Knob Generator
Pick your shaft (6 mm D, knurled splines or round), the grip (fluted, knurled, diamond or smooth), the size and an optional set screw hole and pointer. The 3D preview updates as you type, and you download a watertight STL, a 2-colour 3MF or a ZIP of STLs. It is free, unlimited and runs in your browser.
How to make a 3D printed knob
- 1
Match the shaft
Pick a common shaft from the list, or choose Custom and type the diameter you measured with calipers. For a D shaft, also type the size from the flat to the far side.
- 2
Shape the knob
Choose the grip, the diameter and the height. Make the top smaller for a tapered knob, add a chamfer on the top edge, or a wide skirt at the bottom.
- 3
Add a pointer and a screw
Pick a line or a dot pointer so you can see the position, and an M3 or M4 set screw hole if the knob must not slip.
- 4
Download and test the fit
Press Download STL. Print a short test first, then change the fit clearance by 0.05 mm until the knob pushes on firmly.
Knob generator settings
What each setting does and the range it accepts.
| Shaft | D shaft with one flat side, knurled shaft with splines, or round shaft. Diameter 2 to 20 mm. Presets for 6 mm D, 6 mm knurled with 18 splines, 1/4 inch and 6 mm round. |
|---|---|
| Fit clearance | 0 to 0.6 mm added on each side of the bore. Around 0.1 mm gives a press fit, 0.3 mm a loose fit for a set screw. |
| Bore depth | How far the shaft goes into the knob, at least 3 mm. At least 2 mm of knob stays above the bore. |
| Grip | Fluted: round cuts between flat lands. Knurled: fine straight ridges. Diamond: crossed ridges. Smooth: a plain cylinder. |
| Size | Diameter 10 to 80 mm and height 6 to 50 mm. Top size 60 to 100% of the bottom for a taper, and a top edge chamfer of 0 to 5 mm. |
| Set screw | None, M3 or M4. The hole goes through the side in line with the pointer, sized for the screw to cut its own thread. |
| Pointer and skirt | A line or dot cut into the top, or none. An optional skirt adds a wide flange at the bottom with its own pointer line. |
| Output | Binary STL in millimetres with the knob as one closed part. 3MF with the knob and the pointer as separate coloured parts. ZIP with one STL per part. |
Which shaft do I have?
Most potentiometers and rotary encoders sold for hobby electronics have a 6 mm shaft. A D shaft has one flat side; the size from the flat to the far side is usually 4.5 mm. A knurled shaft has fine splines along its length, often 18 or 20 of them, and is sometimes split down the middle.
Guitar and audio pots in the US often use a 1/4 inch (6.35 mm) round shaft or a knurled shaft. If you are not sure, measure the shaft with calipers and use Custom.
Getting a good fit
Printers make holes a little smaller than the file, so the bore needs some clearance. Start with 0.2 mm on each side. If the knob is loose, lower it; if it will not go on, raise it in steps of 0.05 mm.
A D or knurled bore stops the knob from turning on the shaft. A round shaft needs a set screw: pick M3 or M4 and the hole is placed in line with the pointer, halfway down the bore.
Printing tips
Print the knob standing on its bottom with the bore underneath. Every surface is either vertical or faces up, so no supports are needed. A 0.2 mm layer height works; use 0.12 mm for a fine knurl.
For a pointer in a second colour, download the 3MF for a multi-material printer, or on a single-nozzle printer change filament at the top of the knob where the pointer is cut.
Keep at least 2 mm of wall between the bore and the grip if you use a set screw. The wall is shown under the settings.
Need another part for your project?
Turn a photo or a short text prompt into a 3D model with AI, or make gears, threads and springs with the free generators.