A FreeCAD workbench for designing parametric gears. Every gear is fully parametric — change any value and the 3D model rebuilds automatically.
Alpha: Actively developed. APIs and file formats may change.
Gear types
- Spur, helical, and herringbone (unified in
genericGear.py) - Internal (ring) gear
- Rack gear
- Bevel gear
- Crown gear
- Worm gear and globoid worm gear
- Hypoid gear
- Screw gear
- Non-circular gear
- Cycloid gear and cycloid rack
- Geneva wheel (Maltese cross intermittent mechanism)
Gear systems
- Planetary gear set (sun + planets + ring, auto-calculated)
- Cycloidal gearbox
Tools
- Position Gears — select two gear bodies, dialog places them at the correct center distance with orbit angle and phase controls
- Gear Stack — stack multiple gears on a shared shaft
Each gear type follows the same pattern:
gearMath.py— all the involute math, tooth profile generation, and parameter validation. No FreeCAD dependency; easy to test standalone.genericGear.py/bevelGear.py/ etc. — FreeCAD FeaturePython objects. Each creates aVarSet(FreeCAD's parametric property container) and aPartDesign::Bodybuilt from sketches and pads/pockets.InitGui.py— registers commands and builds the toolbar/menu.
The VarSet holds the parameters. A watcher object observes property changes and triggers a deferred rebuild so rapid slider drags don't queue redundant rebuilds.
VarSet (parameters) → watcher → FeaturePython.execute() → PartDesign::Body
Bores (circular, square, hex, DIN 6885 keyway) are handled in util.py and shared across all gear types.
# Linux / macOS
cd ~/.local/share/FreeCAD/<version>/Mod
git clone https://github.com/iplayfast/GearWorkbench.git
# Windows
cd %APPDATA%\FreeCAD\<version>\Mod
git clone https://github.com/iplayfast/GearWorkbench.gitRequires FreeCAD 1.0+ and Python 3.9+. Restart FreeCAD after cloning.
- Open FreeCAD and select GearWorkbench from the workbench dropdown.
- Click any gear icon to create it with default parameters.
- Expand the gear in the model tree and edit the VarSet properties — the model rebuilds live.
- To mesh two gears: create both with the same module and pressure angle, select both bodies, then click Position Gears.
Gears use the standard involute profile. Key relationships:
| Value | Formula |
|---|---|
| Pitch diameter | module × teeth |
| Base circle | pitch_diameter × cos(pressure_angle) |
| Addendum | 1.0 × module |
| Dedendum | 1.25 × module |
| Center distance (external) | (pd₁ + pd₂) / 2 |
Profile shift (x) moves the cutter radially — positive shift prevents undercutting on gears with fewer than ~17 teeth at 20° pressure angle. The tooth thickness and involute start point are adjusted accordingly.
The involute curve is parameterized as:
x(t) = r_base × (cos(t) + t×sin(t))
y(t) = r_base × (sin(t) − t×cos(t))
See gearMath.py for the full implementation including undercut detection, helical transverse-to-normal conversion, and bevel cone geometry.
LGPL-2.1 — see LICENSE