I needed some knobs for rotary encoders and rotary switches for a project I am working on ( fsx flight panels ).
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They were printed at 100 micron setting on my Replicator 2, there is a channel a nut can be slid into, and then the screw clamps against the switch shaft.
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The small rotary selector switch needs an M2.5 nut and bolt, and I had to hacksaw the bolt to shorten it.
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The larger encoder knob needs am M3 x 12 mm bolt, and will fit without modification.
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I have included the Fusion360 files.