Spur gear sizes are usually measured by module. This refers to the size of the tooth and a larger tooth size means more power can be transferred.
As well as this, gears can also be measured by:
- Number of teeth
- Bore diameter
- Hub diameter
- Pitch diameter
- Face width
Multiplying the module of a gear by pi will give you its pitch. This is the distance between consecutive threads and teeth.
These measurements can help you to identify the right-sized spur gear for your particular application. It is useful to accurately measure and record these sizes as this can help when working in systems where a precise size is required. Gears must be fabricated to precise dimensions in order to ensure maximum effectiveness.
Mating gears must have the same module. A spur gear of the wrong size could mean that meshing does not occur fully, or the gear could stick if it does not smoothly mesh. This could result in increased wear and tear, damage to the gear pair, increased noise levels and vibration, or it could even prevent the system from functioning correctly. Therefore, choosing the right sized gear is imperative.