HTD-3M 20-60Teeth Timing Belt Pulley Pitch 3mm AF-type With Keyway, Width 21mm

The tooth count determines the pitch diameter and your drive ratio. Divide the desired output speed by the input speed to get your ratio, then select tooth counts accordingly. For example, a 20T drive pulley paired with a 40T driven pulley gives a 2:1 reduction. Larger tooth counts also increase the pitch diameter, which affects belt wrap angle and torque capacity.

Measure your motor or drive shaft diameter with calipers. Select the bore that matches exactly — a loose bore will cause runout and vibration. Common NEMA 17 stepper shafts are 5mm; NEMA 23 shafts are typically 6.35mm (1/4") or 8mm. For servo motors, check the datasheet for the shaft diameter before ordering.

A keyway is recommended whenever the pulley must transmit significant torque or resist axial movement under load. The keyway size is determined by the shaft diameter and follows standard DIN 6885 / ISO 773 key dimensions. As a general guide: 8mm bore → 3×1.4mm key; 10mm bore → 3×1.4mm or 4×1.8mm key; 12mm bore → 4×1.8mm key; 14–15mm bore → 5×2.3mm key; 19–20mm bore → 6×2.8mm key; 25mm bore → 8×3.3mm key. Confirm against your shaft's key slot before ordering.

Yes — this pulley is designed for the HTD-3M tooth profile with a 3mm pitch. It is compatible with any HTD-3M timing belt of 21mm width. Ensure the belt width matches the 21mm pulley face. Using a narrower belt is possible but reduces torque capacity; a wider belt will not seat correctly.

The aluminum alloy used is suitable for the torque loads typical of CNC routers, 3D printers, and light-to-medium automation systems. For heavy industrial applications with sustained high torque, verify the pulley's rated torque against your system requirements. The anodized surface adds corrosion resistance and surface hardness without adding significant weight.

The anodized aluminum finish provides good resistance to oxidation and mild corrosion in indoor and semi-protected environments. For prolonged outdoor exposure or contact with aggressive chemicals, consider applying a compatible protective coating or selecting a stainless steel alternative for your application.

Yes. HTD-3M pulleys are widely used in CoreXY and Cartesian 3D printers, CNC router gantry drives, and laser cutter motion systems. Select the tooth count and bore that match your existing belt and motor shaft. The AF-type flange helps keep the belt aligned on the pulley, which is especially useful in high-speed printer motion systems.