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When your motion system demands consistent torque transfer and zero belt slip, a poorly fitted pulley becomes the weakest link. Engineers, makers, and automation builders working with S2M belt drives need a stepped pulley that locks belt alignment and maintains pitch accuracy across thousands of cycles. This S2M 42T stepped timing belt pulley with a 4mm bore is engineered for exactly that — delivering reliable, repeatable motion in compact drive systems.
Each pulley features an S2M tooth profile (2mm pitch) with 42 teeth, a 4mm bore diameter, and integrated flanges (steps) on both sides to keep 10mm wide timing belts tracking true. The body is typically machined from aluminum alloy, offering a balance of low rotational inertia and structural rigidity. Outer diameter is approximately 26–27mm (≈1.02–1.06 in), with an overall hub width suited to 10mm belt width. This listing includes 100 pieces per pack.
Typical use cases include desktop 3D printer X/Y axis drives, small CNC router feed systems, lightweight robotic arm joints, and laboratory automation equipment where S2M belt drives are specified. The stepped flange design is especially valued in multi-axis builds where lateral belt drift would cause positioning errors.
| Belt Profile | S2M (2mm pitch) |
|---|---|
| Number of Teeth | 42T |
| Bore Diameter | 4mm |
| Compatible Belt Width | 10mm |
| Outer Diameter (approx.) | ~26.7mm (~1.05 in) |
| Flange Type | Stepped (double flange) |
| Material | Aluminum alloy |
| Finish | See variant options |
| Hub Width | See variant options |
| Set Screw | See variant options |
| Quantity per Pack | 100 pieces |
S2M refers to a synchronous belt profile with a 2mm tooth pitch and a specific curvilinear tooth geometry. It is not interchangeable with 2GT (GT2) or MXL profiles — each has a different tooth shape and root radius. Always match your pulley profile to your belt profile exactly to avoid skipping or premature wear.
The listed bore is 4mm. Reaming to 5mm is possible on aluminum pulleys if wall thickness allows, but we recommend selecting the correct bore size from our variant options to maintain concentricity and avoid weakening the hub. Check the hub outer diameter before attempting any bore modification.
Drive ratio is determined by the tooth count ratio between the driver and driven pulleys. For example, pairing a 20T driver with this 42T driven pulley gives a 2.1:1 reduction. Calculate your required ratio based on motor RPM and desired output speed, then select pulley tooth counts accordingly. Center distance and belt length must also be recalculated when changing tooth counts.
Aluminum alloy naturally forms a thin oxide layer that provides moderate corrosion resistance in typical indoor environments. For humid, wet, or outdoor applications, consider applying a light coating of dry lubricant or selecting anodized variants if available. Avoid prolonged exposure to salt spray or strong acids without additional protection.
Yes. S2M 42T pulleys are used in various motion systems where S2M belts are specified. Verify that your printer's belt path, motor shaft diameter (4mm), and belt width (10mm) match these specs. Note that many popular desktop 3D printers use 2GT (GT2) belts — confirm your belt profile before ordering.
The 100-piece pack is designed for batch builders, small manufacturers, and workshop stock. If you are building a single machine, this pack provides ample spares for future repairs or upgrades. For single-unit needs, check if we offer smaller quantity options in our variant selector above.
Set screw inclusion varies by variant. Check the variant options above for set screw details. If a set screw is included, use the appropriate hex key to tighten against a flat on the shaft for best holding force. If no set screw is included, the pulley may be press-fit or require a separate fastening method depending on your application.
