# 3D Design / 3D Scanning / 3D Modeling > 3D Modeling, Design, Scanners >  Accurate thread generator?

## Galane

Bolt and nut threads are not simply a 60 degree angle wound around in a helix. They have flat crests and flat or rounded roots. The idea behind that is both to increase strength at the thread root and to make the crests more resistant to damage as well as make the threads easier to screw together.

The Nutjob customizer at Thingiverse makes metric threads with sharp crests and roots. I found a chart with standard UNC, UNF and UNEF thread pitches and major diameters listed in milimeters and was able to get an almost fitting 3/8-16 thread model from Nutjob. With the sharp crests I was able to force it about 3/4 through a metal nut before it bound up too tight and broke. I didn't print the bolt 100% solid, just testing and not wanting to waste too much filament.

I need *solid models*. File formats that are a collection of faces glued together won't do for what I need. I have found some accurate CAD models to download, but they're either in Solidworks format or some format that's not solid. I did find that I can upload Solidworks to the Workbench at grabcad then download converted to STL - but the one example of a ready made 3/8-16 bolt I found on the grabcad site, converted to STL with their workbench, the 3D program* I use flat out refuses to allow it to be used for boolean subtracting or subtract chunks from it.

What would be very nice is an online or standalone program that can crank out accurate STL files for all metric, standard, BSF, BA, Whitworth, buttress, ACME, square, knuckle (used in lightbulbs and sockets) and any other kind of thread, with selectable fit class.

*Caligari trueSpace 6.6. I've used trueSpace since version 2.1. As long as I use the right settings for the scene and model measurements, it outputs perfectly functional STL that works with Cura.

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## Mjolinor

http://dkprojects.net/openscad-threads/

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## iDig3Dprinting

We have managed to create threads in freecad, but I am not too sure that we would be able to say that you could "crank out" different sized threads. The Openscad module is a great thing though, so thanks for that link @Mjolinor

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## Mjolinor

I am sure I had a plugin for Freecad that does threads but after years of using it I stopped a while ago when I moved over to openscad.

Yup, the Freecad one is called Screwmaker.

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## iDig3Dprinting

> I am sure I had a plugin for Freecad that does threads but after years of using it I stopped a while ago when I moved over to openscad.
> 
> Yup, the Freecad one is called Screwmaker.


Thanks I will look for this.

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## curious aardvark

cheers mate - haven't yet found a thread generator on thingiverse that makes sense. 

havge to give this one a go :-)

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## CarterTG

Since the OP mentioned being on the GrabCad site, I'm surprised he didn't stumble across BoltGen. It's a free plug-in for Rhino. 

The plug-in author's resource page is additionally listing a standalone GUI, but it's unclear whether it feeds the resulting bolt model back to Rhino or just leaves a bolt model file -- presumably in Rhino's 3DM nurbs format: http://mcvanaero.com/resources

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## Galane

> Since the OP mentioned being on the GrabCad site, I'm surprised he didn't stumble across BoltGen. It's a free plug-in for Rhino.


I saw it. I don't have Rhino, or Solidworks or other software that costs a ton. :P *looks up Rhino prices* Heyyyy! Why is it half the price for Macintosh!

Looks like it's OpenSCAD for me.

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## Galane

> cheers mate - haven't yet found a thread generator on thingiverse that makes sense. 
> 
> havge to give this one a go :-)


Nutjob on Thingiverse could be much better, if its author could implement roots and crests, and also SAE/UN sizes.

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## Galane

Screwmaker, last updated in 2015 http://forum.freecadweb.org/viewtopi...=6558&start=30 Also found there is the Fasteners Workbench, last updated in 2015. Do they work with the latest FreeCAD???

Addons for FreeCAD, https://github.com/FreeCAD/FreeCAD-addons among them is a bolts library, which includes ANSI and ASME standard Imperial nuts, but for external threaded Imperial fasteners only set screws. ??? Plenty of different metric parts of course.

Downloading the latest FreeCAD, which I last used last year but since the gear functions only did Metric and I needed a plot of a 14 pitch, 14.5 degree pressure angle gear, it did me no good. I had to resort to using HeeksCAD/CAM which allows arbitrary number input into its gear wizard. Combined with a site I found that had precision metric numbers for diametral pitch gears I was able to get a plot to create the gcode to mill the gear.

Gotta love it when an entire industry points its collective finger at something and says "We declare it obsolete! Never to be used or manufactured ever again!". But since 14 pitch worked just fine for many things, the machine tool industry came up with 2.75 Module which is >thisclose< to 14 pitch - only to pitch 2.75 Mod into the bin sometime in the 1980's. Ask anyone who owns a Takang manual metal lathe about 2.75 Mod gears... Then there's 3 horsepower variable speed drives with a 35mm shaft with a single key on the split sheave. Not made any more, the VS drive industry switched to splined shafts for 3HP sometime in the late 90's and parts for the older versions are NOT available. If *Bridgeport* had ever sold a 3HP VS with a keyed shaft, parts would be available. I had to turn my own plastic bushings for my 1990 Acra mill. :P Hrmmm, with nylon filament I could probably 3D print them, but I'm not pulling the drive apart again unless it breaks again.

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## curious aardvark

> I saw it. I don't have Rhino, or Solidworks or other software that costs a ton. :P *looks up Rhino prices* Heyyyy! Why is it half the price for Macintosh!
> 
> Looks like it's OpenSCAD for me.


Because they're taking pity on you for owning  a mac in the first place.  :-)
You've already paid way way way over the odds for a mid range pc with a ridiculously expensive operating system that's not exactly overly functional. Why sting you again for software that most likely won't work correctly anyway :-)

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## Mjolinor

When was Freecad last updated? Last time I checked is was way back, 2014 or something.

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## curious aardvark

you know, I had never considered how many different threads there were or how many words you could use in describing something as apparently simple as a thread - now my brain hurtz !

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## Galane

> When was Freecad last updated? Last time I checked is was way back, 2014 or something.


Sometime in 2016, up to version 0.16.something

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