HTD-5M 15T-72T Timing Belt Pulleys CNC Drive With Keyway Width 21mm BF 45# Steel

The tooth count determines the pulley pitch diameter and, combined with your motor pulley, sets the drive ratio. Divide the desired output speed by the input speed to get the ratio, then select tooth counts accordingly. For example, a 20T drive pulley paired with a 40T driven pulley gives a 2:1 reduction. If you are replacing an existing pulley, match the tooth count exactly.

Measure your shaft diameter with a caliper. The bore must match the shaft exactly — a loose bore causes vibration and keyway wear. Available bores range from 8 mm to 30 mm depending on the tooth count. Larger tooth counts support larger bore options. Check the variant selector for the bore sizes available for your chosen tooth count.

The keyway is matched to the bore per DIN 6885 standards: 8–10 mm bore uses a 3x1.4 mm key; 10–12 mm bore uses 4x1.8 mm; 14–17 mm bore uses 5x2.3 mm; 18–22 mm bore uses 6x2.8 mm; 24–30 mm bore uses 8x3.3 mm. The keyway dimensions are shown in the variant name (e.g., "4x1.8mm & 1Pcs").

No. This pulley is designed exclusively for HTD-5M timing belts with a 5 mm pitch curvilinear tooth profile. GT2 belts use a 2 mm pitch and a different tooth geometry. MXL belts use a trapezoidal profile. Using a mismatched belt will cause poor engagement, noise, and premature wear. Always pair with an HTD-5M belt of 21 mm width.

45# carbon steel has a tensile strength of approximately 600–700 MPa, roughly 3–4x that of common 6061 aluminum alloy. Steel pulleys are preferred for high-torque servo drives, heavy gantry systems, and applications where belt tension is high. The trade-off is added weight — factor this into your moving-mass calculations for acceleration-sensitive axes.

Black oxide provides mild corrosion resistance suitable for typical indoor workshop conditions. It is not equivalent to galvanizing or stainless steel. For humid or outdoor environments, apply a light coat of machine oil or grease to the pulley surface after installation.

The pulley is designed for keyway-and-key shaft coupling. While a set screw alone can work for very light loads, the keyway is the primary torque-transfer feature. Omitting the key in a high-torque application risks shaft damage and pulley slippage. We recommend always using the matching key for reliable operation.