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When a misaligned motor shaft causes vibration, slippage, or premature wear on your RC car or DIY drive system, the root cause is almost always a poorly fitted coupler. Hobbyists, robotics builders, and RC enthusiasts who demand tight tolerances and reliable torque transfer need a flexible shaft coupling that holds its position under load without stripping or loosening.
These flexible coupling couplers are available in two materials — brass and 45 steel — and span a shaft diameter range of 2mm to 8mm (approximately 0.079 in to 0.315 in). Each hex connector is machined to close tolerances, with a set-screw locking mechanism that grips the shaft securely. Packing options include 1, 2, 4, or 10 pieces per order to suit single builds or bulk workshop stock.
Typical use cases include RC car wheel-to-motor shaft connections, small DC motor couplings in desktop CNC and 3D printer extruder drives, and flexible shaft joints in DIY robotics arm assemblies — all scenarios where a rigid coupling would crack under slight angular misalignment.
| Shaft Diameter Range | 2mm – 8mm (0.079" – 0.315") |
|---|---|
| Available Sizes | 2mm, 3mm, 3.17mm, 4mm, 5mm, 6mm, 7mm, 8mm |
| Material Options | Brass / 45 Steel |
| Connector Type | Hex Flexible Coupling with Set Screw |
| Bore Tolerance | See variant options |
| Overall Length | See variant options |
| Outer Diameter | See variant options |
| Finish | Natural machined (Brass) / Oxide-treated (45 Steel) |
| Packing Quantity | 1 pcs / 2 pcs / 4 pcs / 10 pcs |
| Application | RC cars, hobby motors, CNC, robotics, 3D printers |
Measure your motor output shaft with a digital caliper. Match that measurement to the available sizes: 2mm, 3mm, 3.17mm, 4mm, 5mm, 6mm, 7mm, or 8mm. If your shaft falls between sizes, always size down and use the set screw to secure — never force a coupler that is too small onto a shaft.
Brass couplers are lighter, naturally corrosion-resistant, and well-suited for low-to-medium torque applications such as RC car wheel hubs and small hobby motors. The 45 steel variants offer higher tensile strength and are better suited for applications with greater torque demands, such as CNC spindle couplings or heavier drive systems. For most RC car builds, brass is the practical choice.
Brass couplers offer inherent corrosion resistance and perform well in humid or mildly wet outdoor environments. The 45 steel versions have an oxide surface treatment that provides basic protection, but for prolonged outdoor or wet exposure, brass is the recommended choice. Applying a light machine oil to steel couplers after use will extend their service life.
Yes. These flexible shaft couplings are compatible with most standard round motor shafts including DC hobby motors, stepper motors, and small servo output shafts, provided the shaft diameter matches one of the available sizes (2–8mm). Always confirm your shaft is round and within the listed diameter range before ordering.
The hex bore combined with the set screw provides a secure mechanical lock on the shaft. For typical RC car and hobby motor torque levels, slippage is not expected under normal operating conditions. For very high-torque applications, consider applying a small amount of thread-locking compound to the set screw for added security.
No — each coupler listed here is a single-bore size designed for shafts of the same diameter on both ends. If you need to connect two shafts of different diameters, you would require a reducing or stepped coupling, which is a different product type. Check the variant options carefully and match both shaft ends before purchasing.
Most RC car builds require 2 to 4 couplers depending on the drivetrain configuration (2WD vs 4WD). The 2-piece and 4-piece packing options are the most popular for single vehicle builds. The 10-piece pack offers the best per-unit value for workshop stock or multi-vehicle projects.
