KEVOS® MAKEOS · Gears
Inch Spur Gear Pair Check (Diametral Pitch Proportions, Pinion Bending)
For this diametral-pitch spur gear pair, what are the pitch and outside diameters and centre distance, and is the pinion strong enough for the horsepower?
Check of a spur gear pair made to inch diametral-pitch proportions: pitch and outside diameters and centre distance for the tooth system (as the spur gear dimensions by diametral pitch tool), the ratio and gear speed, pinion torque and tangential force from the horsepower, and the Lewis bending stress with the velocity factor for the way the teeth are made (as the Lewis bending stress tool, worked in metric with module = 25.4 ÷ P), against your allowable.
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How this tool works
Inputs, units and where to find them
| Input | Unit | Typical source |
|---|---|---|
| Diametral pitch | 1/in | Diametral pitch (teeth per inch of pitch diameter). |
| Pinion teeth | Teeth on the pinion. | |
| Gear teeth | Teeth on the gear. | |
| Tooth system | choice | Tooth system of the pair. |
| Load | ||
| Power | hp | Power transmitted in horsepower. |
| Pinion speed | rpm | Speed of the pinion. |
| Face width | in | Face width in mesh, in inches. |
| Lewis form factor of the pinion | Lewis form factor for the pinion tooth count and system (from your gear data). | |
| Tooth manufacture | choice | How the teeth are made (sets the velocity factor). |
| Allowable bending stress | MPa | Allowable bending stress of the pinion material. |
Method and formulas
- Pitch diameter = N ÷ P; outside diameter = pitch diameter + 2 × addendum; centre distance = (N₁ + N₂) ÷ 2P (as the spur gear dimensions by diametral pitch tool).
- Torque = hp × 745.7 ÷ ω; tangential force = 2T ÷ pitch diameter.
- Module = 25.4 ÷ P; σ = K_v F_t ÷ (b m Y) (as the Lewis bending stress tool).
- Example: pitch diameters 2 and 4.5 in, centre distance 3.25 in; pinion bending 67.981 MPa.
Limitations
- Lewis bending only; check surface durability separately.
- Standard addendum proportions for the tooth system.
- Example values are illustrations. Replace them with values for your actual task.
Typical uses
- Check a replacement inch gear pair
- Rate an existing DP gear set for a new motor
- Work out blank sizes for inch gears
Who it is for
- Maintenance engineers
- Gear cutters
- Design engineers
What you get
- Pitch and outside diameters and centre distance
- Ratio, torque and tangential force
- Pinion bending stress
Interpreting the result
- If the pinion is overstressed, a wider face or a coarser pitch (smaller P) lowers the bending stress.
References
- Machinery’s Handbook, 29th edition (Industrial Press, 2012), printed pp. 2131–2160, 2249–2251. Topic reference; no source tables or recommended settings are reproduced.
WORKOS tools are screening and decision-support utilities. Verify important financial, engineering, safety, legal or operational decisions using appropriate professional standards and your organisation’s approved data.
Open the Inch Spur Gear Pair Check (Diametral Pitch Proportions, Pinion Bending) calculator
