The gap between the non-drive face of the pinion tooth and the adjacent wheel tooth is known as backlash. Backlash is the error in motion that occurs when gears change direction. The term “backlash” can also be used to refer to the size of the gap, not just the phenomenon it causes; thus, one could speak of a pair of gears as having, for example, “0.1 mm of backlash.”

Practise problems:

1)     Two gears in mesh have a module of 8 mm and a pressure angle of 20°. The larger gear has 57 teeth while the pinion has 23 teeth. If the addenda on pinion and gear wheel are equal to one module (1m), find

a.  The number of pairs of teeth in contact and

b.  The angle of action of the pinion and the gear wheel.

Solution: