Summary

Created this from the 28mm PCO 1881 standard as I'm creating various bird and insect watering stations that will use a standard 1L pop bottle and I found it easier to use this and subtract it from the 3D solid of the station. I also use it test other designs that are on the web. It's very close to the standard with a few simplifications that don't affect it screwing onto a station. I've printed a couple and they do work and they also highlight where instead of the correct thread pattern simplified threads have been used by others and there's some binding. So a good test for your designs. I've included the Alibre file so you can edit it it if you wish

For some reason the stl file is very large at approx 91Mb but the step is small at 350Kb so I recommend using that if possible

EDIT: I have added a threaded ring AKA a bottle cap, although it lacks the top :-) as I use these in some of my water station bee designs so I've added them here so others can save the trouble of modeling the threaded portion and just merge them into their own design- There is a 'lead-in' modeled into the thread as per the std so effectively there is a top and bottom to the ring , although both ways it threads on nicely anyway