Potentiometer knob, customizable: any D-shaft, size and knurl

A replacement knob for potentiometers and other controls with a D-shaped shaft. At the defaults it is 25 mm across and 16 mm tall, with 36 knurl grooves, a pointer line on top and a hole for a 6 mm shaft that measures 4.5 mm across the flat. Set the shaft diameter (3 to 8 mm), the width across the flat (2.5 to 7 mm), the clearance (0 to 0.4 mm), the knob size and the knurl.

Customize Change it with AIFree STL, 3MF and STEP, no accountMeasured on the model

Parameters

Knob diametermm

Knob heightmm

Shaft diametermm

Shaft width across the flatmm

Shaft hole depthmm

Shaft hole clearancemm

Knurl grooves

Knurl depthmm

Pointer line on topM3 set screw hole

Sliders and downloads are free. Changes by the AI designer use credits like any design; new accounts start with free ones.

It prints as modelled, with the shaft hole opening on the bed, and needs no supports. Measure your shaft and its flat with calipers first: 6 mm with a 4.5 mm flat is a common size, not a universal one. The 0.15 mm clearance is the model's assumption, so print one knob and adjust it if the fit is loose or tight. An optional M3 set screw presses on the flat. There is no dial scale.

Parameters

Every slider in the viewer above, with the range the model accepts. The model rebuilds valid at both ends of each range.

Parameter	Range	Default	What it changes
Knob diameter	20 to 40 mm	25 mm	Outside diameter of the grip.
Knob height	10 to 30 mm	16 mm	Total height of the knob. The shaft hole always leaves at least 3 mm of solid top.
Shaft diameter	3 to 8 mm	6 mm	Diameter of the round part of your shaft. Measure it with calipers.
Shaft width across the flat	2.5 to 7 mm	4.5 mm	Distance from the flat to the opposite, round side of the shaft. Set it to the shaft diameter or more for a plain round hole.
Shaft hole depth	6 to 25 mm	12 mm	How deep the shaft goes into the knob. It is capped at the knob height minus 3 mm.
Shaft hole clearance	0 to 0.4 mm	0.15 mm	Clearance added around the shaft hole, on the round side and at the flat. Raise it if the knob will not go on, lower it if it wobbles.
Knurl grooves	12 to 48	36	Number of grip grooves around the knob. On a small knob with deep grooves the count drops so grooves never overlap.
Knurl depth	0.3 to 1.2 mm	0.7 mm	How deep each grip groove cuts into the side.
Pointer line on top	On or off	On	Cuts a 1.4 mm wide, 0.6 mm deep line on top, on the same side as the shaft flat.
M3 set screw hole	On or off	On	Adds a 2.6 mm pilot hole from the side onto the shaft flat, for an M3 grub screw that holds the knob on a loose shaft.

Proof: measured on the model

What the design must satisfy and what our CAD engine measured on the model at the default values. Only measured values are shown here; nothing on this page has been printed by us yet.

Requirement	Wanted	Measured
Knob diameter over the knurl	25 mm (the knurl trims it to 24.97 mm)	24.968 mm
Knob height	16 mm (the slider)	16 mm
Shaft hole across the flat	4.8 mm (4.5 mm flat + 0.15 mm clearance each side)	4.8 mm
Shaft hole across the round side	6.3 mm (6 mm shaft + 0.15 mm clearance each side)	6.3 mm
Shaft hole depth	12 mm (4 mm solid above it)	12 mm
M3 set screw pilot hole, 2.6 mm, onto the flat	1 hole	1

valid solid, one body, 25 x 25 x 16 mm, fits a 256 x 256 x 256 mm printer; overhangs: 2.2% of surface would need support.

Print notes

Orientation: As modelled: shaft hole down on the bed, pointer line on top.
Supports: None
Material: PLA or PETG
Layer height: 0.2 mm
Hardware: 1 x M3 grub screw, 4 to 6 mm long (optional, for the set screw hole)
Time and filament: About 15 min and 4 g at the default size: a rough estimate from the model's volume and surface (PLA, 15% infill, about 1 mm of walls, 0.2 mm layers), not a slicer.

Measure the shaft's round diameter and its width across the flat before printing. Print one knob first; if it is tight or loose, change the clearance in 0.05 mm steps.
The pointer line is on the same side as the flat and the set screw, so you can see where the flat is when you fit the knob.
The set screw hole is a 2.6 mm pilot: drive the M3 grub screw in slowly so it cuts its own thread, and stop once it touches the flat.
The hole is for D-shaped or plain round shafts, not splined (knurled) shafts.

How it was designed

Designed with buildcad's AI agent, checked by the buildcad team. This is the request it started from and an edited account of what it did (more on how text to CAD works).

The request
A replacement knob for a 6 mm D-shaft potentiometer, 25 mm diameter, knurled grip, pointer line on top.

1
It assumed the shaft size
The prompt gave a 6 mm D-shaft but no flat, so the agent used the common 4.5 mm across the flat and 0.15 mm clearance: a 6.3 mm hole on the round side with the flat 1.65 mm from the centre. It wrote checks for the 25 mm diameter, the 16 mm height, one body and one 2.6 mm set screw pilot hole.
2
First build: it probed the shaft hole
The first knob built as one valid body, 24.97 x 24.97 x 16 mm, with 36 grooves and all 4 checks passing. Its first ray toward the flat ran straight out through the set screw hole, so the agent probed lower down and found the flat 1.65 mm from the centre and the round side at 3.15 mm, as planned.
3
The slider sweep ran out of time
Rebuilding the knob at every slider extreme ran out of compute time 3 times, even after the agent cut all the grooves from one sketch and capped the groove count so grooves never overlap. It then built the small extreme by hand (20 mm knob, 10 mm tall, deepest hole, 0.4 mm clearance, 48 grooves 1.2 mm deep): one valid body, with the groove count reduced to 22.
4
What it left to the maker
Its reply asks you to measure the shaft and the flat with calipers, and says it did not build the large extreme (40 mm wide, 30 mm tall).
5
Our check
Because the agent's sweep did not finish, we went through the sliders one at a time after the run. Every slider extreme was rebuilt and checked, and each one built as a single valid body.

One run of the agent: 3 min 6 s, about $0.36 of model time at list price (claude-sonnet-5-5). The model code behind this page is the code it wrote, unchanged.

Change it with AI

Set the sliders, then press Change it with AI: a copy goes to your designs at those sizes and the designer opens with a suggested change you can edit. Its changes use credits like any design; new accounts start with free ones.

Change it with AI Describe your own part Use it from your own AI (MCP)