Making a test print
If you are just learning to design without access to a 3D printer, then you can skip this step. However, since this print is so small, it is cheap, even through 3D-printing services. The ability to quickly make things for testing is one of 3D printing's greatest strengths, but it's not strictly necessary to learn how to design for them.
It's always good, especially when matching things to real-life objects, to test whether the fit is right. Some 3D printers print things smaller or larger than the file dictates. So, while the thing is small, and since 3D printers are so good at quickly testing things, test the ring you've made.
Export an STereoLithography (STL) of the ring through the Export STL option under File | Export. Name the exported file Test Ring.stl. Then, print the test ring and try it on:
It might come as a surprise that the ring doesn't fit. If printing in ABS, the plastic may have shrunk when it cooled, as that is one of the properties of ABS. Or there may be...
