Technology / product information

The key to precision spline machining: Pursuing fitting accuracy with BPD measurement.

Broaching is a processing method used to create precise internal shapes such as splines and gears. In general gear machining, BBD (Bitween Ball Diameter) measurement is the mainstream, but in the case of broached spline holes, BPD (Bitween Pin Diameter) measurement is the best way to check the fitting accuracy. This is because using a pin to measure the minimum tooth thickness allows for an accuracy evaluation that is closer to the actual fitting state.

■ Features
BPD measurement is characterized by using a pin instead of a ball. The pin is grounded at the minimum tooth thickness position in the lead direction, allowing for more accurate tooth thickness measurement. This makes it possible to improve the fitting accuracy of broached spline holes and improve product reliability.

■ Specifications
For BPD measurement, a parallel block with a reference dimension of 25 mm is used. It is important to select a parallel block that does not deviate parallelly no matter what position it is slid to. For the arrangement of the measuring tool, choose a block gauge size 1-2mm larger than the drawing specification and use it together with a measuring pin to obtain accurate measurements. For example, if the illustrated BPD is 35mm and the pin diameter is 1.5mm, the calculation formula is 35(BP)-25(parallel block)+2=12mm.

In this way, BPD measurement is a method that dramatically improves the accuracy of broaching. By utilizing these measurement techniques, it is possible to provide high-quality products to the market in order to achieve accurate fitting.

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