A New Method of Measuring Involute Profile Deviations of Gear Teeth

The principle behind all involute profile measuring machines is to arrange for relative movements between the gear and a stylus, so that the stylus measures only the deviations from a perfect involute curve. Over the years a number of different ways have been devised to produce the relative movements, involving discs and levers, and more recently computer numerical controls (CNC). This paper draws attention to the fact that accurate, large displacement optical gratings remove the need for accurate motion generation by using software compensation. The principle is applied to a base disc type of machine, which can be easily converted so that its full diameter range can be covered by a handful of nominal size discs, rather than needing an accurate and unique size of disc for every gear base diameter. In addition the output display can be made similar to that of a modern CNC machine.