NM Coupling Selection Guide

Start with the mechanical duty, not the shaft diameter. The selected model must satisfy torque, maximum speed, both bores, installation envelope and environment at the same time.

1. Establish operating torque

Where motor power P in kW and rotational speed n in rpm are known, derive a first estimate with T = 9550 × P / n. Label this a calculated running value. Add verified start, acceleration, reversing and jam torque. If those values are unknown, provide motor and driven-machine details instead of selecting from the table by guess.

2. Check the catalogue torque row

Choose a model whose nominal torque is not below the design duty after the project's own service and uncertainty allowances. The website does not invent a universal service factor because the supplied page does not publish one. An engineering review should account for driver type, driven machine, starts per hour, cyclic variation and consequence of failure.

3. Verify rotational speed

The source lists 3,000 rpm for NM50–NM168 and 1,500 rpm for NM194–NM214. The actual maximum, including overspeed, must remain within the published limit. State balancing and runout expectations when operating close to a limit.

4. Verify both shaft interfaces

Compare each shaft diameter with d max, then confirm keyway, bore fit, engagement length, shoulder and assembly access. The source marking example supports different driving and driven bores. It does not publish key dimensions or tolerance classes, so the approved drawing must provide them.

5. Check misalignment and gap

Use the published radial and angular values as ceilings, not targets. Account for thermal movement and structure deflection in addition to initial alignment. Set the printed S gap without hub-to-hub contact.

6. State the environment

The catalogue identifies an NBR element and oil resistance, but no temperature range or comprehensive chemical table. State minimum and maximum temperature, oil type, chemicals, cleaning agents, sunlight, ozone, dust and water exposure.

7. Approve the drawing

The final manufacturing drawing should show model, both bores, keyways, hub lengths, overall assembly, centre gap, fastening method, material or coating requirements if agreed, markings and inspection points.

Web context: current NBK coupling guidance also sequences rated torque, temperature, maximum bore and maximum rotational frequency checks. That methodology supports the workflow, but NBK product factors are not imported into the NM table.