Introduction
Selecting a shaft coupling requires matching torque duty to catalogue ratings. Engineers often need to distinguish continuous (rated) torque from peak, starting or reversing torque before opening a manufacturer size table.
This guide explains torque concepts at methodology level. It complements the Industrial Coupling Selection Guide. Numerical torque ratings, service factors and speed limits are manufacturer-specific — confirm on the relevant family catalogue before ordering.
Continuous vs peak torque
| Term | Typical meaning | Selection relevance |
|---|---|---|
| Continuous / rated torque | Steady-state torque during normal operation | Primary basis for catalogue size selection |
| Peak / maximum torque | Short-duration overload, start-up or transient event | Must remain within manufacturer peak rating for selected size |
| Reversing torque | Torque reversal during deceleration or reciprocating duty | May reduce allowable continuous rating on some designs |
| Motor rated torque | Torque at motor nameplate power and speed | Starting point — not a substitute for driven-load torque |
Coupling catalogues usually publish a rated torque per size. Peak torque allowance depends on the manufacturer, element type and application standard. Do not assume one manufacturer's peak factor applies to another family.
Service factor and application margin
Industrial selection practice often applies a service factor or application margin above calculated continuous torque. The factor accounts for:
- Daily operating hours and start frequency
- Shock or vibration in the driven machine
- Temperature and environment
- Maintenance and inspection intervals
Service factor values are not universal. They may come from plant standards, industry guides or manufacturer application tables. When a manufacturer publishes a service factor for a specific family, use that data for that family only.
Manufacturer catalogue data
Golden Bearing Company publishes governed torque tables on selected coupling family pages. Catalogue fields may include:
| Data field | What to verify |
|---|---|
| Rated / nominal torque | Continuous duty basis for the published size |
| Maximum torque | Short-term limit if stated separately |
| Speed rating | Operating RPM limit for the size |
| Bore capacity | Maximum shaft diameter for the hub |
| Element option | Spider, tire or disc variant affecting rating |
A coupling size that satisfies continuous torque may still be unsuitable if peak torque, speed or bore limits are exceeded. Review all governed fields on the family page.
Selection workflow
- Establish driven-load torque — from motor data, gearbox output or process calculation.
- Identify continuous vs peak duty — note start-up, stall or shock events.
- Apply application margin — per plant standard or manufacturer guidance where published.
- Shortlist coupling technology — elastomeric for damping; disc or bellows for precision; gear/grid for very high torque (see couplings hub).
- Open family catalogue — compare rated torque, speed and bore for candidate sizes.
- Verify peak and reversing limits — against manufacturer data for the selected size.
- Request engineering confirmation — send duty data through engineering enquiry.
Next steps
- Review the industrial couplings category and technology tiles.
- Open the family catalogue that matches your technology shortlist.
- Compare governed torque and speed data for candidate sizes.
- For elastomeric pump and fan duty, see the Elastomeric Coupling Selection Guide.
- For misalignment limits that interact with torque duty, see Coupling Misalignment: Angular, Parallel and Axial.
Scope and limitations
- This article provides general torque selection methodology only; family pages own catalogue data.
- Numerical ratings and service factors must come from manufacturer catalogue or product record data.
- No universal service factor or peak-torque multiplier is stated in this guide.
- Cross-brand interchange or replacement claims are not made in this guide.