Perfect Threads

ZooHead

Well-known member
Modeling threads in Cheetah 3D is not hard, but there are so many different ways to proceed.
Every time I've done it, I've tried various methods to deal with
the triangle or triangles left over at the end of the spiral.

What if you could send that edge back down the spiral or redirect,
recycle and re-purpose it as well as keeping all quad construction.

When you see it, it's so obvious and simple. How did I not figure this out before?
Here's how it looks:

Perfect Thread.jpg



Adding a ring cut to control the edge at the base of the thread.

Perfect Thread 02.jpg



With a Sub Division Modifier Level 3.

Perfect Thread 03.jpg


I'll post the steps soon...
 

MonkeyT

Active member
Here I go getting needlessly obsessive again, but the only question I have left is plumber's threads. The threads used on most plumbing fixtures are actually designed to tighten as you affix them - this allows merely screwing on a connection to tighten it to the point that water shouldn't leak instead of letting the nut ride up the entire length of the cut threads. It's practically invisible without a microscope, so it's really not very important, I was just wondering if the build techniques you laid out could accommodate threads that swell in thickness as they travel?
 

ZooHead

Well-known member
NPT National Pipe Thread also stands for National Pipe Taper.
I'll have to think about that, I've never tried before.

There are a few oddball standards like buttressed threads, like the ones on my Nalgene bottle.
Some are straight inside and tapered outside for special applications.

NPT_Dimensions.jpg
 

ZooHead

Well-known member
You can use a Taper Modifier on the tube before you push out the threads.
And don't use Normal Move when you do, use the Transform Tool
and scale out radially with the shift key.

First try is pretty close although the valleys should be narrower.

Tapered Thread.jpg
 

ZooHead

Well-known member
After some testing it seems plausible to create a "Thread Panel" library by threads per cheetah unit for every thread.
You could have separate panels for the ends and the body. Since the diameter can be infinitely adjusted and larger
diameter threads should have more sections, separate panels can be made for small and large diameter forms.
 

ZooHead

Well-known member
If anyone is interested in this method here's a jas file showing a 20 tpi thread panel being
used to make a 2 inch long section of 1/4" 20 threads plus the ends pieces.

The real star tool hear isn't the Wrap Modifier, it's the Ring Modifier.
I used it to double the length of the thread panel as well
as placing the end pieces with it's offset parameter.

2 inch quarter 20 with ends.jpg
 

Attachments

  • 2 inch quarter 20 with ends.zip
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MonkeyT

Active member
It's nice to see a project that starts as "a solution in search of a problem" evolve into a beautifully comprehensive cure for a well defined issue! I have definitely bookmarked this one.
 

ZooHead

Well-known member
@MonkeyT Thanks, I guess I'm good for one more for the wood/sheet metal screws.
Adding the spline/extrusion step suggested by @EllenM.

Notes:
• Wood screw - This type of screw ends in a sharp point, so there's little hope of an all quad object.
• Wrap Modifier - Leaves a visible seam, until made editable and optimized to weld polygons together.
• Threads per cheetah unit - Who the hell knows. Coarse and fine. Pending further measurement.
 
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