Modeling screw threads (2 of 2)

[@sashajelic9626]

I just finished modelling this in rhino 7. Can this work irl as a screw when 3d printed??

[@oyuki9892]

Thank you for your Tutorials!

[@PaulHirsh]

Thats going to be a pretty tight fit, impossible to screw in some materials. Would you use offsetsrf to make it easier to use?

[@RhinoGuide]

An offset could be needed yes. OffsetSrf could work on the solid but now I would use Rhino 8 and Shrinkwrap followed by OffsetMesh if 3D printing the results.

[@PaulHirsh]

@@RhinoGuide aha. Sounds like something I would need more money for.

[@adamjovicic9006]

how would you make the pitch distance?

[@marloeskroonen4952]

Doesn't the screw need to be a slight bit smaller in order to make it run smoothly? (when 3D printed that is)

[@RhinoGuide]

Possibly yes, but I've heard from users saying it worked without scaling one part slightly so it might have to do with the printer tolerances too.

[@sahrchitect]

Absolutely this. I've had countless students bring me parts to print with zero tolerance. Offset the whole surface by 0.15mm for one of the parts to account for this.

[@jmccann96]

so you don't need to increase the scale of the positive slightly before the Boolean difference?

[@olli77hajnal]

Is it working as a 3d-printed prototype by making it this way?

[@charlesrunyon796]

Very nice. I will learn this one.

[@LeonardoAguiar3D]

This won't be functional. Dimensionally, a threaded hole has a larger cutting diameter than the screw’s outer diameter, and the hole boring diameter is usually bigger than the screw’s inner diameter. The actual contact surfaces can't be the same. There must be an offset between them.

[@peterlaverty9397]

How do you solve that?

[@LeonardoAguiar3D]

There’s different ways to solve this with different sequences of modeling tools and steps, but basically you just need to have the surfaces of the screws threads offset by a small distance relative to the surfaces of the threaded hole.

[@marcusmarcusk830]

@@peterlaverty9397 By drawing two sets of threadprofiles in the first step. Then also scaling the inner screw cylinder down.

[@sahrchitect]

@@peterlaverty9397 scaling does not work for obvious reasons. The pitch of the thread will be different if you scale. You need to offset.

[@sashajelic9626]

@@sahrchitecthow do you offset the threads?

[@jacobboatman]

my booleandifference keeps failing. I think it's because the original screw polysurface is not closed where the filletedge meets the original cylinder. Do you have any tips on how to close it?

[@jacobboatman]

nvm, I was working at such a small scale, I just needed to change my absolute tolerance. Thanks for the great tutorial!

[@Maskltl]

@@jacobboatman , Hi I am having the same problem. I am a novice at this. Can you tell me where the absolute tolerance is set? Thank you

[@val5214]

in my model i had to put threads on a cylinder - after creating them, i realize now that two surfaces have to overlap, not just be touching , in order to do a boolean union. an earlier tutorial said to explode the threads and use "intersection" (under 'curves from objects'). But that seems tedious. Can you get away with just using "join"??? would i need to do anything after that?

[@PaulHirsh]

Sometimes Boolean works even without the overlap. And don't forget you can export to .stl separate solids as one and still get a print.

[@val5214]

​@PaulHirsh ha ha thank you, it's been forever since I got into rhino and sketch up. I was into 3d printing for a while then lost interest. I remember the problem with the threads but don't remember what I wound up doing. Great software had fun learning it

[@joikramotizz]

Amigo me puedes ayudar a hacer un vertedero? No se hacerlo

[@shaddonai2636]

Like si comiste polenta

[@OrucGaziKutluer]

This is not a screw.. Just on monitor :))) Will not work anyway