What is gear backlash and why is it controlled?

• A. The clearance between gear teeth.
• B. The angle between gear teeth.
• C. The lubricant temperature.
• D. The time delay in gear meshing.

Answer: (A)

Backlash is the intentional clearance between gear teeth when the gears are meshed. This gap allows room for a lubricating film, manufacturing tolerances, wear, and thermal expansion, so the teeth don’t grind against each other and the gears can rotate smoothly under load. By controlling the amount of backlash, you prevent binding and excessive friction, which can heat and wear the gear. At the same time, you avoid too much play, which would cause noise, vibration, and uneven load distribution.

The other statements describe different things: the angle between gear teeth relates to helix or spur geometry, not the gap between teeth; lubricant temperature affects lubrication performance but isn’t backlash; and a time delay in meshing isn’t the defined clearance between teeth.