A special-purpose machine has been designed and installed to measure the ki
nematic accuracy of precision worm gears. The primary measurement is the tr
ansmission error (TE) between the worm and wheel, and several measuring met
hods were considered. The chosen method uses optical gratings and a digital
system to process the signals, which has particular advantages for this ap
plication. This method then makes it a straightforward step also to measure
pitch errors of both the worm and the wheel, and lead errors of the worm.
A novel method of measuring backlash very accurately is also described.