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When a rigid coupling transmits every vibration and amplifies shaft misalignment into binding, noise, and premature bearing wear, DIY CNC builders and motion-control engineers need a smarter solution. The D25 L30 flexible plum jaw shaft coupler is engineered for hobbyists and professionals who demand smooth, low-backlash power transmission between stepper motors, servo motors, and lead screws — without the headaches of perfect alignment.
This coupler consists of two aluminum alloy hubs (outer diameter 25 mm / ~0.98 in, length 30 mm / ~1.18 in total) joined by a polyurethane spider insert. Bore sizes span 5 mm to 14 mm on each side, covering both same-bore (e.g., 5×5 mm) and stepped-bore (e.g., 6×10 mm) configurations. Each hub is secured with a radial clamping screw for a firm, slip-free grip on the shaft.
Typical use cases include connecting NEMA 17 or NEMA 23 stepper motors to T8 or T12 lead screws in 3D printers and CNC routers, coupling servo motor output shafts to ball screws in milling machines, and linking encoder shafts in precision measurement rigs where angular misalignment compensation is critical.
| Outer Diameter (OD) | 25 mm (~0.98 in) |
|---|---|
| Overall Length (L) | 30 mm (~1.18 in) |
| Bore Size (Side 1 × Side 2) | See variant options (5 mm – 14 mm per side) |
| Hub Material | Aluminum alloy |
| Spider / Insert Material | Polyurethane (PU) |
| Fastening Method | Radial set screw (hex key) |
| Misalignment Tolerance | Angular: typically ≤1°; Parallel: typically ≤0.2 mm |
| Finish | Natural anodized aluminum |
| Quantity per Order | 1 Pcs |
| Compatible Motor Types | Stepper motor, servo motor, DC motor |
Measure the output shaft diameter of your motor (commonly 5 mm for NEMA 17, 6.35 mm or 8 mm for NEMA 23) and the lead screw shaft diameter (commonly 8 mm for T8, 12 mm for T12). Select the variant that matches both diameters — for example, a 5×8 mm coupler for a NEMA 17 motor driving a T8 lead screw. If both shafts are the same size, choose a same-bore variant such as 8×8 mm.
Yes. The polyurethane spider insert is designed to absorb angular misalignment of typically up to 1° and parallel (radial) misalignment of up to approximately 0.2 mm. This flexibility reduces side-load stress on motor bearings and lead screw nuts, extending the service life of your drivetrain. For best results, minimize misalignment during installation rather than relying on the coupler to compensate for large offsets.
This D25 L30 plum jaw coupler is well-suited for the torque and speed ranges typical of NEMA 17 and NEMA 23 stepper motors in CNC routers, 3D printers, and laser engravers. For very high-torque servo applications or speeds above approximately 3,000 RPM, verify that the polyurethane spider's rated torque capacity matches your system requirements. Contact us to confirm suitability for demanding industrial duty cycles.
The aluminum alloy hubs have a natural anodized finish that provides a base level of corrosion resistance suitable for typical indoor workshop environments. For exposure to cutting fluids, coolants, or humid outdoor conditions, periodic inspection is recommended. Aluminum does not rust, but prolonged exposure to acidic or alkaline fluids may affect the surface finish over time.
Slide each hub onto its respective shaft, aligning the set screw hole with the shaft. Insert the polyurethane spider between the two hubs so the jaw lobes interlock. Tighten the set screws with the appropriate hex key (typically M3 or M4) to the manufacturer's recommended torque — finger-tight plus a quarter turn is a common starting point. Avoid over-tightening, which can deform the bore. Check alignment and re-tighten after the first few hours of operation.
Yes. The polyurethane spider is a separate, replaceable component. You can remove it by sliding the two hubs apart slightly (without removing them from the shafts) and pulling the spider out. Insert a new spider of the same jaw count and OD to restore full coupling performance. This makes maintenance fast and cost-effective on active machines.
A same-bore variant (e.g., 8×8 mm) has identical bore diameters on both sides and is used when the motor shaft and driven shaft are the same size. A stepped-bore variant (e.g., 5×8 mm) has different bore diameters on each side, allowing you to connect shafts of different diameters — common when pairing a NEMA 17 motor (5 mm shaft) with a T8 lead screw (8 mm shaft). Select the variant that matches your specific shaft combination.
