HTD-5M 10T-72T Timing Belt Pulley With Step Bore 5-25mm, For 15mm Width Belt

The tooth count determines your drive ratio. Divide the driven pulley tooth count by the driving pulley tooth count to get the ratio. For example, a 20T driver paired with a 40T driven pulley gives a 2:1 reduction. For CNC axes, smaller tooth counts (10T–20T) are common on motor shafts for higher resolution; larger counts (30T–72T) suit idler or driven shafts where torque multiplication is needed.

Select the bore that matches your shaft diameter exactly. Common NEMA 17 stepper shafts are 5 mm; NEMA 23 shafts are typically 6.35 mm (1/4 in) or 8 mm; servo motors often use 8 mm, 10 mm, or 12 mm shafts. The step bore design means the pulley body is the same — only the bore step differs. If your shaft is metric, choose the matching metric bore; for imperial shafts, the 6.35 mm (1/4 in) and 12.7 mm (1/2 in) options are available.

Standard variants use a set screw to clamp the pulley onto a smooth shaft. K-Type variants include a machined keyway in the bore, which provides a positive mechanical lock between the shaft and pulley — preventing rotation under shock loads or high torque. K-Type is available on 14T and 15T sizes with a 10 mm bore.

HTD-5M and GT2-5M belts share the same 5 mm pitch but have slightly different tooth profiles. In many low-load applications they are interchangeable, but for precision or high-load drives it is recommended to match the pulley profile to the belt profile. These pulleys are designed and optimized for HTD-5M synchronous belts.

Aluminum alloy pulleys are well-suited for the torque levels typical of NEMA 17 and NEMA 23 stepper motors, hobby servo motors, and light industrial drives. For very high-torque applications (e.g., large servo drives above 5 Nm continuous), consider whether a steel pulley is more appropriate. The anodized surface adds hardness to the tooth flanks, extending wear life under normal belt tension.

A standard set screw can leave a small indentation on a smooth shaft, which is normal and helps prevent the pulley from walking axially. If you need to reposition the pulley frequently, consider using a flat on the shaft aligned with the set screw, or apply a thread-locking compound at a fixed position. For shafts where surface damage must be avoided, the K-Type keyway variant is the better choice.

The anodized aluminum finish provides moderate corrosion resistance suitable for indoor and sheltered environments. Prolonged exposure to moisture, salt spray, or harsh chemicals is not recommended without additional protective measures. For outdoor or washdown applications, consider stainless steel or coated alternatives.