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When a slipping or mismatched pulley is costing you positioning accuracy on your CNC router, 3D printer, or laser engraver, the root cause is almost always a pulley that was not engineered to the correct pitch and bore tolerance. This 3M AF-Type timing belt drive pulley is designed for engineers, makers, and machine builders who need repeatable, zero-backlash motion transfer from NEMA 17 and NEMA 23 stepper motors.
Each pulley is machined from aluminum alloy with an anodized finish and conforms to the AF-Type flange profile. The belt pitch is 3mm (3M), and the pulley body accommodates a 11mm-wide belt slot. Tooth counts range from 12T to 32T, and bore diameters span 4mm to 15mm (approximately 0.157 in to 0.591 in), including plain round bores and keyway options (3×1.4mm, 4×1.8mm, and 5×2.3mm) for positive shaft locking.
Typical applications include open-loop CNC axis drives where a 3M GT2-compatible belt is used, direct-drive extruder assemblies on FDM printers requiring a 3M pitch pulley for stepper motor shafts, and light-duty conveyor or indexing table builds where a compact aluminum timing pulley keeps rotating mass low.
| Belt Pitch | 3mm (3M) |
|---|---|
| Pulley Type | AF-Type (flanged) |
| Number of Teeth | 12T, 14T, 15T, 16T, 17T, 18T, 19T, 20T, 22T, 24T, 25T, 26T, 28T, 30T, 32T |
| Belt Width (Slot) | 11mm |
| Bore Diameter | 4mm / 5mm / 6mm / 6.35mm / 7mm / 8mm / 10mm / 11mm / 12mm / 12.7mm / 14mm / 15mm (see variant options) |
| Keyway Options | 3×1.4mm / 4×1.8mm / 5×2.3mm (select variants) |
| Material | Aluminum alloy, anodized finish |
| Pitch Diameter | See variant options |
| Outside Diameter | See variant options |
| Hub Width | See variant options |
| Set Screw | See variant options |
| Compatible Belt Standard | 3M synchronous / GT2-3M |
| Typical Application | CNC routers, 3D printers, laser engravers, stepper motor drives |
The tooth count determines your drive ratio. Divide the driven pulley teeth by the drive pulley teeth to get the ratio. For example, a 20T drive pulley paired with a 40T driven pulley gives a 2:1 reduction, doubling torque while halving speed. For CNC axes, match the tooth count to your desired steps-per-mm calculation based on your stepper motor's step angle and microstepping setting.
Standard NEMA 17 stepper motors have a 5mm output shaft. Select the 5mm bore variant. If your motor has a flat (D-cut) on the shaft, a set screw bore is sufficient. If you need positive locking without a flat, consider a keyway bore variant where available.
NEMA 23 motors typically use a 6.35mm (1/4 inch) or 8mm shaft depending on the manufacturer. Check your motor's datasheet for the exact shaft diameter. Both 6.35mm and 8mm bore options are available, including keyway variants for shaft sizes where keyway locking is required.
A plain bore relies on a set screw pressing against the shaft to prevent rotation. A keyway bore includes a machined slot that accepts a matching key inserted between the shaft and pulley, providing a positive mechanical lock that resists higher torque loads and prevents rotational slip under shock loads. Keyway variants are recommended for applications with frequent direction reversals or high inertia loads.
Yes. The 3M pitch (3mm tooth spacing) used on these AF-type pulleys is dimensionally compatible with GT2-3M profile belts. Confirm that your belt is labeled 3M or GT2-3M with an 11mm width to ensure proper engagement. Standard 2mm pitch GT2 belts (the most common FDM printer belt) are not compatible — verify your belt pitch before ordering.
Pitch diameter (PD) = (Number of Teeth × Pitch) ÷ π. For a 20T pulley: PD = (20 × 3mm) ÷ 3.1416 ≈ 19.1mm. Linear belt speed per motor revolution = PD × π = tooth count × 3mm. For a 20T pulley, one full motor revolution moves the belt 60mm. Use this to set your firmware steps-per-mm value.
The pulleys are machined from aluminum alloy with an anodized surface treatment. Anodizing creates a hard oxide layer that resists oxidation and light corrosion in typical indoor workshop environments. For outdoor or high-humidity enclosures, periodic inspection is recommended, but standard workshop conditions present no corrosion concern.
Yes, provided the load torque and belt tension remain within the rated capacity of the aluminum pulley and the 3M belt. For light-duty conveyor and indexing applications driven by NEMA 17 or NEMA 23 motors, these pulleys are well-suited. For heavy industrial loads, contact us to confirm suitability for your specific torque and speed requirements.
