The distance between one point on a tooth and the same point on the next tooth is called the

• A. Diameter
• B. Radius
• C. Circumference
• D. Pitch

Answer: (D)

Pitch is the spacing between teeth. In gears, marking a point on a tooth and the same point on the next tooth, the distance between those points measured along the pitch circle (the path where teeth effectively engage) is the pitch. This spacing must match on meshing gears so teeth fit smoothly and the gear train maintains a constant velocity ratio. For a gear with a given pitch diameter and number of teeth, the circular pitch can be found from p = π × (pitch diameter) / number of teeth, or p = π × module. The diameter, radius, and circumference describe the overall size of the gear, not the gap between adjacent teeth, so they don’t define this spacing. The distance between corresponding points on adjacent teeth is the pitch.