🔍 Key Concepts

• Whole depth is the full radial distance from the top of the tooth to the bottom of the space between teeth • Whole depth = addendum + dedendum for a single gear tooth • In the illustration, some arrows show radial distances (toward/away from the center), others show along the pitch circle (tooth thickness, pitch, etc.)

💭 Think About

• First, identify on the lower gear which arrow shows the distance from the pitch circle up to the tooth tip (addendum) and which shows the distance from the pitch circle down to the root (dedendum) • Look carefully at what C and D actually measure – are they from the tooth tip, the root, or between circles such as the root circle, addendum circle, and pitch circle? • Ask yourself: if you started at the very top of a tooth and moved straight inward (toward the gear center) to the very bottom of the space between teeth, which labeled dimensions would you pass through and need to add together?

✅ Before You Answer

• Verify which letters represent radial measurements (center-outward) rather than along the tooth or along a circle • Confirm that the sum you choose equals addendum + dedendum, not just the working depth between two meshing teeth • Make sure the combination you select covers the entire distance from the outer circle (tooth tip) down to the root circle (bottom of space) with no gap or overlap