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.
It has similar names in most CAD and CG packages, that only difference are how much control over the end project you have and whether it’s parametrically created and maintained or a “manual” operation. It’s funny how once there’s a common product that’s popular everyone forgets this is a common task long predating that product. And it’s probably not that hard to do.
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.
You can also create a helix and tooth profile and then extrude a profile along the helix (additive or subtractive for the male and female threads). The hardest part is finding the darn helix tool in the parts workbench. The second hardest part was everything else.
Here is a tutorial by MangoJelly Solutions where he makes a custom-threaded jar with a screw-top lid.
https://www.youtube.com/watch?v=_GFoU0SIVG4
He even modifies the ends of the helix so the threads have a lead-in to make it easier for them to start.
I used the technique to create an odd-sized thread I needed for a printer enclosure vent. It took a while to get it right, but I finally got a good mating thread. It was pretty early in my FreeCAD learning, I wonder if I could do a better job now. I started out trying to create a metric pitch and profile but I could not print it right. Ended up using a simple 60 degree wedge, which printed much better.
I need a gas cap for a John Deere 2-stroke engine.
The replacement anywhere on the web is over $30.
I would like to print a cap that will fit.
Yes, I am aware that it may need a vent and gasket added.
So, this may be the route I need to take.
Yes, I will be careful using it, but most 2-stroke engines leak fuel, if not from the cap, then from the fuel lines…
Mind what plastics you use for exposure to oil, fuel and other solvents. These days those caps are rarely vented and are just a chunk of injection molded plastic with a gasket you can probably find at an auto store jammed in. It might be fiberglass reinforced to justify that cost too
I did exactly this when I wanted to design an attachable funnel and pour spout that would fit empty isopropyl bottles I have that I wanted to reuse to hold used/fresh desiccant beads separately. Works a treat and means no more spilling a bunch of beads everywhere.
I’ve seen mechanics use a thread gauge to identify what type a thread is, example here: https://www.amazon.ca/ChgImposs-Imperial-Whitworth-Industrial-Measurement/dp/B07J9V9JTK?th=1
i keep expecting i’ll eventually match some threads on something like this, but what gives me pause is the thought of what PLA would do under a constant tension. like if you left something snugged to tightness over a long period, i just imagine it would self-loosen after some months (from deformation) and then after re-tightening it would turn to splinters after a couple years. i’ll still give it a try when i have the need though :)
I need a replacement cap for my Oxebar barrels (which is a PCO38 thread), and I couldn’t find a 3D model, so I’m going to try to design one with FreeCAD. I found a nice website with many thread specs:
https://www.isbt.com/resources/isbt-threadspecs
I hope this will save me some time from taking all the measurements…
Did you try parameterising all (or more of) the measurements in Fusion so you wouldn’t be starting from scratch every time?