Subtopic: Design and selection of machine elements – gears, pulleys, chains and sprockets and belts
Question Statement:
To avoid interference in a pair of standard $20^\circ$ full-depth involute spur gears with equal number of teeth, the minimum number of teeth on the pinion must be at least:
Options:
(A) 18
(B) 12
(C) 25
(D) 32
Answer Key:
A
Step-by-Step Solution & Explanation
The theoretical minimum number of teeth to avoid interference in standard $20^\circ$ full-depth involute pinion is $z_{min} = \frac{2}{\sin^2 20^\circ} = \frac{2}{(0.342)^2} \approx 17.1 \implies 18$ teeth.