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internal thread (by Alex B)
Folks,

Helix extrusions continue to be puzzling. Has anyone had much success using them in threading applications ? I'm attaching a simple sketch - cube with a threaded hole going through it. Can't get it to work at all.
Fri Jun 5 2020, 15:20:50, download attachment internal_thread.slvs
(no subject) (by Paul)
This seems to be a boolean difference problem. That happens a lot more with helix extrusions. When making threads I recommend using the other cross section of the bolt and doing the helix perpendicular to the sketch plane. The challenge then is getting the right shape. It still doesnt work as difference well, but the helix itself is not self intersecting so screws tend to work better.
Sun Jun 7 2020, 21:46:14
(no subject) (by Alex B)
Paul,

Thanks for the reply, I can't quite understand what you're saying though. Any chance you could do a very simple sketch to demonstrate the principle ? Thanks!
Mon Jun 8 2020, 00:56:19
(no subject) (by Andrew)
If screws work better than nuts, you could always create the screw in a separate file, and use link/assemble and select difference to make the nut.
Mon Jun 8 2020, 05:54:20
(no subject) (by Alex B)
I did actually try to assemble before using external threaded part, and behaved even worse. So it's equally problematic.
Mon Jun 8 2020, 12:40:39
(no subject) (by Andrew)
I managed to improve your model by removing the center of the threaded are by using a cylinder.to in effect remove the bolt core, either before or after creating the thread.
Mon Jun 8 2020, 16:55:31
(no subject) (by Paul)
Andrew is right, Helix tends to be worst when the sketch includes the rotation axis. The steep slope and twist causes problems in addition to the others. I've attached a simple bolt sketch to show the different way of doing the helix extrusion. This works a lot better and does not include the rotation axis as a sketch line. I selected the origin and one of the little vectors as the helix axis. Even doing it this way, Analyze still finds some naked edges unless you force to triangle mesh. Your luck may vary and sometimes it works great.

If you want to make it a pointed screw I would recommend making a sketch plane using the center axis of the blot. Then draw a sort of triangle that includes the bolt head. Then use Lathe and select "intersection" for the boolean to keep everything but the part of the bolt you need to shave off for a pointed tip. Again, this is less likely to work unless you use triangle mesh.

I never tried to make a nut until this post and I have not been able to make it work.
Mon Jun 8 2020, 17:46:15, download attachment bolt.slvs
(no subject) (by Alex B)
Awesome, thanks guys. I will play with this alternative approach.
Mon Jun 8 2020, 19:58:02
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