H-type Timing Belt Pulley Pitch 12.7mm BF-type Synchronous Wheel Width 27mm

The tooth count determines your drive ratio. Divide the driven pulley teeth by the driving pulley teeth to get the ratio. For example, a 20T driving pulley paired with a 40T driven pulley gives a 2:1 reduction. Choose a smaller tooth count for higher speed output and a larger tooth count for more torque. Common CNC and 3D printer builds use H16T–H20T on the motor side.

Measure your motor or shaft diameter precisely with calipers before ordering. Common NEMA 17 stepper motors use a 5mm shaft, NEMA 23 motors typically use 6.35mm or 8mm shafts, and NEMA 34 motors often use 12mm or 14mm shafts. Select the bore that matches your shaft diameter. If your shaft has a keyway, confirm the bore variant accommodates it or plan to machine a keyway after purchase.

Yes. These pulleys are machined to H-series tooth geometry (12.7mm / 1/2 in pitch) and are designed to mesh with standard H-series synchronous belts. Ensure your belt is also rated for 27mm width to achieve full tooth contact across the pulley face. Using a narrower belt is possible but reduces load capacity.

BF stands for Both Flanged — the pulley has a raised flange on both sides of the tooth face. This keeps the timing belt centered on the pulley during operation without requiring external belt guides or tensioners with side rails. BF pulleys are preferred in open-frame machine builds where lateral belt drift would otherwise require additional hardware to control.

Aluminum alloy pulleys are well-suited for light-to-medium duty applications such as desktop CNC machines, 3D printers, small conveyors, and educational robotics. For heavy industrial loads, high-shock environments, or continuous high-torque operation, steel pulleys are generally recommended. If your application involves moderate speeds and loads typical of DIY automation, aluminum provides a good balance of weight, machinability, and durability.

Aluminum alloy has natural oxidation resistance that forms a protective layer in typical indoor workshop conditions. For environments with high humidity, salt air, or exposure to cutting fluids, an anodized finish provides additional corrosion protection. Avoid prolonged contact with strong alkalis or acids. For outdoor or wet environments, consider applying a light protective coating after installation.

The pulley face is designed for a 27mm-wide H-series belt. A narrower belt will fit within the flanges but will only contact a portion of the tooth face, reducing load capacity proportionally. A wider belt will not fit between the flanges. For best performance and belt life, always match the belt width to the pulley face width specification.