Screw Thread Exact Profile


I’ve been following that great tutorial about making screw thread and I was able to make screws:

I need now to build a screw that has the profile reference of UNC 6-32 but I am not succeeding…

I found the BoltGen plugin which makes screws for you and it sounds like a dream:

Followed the steps to install the plugin on mac and even tried to put the file manually. But Rhino tells me the file isn’t compatible.

If I am correct, does it mean that a .rhp file isn’t a cross platform file like I thought but some could be only read from Windows and not Mac?

If this is the case. I would very much appreciate help to how to make a precise profile of screw and/or is there a screw generator that works for Rhino Mac?

Thanks a lot.

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You’ll probably have to pull out your copy of the Machinist’s Handbook (or Google search), to get a dimensioned sketch of your specific thread profile. Draw it in Rhino and sweep it as you have in the tutorial.

Maybe not what you’re looking for, but you’ll find a lot of stuff already drawn here;

I download step files and import directly.



Thanks! Making the screw was just to difficult…

I did find a STEP file of my screw and could import it into Rhino. All good now!

Great, glad I could help. Just a word of warning, I haven’t actually checked if the screw threads are exact or if they’re just a modelisation. If you see what I mean…

I’m the creator for BoltGen, and also am having difficulty getting a Windows python .rhp program to work in Mac. There seems to be a lot of problems porting to Mac. However, I do have a working copy of BoltGen and would be pleased to create what you need and send it to you. Email is:

Regards, Ray McKaig

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I know this “thread” is a couple years old…

However, I’m seeking to model threads with improper (undersized) minor and pitch diameters. It would seem BoltGen doesn’t have the options to alter these numbers.

Looks like I’ll need to carefully specify the profile and do a sweep.


Yep - making one full turn using RailRevolve on a helix and an axis, and then stacking the results as needed is probably an efficient way to go as far as making clean display meshes goes.


Hi Technerdchris.

I modified BoltGen to be able to make any thread and shaft diameter, both Metric and English threads. At the top of the bolt selection list, there is a selection called “special” that allows you to specify any bolt / thread size you desire, such as “0.59375x18 or 19/32x18” formats.
BoltGen is available in the Rhino 5/6 Python version.
Download it from Version 1.88

Regards, Ray

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Oh wow, thanks Ray! It’s been a while since I did anything “new” in Rhino and all this python stuff is fresh to me. How cool is that? For the next person that comes along, you download the rhi file and click it. A Rhino Installer program pops up and installs the plug-in. Then restart Rhino. :slight_smile:

Annnnnd, back to more studying of this weird thread I’m trying to replicate. Some things aren’t adding up…



Didn’t know if this was something you could fix or a McNeel issue, but I thought is should be reported. Running your script in Mac 10.14 dark mode gives me white on while text in the dialog where it asks me to select the type of bolt.
Can this be fixed?

Hi Jason.

I have no control of the menu items, perhaps McNeel could help. However, I have had fix requests in for years and no fixes have been forthcoming on the MAC. Maybe this is strong enough for them to fix. I wish you good luck on trying. It seems that MAC is just an afterthought for them, where the PC has the world market.


Ray McKaig

@dan It appears the the white background displays only when check boxes are present in window. Definitely a bug in the windowing during the script.

I agree. This is something we should be able to fix. Thanks for reporting it @jason

I’m sorry to hear you feel that way @RayM. I’m sorry to say I cannot find those requests, so they must have gotten lost in the shuffle. We’ll be more careful next time. Before I log a bug, are you using Eto for your cross-platform UI?

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Hi Dan.

No, not using ETO. There were several bugs in MAC in 2017. One was sorting the layers in MAC. That was a minor inconvenience. It has been some time since I used the MAC version 6 WIP. Pascal was looking into it.


Ray McKaig

Hey @RayM. @pascal was able to reproduce this in RH-50716. Hopefully this will be an easy fix. It’s just that a color value is getting set explicitly and is throwing macOS’s Dark mode adjustments off kilter.

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Just received this reply:

dan Dan Belcher McNeel
February 6

Hey @RayM. @pascal was able to reproduce this in RH-50716. Hopefully this will be an easy fix. It’s just that a color value is getting set explicitly and is throwing macOS’s Dark mode adjustments off kilter.


Ray McKaig

This should be fixed in the latest RhinoWIP.

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Love your work Ray. Weird that standard threads aren’t implemented in Rhino as part of MakeHole. Unless I’m wrong about that and threading is just hiding somewhere that I haven’t been able to find.

Hi - you are not wrong about that, Rhino doesn’t have a threading feature. It’s not something that comes up so often and there are viable workarounds.

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