KEVOS® MAKEOS · Gears
Spur Gear Pitting Resistance Power Rating (AGMA)
How much power can this spur gear pair transmit before pitting governs?
Allowable transmitted power for pitting resistance by the AGMA power rating formula (metric form), with the external or internal spur gear geometry factor I calculated from the pressure angle and ratio, the dynamic, size, load-distribution, surface and application factors, and the allowable contact stress with its life and hardness factors.
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How this tool works
Inputs, units and where to find them
| Input | Unit | Typical source |
|---|---|---|
| Pinion speed | rpm | Speed of the pinion. |
| Net face width | mm | Net face width in contact. |
| Pinion operating pitch diameter | mm | Operating pitch diameter of the pinion. |
| Gear ratio (gear ÷ pinion teeth) | Gear ratio (always 1 or more). | |
| Gearing | choice | External or internal mesh, for the geometry factor. |
| Pressure angle | ° | Operating transverse pressure angle. |
| Geometry factor I | choice | Calculate I for standard spur gears (load sharing ratio 1), or enter it from AGMA 908. |
| Geometry factor I (entered) | Geometry factor for pitting resistance. | |
| Dynamic factor C_v (≤ 1) | Dynamic factor in the older AGMA form (1 or less). | |
| Size factor C_s | Size factor. | |
| Load distribution factor C_m | Load distribution factor. | |
| Surface condition factor C_f | Surface condition factor. | |
| Application factor C_a | Application (overload) factor. | |
| Allowable contact stress number | MPa | Allowable contact stress number for the material and heat treatment (use the lower of pinion and gear). |
| Life factor C_L | Life factor for the number of cycles. | |
| Hardness ratio factor C_H | Hardness ratio factor (gear only). | |
| Elastic coefficient C_p | √MPa | Elastic coefficient (191 √MPa for steel on steel). |
| Temperature factor C_T | Temperature factor. | |
| Reliability factor C_R | Reliability factor. | |
| Power to transmit | kW | Power you need to transmit. |
Method and formulas
- Geometry factor (spur, m_N = 1): I = cos φ sin φ ÷ 2 × m_G ÷ (m_G ± 1), + for external, − for internal gears.
- P_ac = n_p F ÷ 1.91 × 10⁷ × I C_v ÷ (C_s C_m C_f C_a) × [d S_ac C_L C_H ÷ (C_p C_T C_R)]² kW, with F and d in mm and S_ac in MPa (handbook formula 5a).
- Example: a 60 mm pinion, 30 mm face at 1500 rpm rates 13.795 kW for pitting.
Limitations
- Spur gears without helix; helical gears need the load sharing ratio in I.
- Rate both pinion and gear with their own S_ac C_L C_H and use the lower.
- Example values are illustrations. Replace them with values for your actual task.
Typical uses
- Rate a spur gear pair for power
- Check a gear set against a motor power
- Compare face width or material options for durability
Who it is for
- Gear designers
- Design engineers
- Maintenance engineers
What you get
- Geometry factor I
- Allowable power for pitting
- Service factor against the required power
Interpreting the result
- Pitting capacity rises with the square of pinion diameter and allowable stress, but only linearly with face width.
References
- Machinery’s Handbook, 29th edition (Industrial Press, 2012), printed pp. 3304–3313. Topic reference; no source tables or recommended settings are reproduced.
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Open the Spur Gear Pitting Resistance Power Rating (AGMA) calculator
