Sometimes we paint, and we need a place to put paintbrushes. Sometimes we just want a happy stand of paintbrushes because they're harder to kill than plants.
We (somewhat) duplicated a commercial model (affiliate and direct links below) but with one less ring, because (a) too many brushes spoil the pot, and (b) we wanted to use a chunk of 1/2" ID copper tubing we had sitting next to the desk.
The tubing is a very snug fit using our (shiny new) Method printer. If you don't have pretty good dimensional accuracy you might need to sand either the plastic, the pipe, or both, but probably not too much.
This won't hold giant brushes, but the outer ring will hold two 1/4" diameter chip brushes, and will handle the bulk of our model brushes. For the curious, the outer ring slots are about 9/16" on the outside and 13/32" on the inside, while the inner ring slots are about 7/16" on the outside, 3/16" on the inside.
There are 14 slots on the outer ring, 10 slots on the inner. That's 24. We checked.
You can even put a paintbrush or two into the copper tubing, but we filled one of ours with sand and threw some silicon on top to keep it in so it has a little more weight. That said--it's stable enough. The only thing we'd like to add is a roller bearing/lazy susan bottom but we're out of big-enough bearings at the moment, so that'll wait.
You'll need to rotate the top and bottom to match; there are two "matching" slot dividers 180° opposed--those should match top and bottom, otherwise one on't cross beams gone owt askew on treadle.
There's a mad-dash look at how we designed it on Youtube: https://www.youtube.com/watch?v=2ZZwBOdsANU
A short (likely not relevant if you found it here first) blog post: https://blog.makersend.com/print-simple-paintbrush-holder/
Our second version will use two supports and thicker walls (these are 1.5mm; print accordingly) and probably be more oval- or bean-shaped (we're leaning bean, but it's more annoying, and takes up an oddly-shaped chunk of desk).
Commercial model we emulated (in spirit):
We used the default raft, infill, etc. settings on our Method. It likely doesn't make a huge difference, but note that the rims and slots are ~1.5mm, so it's a little dicey if you're not using a strong material.