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Shaft misalignment is one of the most common causes of premature bearing wear, vibration noise, and lost positional accuracy in CNC routers, 3D printers, and servo-driven automation systems. Engineers, makers, and machine builders who demand tight tolerances need a coupler that compensates for angular, parallel, and axial misalignment without sacrificing torque transmission. This flexible plum coupling — also called a jaw spider shaft coupler — is engineered for exactly that job.
Each coupler consists of two aluminum alloy hubs and a polyurethane spider insert (plum-shaped elastomer). The hubs are precision-bored to accept shaft diameters ranging from 5 mm to 28 mm (approx. 0.20"–1.10"), with outer diameters spanning 20 mm to 55 mm (approx. 0.79"–2.17") and body lengths from 25 mm to 80 mm (approx. 0.98"–3.15"). Set screws lock each hub firmly onto the shaft. Variants with equal bore diameters (e.g., d6-6, d8-8) and reducing bore options (e.g., d15-18, d12-28) are available.
Typical use cases include stepper and servo motor coupling on CNC milling machines and laser engravers, lead-screw connections on Cartesian 3D printers such as Ender and Prusa-style frames, and flexible coupling for rotary encoders and pump drives where vibration damping is critical. Search terms like "flexible jaw coupler for NEMA 23 motor," "spider coupler CNC lead screw," and "plum coupling 3D printer Z-axis" describe exactly what this product solves.
Precision-machined aluminum hubs deliver low rotational inertia and corrosion resistance, keeping your drivetrain responsive and rust-free over long service cycles.
The elastomeric plum insert absorbs shock loads and dampens vibration, protecting downstream components like encoders and ball screws from impact fatigue.
27 variants cover outer diameters from D20 to D55 and bore diameters from 5 mm to 28 mm, making it straightforward to match your motor shaft and driven shaft in one order.
Accommodates angular misalignment (typically up to 1°), parallel offset, and axial displacement, reducing stress on motor bearings and extending machine life.
Each hub is secured with grub set screws for tool-free shaft swaps during maintenance or machine reconfiguration — no press-fit required.
Sized and bored to match common NEMA 17 (5 mm shaft), NEMA 23 (6.35 mm shaft), and servo motor shaft standards used in hobbyist and professional CNC builds.
| Product Type | Flexible Jaw (Plum / Spider) Shaft Coupler |
|---|---|
| Hub Material | Aluminum Alloy |
| Insert Material | Polyurethane Elastomer (Spider / Plum) |
| Outer Diameter (D) | 20 mm – 55 mm (0.79" – 2.17") |
| Body Length (L) | 25 mm – 80 mm (0.98" – 3.15") |
| Bore Diameter (d) | 5 mm – 28 mm (0.20" – 1.10") — See variant options |
| Bore Configuration | Equal bore & reducing bore variants available |
| Clamping Method | Set Screw (Grub Screw) |
| Finish | Natural Aluminum (anodized or brushed) — See variant options |
| Misalignment Tolerance | Angular: typically ≤1°; Parallel: See variant options |
| Application | CNC Router, 3D Printer, Servo / Stepper Motor, Lead Screw, Encoder |
| Quantity per Order | 1 piece |
Check the shaft diameter of both your motor and the driven component (e.g., lead screw or encoder). Select a variant whose bore values match — for example, "d6.35-6.35" for a NEMA 23 motor paired with a 6.35 mm lead screw, or a reducing variant like "d15-18" when the two shafts differ in size. Measure with calipers before ordering to confirm.
Equal-bore couplers (e.g., d8-8) have the same bore diameter on both hubs and are used when the motor shaft and driven shaft are the same size. Reducing-bore couplers (e.g., d12-28) have different bore diameters on each hub, allowing you to connect two shafts of different diameters without an adapter sleeve.
Polyurethane spider inserts are designed for continuous duty in light-to-medium torque applications typical of CNC and 3D printer drives. They resist oil, grease, and moderate heat. Under normal operating loads the insert outlasts many machine service intervals; however, if you notice increased backlash or cracking, the insert can be replaced independently without replacing the aluminum hubs.
The aluminum hubs offer good corrosion resistance in typical indoor workshop and light industrial environments. For prolonged outdoor or high-humidity exposure, applying a light coat of anti-corrosion spray to the hub exterior is recommended. The polyurethane insert itself is moisture-resistant and will not swell or degrade under normal humidity levels.
NEMA 17 motors typically have a 5 mm output shaft — select a variant with d5 bore. NEMA 23 motors commonly use a 6.35 mm (1/4") shaft — choose a d6.35 variant. Always verify your specific motor's datasheet, as some NEMA 23 motors ship with 8 mm or 10 mm shafts depending on the manufacturer.
Yes. This is one of the most common applications. The flexible spider insert compensates for the slight angular misalignment that often exists between a stepper motor shaft and a lead screw, reducing Z-axis wobble artifacts ("Z-banding") in prints. Match the bore to your motor shaft and lead screw diameter, and ensure the outer diameter fits within your printer's frame clearance.
Slide each hub onto its respective shaft, align the hubs so the spider insert seats evenly between the jaw fingers, then tighten the set screws with the appropriate hex key (typically 2–3 mm). Ensure the shaft end is flush with or slightly recessed from the inner face of the hub for maximum grip. Do not overtighten — snug and firm is sufficient to prevent slipping under normal torque loads.
