# How do you model threads? Add matl or subtract matl?

**URL:** <https://discourse.shapr3d.com/t/how-do-you-model-threads-add-matl-or-subtract-matl/20702>\
**Category:** Modeling Questions\
**Created:** [August 2, 2022, 12:30pm UTC](https://discourse.shapr3d.com/t/how-do-you-model-threads-add-matl-or-subtract-matl/20702 "2022-08-02T12:30:58Z")\
**Posts on this page:** 9\
**Page:** 1

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**Author:** ![mikeschn](https://sea2.discourse-cdn.com/flex002/user_avatar/discourse.shapr3d.com/mikeschn/32/10254_2.png) [@mikeschn](https://discourse.shapr3d.com/u/mikeschn)\
**Post date:** [August 2, 2022, 12:30pm UTC](https://discourse.shapr3d.com/t/how-do-you-model-threads-add-matl-or-subtract-matl/20702/1 "2022-08-02T12:30:58Z")

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Just curious, how to you guys model external threads, like on a bolt. Do you create a triangle to add material to a shaft that is at the root diameter? Or do you create a triangle to subtract material from a shaft that is at the major diameter?

For example here is a screenshot of where the matl (fundamental triangle) is added to the root diameter shaft…  
 ![image](https://us1.discourse-cdn.com/flex002/uploads/shapr3d/original/3X/f/9/f9363dbf4811103bebeaf19f3d52c1acf0f4d11d.jpeg)

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**Author:** ![McD](https://sea2.discourse-cdn.com/flex002/user_avatar/discourse.shapr3d.com/mcd/32/15504_2.png) [@McD](https://discourse.shapr3d.com/u/McD)\
**Post date:** [August 2, 2022, 2:37pm UTC](https://discourse.shapr3d.com/t/how-do-you-model-threads-add-matl-or-subtract-matl/20702/2 "2022-08-02T14:37:52Z")

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Most of us do not model the threads. I import bolts, nuts, pipe, etc., from McMaster-Carr using STEP file format. Then add or subtract as necessary.

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**Author:** ![Stephen](https://sea2.discourse-cdn.com/flex002/user_avatar/discourse.shapr3d.com/stephen/32/16350_2.png) [@Stephen](https://discourse.shapr3d.com/u/Stephen)\
**Post date:** [August 2, 2022, 4:51pm UTC](https://discourse.shapr3d.com/t/how-do-you-model-threads-add-matl-or-subtract-matl/20702/3 "2022-08-02T16:51:28Z")

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I often make nuts and bolts in Shapr just for the fun. There are a couple of videos on YouTube showing how to make them.

[https://youtu.be/G6Roo0ztiuM](https://youtu.be/G6Roo0ztiuM)

[https://youtu.be/TS0OmrwH1XI](https://youtu.be/TS0OmrwH1XI)

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**Author:** ![PEC](https://avatars.discourse-cdn.com/v4/letter/p/67e7ee/32.png) [@PEC](https://discourse.shapr3d.com/u/PEC)\
**Post date:** [August 2, 2022, 4:58pm UTC](https://discourse.shapr3d.com/t/how-do-you-model-threads-add-matl-or-subtract-matl/20702/4 "2022-08-02T16:58:26Z")

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Hi  
I always subtract. It is the way bolts and screws are actually manufactured and it is, in my opinion, the best way to get a clean start for the filet when you model chamfer before doing the subtraction.

Best regards  
PEC

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**Author:** ![ProtoFinity](https://sea2.discourse-cdn.com/flex002/user_avatar/discourse.shapr3d.com/protofinity/32/27667_2.png) [@ProtoFinity](https://discourse.shapr3d.com/u/ProtoFinity)\
**Post date:** [August 3, 2022, 5:15am UTC](https://discourse.shapr3d.com/t/how-do-you-model-threads-add-matl-or-subtract-matl/20702/5 "2022-08-03T05:15:41Z")

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This is s great video! This answered what I have been looking for.

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**Author:** ![mikeschn](https://sea2.discourse-cdn.com/flex002/user_avatar/discourse.shapr3d.com/mikeschn/32/10254_2.png) [@mikeschn](https://discourse.shapr3d.com/u/mikeschn)\
**Post date:** [August 4, 2022, 9:34am UTC](https://discourse.shapr3d.com/t/how-do-you-model-threads-add-matl-or-subtract-matl/20702/6 "2022-08-04T09:34:02Z")

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Just for giggles I added a thread to a shaft. Oh yeah, now I have to clean up the thread where it goes past the end of the bolt. Oh and then I’ll have to add a chamfer. Aw, no fun. I think I’ll go back to subtracting my triangles from the bolt! 😅

 ![image](https://us1.discourse-cdn.com/flex002/uploads/shapr3d/original/3X/9/6/96700c5829b7170263298e886ca066a57611a272.jpeg)

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**Author:** ![Stephen](https://sea2.discourse-cdn.com/flex002/user_avatar/discourse.shapr3d.com/stephen/32/16350_2.png) [@Stephen](https://discourse.shapr3d.com/u/Stephen)\
**Post date:** [August 4, 2022, 9:54am UTC](https://discourse.shapr3d.com/t/how-do-you-model-threads-add-matl-or-subtract-matl/20702/7 "2022-08-04T09:54:07Z")

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That’s a good effort.

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**Author:** ![SteveLynch](https://sea2.discourse-cdn.com/flex002/user_avatar/discourse.shapr3d.com/stevelynch/32/12399_2.png) [@SteveLynch](https://discourse.shapr3d.com/u/SteveLynch)\
**Post date:** [August 10, 2022, 6:42am UTC](https://discourse.shapr3d.com/t/how-do-you-model-threads-add-matl-or-subtract-matl/20702/9 "2022-08-10T06:42:31Z")

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haha, I thought I was the only one! Mcmaster’s catalog is My Go-to for threads. Embed the bolt, subtract, voila! Threads!

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**Author:** ![Jonathan](https://avatars.discourse-cdn.com/v4/letter/j/aeb1de/32.png) [@Jonathan](https://discourse.shapr3d.com/u/Jonathan)\
**Post date:** [August 10, 2022, 12:26pm UTC](https://discourse.shapr3d.com/t/how-do-you-model-threads-add-matl-or-subtract-matl/20702/10 "2022-08-10T12:26:08Z")

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Same, so easy to do !