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When your CNC router, conveyor, or automated assembly line demands slip-free torque transfer, a mismatched or worn pulley becomes the weakest link in the entire drive train. These S8M 25mm timing drive pulleys are engineered for makers, machine builders, and automation engineers who need dimensionally consistent, drop-in-ready components without custom machining delays.
Each pulley is machined from aluminum alloy with a black anodized finish, featuring an S8M (8mm pitch) tooth profile and a 25mm belt width capacity. Tooth counts range from 10 to 40 teeth, and bore diameters span 6mm to 28mm (approximately 0.24 in to 1.10 in), covering the most common shaft sizes used in light-to-medium industrial and hobbyist drive systems.
Typical applications include CNC gantry axis drives requiring precise S8M belt synchronization, robotic arm joint actuators needing compact high-tooth-count reduction, and conveyor indexing systems where consistent belt engagement prevents positional drift over long duty cycles.
S8M 8mm Pitch Tooth Profile — Matches standard S8M synchronous belts for zero-slip power transmission in precision motion control applications.
Wide Tooth Count Selection — Available in 10, 12, 13, 14, 15, 16, 17, 18, 19, 20, 22, 24, 25, 26, 28, 30, and 40 teeth to achieve your target gear ratio without custom fabrication.
Broad Bore Range — Bore options from 6mm to 28mm (including 12.7mm for imperial shafts) accommodate most standard motor and gearbox output shafts.
Black Anodized Aluminum Construction — The anodized surface resists oxidation and abrasion while keeping rotating mass low compared to steel alternatives.
25mm Belt Width Capacity — Sized for 25mm-wide S8M belts, balancing load capacity and compact axial footprint in multi-axis machine designs.
Setscrew Hub Design — Typically includes a setscrew bore for secure shaft locking; confirm hub details match your shaft keyway or smooth-shaft requirement before assembly.
| Belt Profile | S8M (Synchronous, 8mm pitch) |
|---|---|
| Belt Width | 25mm |
| Tooth Count Options | 10, 12, 13, 14, 15, 16, 17, 18, 19, 20, 22, 24, 25, 26, 28, 30, 40 teeth |
| Bore Diameter Options | 6, 8, 10, 12, 12.7, 14, 15, 16, 17, 18, 19, 20, 22, 24, 25, 28mm |
| Material | Aluminum alloy |
| Surface Finish | Black anodized |
| Outer Diameter | See variant options |
| Hub Length | See variant options |
| Flange | See variant options |
| Keyway | See variant options |
| Weight | See variant options |
The tooth count determines your drive ratio when paired with a driven pulley. Divide the driven pulley tooth count by the drive pulley tooth count to get the speed reduction ratio. For example, a 10-tooth drive pulley paired with a 30-tooth driven pulley gives a 3:1 reduction. Select a tooth count that achieves your target RPM or torque output at the motor shaft speed you are running.
Measure your motor or gearbox output shaft diameter with a caliper before ordering. Available bores include 6, 8, 10, 12, 12.7, 14, 15, 16, 17, 18, 19, 20, 22, 24, 25, and 28mm. The 12.7mm bore is sized for 1/2-inch imperial shafts. If your shaft is slightly undersized, a bore that matches exactly is preferred; do not order a bore smaller than your shaft diameter.
Yes. These pulleys are machined to the S8M tooth profile standard with an 8mm pitch, and are designed to mesh with any S8M synchronous timing belt of 25mm width. Ensure the belt width matches the 25mm pulley face width for proper tracking and load distribution.
Aluminum alloy pulleys offer a favorable strength-to-weight ratio suitable for most CNC, robotics, and light-to-medium conveyor applications. For very high torque or heavy industrial duty cycles where surface hardness is critical, steel pulleys may be more appropriate. For the majority of maker and automation builds running S8M belts, aluminum provides adequate strength while reducing rotational inertia.
Black anodizing creates an aluminum oxide layer that significantly improves corrosion resistance compared to bare aluminum, and also increases surface hardness. This finish is suitable for indoor environments and light-duty outdoor enclosures. For harsh chemical or salt-spray environments, additional protective measures may be needed.
S8M pulleys are commonly used in both horizontal and vertical drive configurations. For high-speed applications, ensure the belt tension is correctly set to avoid resonance and tooth skip. Consult the belt manufacturer's speed rating for the S8M profile at your operating RPM, and verify that the bore setscrew is properly torqued to prevent shaft slippage under dynamic loads.
A higher tooth count results in a larger outer diameter pulley. The 10-tooth variant has a significantly smaller outer diameter than the 40-tooth variant. The outer diameter of an S8M pulley is approximately equal to (number of teeth × 8mm pitch) ÷ π. For example, a 20-tooth S8M pulley has an outer diameter of roughly 50.9mm (~2.0 in), while a 40-tooth variant is approximately 101.9mm (~4.0 in). Confirm the outer diameter fits within your machine's spatial constraints before ordering.
