Involute spline generator (ISO 4156 shaft & hub)
Splines transmit torque between a shaft and a hub across many teeth at once — stronger and better-centred than a single key. Involute splines (ISO 4156 / ANSI B92.1) are the most common, and the tricky part is generating a shaft and a hub that actually fit. GearForge produces both mating cross-sections from the same standard, ready to laser-cut or drop into CAD.
⚙️ Open the free spline generatorWhy involute splines?
- Load sharing — torque spreads over every tooth, so a spline carries far more than an equivalent keyway.
- Self-centring — the involute flanks push the shaft to concentric under load.
- Standardised — ISO 4156 fixes the 30° pressure angle and tooth proportions, so parts made to the standard interchange.
The parameters that matter
| Parameter | What it does |
|---|---|
| Module (m) | Tooth size; with tooth count sets the spline diameter. |
| Number of teeth (z) | More teeth = more contact and finer indexing. |
| Pressure angle | 30° for ISO 4156 involute splines (fixed by the standard). |
| Root form | Flat root (simpler) or fillet root (stronger, better fatigue life). |
| Fit / side clearance | Side-fit clearance controls how tight the shaft sits in the hub. |
Shaft and hub are not the same part. The external (shaft) and internal (hub) teeth are complementary — GearForge generates both so the pair mates, with the correct ISO 4156 major/minor diameters.
Making splines on a laser
Laser-cut spline plates work well for light-to-moderate torque couplers and for prototyping a fit before you commit to broaching or machining. Enter your measured kerf so the flanks stay on the pitch line, pick a side-fit clearance, and test the shaft-in-hub feel on scrap first. For serious drive loads, use the exported profile as a verified CAD sketch for machining.
Step by step
- Open the generator and pick Spline (or load the “Spline 20×1 shaft + hub” preset).
- Enter module and tooth count; choose flat or fillet root.
- Set the side-fit clearance for the fit you want.
- Generate the shaft and hub cross-sections and export mm-true SVG or DXF R12.