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When a worn or mismatched shaft coupling causes vibration, noise, or power loss in your motor drive system, the fix starts with the right universal flexible shaft coupling. These U joint connectors are built for engineers, machine builders, and DIY automation enthusiasts who need a dependable, torque-transmitting connection between shafts that are not perfectly aligned.
Each universal flexible shaft coupling is machined from 45# carbon steel — a medium-carbon steel known for its balanced strength, toughness, and machinability. The range covers inner diameters (I.D.) from 5 mm (0.20 in) to 30 mm (1.18 in), outer diameters (O.D.) from 10 mm (0.39 in) to 48 mm (1.89 in), and lengths from 31 mm (1.22 in) to 123 mm (4.84 in), giving you a wide selection to match your specific shaft and housing dimensions.
Typical applications include CNC machine tool spindle drives, robotic arm joint connections, conveyor and feed-axis motor couplings, and general industrial machinery where angular or parallel shaft misalignment must be accommodated without sacrificing torque transmission efficiency.
Machined from 45# medium-carbon steel for a strong combination of tensile strength and impact toughness. Suitable for continuous-duty motor coupling applications where cast or aluminum alternatives would wear prematurely.
The Cardan-style universal joint design transmits torque across angular misalignment between two shafts, making it suitable for drives where the motor and load axes are not perfectly collinear.
Available in 24 size combinations spanning I.D. 5–30 mm, O.D. 10–48 mm, and lengths 31–123 mm. This breadth covers small servo motor shafts up to larger industrial drive shafts in a single product line.
The rigid steel yoke and cross-pin construction minimizes power loss during torque transfer, maintaining consistent rotational speed and reducing heat buildup compared to elastomeric coupling designs.
Available in 1 pc, 3 pcs, and 5 pcs quantities. Multi-pack options reduce per-unit cost for machine builders stocking spares or outfitting multiple axes simultaneously.
Standard bore and yoke dimensions allow direct installation onto motor and driven shafts using set screws or keyway arrangements (confirm bore style for your selected size). No special tooling required for assembly.
| Product Type | Universal Flexible Shaft Coupling (U Joint / Cardan Style) |
|---|---|
| Material | 45# Carbon Steel |
| Inner Diameter (I.D.) Range | 5 mm – 30 mm (0.20 in – 1.18 in) |
| Outer Diameter (O.D.) Range | 10 mm – 48 mm (0.39 in – 1.89 in) |
| Length Range | 31 mm – 123 mm (1.22 in – 4.84 in) |
| Coupler Size (I.D. × O.D. × Length) | See variant options |
| Surface Finish | See variant options |
| Clamping Method | See variant options |
| Quantity per Order | 1 pcs / 3 pcs / 5 pcs (select Amount variant) |
| Typical Application | CNC drives, robotic joints, conveyor motors, industrial machinery |
| Compatible Shaft Types | Motor shafts, lead screws, drive shafts within I.D. range |
| Weight per Unit | See variant options |
Measure the outer diameter of your motor shaft (this becomes the I.D. of the coupling bore) and the outer diameter of your driven shaft. Then choose the variant whose I.D. matches both shaft diameters. Also check that the O.D. fits within your housing or frame clearance, and that the length suits your shaft-to-shaft gap. If your two shafts have different diameters, contact us to confirm availability of stepped-bore variants.
A universal joint (U joint / Cardan joint) uses a cross-pin and yoke mechanism to transmit torque across a significant angular misalignment — typically up to 15–30° depending on the design. A helical flexible coupling is machined from a single piece of metal with a spiral slot and handles only small angular misalignment (typically under 3°) but with near-zero backlash. Choose a U joint when you need to accommodate larger angular offsets between shafts; choose a helical coupling when positional accuracy and zero backlash are the priority.
45# carbon steel (equivalent to SAE 1045) has a typical tensile strength of approximately 600–800 MPa in the normalized condition, making it suitable for most motor coupling applications in CNC machines, conveyors, and light-to-medium industrial drives. For very high-torque or shock-load applications, verify that the selected coupling size's torque rating meets your system requirements. Contact us if you need specific torque capacity data for your chosen size.
45# carbon steel has moderate corrosion resistance — it will oxidize if exposed to moisture without protection. For indoor, dry, or lightly oiled environments (typical of most machine tool and CNC applications), the material performs well. If your application involves exposure to water, coolant mist, or outdoor conditions, consider applying a rust-inhibiting oil or grease to the coupling surfaces, or contact us about surface-treated options.
The standard variants listed have a single I.D. dimension, meaning both bore ends are the same diameter. If your motor shaft and driven shaft have different diameters, check the variant list carefully — some sizes (e.g., 6 × 16 × 42 mm vs. 8 × 16 × 42 mm) share the same O.D. and length but differ in I.D., which may allow you to select a size that fits one shaft while using a shaft adapter or sleeve on the other. Contact us to confirm the best approach for mixed-diameter shaft pairings.
Order 1 pc if you need a single replacement or are prototyping a new machine. Order 3 pcs or 5 pcs if you are outfitting multiple axes on the same machine, building a batch of machines, or want to keep spares on hand for maintenance. Multi-pack options offer a lower per-unit cost compared to ordering individual pieces separately.
Universal joint couplings of this type can typically accommodate angular misalignment in the range of 10–30° depending on the specific size and operating speed. Higher misalignment angles reduce the coupling's torque capacity and increase vibration at the output shaft. For best performance and longevity, keep misalignment as low as practically possible and verify the operating angle against the coupling's rated capacity for your chosen size.
