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When a misaligned or slipping shaft coupling causes your CNC axis to lose steps or your motor drive to vibrate under load, the root cause is almost always a coupler that can't hold tolerance. Machinists, robotics builders, and DIY automation enthusiasts who need a repeatable, zero-backlash connection between two shafts will find this brass rigid coupler a dependable solution.
Each coupler is machined from brass, offering a balance of machinability, corrosion resistance, and moderate weight. The body accommodates two bore diameters simultaneously — input and output bores ranging from 2 mm (approx. 0.079 in) up to 6 mm (approx. 0.236 in) — making it suitable for mixed-shaft assemblies where the motor shaft and lead screw differ in diameter. Overall coupler length is typically 25–35 mm depending on bore combination; outer diameter is typically 12–20 mm. Exact dimensions vary by variant — see variant options for your specific combination.
Typical use cases include NEMA 17/23 stepper motor to lead screw connections on 3D printers and CNC routers, encoder shaft extensions on servo drives, and small DC gear-motor output shaft connections in robotics and automation rigs where a rigid, non-flexible coupling is preferred for positional accuracy.
Accepts two different shaft diameters simultaneously — ideal for connecting a motor shaft to a lead screw or encoder of a different size without adapters.
Solid one-piece body transmits torque directly with minimal angular or radial play, supporting positional accuracy in CNC and motion-control applications.
Brass construction provides good machinability for field modification, natural corrosion resistance in typical workshop environments, and a lower magnetic signature than steel couplers.
Available in bore combinations spanning 2 mm to 6 mm (approx. 0.079–0.236 in), covering the most common shaft sizes used in hobby CNC, 3D printing, and small automation builds.
Secured to each shaft via set screws (typically M3 or M4 depending on bore size), allowing tool-free removal and repositioning during prototyping or maintenance.
Available in packs of 1, 3, 5, 10, 20, or 30 pieces — order a single coupler for a repair or stock up for a multi-axis build or production run.
| Material | Brass |
|---|---|
| Bore Diameter (Input) | See variant options (2 mm / 2.3 mm / 3 mm / 3.17 mm / 4 mm / 5 mm / 6 mm) |
| Bore Diameter (Output) | See variant options (2 mm / 3 mm / 3.17 mm / 4 mm / 5 mm / 6 mm) |
| Outer Diameter | Typically 12–20 mm (varies by bore combination) |
| Coupler Length | Typically 25–35 mm (varies by bore combination) |
| Retention Method | Set screw (M3 or M4, varies by bore size) |
| Coupler Type | Rigid (non-flexible) |
| Finish | Natural brass |
| Pack Quantity | See variant options (1 / 3 / 5 / 10 / 20 / 30 pcs) |
| Compatible Shaft Types | Round shafts with flat (D-cut) or round cross-section |
Select the bore that matches your motor shaft diameter as the input bore, and the bore that matches your lead screw or driven shaft as the output bore. For example, if your NEMA 17 stepper has a 5 mm shaft and your lead screw is 8 mm — that combination is not listed, so you would need an intermediate adapter. All available combinations are listed in the variant selector above.
This is a rigid coupler. It does not absorb angular or parallel misalignment between shafts. For best results, ensure your motor and driven shaft are well-aligned before installation. If your application requires misalignment compensation, consider a jaw-type or bellows flexible coupling instead.
Brass has good natural corrosion resistance in typical indoor workshop and light industrial environments. In high-humidity or salt-air outdoor conditions, surface oxidation (patina) may develop over time but generally does not affect structural integrity. For harsh outdoor or marine environments, a stainless steel coupler would be a more suitable choice.
Set screw size varies by bore diameter. Smaller bores (2–3 mm) typically use M3 set screws, while larger bores (4–6 mm) typically use M4 set screws. A standard hex key (Allen key) is used for tightening. We recommend applying a small amount of thread-locking compound for vibration-prone applications.
Yes. These couplers are commonly used to connect NEMA 17 stepper motor shafts (typically 5 mm) to T8 or T12 lead screws (typically 8 mm — note: 8 mm bore is not in this listing) or to other lead screw diameters available in the variant list. Check your motor shaft and lead screw diameters before ordering to confirm the correct bore combination.
A standard 3-axis CNC router or 3D printer typically requires 3 couplers (one per axis). A 4-axis machine needs 4. Ordering a 5-pack or 10-pack provides spares for future maintenance or prototyping. The per-unit cost decreases with larger pack quantities, so stocking up is cost-effective for multi-machine builds.
Specific RPM and torque ratings depend on the bore combination and application conditions. As a general guide, brass rigid couplers in this size range are suitable for low-to-medium speed applications (typically up to 3,000–5,000 RPM) and light-to-moderate torque loads consistent with hobby CNC and small automation use. Contact us to confirm suitability for high-speed or high-torque applications.
