Hi Guys, so I've taken to freeCad as I'm getting the hang of it, and wanted to make a bolt and nut (this one is round... it's just a test) while I wait for my reprap parts to arrive. Attached is a picture - I used parametric helix objects, offset them, and then used "Create a ruled surface between two curves" to flesh out the threads. I think it works pretty well as a technique, and I can then use cubes and stuff (with some effort) to then cut the threads to length. The bolt works pretty well, and with some repairing (this technique does seem to create holes and stuff... weird) using netfabb it seems fine. I checked the layers with pronterface, and it all seems good (neat to see the threads being printed. It's just a spinning oval.) However, when I try and slice up the nut, I have some real problems I guess due to the "hole"-ness of the helix curves. Basically to make the nut I do the same thing as the threads, but I increase the radius of the threads by some small amount to make sure that the bolt will slide in. I then took a cylinder, created a second one the same size as the outer helix of the threads, and then cut the larger one with the smaller one so that the helix threads fit perfectly in the big cylinder (and there's a hole for them in there). If I then use netfabb to repair the model (it needs it, apparently), it treats the threads on the inside of the nut like the threads of the bolt, and fills them inwards instead of joining them with the outer shell - thereby filling the nut's ends. I can't seem to figure out a better way to make threads with freeCAD or fix this. Anyone have any ideas? Attached is the freecad file for you to play with also https://reprap.org/forum/read.php?166,128925,128925#msg-128925 Sat, 08 Aug 2026 20:39:32 -0400 Phorum 5.2.23 https://reprap.org/forum/read.php?166,128925,380156#msg-380156 https://reprap.org/forum/read.php?166,128925,380156#msg-380156 Feign Look what I made! Tue, 08 Jul 2014 16:46:28 -0400 https://reprap.org/forum/read.php?166,128925,379645#msg-379645 https://reprap.org/forum/read.php?166,128925,379645#msg-379645 semitonesonata Look what I made! Mon, 07 Jul 2014 18:07:47 -0400 https://reprap.org/forum/read.php?166,128925,162035#msg-162035 https://reprap.org/forum/read.php?166,128925,162035#msg-162035 ben11c Look what I made! Mon, 22 Oct 2012 04:13:55 -0400 https://reprap.org/forum/read.php?166,128925,161971#msg-161971 https://reprap.org/forum/read.php?166,128925,161971#msg-161971 a boolean subtract operation to get internal threads - might have to scale the model diameter to make it look like the clearance distance
has been added.

Again, this would be only for visual appeal, I assume you would be just specifying the threading.

I just started playing with all this type of thing 2 days ago so here goes a real newbie question - can you change the color of the crosshair in freeCAD, the default white is driving me crazy.]]> Newbie15 Look what I made! Sun, 21 Oct 2012 15:05:37 -0400 https://reprap.org/forum/read.php?166,128925,132636#msg-132636 https://reprap.org/forum/read.php?166,128925,132636#msg-132636 -------------------------------------------------------
> Modeling bolts and nuts with a thread is nice for
> learning the application, in the "real" world,
> however, you wouldn't do that.

You would if you were going to make them by an additive process, rather than machine them.
I agree that normally there would be a thread spec callout on the drawing, but that's no good for a RepRap or similar.]]> andypugh Look what I made! Sun, 13 May 2012 14:19:44 -0400 https://reprap.org/forum/read.php?166,128925,129510#msg-129510 https://reprap.org/forum/read.php?166,128925,129510#msg-129510 Traumflug Look what I made! Fri, 20 Apr 2012 07:08:29 -0400 https://reprap.org/forum/read.php?166,128925,129474#msg-129474 https://reprap.org/forum/read.php?166,128925,129474#msg-129474 pwn4 Look what I made! Fri, 20 Apr 2012 00:46:17 -0400 https://reprap.org/forum/read.php?166,128925,128966#msg-128966 https://reprap.org/forum/read.php?166,128925,128966#msg-128966
Most mechanical CAD applications have a special function for "this cylinder is a thread", FreeCAD might be too young for that.]]> Traumflug Look what I made! Mon, 16 Apr 2012 08:35:01 -0400 https://reprap.org/forum/read.php?166,128925,128925#msg-128925 https://reprap.org/forum/read.php?166,128925,128925#msg-128925
The bolt works pretty well, and with some repairing (this technique does seem to create holes and stuff... weird) using netfabb it seems fine. I checked the layers with pronterface, and it all seems good (neat to see the threads being printed. It's just a spinning oval.)

However, when I try and slice up the nut, I have some real problems I guess due to the "hole"-ness of the helix curves. Basically to make the nut I do the same thing as the threads, but I increase the radius of the threads by some small amount to make sure that the bolt will slide in. I then took a cylinder, created a second one the same size as the outer helix of the threads, and then cut the larger one with the smaller one so that the helix threads fit perfectly in the big cylinder (and there's a hole for them in there).

If I then use netfabb to repair the model (it needs it, apparently), it treats the threads on the inside of the nut like the threads of the bolt, and fills them inwards instead of joining them with the outer shell - thereby filling the nut's ends. I can't seem to figure out a better way to make threads with freeCAD or fix this. Anyone have any ideas? Attached is the freecad file for you to play with also]]> pwn4 Look what I made! Mon, 16 Apr 2012 03:48:59 -0400