S2M 90-120T Timing Belt Pulley Pitch 2mm With Keyway CNC Drive Pulley Width 7mm

The tooth count determines the pulley's pitch diameter and, together with your motor pulley's tooth count, sets the drive ratio. A higher tooth count gives a larger diameter and a lower speed ratio (more torque, less speed) when paired with a smaller drive pulley. Calculate your required ratio first, then select the tooth count that achieves it. If you are replacing an existing pulley, match the tooth count exactly to maintain the same belt length and tension.

Measure your motor shaft diameter with a caliper before ordering. Common stepper motor shaft sizes are 5mm, 6.35mm (1/4 in), 8mm, and 10mm. This pulley range starts at 8mm bore — if your shaft is smaller, this series is not the right fit. For 8mm shafts choose the 8mm bore with the 3×1.4mm keyway; for 10mm shafts choose 10mm bore with either the 3×1.4mm or 4×1.8mm keyway depending on your key stock.

The keyway size is paired with the bore in each variant: 8mm and 10mm bores use a 3×1.4mm keyway; 10mm and 12mm bores are also available with a 4×1.8mm keyway; 12.7mm, 14mm, 15mm, 16mm, and 17mm bores use a 5×2.3mm keyway; 18mm, 19mm, and 20mm bores use a 6×2.8mm keyway; and the 25mm bore uses an 8×3.3mm keyway. Select the variant whose keyway matches the key stock already cut on your shaft.

Yes, provided your belt is an S2M profile with a 2mm pitch and a width of 6–7mm. The S2M tooth profile is standardized, so any S2M belt from any manufacturer will mesh correctly with these pulleys. If your belt is wider than 7mm it will overhang the groove flanges and may track poorly — in that case you need a wider-groove pulley. Confirm both the pitch and the belt width before ordering.

A keyed connection is significantly stronger than a set-screw-only connection because the key bears the shear load across its full cross-section rather than relying on friction. For the light-to-medium torque levels typical of CNC routers, 3D printers, and small conveyor drives, the keyway connection on these aluminum pulleys is more than adequate. For very high-torque or shock-load applications, consider a steel pulley or a tapered-bushing design instead.

Aluminum alloy is the right choice for the vast majority of DIY and light-industrial S2M drive applications. It keeps rotating inertia low (critical for fast-accelerating CNC axes), is easy to machine if you need to modify the bore, and resists corrosion without surface treatment. Steel pulleys are generally only necessary when belt tension is very high, operating temperatures exceed 120°C, or the pulley is subject to repeated impact loads. If you are unsure, aluminum is the standard choice for S2M drives.

Technically the pulley will fit on a plain shaft without a key, and you can secure it with a set-screw through the existing threaded hole (if present) or by adding one. However, running without a key under any meaningful torque load risks the pulley spinning on the shaft and damaging both the bore and the shaft surface. We recommend always using the correct key for reliable, long-term operation.

Belt length depends on the center distance between the two pulleys and the pitch diameters of both pulleys. Use the standard timing belt length formula: L = 2C + π(D₁+D₂)/2 + (D₂−D₁)²/(4C), where C is center distance and D₁, D₂ are the pitch diameters. The pitch diameters for these pulleys are approximately: 90T ≈ 57.3mm, 100T ≈ 63.7mm, 110T ≈ 70.0mm, 120T ≈ 76.4mm. Round up to the nearest available S2M belt length.