Printing an object with threads is nothing new. If you know the specifications on the other thread or you are in control of it, no problem. But [Shop Therapy] wanted to print parts that mate with an existing unknown thread. Out come the calipers.
The first measurement is the height. He rounded that up in the video but mentioned in the comments that it should really be a little smaller so that it seats properly.
After that, he measures the pitch and the major diameter. Next, of course, is the minor diameter. The pitch is related to the spacing of the threads, the major diameter is the diameter of the outside part of the threads, and the minor diameter is the neck without threads.
Next, he’s off to Fusion 360 to design the matching cap. Of course, you could use whatever 3D CAD software you like. Fusion does have some nice thread-related operations, and while it isn’t exactly free, you can get licenses for personal use with no difficulty.
Printing threads has its ups and downs. We prefer embedding metal threads into our prints.
I’m surprised the “related” article at the bottom wasn’t https://hackaday.com/2020/07/12/learn-the-secrets-of-matching-bottle-cap-threads-to-one-another/
But maybe that was too close to the current article?
Wish it showed a test with liquid in the bottle. Without the gasket it would probably leak, but who knows
Fusion is good at standard threads but if you need something custom it’s a pain in the butt. It’s so bad that I can only assume that there’s some patent keeping them from letting you do helical revolves and making helical paths ( you can hack your way into but it takes several steps and requires you make a new helical body just for the path)
The coil generator works pretty well for me to make arbitrary threads.
This has been my biggest problem with fusion 360. It’s only become a bigger issue over the years due to more people having access to 3D printers. I end up just copying threads from mcmaster parts.
With Autocad (not fusion)… the function name is sweep. You can make helix or one with a taper, you can copy and rotate it, and can make what ever tooth shape you want (I like 3d printing 45 degree buttress threads, and have done single, double, and triple threads on some kid toys).
I also normal make the negative and subtract it from a cylinder with a chamferred tip…and make the respective bolt threads major diameter 3-5% bigger than the bolt threads.
There’s a plug-in for custom threads.
The other way is Fusion 360 stores threads as XML files, so you copy a standard thread and modify it.
Fusion is indeed not exactly free.
Bosl2 for OpenSCAD https://github.com/BelfrySCAD/BOSL2 has a great threading library and even better documentation. (better than OpenSCAD?) Plus it’s free, even for commercial use.
BOSL (and now BOSL2) did wonders for my OpenSCAD projects. I’ve used the various screw/bolt oriented features, but I hadn’t realized it also includes capabilities for bottles and threads in general.
Now if I can just remember what I wanted to attach to a bottle, and why…
FreeCAD has a great threads workspace. (Which might be newish? Was new to me.)
I made a spool-like thing in two parts where the two halves screw together with a chonky M10 size screw/bolt combo. You tell it the tolerance you want (0.2 mm) and it gives you a screw. You can then just put a hole in the other part, tell it you want a threaded hole, and you’re done.
My first time using the library, but it was so awesome, I think I’m going to add screw/threads to everything I print now. It took like 5 seconds to add the features to the model.