Question 1

How do I select the right module for my application?

Accepted Answer

Module selection balances tooth strength, noise, and size. Calculate the required module from torque: m ≈ ∛(2T/(σ_b × y × b × z)) where T is torque, σ_b is allowable bending stress, y is Lewis form factor, b is face width, and z is tooth count. Then round up to the nearest standard module. For quiet operation (e.g., instruments), use smaller module with more teeth. For heavy loads (e.g., mining equipment), use larger module.

Question 2

What is the minimum number of teeth to avoid undercutting?

Accepted Answer

For standard 20° pressure angle involute gears, the minimum number of teeth to avoid undercutting is 17. Below this, the dedendum interferes with the mating gear's addendum, weakening the tooth root. Solutions for fewer teeth: use profile shift (addendum modification x > 0), increase pressure angle to 25°, or use stub teeth (shorter addendum). In practice, 14-tooth minimum is common with positive profile shift.