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Saturday, January 17, 2009
Modeling screw threads (2 of 2)
Learn how to model screw threads using helical curves and booleans in Rhino. The threads shown are the type you would see on the end of a light bulb. Changes to the cross section profile and path will provide you with ways of making alternate styles of threads as well.
Video: 2 of 2
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10 comments:
The tip on orienting the thread form to the helix was great, but why didn't you model an industry standard vee thread? The only place I've seen round threads like that is on lightbulbs. It would be nice to cover modelling an actual thread form (root and crest are particularly important) with proper clearances for a particular thread fit tolerance.
But the principles and demonstration were excellent, and I thank you.
Hi Nick,
The idea for this video tutorial did come out of a light bulb model I made recently. So you are exactly right... they are definitely that type of thread. I think I could re-post this with a introductory explanation that might set the proper expectations. Thanks for the feedback!
I thought it looked lightbulb-ey. Don't let my comments detract from the excellence of the video, it helped me tremendously.
Excellent, as a new user I was excited to see this tutorial as I had been wondering how to model screw threads for a project I am working on. Some times all we ned is the concept. After making several light bulb threads I started experimenting with other tread profiles and was pleased to see how easy it was to make threads of various types.
Thank you very much for this one. One thing I have not figured out is how to do this on a tapered thread such as an NPT fitting would be. Hope you can expand on this subject as I'm sure others would also like to do this.
Hi Tom,
You can use the same techniques to make the NPT threads as well. These two wiki pages are very useful if you don't have a machinery handbook. http://en.wikipedia.org/wiki/Screw_thread and http://en.wikipedia.org/wiki/National_pipe_thread
The key difference is to use an equilateral triangle as the cross section and then sweep it along the helix from the mid point of it's base. Also make sure to use the correct number of turns per inch in your helical curve for a given thread size. Hope this helps and thanks for the comments.
Hi Brian,
I probable did a poor job of explaining my problem with the NPT threads. How do I get the Helix coil to follow the contour of lets say a Truncated Cone. Were the the bottom of the cone is a smaller diameter than the top of the cone. Thanks for the web sites they are very useful. Cheers.
Tom,
Try the "Pull" command to pull the helical curve to the surface of your truncated cone. Does this do what you'd like?
Tom, I just had another thought... you could also use the "Spiral" command which would maintain the desired pitch better then a projected helix.
Hi Brian,
Your second thought is a keeper, brilliant.
All the lights are on, thanks so much. Cheers.
This is a great instructional video for a very common application. I only wish I had this knowledge about a month ago.
Thank you.
Jason
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