CHALLENGE 01 / PRACTICE EXAMPLE
Identify an unknown gear’s module
A replacement gear has no markings. You have a tooth count and a tip-diameter measurement. Recover its nominal module and pitch diameter.
Measurement · Foundation · 15 minutes
- Tooth count
- 38
- Measured tip diameter
- 80.00 mm
Published 28 Oct 2026, 10:40 UTC · Version 1
Prepared teaching example; not a client part or verified inspection result.
Illustrative tooth shape; not an involute manufacturing profile.
Your task
- Calculate the nominal module in millimetres.
- Calculate the pitch diameter in millimetres.
- Explain at least two situations where this tip-diameter shortcut would be unreliable.
Assumptions
- Standard external spur gear with straight teeth.
- Unshifted, standard full-depth teeth; negligible wear.
- Tip diameter is measured across the tooth tips, not the root.
- All dimensions are in millimetres. Measurement uncertainty is ignored for this practice example.
- Pressure angle is not determined by tooth count and tip diameter alone.
Your attempt
Saved locally on this device, not submitted to CADfinity. Numeric feedback becomes available with the solution.
Worked solution
Solution release: 4 Nov 2026, 10:40 UTC
Try the calculation first. The worked answer opens seven days after publication; return here to compare your reasoning.
