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When your drive system demands consistent belt tracking and minimal slip, a poorly matched pulley becomes the weakest link. Engineers, makers, and DIY builders working with flat or round PU belts need a U-grooved pulley that holds the belt firmly in the groove without wandering — especially in compact, high-cycle applications like 3D printers, CNC routers, and conveyor prototypes.
These U-grooved pulleys are machined from aluminum alloy and feature a precisely milled U-profile groove designed to seat 4mm, 5mm, 6mm, or 8mm width PU belts. Outer diameters range from 20mm to 80mm (approximately 0.79" to 3.15"), with hub thickness typically 10mm (12mm for the 8mm-slot variants). Bore diameters span 5mm to 20mm to accommodate a wide range of shaft sizes.
Typical use cases include idler and drive pulleys in desktop 3D printers, belt-driven linear motion stages, small conveyor systems, and hobbyist robotics platforms where a U-grooved pulley for PU flat belt drives is required. The aluminum construction keeps rotating mass low while providing the rigidity needed for repeatable positioning.
Machined from aluminum alloy for a lightweight, rigid body that reduces rotational inertia in high-speed drive applications.
The U-shaped groove profile seats 4mm, 5mm, 6mm, and 8mm width PU belts securely, preventing lateral belt drift during operation.
Available in outer diameters from 20mm (~0.79") to 80mm (~3.15"), enabling precise gear-ratio selection for your drive system.
Bore diameters from 5mm to 20mm cover a broad range of motor and idler shaft sizes without requiring custom machining.
The aluminum body keeps the pulley light, reducing load on bearings and motors — critical for responsive motion control in robotics and CNC systems.
Suitable as both drive and idler pulleys in 3D printers, linear actuators, small conveyors, and DIY automation rigs using PU belt drive systems.
| Material | Aluminum Alloy |
|---|---|
| Groove Profile | U-Groove |
| Compatible Belt Width | 4mm / 5mm / 6mm / 8mm |
| Outer Diameter (OD) | 20mm – 80mm (0.79" – 3.15") |
| Bore Diameter | 5mm – 20mm (see variant options) |
| Hub Thickness | 10mm (12mm for 8mm-slot variants) |
| Slot Width | 4mm / 5mm / 6mm / 8mm (see variant options) |
| Surface Finish | See variant options |
| Quantity per Order | 1 Pcs |
The outer diameter determines your drive ratio. Divide the driven pulley OD by the drive pulley OD to get the speed reduction ratio. For example, a 20mm drive pulley paired with a 40mm driven pulley gives a 2:1 reduction. Choose an OD that fits within your frame clearance and achieves your target belt speed or torque.
These U-grooved pulleys are designed for PU (polyurethane) belts with widths of 4mm, 5mm, 6mm, or 8mm. The slot width in the variant name (e.g., "20mm x 4mm x 10mm" = OD × slot width × thickness) must match your belt width exactly for proper seating and tracking.
Measure your motor or idler shaft diameter precisely with calipers. The bore must match the shaft diameter. Available bores range from 5mm to 20mm. If your shaft uses a keyway or set screw, confirm the hub thickness (10mm or 12mm) provides enough material for your fastening method.
Aluminum alloy provides a good strength-to-weight ratio for light-to-medium duty drive applications such as 3D printers, CNC routers, and small conveyors. For heavy industrial loads or high-impact environments, evaluate whether a steel pulley would be more appropriate for your torque and cycle requirements.
Aluminum alloy has inherent oxidation resistance suitable for indoor and dry environments. For humid or mildly corrosive environments, the natural oxide layer provides basic protection. For harsh chemical or marine environments, consider additional surface treatment or a different material.
Yes. These pulleys can be used as idler pulleys by mounting them on a fixed shaft or bolt with a bearing inserted into the bore. Note that bearings are not included — you will need to source a bearing that matches the bore diameter and your shaft size separately.
The hub thickness (the third dimension in the variant name, e.g., "x 10mm" or "x 12mm") refers to the overall width of the pulley body. The 12mm thickness variants are paired with the 8mm slot width to provide adequate material around the wider groove. All other slot widths (4mm, 5mm, 6mm) use a 10mm hub thickness.
