In the last section, we discussed gear inspection; the types of errors found by single and double flank composite and analytical tests; involute geometry; the involute cam and the causes and symptoms of profile errors. In this section, we go into tooth alignment and line of contact issues including lead, helix angles, pitch, pitchline runout, testing and errors in pitch and alignment.

It is very common for those working in the gear manufacturing industry to have only a limited understanding of the fundamental principals of involute helicoid gear metrology, the tendency being to leave the topic to specialists in the gear lab. It is well known that quiet, reliable gears can only be made using the information gleaned from proper gear metrology.

Gears are toothed wheels used primarily to transmit motion and power between rotating shafts. Gearing is an assembly of two or more gears. The most durable of all mechanical drives, gearing can transmit high power at efficiencies approaching 0.99 and with long service life. As precision machine elements gears must be designed.