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When misalignment, vibration, or shaft runout causes your CNC machine to skip steps or lose accuracy, the coupling between your motor and lead screw is often the culprit. Engineers, makers, and machine builders who demand repeatable positioning need a coupling that absorbs shock without sacrificing torque transmission — and that's exactly what these flexible plum couplings deliver.
Each coupler consists of two aluminum alloy hubs and a polyurethane spider insert (plum-shaped elastomer). The body diameter ranges from 14 mm to 25 mm (0.55" to 0.98") and the overall length from 22 mm to 35 mm (0.87" to 1.38"), with bore diameters spanning 3 mm to 12 mm (0.12" to 0.47") to cover the most common stepper and servo motor shaft sizes. Set screws on each hub clamp securely to the shaft.
Typical applications include 3D printer Z-axis lead screws, CNC router spindle drives, laser engraver feed axes, and small robotic joint actuators — anywhere a flexible shaft coupler for stepper motor or servo motor is needed to compensate for minor angular or parallel misalignment.
| Coupler Type | Jaw / Plum (Spider) Flexible Coupling |
|---|---|
| Hub Material | Aluminum Alloy (anodized) |
| Insert Material | Polyurethane Elastomer |
| Body Diameter Options | D14 mm / D20 mm / D25 mm (0.55" / 0.79" / 0.98") |
| Overall Length Options | L22 mm / L25 mm / L30 mm / L35 mm (0.87"–1.38") |
| Bore Diameter Range | 3 mm – 12 mm (0.12" – 0.47") |
| Bore Combinations | Same-bore and mixed-bore (see variant options) |
| Clamping Method | Set Screw (hex key) |
| Finish | See variant options |
| Pack Quantity | 1 / 3 / 5 / 10 / 15 pcs (see variant options) |
| Typical Application | CNC router, 3D printer, laser engraver, servo drive |
| Weight per Piece | See variant options |
Match the body diameter to your motor frame size. D14 mm couplers suit compact NEMA 14/17 setups with limited clearance. D20 mm fits most NEMA 17 and small NEMA 23 motors. D25 mm is recommended for NEMA 23 and larger motors where higher torque is transmitted. Always verify the bore options match both your motor shaft and lead screw diameter before ordering.
Yes. Many variants in this listing are specifically designed for mixed-bore applications — for example, 4 mm × 10 mm or 4 mm × 12 mm. Select the Shaft Diameter option that shows two different values (e.g., "4mm × 10mm") to get a coupler bored differently on each end. Same-bore options (e.g., "6mm × 6mm") are also available if both shafts share the same diameter.
The polyurethane spider insert is rated for continuous torque typical of NEMA 17 and NEMA 23 stepper motors in CNC and 3D printing applications. It is designed to flex slightly under shock loads rather than transmitting the full impulse to motor bearings. For very high-torque servo applications, verify the rated torque of the specific coupler size against your motor's peak torque output. The insert can be replaced independently if it wears over time.
The aluminum alloy hubs offer good natural corrosion resistance and are anodized for additional surface protection. They are suitable for indoor workshop environments and light-duty outdoor enclosures. For highly corrosive or fully outdoor environments, consider applying a light coating of anti-corrosion spray to the set screw areas, as bare steel set screws can rust if exposed to moisture over time.
Set screw hex key size varies by coupler body diameter: D14 mm couplers typically use an M2.5 or M3 hex key, D20 mm couplers typically use M3, and D25 mm couplers typically use M4. A standard metric hex key set will cover all sizes. Tighten firmly but avoid overtightening, which can deform the shaft or strip the set screw thread.
Flexible plum couplers of this type typically accommodate angular misalignment of up to approximately 1°–3° and parallel (radial) offset of up to approximately 0.2–0.5 mm, depending on body size and elastomer hardness. They are not designed to compensate for large misalignments — always align your motor and lead screw as accurately as possible during installation to maximize coupling life and positioning accuracy.
Multi-packs (3, 5, 10, or 15 pcs) offer a lower per-unit cost and ensure you have spares on hand for future builds or maintenance. CNC machines and 3D printers often use multiple axes, each requiring its own coupler. Buying a pack upfront avoids delays when you need a replacement mid-project.
