Diametrical Size at Reversal Point

There are different instruments to inspect the size over/between two balls. The most simple instrument is based on the rocking method: These hand-held instruments are equipped with measuring inserts and a dial indicator. The nominal size is adjusted by gauge blocks. Afterwards, the operator needs to find the reversal point to receive the relative deviation.

Special case: Helical gears with odd number of teeth

Here the reversal point will not coincide with the required measuring plane (perpendicular to the gear axis) but in a plane tilted towards it. As a consequence, the operator usually detects a higher deviation.

To use the available measuring instrument anyway, it must not be adjusted to the nominal size but to the dimension at the reversal point. This can be calculated with the following tool, just enter your gear data below.

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Further information

FRENCO held a lecture regarding this topic at at GETPRO 2015. The transcript (in German language) can be downloaded here:

GETPRO 2015: Lecture "Diametrical Size at Reversal Point" in German