3M Timing Belt Pulley AF-Type 50T-120T Applicable Belt Width 15mm Bore 5mm~40mm

The tooth count determines the pitch diameter and, combined with your motor pulley, sets the drive ratio. A higher tooth count (e.g., 120T) gives a larger pitch diameter and slower output speed with more torque; a lower count (e.g., 50T) gives a smaller diameter and faster output. Calculate your required ratio by dividing the driven pulley teeth by the driver pulley teeth. For 3D printers, 20T driver + 60T driven = 3:1 reduction is a common starting point for Z-axis drives.

Measure your motor or drive shaft diameter with a caliper. Select the bore that matches exactly — a loose bore causes runout and positioning errors. If your shaft has a flat (D-cut) or keyway, choose a keyway bore variant (e.g., 5×2.3 mm for a 14 mm shaft with a 5 mm key) to prevent rotational slip. Round bores are suitable for shafts secured with a set screw.

No. This pulley uses the 3M trapezoidal tooth profile with a 3 mm pitch. It is not interchangeable with GT2 (2 mm pitch, curvilinear) or HTD 3M (3 mm pitch, curvilinear) profiles. Always match the pulley tooth profile to your belt profile. If you are unsure, check your belt's part number for the pitch designation (3M = 3 mm trapezoidal).

Aluminum alloy pulleys are well-suited for light-to-medium CNC routing, 3D printing, and robotics where rotational inertia and weight matter. For heavy-duty industrial applications with sustained high torque or abrasive environments, steel pulleys may be preferred. For most DIY CNC routers and desktop machines operating within the belt's rated tension, aluminum provides adequate strength and significantly reduces moving mass.

The anodized aluminum finish provides a layer of corrosion resistance suitable for typical indoor workshop conditions, including moderate humidity. Anodizing is not a substitute for stainless steel in wet or salt-spray environments. For outdoor or high-moisture applications, apply a light coat of dry lubricant or corrosion inhibitor to the bore and hub area periodically.

A round bore relies on one or two set screws to grip the shaft. This is adequate for low-to-medium torque applications but can slip under shock loads. A keyway bore uses a machined slot that accepts a matching key inserted between the shaft and pulley, creating a positive mechanical lock. Keyway variants (4×1.8 mm, 5×2.3 mm, 6×2.8 mm, 8×3.3 mm) are recommended for CNC spindles, servo motors, and any application where consistent positioning under varying torque is critical.

Yes. AF-Type pulleys work with both open-ended (cut-to-length) and closed-loop (endless) 3M timing belts of 15 mm width. When using a closed-loop belt, ensure the belt's inner circumference is compatible with your center-to-center distance and the pitch diameters of both pulleys in the drive system.