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When misaligned shafts cause vibration, noise, or premature wear in your CNC router, stepper motor drive, or 3D printer axis, a rigid coupling simply won't cut it. Engineers, makers, and machine builders who demand smooth, reliable torque transmission need a flexible jaw coupling that absorbs angular and parallel misalignment without sacrificing rotational accuracy.
This flexible plum coupling features a two-piece aluminum alloy spider-jaw body with a polyurethane (PU) spider insert. The outer diameter is 30 mm (≈1.18 in), available in two body lengths: L35 (35 mm / ≈1.38 in) and L40 (40 mm / ≈1.57 in). Bore combinations span d1 × d2 from 5 mm × 5 mm up to 16 mm × 16 mm, covering both metric and 1/4-inch (6.35 mm) imperial shaft sizes.
Typical use cases include CNC stepper motor shaft-to-leadscrew connections, 3D printer Z-axis couplings, and light-duty servo drive systems where vibration damping and zero-backlash torque transfer are required. Long-tail applications: "D30 flexible jaw coupling for NEMA 17 stepper," "plum coupling 5mm to 8mm bore CNC," "spider coupling 3D printer Z axis."
| Outer Diameter (D) | 30 mm (≈1.18 in) |
|---|---|
| Body Length (L) | 35 mm or 40 mm — see variant options |
| Bore d1 (Motor Side) | 5 mm – 16 mm — see variant options |
| Bore d2 (Leadscrew Side) | 5 mm – 16 mm — see variant options |
| Imperial Bore Available | 6.35 mm (1/4 in) |
| Body Material | Aluminum alloy |
| Spider Insert Material | Polyurethane (PU) |
| Coupling Type | Flexible jaw / plum spider |
| Clamping Style | Split-clamp with socket-head cap screws |
| Angular Misalignment Tolerance | Typically up to 1° |
| Max Torque | See variant options |
| Units per Order | 1 piece |
Choose L35 (35 mm) when your motor-to-leadscrew gap is tight and you need a compact coupling. Choose L40 (40 mm) when you want a slightly longer spider engagement zone for improved vibration damping or when your axis layout has more clearance. Both share the same D30 outer diameter and bore range, so the choice is purely based on your axial space and damping preference.
Yes. The "Hole (d1 × d2)" option lets you select mismatched bores — for example, 5 mm on the motor side and 8 mm on the leadscrew side. This is one of the main advantages of a two-piece jaw coupling over a rigid sleeve coupling. Simply select the d1 × d2 combination that matches your specific shaft diameters.
Yes — 6.35 mm is exactly 1/4 inch (6.35 mm = 0.25 in). Variants listed as "6.35 mm" on either d1 or d2 are designed for 1/4-inch imperial shafts, which are common on North American stepper motors and some servo motors. You can mix metric and imperial bores freely across the two ends.
The polyurethane spider insert accommodates angular misalignment of typically up to approximately 1° and small amounts of parallel (radial) offset. It is not designed for large misalignment — if your motor and leadscrew are significantly out of alignment, correct the mechanical alignment first. The coupling's primary role is to absorb minor residual misalignment and dampen vibration, not to compensate for poor machine assembly.
Under normal operating loads, the jaw-and-spider engagement maintains near-zero backlash. The PU spider is slightly compliant, which provides vibration damping, but this compliance is minimal under the reversing loads typical of CNC and 3D printer axes. For high-precision applications, ensure the clamp screws are torqued correctly so the coupling does not slip on the shaft — shaft slip is the most common source of apparent "backlash" with clamp-style couplings.
Slide each half of the coupling onto its respective shaft, insert the PU spider between the two halves, then align the shafts and tighten the split-clamp screws with a hex key (Allen wrench). Tighten evenly and to the screw manufacturer's recommended torque for the screw size used. Do not overtighten — the aluminum body can crack if the clamp screws are over-torqued. Check tightness after the first few hours of operation as screws may settle slightly.
A rigid coupling transmits torque with zero compliance — any misalignment between shafts is transferred directly to bearings, causing accelerated wear and noise. A plum (jaw/spider) coupling uses a flexible PU insert between the two aluminum jaws to absorb misalignment and vibration. This protects motor bearings and frame components, making it the preferred choice for CNC routers, 3D printers, and light automation where perfect shaft alignment is difficult to achieve mechanically.
