Buying guide
Shaft Coupling Types: Jaw, Flexible, Rigid, Oldham and Diaphragm
Which coupling to use between a stepper or servo motor and a lead screw, ball screw or shaft.
A shaft coupling joins two shafts, usually a motor shaft and a lead screw or ball screw. The right type depends on how well the shafts are aligned and how much backlash your machine can accept.
Common types
| Type | Good for | Note |
|---|---|---|
| Rigid / rigid clamp | Shafts that are already well aligned | No flex, so any misalignment loads the bearings |
| Flexible (helical / beam) | 3D printer Z axes, small CNC, encoders | Tolerates small misalignment; low cost |
| Jaw (spider) | Stepper and servo drives on CNC routers | Elastic spider absorbs shock and vibration |
| Oldham | Lead screws with parallel offset (e.g. Z axis wobble) | Handles offset between shafts well |
| Diaphragm | Servo motors and ball screws needing high stiffness | Zero backlash, higher torsional stiffness |
Set screw or clamp?
Set screw hubs are simple and cheap; tighten the screw onto a flat on the shaft. Clamp hubs grip the whole shaft circumference, do not mark the shaft and hold better under reversing loads, so they are preferred on servo and ball screw axes.
How to order the right size
- Measure both shaft diameters (for example 5 mm motor shaft to 8 mm lead screw: a 5 x 8 coupling).
- Check the outer diameter and length fit your space.
- Choose the type from the table above.
See also: all couplings · pulley bore size · GT2 steps per mm
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