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When your motion control project demands repeatable, slip-free power transmission, a mismatched or worn pulley becomes the weakest link in the chain. Engineers, CNC builders, and robotics hobbyists who need a reliable S3M timing belt pulley with a keyed bore will find this AF-type drive wheel a dependable fit for both prototyping and production runs.
This S3M timing belt pulley features a 3mm pitch synchronous tooth profile machined to AF-type standards, with a fixed 16mm belt width and a through-bore ranging from 8mm to 25mm (approximately 0.31" to 0.98"). Tooth counts span 18T through 90T, covering pitch diameters from roughly 17.2mm (0.68") up to approximately 85.9mm (3.38"). Each unit ships with a matching keyway — available in 3×1.4mm, 4×1.8mm, 5×2.3mm, 6×2.8mm, or 8×3.3mm — to lock the pulley securely to the shaft.
Typical use cases include CNC router and laser cutter X/Y axis drives, 3D printer extruder and gantry systems, and light industrial conveyor or indexing mechanisms where an S3M synchronous belt pulley with keyway bore provides the torque transfer accuracy these applications require.
| Belt Type | S3M (Synchronous, 3mm pitch) |
|---|---|
| Pulley Type | AF-type (with keyway) |
| Belt Width | 16mm (0.63") |
| Tooth Count Range | 18T – 90T |
| Bore Diameter Range | 8mm – 25mm (0.31" – 0.98") |
| Keyway Options | 3×1.4mm / 4×1.8mm / 5×2.3mm / 6×2.8mm / 8×3.3mm |
| Pitch Diameter (18T) | ~17.2mm (~0.68") |
| Pitch Diameter (90T) | ~85.9mm (~3.38") |
| Material | See variant options |
| Surface Finish | See variant options |
| Quantity per Order | 1 piece |
The tooth count determines the pitch diameter of the pulley. To achieve a specific gear ratio, divide the driven pulley tooth count by the driving pulley tooth count. For example, a 40T drive pulley paired with a 20T driven pulley gives a 2:1 speed reduction. Use the pitch diameter formula: PD = (Teeth × Pitch) ÷ π. For S3M, pitch = 3mm.
Measure your motor or drive shaft diameter precisely with calipers. Select the bore that matches your shaft — available options are 8mm, 10mm, 12mm, 12.7mm, 14mm, 15mm, 16mm, 17mm, 18mm, 19mm, 20mm, and 25mm. The keyway size is automatically matched to the bore diameter in each variant listing.
Keyway dimensions are paired to bore size following standard engineering conventions: 8–10mm bore uses 3×1.4mm keyway; 12–12.7mm bore uses 4×1.8mm or 5×2.3mm; 14–17mm bore uses 5×2.3mm; 18–20mm bore uses 6×2.8mm; 25mm bore uses 8×3.3mm. Check the specific variant you select for the exact keyway included.
Yes. This pulley is designed for standard S3M synchronous timing belts with a 3mm pitch. It is compatible with 15mm or 16mm wide S3M belts. Always confirm the belt width matches the pulley's 16mm groove width before assembly.
The AF-type keyway design provides a positive mechanical lock between the pulley and shaft when a matching key and set screw are used. For light-to-medium CNC and automation loads, this connection is reliable. For very high torque applications, verify the shaft material and key fit tolerance. Always use a properly sized key and tighten the set screw to the recommended torque.
The corrosion resistance depends on the pulley material and surface finish, which varies by variant. For outdoor or high-humidity environments, we recommend confirming the material specification for your selected variant. If corrosion resistance is critical, consider applying a protective coating or selecting a variant with an appropriate finish.
AF-type pulleys feature a through-bore with a machined keyway slot, designed to be mounted on a shaft using a key and set screw for a fixed, non-slip connection. This is distinct from taper-lock or QD-bushing types, which use a separate bushing for mounting. AF-type is the most common choice for direct shaft mounting in CNC and robotics builds.
