Golf Ball User Interface Knob

While I don't play golf myself, the balls used for the sport are quite beautiful in their own right. At 1.68" in diameter, and with a smooth semi-rubberized coating, they could make an excellent interface knob. Or that's what I thought when looking at one next to my ATmega32U4-based JC Pro Macro 2 pad with its comparatively puny 1" diameter aluminum encoder knob.

As seen in the video below, to transform a golf ball into an interface knob, I designed and 3D-printed a jig to hold the ball securely in a vise without damage to the surface. The ball was drilled with a 5/8" paddle bit and milled not-quite-in-half, before turning 90º in to drill a clearance hole. A 3D-printed plug adapter was then inserted into the ball and secured with a set screw, providing a functional but rather rough first iteration of this interface.

The interface ball was then refined, including a spring-loaded jig, adapter iterations, and a less worn golf ball. The final result is something that looks quite good, and fits securely on a common 6mm shaft EC11 encoder.

While a golf ball is visually interesting, at the end of the day I found it hard to use in my current setup. Perhaps it should be no surprise that a macro pad designed around a 1" encoder knob would perform poorly with something so oversized. At the same time, the jig and/or plug used here should be applicable to other projects. STL files are up on Printables if you’d like to modify a golf ball to fit an encoder, or for other uses.