Screw Thread

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?

Hi Chris - can you post the input curves?



ScrewFail.3dm (40.6 KB)

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.


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…


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.

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, right?