Timing-belt pulley generator: GT2, HTD, T5 and more
Whether you're building a 3D printer, a CoreXY, a camera slider or a small conveyor, the pulley has to match the belt's tooth profile exactly — get the groove shape or the pitch-line differential wrong and the belt skips or binds. GearForge ships 14 standard belt profiles with the correct dimensional groove data, and exports laser-ready or 3D-printable SVG/DXF.
⚙️ Open the free pulley generatorWhich belt profile do I have?
Pulleys are not interchangeable between profiles — you must match the belt. The common families:
| Profile | Pitch | Typical use |
|---|---|---|
| GT2 (2 mm) | 2 mm | 3D printers, small CoreXY, light positioning — the hobby default. |
| GT2 3 mm / GT3 | 3 mm | Higher load positioning, larger printers. |
| HTD 3M / 5M / 8M | 3 / 5 / 8 mm | Torque transmission — CNC, robotics, drivetrains. |
| T2.5 / T5 / T10 | 2.5 / 5 / 10 mm | Metric trapezoidal — linear stages, automation. |
| AT5 | 5 mm | Reinforced T-series for higher force linear drives. |
| MXL / 40DP / XL / H | imperial | Legacy imperial machinery and kits. |
The one formula that matters: outside diameter
A toothed pulley's outside diameter isn't z × p / π — that's the pitch diameter, which sits inside the belt. The real cut diameter is offset inward by twice the pitch-line differential (PLD), the distance from the belt's tension cords to the tooth valley:
OD = z · p / π − 2 · PLDEvery profile has its own PLD from the belt spec, and getting it right is what makes the belt track true. GearForge bakes in the SDP/SI dimensional values, so a GT2 20T pulley comes out at the commercial 12.224 mm OD automatically — you just enter the tooth count.
Laser-cutting vs 3D-printing pulleys
- 3D printing is the usual choice for pulleys — the full tooth height prints cleanly and you can add a flange. Export the SVG/DXF and extrude, or use the profile as a sketch.
- Laser cutting works for stacked-plate pulleys and idlers; enter your kerf so the groove pitch stays true. Acetal idlers cut on a CO₂ laser run smooth and quiet.
Step by step
- Open the generator and pick Pulley (or load the “GT2 20T idler” preset).
- Select your belt profile and enter the tooth count. The outside diameter and groove geometry update live.
- Tune belt-fit clearance if your printer/laser runs tight, then choose a bore — round, keyed (DIN 6885), D-flat, hex or square.
- Export SVG or DXF R12 with mm-true dimensions and CUT/ENGRAVE layers.