🔍 Key Concepts

• Gear clearance (radial space between the top of one tooth and the bottom of the mating tooth space) • Difference between addendum circle (top of teeth) and dedendum/root circle (bottom of tooth spaces) • Distinguish backlash (circumferential space along pitch line) from clearance (radial space toward the center)

💭 Think About

• Look closely at which arrow shows a radial gap between the tip of one gear tooth and the root of the mating gear tooth space, not along the pitch circle • Compare the labeled dimensions that run roughly toward the center of the gear with those that run around the gear • Ask yourself which label would still exist even if the gears had zero backlash along the pitch circle

✅ Before You Answer

• Make sure the label you choose is measuring radial distance (toward the center), not tangential distance along the pitch line • Confirm that the chosen label is between the top land of one gear and the root of the other gear when meshed • Verify that the label you select is not showing tooth thickness, outside diameter, or pitch-circle spacing