Issue
Threads modeled in Fusion 360 for 3D-printing don't actually work. The 3D-printed parts fit together, but just barely, and I can just barely start threading them together before they are too tight to move. This occurs even though they were designed to match up with the same thread settings.
Cause
Fusion 360 doesn't account for tolerances for extruded plastic through 3D printers. Even though the threads are designed to match up in the program, when printed the plastic simply adds volume and the parts are just too tight to work. This will be different depending on your printer, print settings, material, and calibration.
Resolution
Use scaling to give your 3D-printed parts a bit of wiggle room.
While there isn't a way in Fusion 360 (that I've found) in the threading settings to give them a bit of space so that the printed part can turn, you can definitely scale parts up or down.
In my case, I was trying to make a canister holder with a screw-on cap. I even used the "Remember settings" checkbox on my threading settings, but of course when printing everything was wayyy too tight to work.
To fix this, I simply scaled up the "cap", or the female-threaded piece, up to 1.02.
