Learn/Shape Generator/Built-in profiles
Timing Pulley
At a glance
- Imperial trapezoidal: MXL, XL, L, H, XH, XXH
- Metric T-series: T2.5, T5, T10, T20
- AT-series: AT3, AT5, AT10, AT20
- HTD: 3M, 5M, 8M, 14M, 20M
- Gates GT: GT2, GT3, GT5
- Set tooth count and bore; displays pitch diameter and OD
The Timing Pulley shape (Power Transmission category) generates synchronous-belt pulley profiles — the 2D tooth form you extrude, stack, or cut directly for CNC axis drives, engine accessories, and positioners. Pick a belt standard and the groove dimensions fill themselves in.
Belt standards
The Standard dropdown spans five families plus Custom:
- Imperial trapezoidal: MXL, XL, L, H, XH, XXH (20° flanks)
- Metric T-series: T2.5, T5, T10, T20 (20° flanks)
- AT-series: AT3, AT5, AT10, AT20 (15° flanks)
- HTD: 3M, 5M, 8M, 14M, 20M (arc groove)
- Gates PowerGrip GT: GT2, GT3, GT5 (arc groove)
The default is HTD 3M. Every preset just populates the dimension fields below it, so any value can be tweaked afterward — or start from Custom and enter a groove spec directly.
Two groove profiles
The Profile selector matches the belt family. Trapezoidal grooves (MXL through AT20) are straight-flanked: pitch, addendum, tooth depth, space width at the OD, and flank angle define the groove. Arc Groove (HTD and GT) is curvilinear: a groove-bottom radius and a flank blend radius, with the blend arcs computed tangent to both the root arc and the OD so the profile comes out as smooth connected arcs — no polygon approximation of the round HTD tooth.
Under Pulley Parameters, set Num Teeth (default 20, minimum 6) and Bore Dia (default 0.3937 in = 10 mm; 0 omits the bore). Pitch diameter follows from tooth count × belt pitch, and the OD sits one addendum above it, so the belt rides at the correct pitch line.
Tips
- Metric belt specs are stored behind the scenes in millimeters and converted for the inch-based
fields — type values with a
mmsuffix if you're working from a metric datasheet. - Groove fit is everything on small pitches like GT2: cut a test pulley and check belt seating before committing to a stack of them. The live preview zooms deep enough to inspect individual grooves first.