Backlash
Backlash is the amount by which a tooth space exceeds the thickness of an engaging tooth. It is measured along the pitch circle and is equal to the difference between the tooth space and the tooth thickness. Backlash is required to prevent binding of the teeth and to allow for manufacturing tolerances.
Backlash is usually measured in the direction of the pitch circle. However, it can also be measured in the direction of the line of action.
In general, there are two ways to generate backlash:
Increase gear centre distance
Reduce tooth thickness
Control of backlash by reduction of tooth thickness is most frequently used.
Linear Backlash is the distance the gear can move without engaging the teeth of the mating gear.
The angular backlash can be calculated by dividing the circumferential clearance required by the operating pitch diameter:
Modification of the total profile shift required to achive a specified circular backlash can be calculated as follows:
Gear Type | Normal - Circular | Circular - Centre |
|---|---|---|
Spur | ||
Helical |
Gear Type | Angular - Circular |
|---|---|
All |