Sprocket Index circle measurement method

The formula for calculating the circle diameter is: d=p/[sin(180°/z)]. p is the pitch 25.4, z is the number of teeth 25, and the calculated d = 202.66.

The index circle is a size reference chosen for Gear design and manufacturing. The  ISO Sprocket index circle has a standard modulus and a standard pressure angle, so it is used as the basis for calculating the dimensions of each part of the gear.

The index circle of the ANSI Sprocket is the reference for designing and calculating the dimensions of each part of the gear, and the circumference of the gear index circle = πd = z p, so the diameter of the score circle is d = z p / π.

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Extended information:

Index circle measurement method:

The tooth thickness on the gear index circle is the arc length, which is inconvenient to measure. The chord length AB is easy to measure. The chord length is represented by S, which is called the indexing circle chord tooth thickness. In machining and measurement, the radial height h of the crest to the chord AB is referred to as the indexing chord height based on the crest.

The measurement of the indexing circular chord tooth thickness requires a special measuring instrument, and the measurement must be based on the tip circle, and the measurement result is undoubtedly affected by the accuracy of the tip circle. Therefore, for gears with m>10 mm, it is often preferred to use the method of measuring the length of the common normal to detect the machining accuracy of the gear.