The area between the back of the driver tooth and the front of the next driven tooth is called the _______________.

• A. Backlash
• B. Clearance
• C. Tooth thickness
• D. Mesh clearance

Answer: (A)

Backlash is the gap between mating gear teeth when they are in mesh. Specifically, it’s the space between the back of a driving tooth and the front of the next driven tooth as the gear pair engages. This clearance comes from manufacturing tolerances, lubrication, and the need to allow for wear and thermal expansion. It lets gears avoid binding and run smoothly. If there’s too little backlash, teeth can bind and wear quickly; too much backlash reduces precision and can cause noise. The described area matches the defined gap that enables mesh motion, so the best term is backlash. Clearance refers to the idle separation when gears aren’t meshing, tooth thickness is a single tooth’s width, and mesh clearance isn’t a standard term for this feature.