Couplers, couplers, couplers.

When you need to join a stepper or servo motor to a screw shaft, you use a coupler. There are several types available.

Jaw (Spider) Couplers

Design: Two metal hubs with interlocking teeth separated by a rubber or polyurethane insert (the "spider").

Pros: Great at absorbing vibration, handles angular and parallel misalignments, cheap.

Cons: Very soft spiders can introduce tiny amounts of backlash or wind-up under heavy dynamic loads.

Best Use: 3D printers and DIY CNC routers using StepperOnline motors or similar small machines.

Beam (Helical) Couplers

Design: Machined from a single block of aluminum with a spiral or helical cut pattern carved into the middle.

Pros: Accommodates angular misalignment and minor parallel offset while maintaining smooth rotation.

Cons: Can act like a spring, compressing up and down or twisting under heavy axial load variations.

Best Use: Light-duty positioning, encoders, and small measurement tools. Not recommended for CNC machines.

Oldham Couplers

Design: Composed of two hubs and a central floating disc that slides back and forth on tongue-and-groove tracks.

Pros: Handles large parallel misalignments smoothly without placing side-load stress on the motor shaft or compressing axially.

Cons: More complex parts; can wear out over long-term high-speed use if not lubricated or fitted tightly.

Best Use: CNC machines where heavier loads are encountered.

Rigid Couplers

Design: Machined from a single block. Set screws lock to both shafts.

Pros: Cheap. Handles load.

Cons: Requires perfect alignment of shafts. Transfers vibrations. Causes rapid wear with even slight misalignment. Best Use: Not recommended due to difficulty of alignment.

About Me.

I'm Phil Barrett, a long time CNC enthusiast. I run a small company, Brookwood Design, that makes several breakout boards for grblHAL and love to help people get the most out of their CNC machines.