Knurled knob with D hole: parametric template

Parameters

Open in the editor opens the design with these defaults; change them afterwards in Modify › Parameters, and everything that depends on them follows. Opened from the editor’s template library instead (New ▾ › New from template…), the template asks for its values first and checks them against these ranges and against each other, and Copy link gives an address that opens it with your values.

Name	What it sets	Default	Range
`knobDiameter`	Knob diameter	30 mm	12 to 80 mm, steps of 1
`height`	Height	16 mm	8 to 40 mm, steps of 0.5
`grooves`	Number of grooves	30	8 to 72, steps of 1
`grooveDepth`	Groove depth	0.8 mm	0.3 to 2.5 mm, steps of 0.1
`shaftDiameter`	Shaft diameter	6 mm	3 to 12 mm, steps of 0.1
`shaftFlat`	Shaft across the flat	4.5 mm	2 to 12 mm, steps of 0.1
`holeDepth`	Hole depth	12 mm	4 to 38 mm, steps of 0.5
`fit`	Hole clearance	0.15 mm	0 to 0.5 mm, steps of 0.05

Notes

Set the knob diameter and height first, then the knurl: more grooves give a finer grip; the groove depth is limited automatically so each groove stays narrower than the spacing (a 90-degree V is twice as wide as it is deep). The knurl stops below a smooth rim, and the top edge is chamfered.

The D hole defaults to the common 6 mm potentiometer shaft with a 4.5 mm flat (measure across the flat to the round side). Hole clearance is added to both the diameter and the flat: 0.1 to 0.2 mm suits most FDM printers for a snug push fit; use 0 for a hole you will drill or ream. The hole stops 1 mm under the top. For a set screw instead of a press fit, add a radial M3 hole from the side.

Print it upside down (top face on the bed) so the chamfer and rim come out clean and the hole needs no support.