I've bought a ton of 10mm button caps in black sandblasted aluminium. They match my larger potentiometer caps perfectly and I want to use them as potentiometer caps. Only problem is, they are meant for 3.3mm square shafts, not D-shafts, so I had to find a way of replacing the insert inside.
I've experimented with various sizes of 3D-printed inserts and this is my best result:
The inner diameter is 6.2mm, the outer is 7.9-7.95.
7.95 works with press fit, but 6.2 inner and 7.95 outer made the part stick too hard to the shaft.
6.3 was too loose for the plastic shaft but may work on the metal one - however, there we need a section without D as the D-part is much shorter.
I didn't have time to try 6.25.
The insert height is 9.5mm. The inner height of the cap after removing the existing plastic is barely more than this. However, this seems like the perfect height - it leaves a 2mm gap on the prototype, but that prototype is 2mm lower than the button prototype, meaning that it will be a perfect match if the panel is similar to the button prototype.
The turning force necessary for the metal pot with this 10mm cap is actually ok. Quite heavy but a certain quality feel. The plastic shaft on the other hand feels a bit too light, especially when compared to the bigger caps on the metal pot. However, it is comparable to the force necessary on my other gear (Prophet 5, Little phatty) so I need to make a full mockup to try it properly.
I removed theexisting insert by
- Drilling a 10mm hole in a wood block, then cutting it in half to make a clamp.
- I then put the clamp around a cap and inserted it into a vice to prevent the cap from rotating during drilling
- Then I drilled a progressively larger hole - 5mm, 6.5mm and finally 8mm.
Putting time in these thing hurts but is rewarding in the end!
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