Question

Which of the following is not the correct formula for base pitch?

(a) Base circumference / Number of teeth

(b) π x Base circle diameter / N

(c) π x D sinφ / N

(d) π x m x cosφ

This question was addressed to me in quiz.

This interesting question is from Terminology of Gear Tooth in chapter Measurement and Testing of Gears of Engineering Metrology

Answer 1

Correct answer is (c) π x D sinφ / N

To elaborate: Base pitch is the distance which is measured around the base circle from the origin of the involute on the tooth to the origin of a involute (similar) on the next tooth.

Base pitch =  Base circumference / Number of teeth

                   =  π x Base circle diameter / N =  π x D cosφ / N =  π x m x cosφ.