HTD-3M 90T-120T Timing Belt Pulley Pitch 3mm AF-type With Keyway Width 11mm

The tooth count determines the pitch diameter and, combined with your motor-side pulley tooth count, sets your drive ratio. A larger tooth count gives a larger pitch diameter and a lower reduction ratio when paired with a smaller drive pulley. Calculate your required ratio first, then select the tooth count that achieves it. Use the pitch diameter values in the spec table above to verify belt length compatibility.

Measure your motor or gearbox output shaft diameter with a caliper. Select the bore that matches exactly — available options are 8, 10, 12, 14, 15, 17, 19, 20, and 25mm. Each bore comes with a pre-cut keyway matched to standard DIN dimensions for that shaft size, so no additional machining is required for a keyed shaft.

Keyway dimensions are matched to the bore per standard practice: 8mm and 10mm bores use a 3×1.4mm keyway; 10mm (alt) and 12mm bores use 4×1.8mm; 14mm and 15mm bores use 5×2.3mm; 17mm bore also uses 5×2.3mm; 19mm and 20mm bores use 6×2.8mm; 25mm bore uses 8×3.3mm. The keyway is already cut — you supply the matching key stock.

Yes. These pulleys are designed specifically for HTD-3M belts with a 3mm pitch and 11mm width. They will not fit GT2 or MXL belts, which use different tooth profiles. Confirm your belt is labeled HTD-3M (or 3M) and is 11mm wide before ordering.

Aluminum alloy pulleys are well-suited for the torque levels typical of NEMA 17/23 stepper motors and small servo motors used in desktop CNC, 3D printing, and light automation. For very high-torque industrial applications (e.g., large servo drives above 5 Nm continuous), consider whether a steel pulley would be more appropriate. The keyway connection significantly increases torque capacity compared to a set-screw-only bore.

Aluminum alloy naturally forms a thin oxide layer that provides moderate corrosion resistance in typical indoor workshop or light industrial environments. For prolonged exposure to moisture, salt spray, or aggressive chemicals, applying a clear anodize coating or protective spray after installation is recommended to extend service life.

The keyway is pre-cut into the bore, but you are not required to use a key. You can secure the pulley with a set screw alone if your shaft does not have a keyway slot. However, for applications with reversing loads or high torque, using the keyway with a matching key is strongly recommended to prevent rotational slippage.