🔍 Key Concepts

• gear backlash is the clearance between mating gear teeth measured along the pitch circle, in the direction of rotation • Distinguish between radial clearance (toward/away from the center) and tangential clearance (around the gear, along the pitch circle) • Look at how the upper and lower gears mesh and where there is free motion before one tooth contacts the other

💭 Think About

• On the illustration, which arrow label shows a gap or clearance measured along the direction of tooth movement at the pitch circle, rather than straight in toward the center? • Which of the labeled dimensions (G, M, N, O) represents clearance between the non-contacting sides of two mating teeth when they are properly engaged? • Compare the dimension near the tips/roots of teeth vs. the one that runs roughly along the pitch-circle arc— which best matches the definition of backlash?

✅ Before You Answer

• Verify that the dimension you pick is measured tangentially at the pitch circle, not radially • Confirm it represents clearance between two mating teeth, not thickness of a single tooth or whole pitch distance • Ensure the arrows show free space before contact in the direction the gear would turn, consistent with backlash/play