Buying guide
How to Choose a Coupling for a NEMA 17 Stepper Motor
Bore sizes, coupling types and the mistakes to avoid when joining a stepper shaft to a lead screw.
A coupling joins the motor shaft to a lead screw or another shaft. Two numbers matter first: the bore diameters of both ends. A NEMA 17 motor has a 5 mm shaft, and many T8 lead screws are 8 mm, which is why a 5x8 coupling is so common.
Coupling types
| Type | Good for | Notes |
|---|---|---|
| Flexible clamp / set screw | Lead screws, general drives | Absorbs small misalignment; clamp grips better than set screw |
| Jaw | Motors with moderate torque | Rubber spider damps vibration |
| Oldham | Parallel offset between shafts | Three-part design, low backlash |
| Diaphragm | Precision positioning | High torsional stiffness |
| Rigid | Perfectly aligned shafts | No misalignment tolerance; can bind and wear bearings |
Selection checklist
- Measure both shaft diameters (for example 5 mm motor, 8 mm screw).
- Check shaft flats: a D-cut shaft suits a set screw, a smooth shaft suits a clamp.
- Pick rigid only when the shafts are truly aligned; otherwise use a flexible type.
- Check the outer diameter and length fit your bracket.
Shop: all couplings · stepper motors · lead screws
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