Question 1

How do I calculate gear centre distance?

Accepted Answer

For two spur gears, C = m(N₁ + N₂)/2, where m is the module and N the tooth counts. Pitch diameter is d = m·N. For helical gears the transverse module (m/cos β) increases the centre distance.

Question 2

What is module in a gear?

Accepted Answer

Module (mm) is pitch diameter divided by tooth count — the metric measure of tooth size. Two gears must share the same module (and pressure angle) to mesh.

Spur & Helical Gear Geometry

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