# Using CAXA to figure out the proper measuring ball diameter of helical gear

In the manufacture, inspection and design of gears, the span of measuring ball is widely used to measure the tooth thickness of helical gears. The reason is not only that the measurement is convenient, but also that the measurement accuracy is high because it does not take the addendum circle as the benchmark. After the diameter DP of the measuring ball is determined, the measuring ball can be selected to measure the tooth thickness of the helical gear.

The proper diameter of measuring ball recommended in the mechanical design manual and data is different between the internal helical gear and the external helical gear. For the internal helical gear, DP = 1.44mn or 1.68mn, Mn is the normal modulus, while for the external helical gear, DP = kpmn. If KP is selected according to 1.68 ~ 1.9, the influence of helix angle, pressure angle, modification coefficient and tooth number is not considered in the selection of DP, and for the large modification helical gear, DP cannot be obtained. The selection of KP in DP = kpmn can also be based on the equivalent number of teeth zv and normal modification coefficient χ The size of n is determined by the ball diameter coefficient DP / Mn, the equivalent number of teeth zv and the modification coefficient χ However, when the normal pressure angle α N and normal modification coefficient χ If one of the terms of n is inconsistent with the graph, it is impossible to find out.

Using caxa2009 software (hereinafter referred to as CAXA) to obtain the appropriate measuring ball diameter of helical gear. In this paper, the tooth profile of helical gear end face is drawn with CAXA through an example, and the specific steps, methods and skills of solving the proper measuring ball diameter of helical gear by graphic method are introduced in detail.

This paper introduces the graphic method for calculating the proper measuring ball diameter of helical gear, which takes into account the influence of helix angle, pressure angle, modification coefficient and tooth number. It does not involve the equivalent tooth number and involute function, and is easy to realize. The obtained measuring ball diameter is appropriate and reasonable. This method provides a new idea for calculating the proper measuring ball diameter of helical gear, which is simple and easy to use. 