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When shaft misalignment causes vibration, noise, or premature wear in your CNC router, stepper motor drive, or 3D printer, the root cause is often a rigid coupling that cannot compensate for angular or parallel offset. This flexible plum coupling shaft coupler is designed for engineers, makers, and machine builders who need reliable torque transmission without sacrificing flexibility.
Each coupler consists of two aluminum alloy hubs and a polyurethane (PU) spider insert (plum element). The D35 outer diameter body is available in two lengths — L50 (50 mm / 1.97 in) and L60 (60 mm / 2.36 in) — with bore hole combinations ranging from 6 mm to 19 mm (0.24 in to 0.75 in) on both the d1 and d2 sides, covering metric and inch shaft sizes including 6.35 mm (1/4") and 12.7 mm (1/2") imperial bores.
Typical applications include flexible plum coupling for NEMA 17 / NEMA 23 stepper motor shaft connections, CNC lead screw to motor coupling, 3D printer Z-axis coupler replacement, and servo motor shaft adapter for light-duty automation. The spider insert dampens vibration and accommodates angular misalignment up to approximately 1°–3° and parallel offset up to approximately 0.2–0.5 mm, making it a reliable choice for precision motion control shaft coupler applications.
Hole combinations from 6 mm × 6 mm up to 19 mm × 19 mm, including mixed metric/imperial sizes (e.g., 6 mm × 6.35 mm, 8 mm × 12.7 mm), covering the most common CNC and 3D printer shaft diameters in a single product family.
The polyurethane plum element absorbs shock loads and reduces transmitted vibration between motor and driven shaft, helping protect bearings and extending the service life of connected components.
Lightweight yet rigid aluminum alloy hub bodies keep rotational inertia low — important for responsive stepper motor positioning — while providing the structural strength needed for consistent torque transmission.
Choose D35 × L50 (50 mm) for compact installations or D35 × L60 (60 mm) where additional shaft engagement length or clearance is required. Both share the same 35 mm outer diameter for interchangeability.
Each hub is secured to the shaft via set screws (grub screws), allowing tool-free shaft changes and straightforward installation without special press-fit tooling. Suitable for both solid and hollow shafts within the bore range.
Accommodates angular misalignment (typically 1°–3°) and parallel offset (typically 0.2–0.5 mm), reducing stress on motor bearings and lead screw nuts caused by minor shaft alignment errors during machine assembly.
| Coupling Type | Flexible Jaw / Plum (Spider) Coupling |
|---|---|
| Hub Material | Aluminum Alloy |
| Spider Insert Material | Polyurethane (PU) |
| Outer Diameter (D) | 35 mm (1.38 in) |
| Body Length (L) | 50 mm (1.97 in) — D35 × L50 / 60 mm (2.36 in) — D35 × L60 |
| Bore d1 Range | 6 mm – 19 mm (0.24 in – 0.75 in); includes 6.35 mm & 12.7 mm imperial |
| Bore d2 Range | 6 mm – 19 mm (0.24 in – 0.75 in); includes 6.35 mm & 12.7 mm imperial |
| Angular Misalignment | Typically 1°–3° |
| Parallel Offset | Typically 0.2–0.5 mm |
| Shaft Fixing Method | Set Screw (Grub Screw) |
| Quantity per Order | 1 piece |
| Finish | See variant options |
| Max Torque | See variant options |
Measure the outer diameter of each shaft you need to connect. The d1 bore fits one shaft end and d2 fits the other. If both shafts are the same diameter (e.g., 8 mm motor shaft to 8 mm lead screw), select a same-size combination like 8 mm × 8 mm. For mixed setups — such as a 6.35 mm (1/4") motor shaft to an 8 mm lead screw — choose the matching mixed bore option. Always verify shaft diameter with calipers before ordering.
Both share the same 35 mm outer diameter. The L50 version is 50 mm long (1.97 in) and suits compact motor mounts where axial space is limited. The L60 version is 60 mm long (2.36 in) and provides more shaft engagement length, which can be useful when connecting shafts with shorter usable ends or when additional clearance between motor face and driven component is needed.
This plum coupling is suitable for light-to-medium duty applications typical of NEMA 17 and NEMA 23 stepper motors used in CNC routers, 3D printers, and similar machines. For high-torque servo or industrial motor applications, please contact us to confirm suitability for your specific torque and speed requirements before ordering.
Yes. The PU spider insert sits between the two aluminum hubs and can be removed and replaced without disassembling the entire drive train. This makes maintenance straightforward — if the insert shows wear or cracking after extended use, only the spider element needs to be replaced rather than the entire coupling.
Yes. The bore range includes common imperial sizes: 6.35 mm (1/4") and 12.7 mm (1/2"). Mixed metric/imperial combinations are available, such as 6 mm × 6.35 mm or 8 mm × 12.7 mm, making this coupler compatible with machines that mix metric motors with imperial lead screws or vice versa.
The flexible plum design typically accommodates angular misalignment of approximately 1°–3° and parallel (radial) offset of approximately 0.2–0.5 mm. While it provides more forgiveness than a rigid coupling, it is not a substitute for proper shaft alignment. For best results, align shafts as accurately as possible during installation and use the coupler's flexibility as a buffer for minor residual misalignment.
Slide each hub onto its respective shaft, position the coupler so the spider insert is centered between the two hubs, then tighten the set screws (grub screws) on each hub using an appropriate hex key. Ensure the shaft is inserted to the full depth of the bore for maximum grip. Do not overtighten set screws on small-diameter shafts to avoid deforming the bore.
