Question

Which of the following is true for an involute curve?

(a) Tangent to any point on involute is parallel to the generator at that point

(b) Tangent to any point on involute is perpendicular to the generator at that point

(c) Tangent to any point on involute is at 45 degree to the generator at that point

(d) Tangent to any point on involute is at 30 degree to the generator at that point

I got this question during an interview.

Origin of the question is Involute Curve topic in chapter Measurement and Testing of Gears of Engineering Metrology

Answer 1

Right answer is (b) Tangent to any point on involute is perpendicular to the generator at that point

To elaborate: It is important to fulfill the requirements of law of gearing for an involute curve. The tangent at any point on involute will be perpendicular to the generator at that point. This condition fulfils the requirements needed for laws of gearing.