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When shaft misalignment, vibration, or torque shock threatens the precision of your CNC router, 3D printer, or automation rig, a rigid coupling simply isn't enough. Engineers and DIY builders who demand consistent, low-backlash motion transfer rely on flexible jaw couplings to protect their motors and lead screws from the stresses of real-world operation.
This flexible plum spider jaw shaft coupling features an outer diameter of Ø20 mm (~0.79 in) and a length of 25 mm (~0.98 in). The two-piece aluminum alloy hubs grip each shaft independently, while a polyurethane spider insert sits between them to absorb shock and dampen vibration. Bore sizes range from 4 mm to 10 mm (d1 and d2), covering a wide range of motor shaft and lead screw combinations.
Typical applications include stepper motor to lead screw connections on CNC milling machines, flexible coupling for 3D printer Z-axis drives, and servo motor shaft connectors in light industrial automation — all scenarios where angular and parallel misalignment compensation is critical for long-term accuracy.
Each hub clamps independently onto its shaft via set screws, allowing different bore sizes on each end (d1 ≠ d2) — ideal for mixed motor and lead screw shaft diameters.
The star-shaped elastomer spider absorbs torque shock, reduces vibration transmission, and compensates for angular, parallel, and axial misalignment between connected shafts.
Compact form factor fits within tight motor mounts and gantry assemblies. Outer diameter of 20 mm (~0.79 in) and length of 25 mm (~0.98 in) suit most desktop CNC and 3D printer builds.
The interference-fit spider insert minimizes rotational play, maintaining positioning repeatability in open-loop stepper motor systems where backlash directly affects part accuracy.
Lightweight aluminum alloy construction resists oxidation in workshop environments. Anodized finish (where applicable) adds surface hardness and extends service life.
Available in 28 bore size combinations from 4×4 mm up to 9×10 mm, covering the most common stepper motor shaft and lead screw diameter pairings used in DIY CNC and automation projects.
| Outer Diameter (Ø) | 20 mm (0.79 in) |
|---|---|
| Coupling Length | 25 mm (0.98 in) |
| Bore Size d1 Range | 4 mm – 9 mm |
| Bore Size d2 Range | 4 mm – 10 mm |
| Hub Material | Aluminum Alloy |
| Spider Insert Material | Polyurethane (PU) |
| Coupling Type | Flexible Jaw / Plum Spider |
| Misalignment Compensation | Angular, Parallel, Axial |
| Fastening Method | Set Screw (grub screw) |
| Finish | See variant options |
| Max Recommended RPM | See variant options |
| Max Torque | See variant options |
Measure the shaft diameter of your motor (d1) and the shaft or lead screw it connects to (d2) using a caliper. Select the variant where d1 matches your motor shaft and d2 matches your lead screw or driven shaft. Both bores are clamped independently, so d1 and d2 do not need to be equal.
Yes. The polyurethane spider insert flexes to accommodate angular misalignment (typically up to 1°–3°) and small amounts of parallel offset. For best results, align shafts as closely as possible — the spider compensates for residual misalignment rather than replacing proper alignment practice.
Aluminum alloy naturally forms a thin oxide layer that resists further corrosion in typical indoor workshop conditions. For environments with exposure to cutting fluids or high humidity, periodic inspection of the set screws is recommended to prevent galvanic corrosion at the fastener contact points.
Yes. NEMA 17 motors typically have 5 mm shafts and NEMA 23 motors commonly use 6.35 mm or 8 mm shafts — all within the 4–10 mm bore range of this coupling. Select the bore size that matches your specific motor shaft diameter.
The polyurethane spider is designed to fit snugly between the hub jaws, minimizing rotational play. In open-loop stepper motor systems, low backlash is essential for repeatable positioning. The interference fit of the spider insert keeps backlash to a minimum under normal operating loads.
The spider insert is a separate component from the aluminum hubs. In many cases, replacement spiders of the same jaw count and outer diameter can be sourced independently, extending the service life of the aluminum hubs. Contact us to confirm compatibility with your specific coupling size.
A rigid coupling transmits torque without any flex, requiring near-perfect shaft alignment. A plum spider jaw coupling uses an elastomer insert to absorb vibration, compensate for minor misalignment, and protect motor bearings from shock loads — making it the preferred choice for CNC and 3D printer applications where some shaft runout is unavoidable.
