HTD-5M 10T-72T Timing Belt Pulley With Step Bore 5-25mm, For 20mm Width Belt

Tooth count determines your drive ratio. Divide the driven pulley tooth count by the driver pulley tooth count to get the ratio. For example, a 20T driver paired with a 40T driven pulley gives a 2:1 reduction. Use a higher tooth count on the driven side to reduce speed and increase torque, or match tooth counts for a 1:1 synchronous drive. The 10T–72T range available here covers ratios from 1:1 up to approximately 7.2:1 in a single-stage belt drive.

Standard NEMA 17 stepper motors have a 5 mm output shaft. Select the 5 mm bore option. If your motor has a flat (D-shaft), ensure the set-screw is tightened against the flat for a secure connection. For NEMA 23 motors with an 8 mm shaft, choose the 8 mm bore variant.

Standard variants use a set-screw to clamp the pulley onto the shaft — suitable for most light-to-medium torque applications. K-Type variants include a machined keyway slot that accepts a standard key, providing a positive mechanical lock between shaft and pulley. K-Type is recommended when transmitting higher torques or when the drive direction reverses frequently, as it prevents rotational slippage that can occur with set-screw-only retention under shock loads.

The pulley tooth profile is standard HTD-5M (5 mm pitch, curvilinear tooth form) and will mesh correctly with any HTD-5M belt regardless of width. However, the pulley face width is 21 mm, which is optimized for 20 mm wide belts. Using a narrower belt (e.g., 15 mm) is possible but reduces load capacity. Using a wider belt is not recommended as the belt will overhang the pulley face and may track poorly or wear unevenly.

Torque capacity depends on tooth count, belt tension, and the number of teeth in mesh. As a conservative guideline, aluminum HTD-5M pulleys in this size range are commonly used in applications up to approximately 10–30 Nm depending on configuration. For precise load calculations, use the belt manufacturer's published power rating tables for HTD-5M belts at your operating speed and tension. If your application exceeds these ranges, contact us to confirm suitability or inquire about steel variants.

No additional machining is required for standard use. The step bore is pre-machined to the diameter you select, and the set-screw is included. Simply slide the pulley onto your shaft, align it with your belt path, and tighten the set-screw against the shaft flat (or use a key for K-Type variants). If your shaft diameter falls between available bore sizes, a shaft adapter sleeve or bore-up machining service may be needed — contact us for guidance.

Yes. HTD-5M belt drives are commonly used on vertical axes in CNC machines and 3D printers (Z-axis). Ensure your belt tension is set correctly to prevent back-driving under gravity load, and consider adding a motor brake or lead-screw backup if the load must hold position when power is removed. The curvilinear HTD tooth profile provides better load distribution than trapezoidal profiles, making it a reliable choice for vertical drive applications.