8M 20/25/30/40/mm Timing Belt Smooth Tooth Idler Drive Pulley 15 16 20 -30 Teeth

Use a toothed idler when you need the pulley to engage the tooth face of the belt — for example, to re-route the belt around a corner or to add a second drive point. Use a smooth idler when the pulley contacts the back (flat) face of the belt purely to maintain tension. Applying a toothed pulley to the back face can damage belt teeth over time.

The idler tooth count affects the wrap angle and the minimum bend radius imposed on the belt. A larger tooth count (e.g., 24T or 30T) gives a gentler curve and is preferred for high-tension or high-speed drives. Smaller counts (15T or 16T) are compact and suit space-constrained layouts. Match the tooth count to your available mounting space and the belt manufacturer's minimum pulley diameter recommendation.

Select the bore that matches your shaft diameter. Available bores range from 5 mm to 25 mm depending on the model and belt width combination. If your shaft uses a keyway, confirm the bore variant includes a keyway slot, or plan to use a set-screw collar for axial retention. Bore sizes are listed in the Product Type & Bore variant option.

Yes — the tooth profile follows the standard HTD 8M curvilinear geometry (8 mm pitch, ~3.4 mm tooth height), which is compatible with 8M timing belts from all major belt manufacturers. Verify that your belt width matches the pulley's rated belt width (20, 25, 30, or 40 mm) to ensure the belt tracks correctly within the pulley flanges.

Aluminum alloy pulleys perform well in light-to-medium duty continuous applications such as CNC routers, 3D printers, and packaging conveyors. For heavy industrial drives with high belt tension (above ~500 N) or abrasive environments, consider adding a bearing insert or selecting a steel pulley. In typical maker and automation lab conditions, aluminum idlers offer a good balance of weight, machinability, and service life.

These pulleys are supplied as bare pulleys (hub only) intended to be mounted on a fixed or rotating shaft. If you need the pulley to spin freely on a stationary shaft (as a true idler), you will need to press in or mount a suitable ball bearing (e.g., a standard metric deep-groove bearing matching the bore diameter) before installation. If the pulley is keyed to a rotating shaft, no bearing is required in the pulley itself.

The belt width dimension refers to the width of the timing belt the pulley is designed to guide. A wider belt carries more load and is used in higher-torque or higher-tension drives. Select the belt width that matches your existing belt. Using a pulley narrower than your belt will cause the belt to overhang the flanges; using one wider than your belt is generally acceptable but may reduce lateral guidance.