduces how to eliminate the tooth error of the precision rack shaft and how to turn the precision rack shaft. It is not only simple, but also can eliminate the error. In order to overcome the troublesome and error prone phenomenon of processing rack and shaft teeth on lathe in the past, the method introduced in this paper can be used to precisely eliminate the accumulated error and improve the processing efficiency. In the past, when machining the teeth of the rack shaft on the lathe, a small carriage was used to move a pitch and cut a tooth, and the number of thousands of hoop grids per pitch was calculated. Because it is a small number, it is very troublesome, often prone to errors, and prone to cumulative errors of pitch. In order to overcome the above phenomenon, the lead screw pitch of the small carriage is changed to the same as the pitch of the precision rack, and a screw nut is provided. In this way, as long as a small pitch is moved, the rack tip degree is ensured, and the lead screw of the carriage is rotated once, the accumulated error of the cutter is eliminated accurately, and the machining efficiency is improved.

Introduction of various technical indexes of rack

1. Determine the modulus m according to the load (check the value of m in the mechanical design manual)

2. Determine the diameter of the graduation circle of the driven gear d, d = m * Z (where Z is the number of teeth of the gear)

3. The number of teeth of the gear needs to be considered comprehensively according to the torque and structure of the load. When the torque is large, the number of teeth of the gear can be larger, so the diameter of the gear is larger, otherwise the diameter can be smaller. Remember the key formula above: D = m * Z, which is an important formula

4. After determining the pitch circle diameter D of the rack, the circumference of the pitch circle diameter can be calculated, assuming L

5. L is the effective length of the rack. Considering the operation and installation of this strip, generally, the actual length should be greater than l, and the specific length should be considered in the structural design.

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