# Screw Thread

**URL:** <https://discourse.mcneel.com/t/screw-thread/11959>\
**Category:** Rhino for Windows\
**Created:** [September 26, 2014, 3:13pm UTC](https://discourse.mcneel.com/t/screw-thread/11959 "2014-09-26T15:13:21Z")\
**Posts on this page:** 7\
**Page:** 1

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**Author:** ![ChrisK](https://sea3.discourse-cdn.com/mcneel/user_avatar/discourse.mcneel.com/chrisk/32/43358_2.png) [@ChrisK](https://discourse.mcneel.com/u/ChrisK)\
**Post date:** [September 26, 2014, 3:13pm UTC](https://discourse.mcneel.com/t/screw-thread/11959/1 "2014-09-26T15:13:21Z")

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I’ve done it before: build a helix of proper diameter and pitch, layout a thread xsection, choose one lap of the helix, and sweep1. Today I don’t even get a preview. Ideas?

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**Author:** ![pascal](https://sea3.discourse-cdn.com/mcneel/user_avatar/discourse.mcneel.com/pascal/32/479395_2.png) [@pascal](https://discourse.mcneel.com/u/pascal)\
**Post date:** [September 26, 2014, 3:49pm UTC](https://discourse.mcneel.com/t/screw-thread/11959/3 "2014-09-26T15:49:41Z")

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Hi Chris - can you post the input curves?

thanks,

-Pascal

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<div class="post-metadata">

**Author:** ![ChrisK](https://sea3.discourse-cdn.com/mcneel/user_avatar/discourse.mcneel.com/chrisk/32/43358_2.png) [@ChrisK](https://discourse.mcneel.com/u/ChrisK)\
**Post date:** [September 26, 2014, 3:52pm UTC](https://discourse.mcneel.com/t/screw-thread/11959/4 "2014-09-26T15:52:18Z")

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[ScrewFail.3dm](https://sea3.discourse-cdn.com/mcneel/uploads/default/12385/02b2029192a42512.3dm) (40.6 KB)

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**Author:** ![pascal](https://sea3.discourse-cdn.com/mcneel/user_avatar/discourse.mcneel.com/pascal/32/479395_2.png) [@pascal](https://discourse.mcneel.com/u/pascal)\
**Post date:** [September 26, 2014, 3:58pm UTC](https://discourse.mcneel.com/t/screw-thread/11959/5 "2014-09-26T15:58:35Z")

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Hi Chris- try just sweeping one ‘V’ and not the whole thread- use Roadlike-Top as the sweep ‘Style’. You can also, using your more complex profile curve and a vertical axis line, use RailRevolve to make the full thread. Explode/Join when done to get rid of all the open edges along the ‘seam’.

Update - Lowell found that it (Sweep1) will work the way you have it if you move the helix , like to the bottom of the threads- for some reason it does not like it where it is.

-Pascal

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<div class="post-metadata">

**Author:** ![ChrisK](https://sea3.discourse-cdn.com/mcneel/user_avatar/discourse.mcneel.com/chrisk/32/43358_2.png) [@ChrisK](https://discourse.mcneel.com/u/ChrisK)\
**Post date:** [September 26, 2014, 4:09pm UTC](https://discourse.mcneel.com/t/screw-thread/11959/6 "2014-09-26T16:09:27Z")

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The railrevolve worked just fine. Then joinedge along the seam.

Lowell’s discovery is interesting!! Sweep1 has ALWAYS worked in the past.

Problem solved. Many Thankyous, too…

clk

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**Author:** ![lowell](https://sea3.discourse-cdn.com/mcneel/user_avatar/discourse.mcneel.com/lowell/32/270099_2.png) [@lowell](https://discourse.mcneel.com/u/lowell)\
**Post date:** [September 26, 2014, 4:23pm UTC](https://discourse.mcneel.com/t/screw-thread/11959/7 "2014-09-26T16:23:03Z")

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It should work as you tried first.  
The endpoints of the helix are very close to the polyline kinks - about 10^-12 apart.  
Its a strange case.  
I’ll see if there’s something obvious I can adjust.

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**Author:** ![Brenda](https://sea3.discourse-cdn.com/mcneel/user_avatar/discourse.mcneel.com/brenda/32/770181_2.png) [@Brenda](https://discourse.mcneel.com/u/Brenda)\
**Post date:** [September 26, 2014, 8:02pm UTC](https://discourse.mcneel.com/t/screw-thread/11959/8 "2014-09-26T20:02:00Z")

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You can also chamfer the end of the shaft to be threaded, depending on whether you want to do rolled or cut threads.

I also wake my subtraction tools larger than they need, so there is no near-co-planer surfaces so they subtract easily.

I once made National Pipe Threads, which are tapered and time consuming thing to make.

BTW, you know about [Boltgen](http://www.food4rhino.com/project/boltgen), right?