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When a misaligned or slipping shaft coupling causes your CNC router to lose steps or your 3D printer to produce layer shifts, the root cause is almost always a poorly fitted coupler. Engineers, hobbyists, and workshop professionals who demand repeatable, backlash-free motion need a shaft coupling that grips firmly and transfers torque without play. The D15*L20 flexible shaft coupling rigid CNC motor coupler is engineered for exactly that application.
This coupler features an aluminum alloy body with an outer diameter of 15 mm (0.59 in) and a length of 20 mm (0.79 in). The dual-bore design accepts two independent shaft diameters (d1 × d2), spanning from 2 mm up to 6.35 mm (approximately 1/4 in), covering both metric and imperial shaft sizes. Each coupler is secured by set screws that clamp directly onto the shaft, providing a firm mechanical grip without adhesives.
Typical use cases include connecting stepper motor shafts to lead screws on CNC milling machines, coupling motor output shafts to encoder shafts in robotics projects, and linking drive shafts to ball screws on DIY 3D printer Z-axis assemblies. Long-tail applications such as "2mm to 6.35mm shaft adapter for NEMA 17" and "rigid coupler for CNC lead screw" are well served by this product's wide bore range.
Each coupler accepts two independently sized bores (d1 × d2), letting you connect shafts of different diameters — from 2 mm up to 6.35 mm — without adapters or sleeves.
At just 15 mm outer diameter and 20 mm length, this coupler fits into tight motor-mount cavities common on desktop CNC machines and compact 3D printer frames.
The aluminum alloy body delivers a strong strength-to-weight ratio, resists corrosion in workshop environments, and dissipates heat generated during continuous motor operation.
Radial set screws lock the coupler firmly onto each shaft, preventing rotational slip under load and maintaining zero-backlash torque transmission during direction reversals.
Bore options span standard metric sizes (2, 3, 4, 5, 6 mm) and common imperial sizes (3.17 mm ≈ 1/8 in; 6.35 mm = 1/4 in), covering the most widely used stepper motor and lead-screw shaft standards.
Unlike flexible jaw or spider couplings, this rigid design transmits torque with no angular deflection, making it ideal for applications where positional accuracy — such as CNC axis repeatability — is critical.
| Outer Diameter (D) | 15 mm (0.59 in) |
|---|---|
| Length (L) | 20 mm (0.79 in) |
| Bore 1 (d1) Range | 2 mm – 6.35 mm (see variant options) |
| Bore 2 (d2) Range | 2 mm – 6.35 mm (see variant options) |
| Material | Aluminum alloy |
| Finish | Natural anodized / mill finish |
| Clamping Method | Set screw |
| Coupling Type | Rigid |
| Bore Size Combination | See variant options |
| Quantity per Order | 1 / 5 / 10 / 20 pcs (see variant options) |
Measure the outer diameter of each shaft you need to connect — your motor shaft (d1) and your lead screw or encoder shaft (d2). Select the variant that matches both diameters exactly. Common pairings include 5 mm × 8 mm for NEMA 17 to standard lead screws, or 6.35 mm × 6.35 mm for 1/4-inch imperial shafts. If your shafts are the same size, choose a same-diameter variant such as 4 mm × 4 mm.
This is a rigid coupling, meaning it transmits torque without any angular or axial compliance. This is ideal for CNC axes and 3D printer lead screws where positional accuracy matters, because there is no spring-back or deflection. However, if your motor and driven shaft have significant angular misalignment, a flexible (jaw or bellows) coupler would be more appropriate to avoid bearing wear.
The torque capacity depends on the set-screw clamping force and the aluminum alloy shear strength. For typical NEMA 17 stepper motors (holding torque up to approximately 0.4–0.6 N·m) and NEMA 23 motors (up to approximately 1–3 N·m), this D15 × L20 coupler is well within its operating range. For higher-torque applications, contact us to confirm suitability.
The aluminum alloy body forms a natural oxide layer that provides good corrosion resistance in typical indoor workshop conditions, including moderate humidity. For prolonged outdoor exposure or contact with cutting fluids, applying a light coat of machine oil to the exterior surface is recommended to maintain appearance and prevent surface oxidation.
Yes — 3.17 mm is the metric equivalent of 1/8 inch (3.175 mm), which is a common shaft size on small DC motors, micro stepper motors, and some encoder shafts. The bore is machined to accept this size. Similarly, 6.35 mm equals exactly 1/4 inch, covering many servo motor and gearbox output shafts.
Yes. This is one of the most common applications. Select the variant where d1 matches your stepper motor shaft (typically 5 mm for NEMA 17) and d2 matches your lead screw shaft (typically 5 mm or 8 mm). The rigid design ensures that motor steps translate directly into vertical movement without rotational play, which is critical for consistent layer height.
You can select 1, 5, 10, or 20 pieces per order using the Units (pcs) variant option. Bulk quantities are priced at a lower per-unit cost — the 20-piece option offers the best per-unit value. If you need quantities beyond 20 pieces, please contact us for a custom quote.
