S3M Zahnrad - Pulley/ Riemenscheibe /Zahnriemenrad-21- 150Zähne/Breite 10/15mm

The tooth count determines the pitch diameter of the pulley. A higher tooth count gives a larger diameter and a lower drive ratio when paired with a smaller pulley. Calculate your required speed ratio first, then select tooth counts for driver and driven pulleys accordingly. For example, a 21Z driver paired with a 42Z driven pulley gives a 2:1 reduction.

The belt width affects the torque capacity of the drive. A 15mm wide S3M belt and matching pulley can transmit more torque than a 10mm setup. For light-duty 3D printer axes, 10mm is typically sufficient. For heavier CNC or conveyor loads, 15mm provides greater load capacity. Always match the pulley belt width to your belt width exactly.

The keyway designation indicates the keyway width cut into the bore. K3 = 3mm keyway, K4 = 4mm keyway, K5 = 5mm keyway. Keyway bores are used with a matching key on the shaft to prevent the pulley from rotating independently under load. If your shaft has no keyway, select a plain bore variant and secure with a set screw if needed.

No. S3M and HTD 3M both have a 3mm pitch but use different tooth profiles — S3M is trapezoidal while HTD 3M is curvilinear (rounded). They are not interchangeable. These pulleys are designed specifically for S3M trapezoidal belts. Using an HTD belt on an S3M pulley will result in poor meshing and accelerated wear.

Count the number of teeth on your existing pulley — this is your tooth count (Z). Measure the bore diameter with calipers. Check whether there is a keyway slot in the bore. Measure the belt width to confirm 10mm or 15mm. With these three values (tooth count, bore size, belt width) you can select the correct variant from the options above.

Yes. S3M pulleys are widely used in DIY 3D printers and light-duty CNC routers. Smaller tooth counts (21Z–36Z) are common for compact axis drives, while larger counts suit reduction stages. Confirm your printer or router uses S3M belts (3mm pitch, trapezoidal) before ordering, as many modern machines use GT2 (2mm pitch) belts which require different pulleys.

Measure your motor shaft diameter precisely with calipers. Select the bore size that matches your shaft. For NEMA 17 stepper motors, the shaft is typically 5mm. For NEMA 23, it is typically 6.35mm or 8mm. If your shaft has a flat or keyway, choose the corresponding keyway bore variant (K3/K4/K5) for a secure fit.