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When your 3D printer skips steps or your CNC axis loses position, the culprit is often a worn or mismatched pulley. Engineers, makers, and machine builders who demand repeatable, backlash-free motion need a GT2 timing belt pulley they can rely on — one that fits their shaft exactly and meshes cleanly with standard GT2 belts.
These GT2 timing belt pulleys feature an aluminum alloy body with a 2mm pitch GT2 tooth profile and an 11mm belt-contact width. Tooth counts range from 20T to 80T, and bore diameters span 4mm to 15mm (including 6.35mm / 0.25 in and 12.7mm / 0.5 in imperial sizes), covering the most common motor shaft dimensions used in desktop fabrication and automation equipment.
Typical applications include RepRap and CoreXY 3D printer X/Y axis drives, GRBL-based desktop CNC router feed axes, and lightweight robotic arm joint drives where a GT2 belt pulley with a precise bore fit eliminates shaft wobble and improves positioning accuracy.
| Belt Pitch | 2mm (GT2) |
|---|---|
| Tooth Count | 20T, 22T, 24T, 25T, 26T, 28T, 30T, 32T, 34T, 35T, 36T, 38T, 40T, 45T, 48T, 50T, 55T, 60T, 70T, 80T |
| Belt Width (Teeth Width) | 11mm |
| Bore Diameter | 4mm, 5mm, 6mm, 6.35mm, 8mm, 10mm, 12mm, 12.7mm, 14mm, 15mm |
| Material | Aluminum alloy |
| Tooth Profile | GT2 curvilinear (2mm pitch) |
| Shaft Retention | Set screw(s) |
| Outer Diameter | See variant options |
| Hub Length | See variant options |
| Compatible Belt Width | 11mm GT2 open or closed loop belt |
| Finish | Natural aluminum / anodized (see variant options) |
| Unit Sold | 1 piece per order |
The most common choice for RepRap, Prusa, and CoreXY printers is a 20T pulley paired with a GT2 belt and a NEMA 17 motor. A 20T pulley gives approximately 40mm of belt travel per motor revolution (20 teeth × 2mm pitch), which is the standard steps-per-mm baseline for most firmware configurations. Larger tooth counts reduce speed but increase torque — useful for heavy gantry or Z-axis applications.
Standard NEMA 17 stepper motors have a 5mm diameter output shaft. Select the 5mm bore variant. If your motor has a D-cut (flat) shaft, align the set screw with the flat for a secure, slip-free connection. NEMA 23 motors typically use an 8mm shaft — choose the 8mm bore in that case.
Yes. The GT2 tooth profile is an open industry standard defined by a 2mm pitch curvilinear geometry. These pulleys are dimensionally compatible with any GT2 belt (open-ended or closed loop) with an 11mm width, regardless of brand. Always verify the belt width matches the pulley's 11mm tooth width to ensure full engagement.
Aluminum alloy pulleys are significantly more rigid and dimensionally stable than injection-molded plastic pulleys. They resist deformation under belt tension, maintain tooth geometry at elevated temperatures (e.g., near heated beds), and do not creep over time. For any application requiring consistent positioning accuracy, aluminum is the recommended choice over plastic.
The pitch diameter of a GT2 pulley is calculated as: PD = (Tooth Count × Pitch) ÷ π. For example, a 20T pulley has a pitch diameter of approximately 12.73mm (20 × 2 ÷ π). The outer diameter is slightly larger. Exact outer diameter values vary by variant — please refer to the variant options or contact us to confirm before ordering for tight-clearance installations.
Yes. 6.35mm is the metric equivalent of ¼ inch (0.25 in), so the 6.35mm bore variant is designed for standard ¼-inch shafts commonly found in North American servo motors and small DC gearmotors. Similarly, the 12.7mm bore corresponds to ½ inch (0.5 in). These sizes are included specifically to support imperial-shaft applications.
Tighten the set screw firmly against the shaft flat (if present). For smooth round shafts, apply a small amount of thread-locking compound (e.g., Loctite 243) to the set screw threads before tightening. Avoid over-tightening, which can strip the set screw threads. For high-torque applications, consider using a pulley with a keyway or a shaft collar in addition to the set screw.
