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When your belt drive slips, skips, or runs out of alignment, the culprit is often a pulley that was never machined to spec. Engineers, robotics builders, and CNC hobbyists who need repeatable, low-backlash motion demand a T5 timing pulley that holds its tooth profile under load — and that is exactly what this aluminum AF-shape pulley delivers.
Each pulley is machined from aluminum alloy in the AF (with flange) body style, sized for 20mm wide T5 pitch belts. Tooth counts run from 10T to 28T, and bore diameters span 5 mm to 20 mm (approximately 0.197 in to 0.787 in), with optional keyway widths of 3 mm, 4 mm, 5 mm, or 6 mm depending on the bore size selected. The flanged rim keeps the belt tracking straight without additional guides.
Typical applications include desktop CNC routers requiring T5 20mm belt pulley replacements, 3D printer X/Y axis drives using aluminum T5 pulleys with keyway, and linear motion systems where a lightweight aluminum timing pulley with flange reduces rotational inertia.
| Belt Pitch | T5 (5 mm) |
|---|---|
| Belt Width | 20 mm |
| Number of Teeth | 10T, 12T, 14T, 15T, 16T, 17T, 18T, 19T, 20T, 22T, 24T, 25T, 26T, 28T |
| Bore Diameter | 5 / 6 / 6.35 / 8 / 10 / 12 / 12.7 / 14 / 15 / 16 / 17 / 18 / 19 / 20 mm |
| Keyway Width | Without keyway / 3 mm / 4 mm / 5 mm / 6 mm (availability varies by bore) |
| Body Style | AF Shape (flanged) |
| Material | Aluminum alloy |
| Flange | Integrated, both sides |
| Outer Diameter | See variant options |
| Hub Length | See variant options |
| Weight | See variant options |
The tooth count determines your drive ratio. Divide the driven pulley teeth by the driving pulley teeth to get the ratio. For example, a 20T driving pulley paired with a 10T driven pulley gives a 2:1 speed increase. Choose a smaller tooth count for higher speed and a larger count for more torque. Also confirm the resulting pitch diameter fits within your center-distance constraints.
Measure your motor or drive shaft diameter with calipers before ordering. The bore must match the shaft exactly — a loose bore causes runout and belt skip. Common motor shaft sizes are 5 mm, 6 mm, 6.35 mm (1/4"), 8 mm, and 10 mm. For larger shafts up to 20 mm, select the matching bore from the variant options.
A keyway is needed when your shaft has a matching keyway slot and you require positive torque transmission without relying solely on a set screw. If your shaft is smooth or you plan to use a set screw only, choose "without keyway." Keyway width must match the key on your shaft: 3 mm keys are common on 8–10 mm shafts, 4 mm on 10–12 mm shafts, 5 mm on 14–17 mm shafts, and 6 mm on 18–20 mm shafts. Check your shaft specification to confirm.
Aluminum alloy is the standard material for T5 timing pulleys in light-to-medium duty applications such as CNC routers, 3D printers, laser cutters, and general automation. It offers a good strength-to-weight ratio and machines to tight tolerances. For very high torque or abrasive environments, consider whether a steel pulley would be more appropriate for your specific load conditions.
Aluminum naturally forms a thin oxide layer that provides moderate corrosion resistance in typical indoor environments. For applications exposed to moisture, cutting fluids, or outdoor conditions, consider applying a light coating of machine oil or using an anodized variant if available. Avoid prolonged contact with strong acids or alkalis.
These pulleys are specifically designed for 20 mm wide T5 pitch belts. The flanges are sized to retain a 20 mm belt. Using a narrower belt (e.g., 10 mm or 16 mm) may work mechanically but the belt will not be fully retained by the flanges. Using a wider belt is not recommended as it will not seat correctly. Always match the belt width to the pulley specification.
"AF shape" refers to the body profile of the pulley. In standard timing pulley nomenclature, AF indicates a flanged design where both sides of the toothed rim have raised flanges. These flanges keep the belt centered on the pulley during operation, which is especially useful in open-loop belt systems or where belt tension varies.
