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When your CNC router skips steps or your 3D printer loses positional accuracy, the culprit is often a mismatched or worn drive pulley. Engineers, makers, and automation builders who demand repeatable motion need a pulley that holds tolerance under continuous load — and that is exactly what the AF-Type 3M timing belt drive pulley is designed to deliver.
This pulley series features an AF-Type flange profile machined to accept standard 3M pitch (3 mm / 0.118 in) synchronous belts. The hub is precision-bored with a set-screw slot for secure shaft clamping. Bore sizes range from 4 mm to 20 mm (approx. 0.157 in – 0.787 in), and tooth counts span 12 T through 40 T, covering a wide range of drive ratios. The slot width is 16 mm across all variants, matching standard 3M belt widths. Body material is aluminum alloy with a natural anodized or machined finish, keeping rotating mass low while maintaining dimensional stability.
Typical use cases include CNC router X/Y axis drives requiring low-backlash 3M belt pulley replacement, stepper motor timing pulley upgrades for RepRap or CoreXY 3D printers, and light-duty conveyor or indexing table synchronous drive systems where a 3M pitch aluminum pulley with selectable bore is needed.
Machined AF-Type tooth geometry matches standard 3M synchronous belts for positive, slip-free engagement and consistent step accuracy.
Available bore diameters from 4 mm to 20 mm (0.157 in – 0.787 in) accommodate common stepper motor shaft sizes including 4, 5, 6, 6.35, 8, 10, 12, 12.7, 14, 15, 16, 17, 19, and 20 mm.
Lightweight aluminum alloy body reduces rotational inertia, enabling faster acceleration and deceleration in motion control applications.
Thirteen tooth-count options (12 T, 15 T, 16 T, 18 T, 20 T, 24 T, 25 T, 28 T, 30 T, 32 T, 35 T, 36 T, 40 T) let you dial in the exact drive ratio your system requires.
The AF-Type hub includes a machined keyway slot for set-screw or key-based shaft retention, preventing rotational slip under load.
All variants are sized for 16 mm wide 3M belts, a widely stocked standard width that simplifies belt sourcing for repairs and new builds.
| Belt Pitch | 3 mm (3M) |
|---|---|
| Pulley Type | AF-Type (flanged, set-screw hub) |
| Number of Teeth | See variant options (12 T – 40 T) |
| Bore Diameter | See variant options (4 mm – 20 mm) |
| Compatible Belt Width | 16 mm |
| Material | Aluminum alloy |
| Finish | Natural machined / anodized |
| Outer Diameter | See variant options (varies by tooth count) |
| Hub Style | AF-Type with set-screw slot |
| Quantity | 1 piece per order |
The tooth count determines your drive ratio. Divide the driven pulley teeth by the drive pulley teeth to get the ratio. For a 1:1 ratio use matching tooth counts on both pulleys. For speed reduction, use fewer teeth on the motor pulley and more on the driven pulley. Common CNC and 3D printer setups use 20 T pulleys on the motor shaft paired with a matching 20 T idler, or a 16 T / 20 T combination for a slight reduction.
Measure your motor shaft diameter with calipers before ordering. NEMA 17 stepper motors typically have a 5 mm shaft; NEMA 23 motors commonly use 6.35 mm (1/4 in) or 8 mm shafts. Select the bore that matches your shaft exactly — a loose bore will cause runout and positional error even with the set screw tightened.
The slot width (16 mm) refers to the usable belt-running width between the flanges. You need a 3M pitch timing belt that is 16 mm wide (commonly listed as 3M-16 or T3-16). Verify both the pitch (3 mm tooth spacing) and the width (16 mm) when purchasing a replacement or mating belt.
No. This pulley is machined for the 3M (trapezoidal) tooth profile with a 3 mm pitch. GT2 belts use a 2 mm pitch curvilinear profile, and HTD 3M belts use a rounded tooth profile — neither is interchangeable with this AF-Type 3M trapezoidal pulley. Always match the belt tooth profile and pitch to the pulley specification.
The AF-Type hub includes a machined flat or keyway slot designed for set-screw retention. For light-to-medium CNC and 3D printer loads this is sufficient. For higher-torque applications, select a variant with a keyed bore slot (indicated by the slot dimension in the variant name, e.g., 8mm(3×1.4mm)) and use a matching key for positive torque transmission.
Aluminum alloy has good natural corrosion resistance in typical indoor environments. The anodized or machined surface finish adds a further protective layer. For outdoor or high-humidity environments, periodic inspection is recommended. Belt wear is typically the limiting factor in service life rather than pulley wear, provided the belt tension and alignment are correctly set.
Yes, provided the shaft diameter matches the selected bore and the torque requirement is within the set-screw clamping capacity. This pulley is not limited to stepper motors — it is suitable for any motor or shaft application requiring a 3M pitch synchronous belt drive with a 16 mm belt width.
