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When your project demands repeatable, slip-free linear or rotary motion, a mismatched or undersized pulley becomes the weakest link in the entire drive system. Engineers, makers, and hobbyists building CNC routers, 3D printers, robotic arms, or custom automation rigs need a pulley that locks onto the shaft cleanly and meshes with the belt without backlash. These XL pitch timing belt drive pulleys are designed exactly for that scenario.
Each pulley is machined from aluminum alloy with a hub (flanged body), available in two hub styles — Type BF (through-bore with set-screw flange) and Type K (keyed bore for positive torque transfer). Tooth counts range from 10 to 40 teeth, and bore diameters span 4 mm to 25 mm (approximately 0.16" to 0.98"), with optional keyway bores for larger shaft sizes. The XL belt pitch is 5.08 mm (0.200"), the industry-standard "Extra Light" series for light-to-medium duty synchronous drives.
Typical use cases include CNC router X/Y axis drives requiring low backlash, 3D printer extruder and motion systems using GT2 or XL belts, robotic joint actuators needing keyed shaft retention, and DIY linear actuators or pick-and-place machines where timing accuracy matters.
| Belt Standard | XL (Extra Light) |
|---|---|
| Belt Pitch | 5.08 mm (0.200" / 3/8") |
| Tooth Count Options | 10, 12, 15, 16, 18, 20, 25, 30, 40 teeth |
| Hub Style | Type BF (set-screw, smooth bore) / Type K (keyed bore) |
| Bore Diameter Range | 4 mm – 25 mm (approx. 0.16" – 0.98") |
| Keyway Options | 4 mm keyway (for 10–12 mm bore), 5 mm keyway (for 14–16 mm bore), 6 mm keyway (for 18–20 mm bore) |
| Material | Aluminum alloy |
| Flange / Hub | Integrated hub (flanged body) |
| Outer Diameter | See variant options |
| Belt Width Compatibility | Typically 9.5 mm (3/8") wide XL belts |
| Pack Quantity | 1 piece or 2 pieces (select in Bore Size & Amount) |
| Finish | Natural aluminum (uncoated) |
The tooth count determines your pulley's pitch diameter and, combined with the driven pulley's tooth count, sets your drive ratio. For a 1:1 ratio use identical tooth counts on both pulleys. For speed reduction (more torque), use a smaller tooth count on the motor pulley and a larger count on the driven pulley. Common starting points for CNC and 3D printer builds are 16–20 tooth drive pulleys paired with 20–40 tooth idlers or driven pulleys.
Type BF has a smooth through-bore with one or two set-screw holes on the hub. It is suitable for smooth round shafts where the set screw provides adequate retention for light-to-medium torque. Type K has a machined keyway slot in the bore that accepts a standard key, creating a positive mechanical lock between the shaft and pulley. Type K is recommended when higher torque, shock loads, or reversing loads are present, as it prevents rotational slip that a set screw alone may not resist.
Measure your motor or drive shaft diameter precisely with a caliper. Select the bore size that matches your shaft diameter exactly — the bore is machined to a close tolerance fit. For keyed shafts, also confirm the keyway width matches the available keyway options (4 mm, 5 mm, or 6 mm depending on bore size). If your shaft is imperial (e.g., 1/4", 5/16", 3/8"), convert to millimeters: 1/4" ≈ 6.35 mm → select 6 mm bore; 5/16" ≈ 7.94 mm → select 8 mm bore; 3/8" ≈ 9.53 mm → select 10 mm bore.
No. These pulleys are designed specifically for XL-profile timing belts with a 5.08 mm (0.200") pitch. GT2 belts use a 2 mm pitch with a different tooth profile. Mixing XL pulleys with GT2 belts — or vice versa — will result in poor mesh, skipping, and accelerated belt wear. Always match the pulley tooth profile and pitch to your belt specification.
Aluminum alloy pulleys are well-suited for light-to-medium duty synchronous drives typical of CNC routers, 3D printers, laser cutters, and small robotic systems. Aluminum offers a good strength-to-weight ratio and low rotational inertia, which benefits high-speed or high-acceleration applications. For heavy industrial drives with sustained high torque or abrasive environments, steel pulleys may be more appropriate. For most DIY and maker applications, aluminum XL pulleys are the standard choice.
A basic belt drive requires at least two pulleys — one on the drive shaft (motor) and one on the driven shaft. If both pulleys are the same specification, select the 2-piece pack option in the "Bore Size & Amount" selector for convenience. If your drive and driven pulleys have different tooth counts or bore sizes, order each variant separately. The 2-piece pack offers a cost saving compared to purchasing two individual units.
These pulleys are designed for XL-series belts that are typically 9.5 mm (3/8") wide. The flanged hub helps keep the belt centered on the pulley face during operation. Always verify the belt width against the pulley face width for your specific variant before ordering, especially for higher tooth count pulleys where the face width may vary.
