Best way to model machine threads?
 

I'm making a light bulb, and I need to model the "threads" on the metal part of the bulb that let you screw it in to something. I model everything in polygons, but I have no idea how to model a screw shape, rather than just parallel rings on a cylinder.

So I made a bucket shape in NURBS, but I'm totally lost when it comes to trying to get the threads onto it. Can you draw curves onto a 3D surface? Help!

Hi Ayelar

If you go to the Alias community - search for the Spiral tutorial - this is possibly the easiest way to make threads.....

good luck

Keith

Thanks for the quick reply, Keith! I found the Alias sprial tutorial, and yeah, it rocks. I knew there had to be an easy way to create a spiral like that.

Unfortunately, if I'm reading it right, I would end up with a second object for the threads, not a single threaded metal cap for the bulb. I'm not sure how I would combine them without an obvious seam.

This is the lightbulb I'm trying to recreate, see how the threads are totally seamless?

seamless bulb
 

Well, the way I figured to do it is to place your threads right over the buld, then go Edit NURBS>>Surface Fillet>>Circular fillet

be wary that this is a tricky tool to use, and depends heavily on the history of the objects you're filleting, some advice :
*Make sure to turn on "Create curve on surface" so that you can trim it later
*reverse primary surface normal and reverse secondary surface normal determine which of the four possible corners will be filleted
*Its good to make it huge and then shrink it when your done b/c the tool generally gets wierd on small surfaces

Once you have the suface filleted the way you want, use the trim tool to cut off extra bits, and set your NURBS tesselation pretty high to avoid holes, and turn you render up to production quality, because the antialiasing will help this too

This will create a smooth transition between your spiral and your bucket

Hmm, okay, I'll give it a shot.

This is what I have so far, btw:

Well, okay, I ran out of time and decided to cheat. This is with polygons. What do you think?