Put the numbers in the link
Every parameter is a link parameter; the link below opens the example part. ChatGPT, Claude or any assistant can write one like it from the parameter list (names, units, ranges) at: parameter list (JSON)
Helical gear generator with true involute teeth
Set the normal module, tooth count, helix angle and hand — the generator cuts the tooth across the axis with the same ISO 53 rack as our spur gears, then twists it along the axis, so a left-hand and a right-hand gear with the same module and helix angle mesh on parallel shafts. Helical teeth take up the load gradually, so a pair runs quieter than spur gears.
Use it right here
The real generator runs in your browser: set the parameters, then download STEP or STL. Nothing to install, no sign-up.
The first open downloads the CAD engine (about 20 MB).
- - Normal module and pressure angle — the way KHK SH, MISUMI and Chinese catalogues list them
- - Left or right hand: parallel shafts take opposite hands, 90° crossed shafts the same hand at 45°
- - Default face width spans one axial pitch (overlap ratio ≈ 1), like catalogue gears
- - Round or hex bore, cut as a true cylinder or prism after the twist
Parameters you can tune
Each parameter below rebuilds real geometry on every change — this is parametric CAD, not a scaled mesh.
| Parameter | Default | Range | What it does |
|---|---|---|---|
| Module (normal)MODULE | 2 mm | 1 – 5 | Normal module, as KHK SH, MISUMI and Chinese catalogues list it; mating gears share it. |
| Number of teethTEETH | 20 | 8 – 40 | Pitch diameter = module × teeth / cos(helix angle). |
| Pressure angle (normal)PRESSURE_ANGLE | 20 ° | 20 / 25 | 20° standard. |
| Helix angleHELIX_ANGLE | 20 ° | 5 – 45 | 15–21.5° on catalogue parallel-shaft gears; 45° for shafts crossed at 90°. |
| HandHAND | right | right / left | Parallel shafts: opposite hands. 90° crossed shafts: the same hand. |
| Face widthFACE_WIDTH | 20 mm | 3 – 40 | 20 at module 2 and 20° spans one axial pitch (overlap ratio ≈ 1), like catalogue gears. |
| Bore styleBORE_STYLE | circular | none / circular / hex | Round shaft or hex socket. |
| Bore sizeBORE_D | 5 mm | 2 – 30 | Shaft diameter, or hex across flats; 5 fits a NEMA 17 motor. |
Every parameter can go in the page's link, so one link opens exactly the part you want. Example (Module 1.5, 30 teeth, 20° left-hand helix):https://www.forgent3d.com/en/generators/helical-gear-generator?MODULE=1.5&TEETH=30&HELIX_ANGLE=20&HAND=left
What's in the STEP file
- - Every tooth surface is one smooth B-spline face that follows the helix: the default 20-tooth gear exports as 83 faces — 80 tooth surfaces, the two end faces, and the bore as a true cylinder, cut after the twist so its diameter reads exactly in CAD.
STEP AP214 in millimetres, exact B-rep — it opens directly in SolidWorks, Fusion, FreeCAD, Onshape or Inventor, and goes straight into a CNC quote form. STL for the slicer is one click too.
How it compares
| This generator | Typical online STL generator | Vendor CAD library | |
|---|---|---|---|
| Any size within the range | Yes | Yes | Catalog sizes only |
| STEP with exact surfaces | Yes | Usually an STL mesh only | Yes |
| Changes the sliders don't cover | “AI edit” on the page | No | No |
| Account needed to download | No | Usually no | Often |
Let AI change it
Edit with AI on the page
Press “AI edit” in the generator and say what to change — a keyway, holes, a different shape. The AI edits the part's model.py and it rebuilds in your browser, with undo. A few edits a day are free without signing in; to keep the result or go further, copy it into your models and continue with the AI agent.
Edit with AI →Keep going in your workspace
For bigger changes, several rounds, or a part you want to keep: copy it into your models (free account). The Forgent3D AI agent reads the model.py, edits it, rebuilds it and checks the result itself.
Copy and continue with the AI agent →How it works
- 1.Open the generator — the model builds right in your browser, nothing to install.
- 2.Tune dimensions and options in the parameter panel; the geometry rebuilds live in 3D.
- 3.Export STL / STEP for printing — or ask the AI agent for features beyond the sliders.
FAQ
What centre distance do two helical gears need?
Normal module × (teeth₁ + teeth₂) / (2 × cos helix angle). KHK's own centre-distance table matches it to the hundredth: their SH2-15 with SH2-20 at 15° sit 36.23 mm apart.
Do helical gears print without supports?
Yes: every printed helical and herringbone gear we found that states its settings prints flat on the bed with no supports, at helix angles of 15–30°. Use 4–6 walls, 0.16–0.2 mm layers, PETG or nylon for load.
Why does it stop at 40 teeth?
Each change rebuilds the gear in your browser, and the twisted tooth surfaces add about 0.12 s per tooth to the rest of the build: at 40 teeth the slowest allowed gear takes about 6 s. 8–40 covers pinions and wheels up to Wade's 39-tooth extruder gear; for a bigger wheel, copy the gear into your models and ask the AI agent — it just rebuilds more slowly.
How do I make a pair of helical gears, 15 and 30 teeth, module 2?
Open https://www.forgent3d.com/en/generators/helical-gear-generator?MODULE=2&TEETH=15&HAND=right and https://www.forgent3d.com/en/generators/helical-gear-generator?MODULE=2&TEETH=30&HAND=left — parallel shafts need the same helix angle and opposite hands. At the default 20° they mesh at 2 × (15 + 30) / (2 × cos 20°) = 47.89 mm.
Which helix angle should I use?
Catalogue gears for parallel shafts use 15° (KHK SH) to 21.5° (KHK KHG); printed helical gears sit at 15–30° and print flat without supports. For shafts crossed at 90°, use 45° on both gears with the same hand, as MISUMI and HPC do: https://www.forgent3d.com/en/generators/helical-gear-generator?HELIX_ANGLE=45&FACE_WIDTH=10
Can I sell prints made with these generators?
Yes. Models you generate and the STL / STEP files you export are yours: print them, sell the prints, or use them in a product. No attribution to Forgent3D is required.
More generators
Spur Gear GeneratorGear Rack GeneratorBevel Gear GeneratorWasher & Spacer Generator3D print generators →
Already have your own .scad file? Convert OpenSCAD to STEP → · Preview it in the browser →