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When misalignment, vibration, or backlash causes positioning errors in your CNC machine or stepper motor drive system, a rigid coupling simply won't cut it. The D40mm L78mm flexible plum coupling is engineered for builders, machinists, and automation engineers who need reliable torque transmission with built-in compensation for angular, parallel, and axial shaft misalignment — without sacrificing rotational accuracy.
This jaw spider coupling consists of two aluminum alloy hubs and a polyurethane (PU) spider insert. The outer diameter is 40mm (1.57 in) and the overall length is 78mm (3.07 in). Shaft bore options span from 8mm to 22mm (0.31 in – 0.87 in), covering both same-diameter and stepped-bore configurations. Each hub is secured via set screws for tool-free shaft changes.
Typical use cases include CNC router Z-axis lead screw coupling, 3D printer stepper motor to ball screw connection, laser engraver drive shaft coupling, and general industrial automation flexible shaft coupling for servo and stepper motor applications.
Both coupling hubs are machined from aluminum alloy for a lightweight yet rigid structure that resists deformation under continuous torque loads.
The PU jaw spider insert absorbs shock and vibration between hubs, reducing noise and protecting motor bearings from impact loads during direction reversals.
120 shaft diameter combinations available — both equal-bore (e.g., 10mm × 10mm) and stepped-bore (e.g., 8mm × 14mm) — to match virtually any motor-to-screw pairing.
Accommodates angular misalignment (typically up to 1°), parallel offset, and axial displacement, reducing stress on motor shafts and linear guide components.
Each hub is secured with set screws for a firm, slip-resistant grip on the shaft. No special tools required for installation or shaft swaps.
Designed for CNC routers, 3D printers, laser engravers, and industrial automation systems where consistent torque transmission and low backlash are critical.
| Outer Diameter (OD) | 40mm (1.57 in) |
|---|---|
| Overall Length (L) | 78mm (3.07 in) |
| Shaft Bore Range | 8mm – 22mm (0.31 in – 0.87 in) |
| Bore Configuration | Equal-bore and stepped-bore (see variant options) |
| Hub Material | Aluminum alloy |
| Spider Insert Material | Polyurethane (PU) |
| Coupling Type | Jaw / Plum / Spider flexible coupling |
| Clamping Method | Set screw |
| Angular Misalignment | Typically up to 1° |
| Max RPM | See variant options |
| Max Torque | See variant options |
| Quantity per Order | 1 Pcs |
| Surface Finish | Anodized / natural aluminum |
| Weight | See variant options |
Select the variant that matches your motor shaft diameter (first number) and your lead screw or ball screw shaft diameter (second number). For example, if your NEMA 23 stepper motor has a 10mm shaft and your ball screw has a 12mm shaft, choose the 10mm × 12mm variant. If both shafts are the same size, choose the equal-bore option (e.g., 10mm × 10mm).
A rigid coupling transmits torque with zero flex, which means any shaft misalignment directly stresses the motor bearings and screw supports. A plum (jaw/spider) coupling uses a flexible PU insert between the two aluminum hubs to absorb angular and parallel misalignment, vibration, and shock loads — extending the service life of your motor and linear components.
Yes. The bore range of 8mm to 22mm covers the standard shaft diameters for NEMA 23 (typically 6.35mm or 8mm) and NEMA 34 (typically 12mm or 14mm) stepper motors. Please verify your motor's exact shaft diameter before ordering. For shafts below 8mm, this specific coupling is not suitable.
The hubs are machined from aluminum alloy, which provides a good strength-to-weight ratio for CNC and automation applications. For exact torque ratings, contact us to confirm. The set screw clamping ensures the hub stays firmly seated on the shaft under normal operating loads.
The polyurethane spider insert is a wear component that absorbs vibration and shock between the two hubs. In high-cycle or high-load applications, the insert may show wear before the aluminum hubs. The three-piece design (two hubs + one spider) allows you to replace only the insert without replacing the entire coupling, reducing long-term maintenance costs.
Yes — this is one of the most common applications. The D40mm L78mm flexible plum coupling is widely used to connect stepper or servo motor shafts to lead screws and ball screws on CNC routers, laser engravers, and 3D printers. The flexible insert compensates for minor misalignment between the motor and screw supports, reducing binding and improving positioning accuracy.
"D40mm" refers to the outer diameter of the coupling body (40mm / 1.57 in), and "L78mm" refers to the total assembled length of the coupling (78mm / 3.07 in). These dimensions determine whether the coupling will physically fit within your machine's frame clearance. Always verify available space before ordering.
