🔍 Key Concepts

• Gear tooth geometry: Know where the top, sides, and bottom of a tooth space are located. • Top land vs. bottom land: One is at the outer diameter of the gear, the other at the root diameter between teeth. • Tooth profile and fillet: The profile is the working side surface; the fillet is the curved blend near the root.

💭 Think About

• Look closely at where the arrow marked "H" begins and ends: is it measuring along the top of the tooth, the bottom between teeth, or along the side surface? • Ask yourself whether "H" is indicating a flat surface, a curved radius, or the full shape of the side of the tooth. • Compare "H" with letters that clearly point to the side of the tooth (profile) and to the curved root (fillet) elsewhere in the figure; how is it different?

✅ Before You Answer

• Verify whether "H" lies at the outer diameter of the gear or down near the root between teeth. • Confirm if "H" is showing a width between tooth flanks or a curved transition radius. • Make sure you can clearly distinguish the top land (flat on top of a tooth) from the bottom land (flat at the bottom between two teeth) before choosing.