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When misaligned shafts cause vibration, noise, or premature motor wear, hobbyists and engineers alike need a coupling solution that holds tight under load. This brass flexible shaft coupler is designed for RC car builders, RC boat enthusiasts, and CNC machine operators who demand a secure, low-backlash connection between motor and drive shaft.
Each coupler is machined from solid brass, offering a balance of machinability, corrosion resistance, and mechanical strength. The rigid coupling design features two bored ends joined by a flexible intermediate section, accommodating minor angular and parallel misalignment. Available shaft diameter combinations range from 2mm/2mm up to 6mm/6mm (approximately 0.079" to 0.236"), with both same-diameter and stepped configurations to suit mixed motor-shaft pairings.
Typical use cases include connecting a brushless motor to a drive shaft in an RC boat, linking a stepper motor output to a lead screw on a desktop CNC router, or replacing a worn coupling on a small RC car drivetrain. Long-tail applications such as "2mm to 4mm shaft coupler for RC boat" and "CNC stepper motor flexible coupling" are directly addressed by the variant range available.
Machined from brass for reliable mechanical strength, natural corrosion resistance, and smooth bore finish that grips shaft surfaces securely.
Covers shaft combinations from 2mm/2mm through 6mm/6mm, including stepped variants (e.g., 2mm/4mm, 3mm/5mm) for mixed motor-to-shaft pairings.
Accommodates minor angular and parallel shaft misalignment, reducing stress on motor bearings and extending drivetrain service life.
Rigid bore ends deliver direct torque transfer with minimal rotational play — critical for CNC positioning accuracy and RC drivetrain responsiveness.
Each bore end is secured with a set screw (typically M2–M3 depending on bore size) for tool-free shaft locking and quick field replacement.
Available in 1, 2, 3, 5, 10, 25, and 50-piece quantities — order a single unit for a repair or stock up for a build batch at a lower per-unit cost.
| Material | Brass |
|---|---|
| Shaft Diameter (Input / Output) | See variant options (2mm/2mm to 6mm/6mm) |
| Coupling Type | Flexible shaft coupler with rigid bore ends |
| Retention Method | Set screw (M2–M3, size varies by bore diameter) |
| Overall Length | See variant options |
| Outer Diameter | See variant options |
| Max Recommended RPM | Contact us to confirm |
| Max Torque | Contact us to confirm |
| Finish | Natural brass (uncoated) |
| Package Quantity | 1 / 2 / 3 / 5 / 10 / 25 / 50 PCS (see variant options) |
Measure both your motor output shaft and your driven shaft (e.g., lead screw or drive shaft) with a digital caliper. Select the variant that matches both diameters — for example, if your motor shaft is 3mm and your drive shaft is 5mm, choose the 3mm/5mm variant. Same-diameter variants (e.g., 3mm/3mm) are used when both shafts are identical in size.
Brass provides adequate mechanical strength for the torque levels typical of small brushed and brushless motors used in RC cars and boats. For high-torque or high-RPM applications, confirm the coupler's rated torque with us before ordering. The set screw retention keeps the coupler locked on the shaft during normal operation.
Brass has inherent corrosion resistance and performs well in moist or splash environments typical of RC boat use. It is not fully submersion-rated, but surface oxidation (patina) does not significantly affect mechanical performance. For fully submerged or saltwater applications, consider applying a light coat of corrosion-inhibiting grease to the set screw area.
Yes. These couplers are widely used to connect NEMA 17 and NEMA 23 stepper motor shafts (typically 5mm or 6.35mm / 1/4") to lead screws or ball screws on desktop CNC routers and 3D printer Z-axis assemblies. Select the variant matching your motor shaft and lead screw diameter. Note: 3.17mm corresponds to 1/8" (imperial) shaft sizing.
The "flexible" designation refers to the coupler's ability to accommodate minor shaft misalignment (angular or parallel offset), not to elastic deformation under torque. The bore ends are rigid and transmit torque directly. A small amount of misalignment tolerance prevents binding and reduces bearing wear, but the coupler should not be used as a substitute for proper shaft alignment.
Slide each bore end onto the corresponding shaft until the shaft is flush with or slightly past the set screw hole. Use an appropriate hex key (Allen wrench) to tighten the set screw firmly against the shaft flat or surface. For shafts without a flat, tighten the set screw against the round shaft surface and check periodically for slippage during initial use. Do not overtighten, as this may deform the brass bore.
Single-piece (1 PCS) orders suit one-off repairs or prototype builds. Multi-pack options (2, 3, 5 PCS) are ideal for small batch builds or keeping a spare on hand. Larger packs (10, 25, 50 PCS) offer a lower per-unit cost for workshop stock, maker spaces, or small-scale production runs. The per-piece price decreases as quantity increases.
