# Add construction plane on inner surface

**URL:** <https://discourse.shapr3d.com/t/add-construction-plane-on-inner-surface/16869>\
**Category:** Modeling Questions\
**Created:** [January 13, 2022, 10:18am UTC](https://discourse.shapr3d.com/t/add-construction-plane-on-inner-surface/16869 "2022-01-13T10:18:40Z")\
**Posts on this page:** 9\
**Page:** 1

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**Author:** ![davorin](https://sea2.discourse-cdn.com/flex002/user_avatar/discourse.shapr3d.com/davorin/32/12827_2.png) [@davorin](https://discourse.shapr3d.com/u/davorin)\
**Post date:** [January 13, 2022, 10:18am UTC](https://discourse.shapr3d.com/t/add-construction-plane-on-inner-surface/16869/1 "2022-01-13T10:18:40Z")

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Good morning

Trying to do a simple speaker ball…the cutout is already made and now I need to cutout from the inner side 4 polygons for the the nuts.

The add construction plane offers the possibility to align it flat to a selected surface…but I can’t select the surface which is inside…and since the outer parallel surface is angled, i can’t use that for drawing because it would move the polygon sketch not at the angle the construction plane is.

So how can I add a construction plane inside? Or is there a trick to move the sketch perpendicular to the plane?

Here’s how it looks like so far:

 ![Lautsprecher](https://us1.discourse-cdn.com/flex002/uploads/shapr3d/original/2X/2/24be918bb11122f9c1fc66fc3cb0497e8438ccb7.jpeg)

And as you can see…when I move the polygon, it is moved in the y-axis, but when extruding it follows perpendicular to the sketch plane:  
 ![Bildschirmfoto 2022-01-13 um 11.34.18](https://us1.discourse-cdn.com/flex002/uploads/shapr3d/original/2X/8/84e8a82bc09b2efdb46b2ffd5efb6aa151dd68dc.png)

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**Author:** ![TigerMike](https://sea2.discourse-cdn.com/flex002/user_avatar/discourse.shapr3d.com/tigermike/32/32650_2.png) [@TigerMike](https://discourse.shapr3d.com/u/TigerMike)\
**Post date:** [January 13, 2022, 4:00pm UTC](https://discourse.shapr3d.com/t/add-construction-plane-on-inner-surface/16869/2 "2022-01-13T16:00:25Z")

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I’m not sure what you are trying to achieve. But, if it’s what I think it is, here’s a way.  
First, you don’t need to use a construction plane, nor make any polygon sketches on the inside. Make you polygon externally and extrude the nut. Align the nut with flat surface and then move the nut inward to the desired location. Then subtract the nut from the sphere and you’ll have hex recesses.

[https://us1.discourse-cdn.com/flex002/uploads/shapr3d/original/2X/3/3daaf634f16604da090d005b0e49d90f9ebb39b4.mov](https://us1.discourse-cdn.com/flex002/uploads/shapr3d/original/2X/3/3daaf634f16604da090d005b0e49d90f9ebb39b4.mov)

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**Author:** ![davorin](https://sea2.discourse-cdn.com/flex002/user_avatar/discourse.shapr3d.com/davorin/32/12827_2.png) [@davorin](https://discourse.shapr3d.com/u/davorin)\
**Post date:** [January 13, 2022, 6:10pm UTC](https://discourse.shapr3d.com/t/add-construction-plane-on-inner-surface/16869/3 "2022-01-13T18:10:31Z")

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Yes that would work…but now I rembered the cross section view option 😉

So I just move the angled front sketch plane and use it for the section cut:

 ![image](https://us1.discourse-cdn.com/flex002/uploads/shapr3d/original/2X/d/d5265de847503c006b5b586b596c3d8e17d3df11.jpeg)

And there I can easily sketch from the inside of the body…

Guess I need to re-watch the video tutorials…which are btw very good for starters like me 🙂

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**Author:** ![davorin](https://sea2.discourse-cdn.com/flex002/user_avatar/discourse.shapr3d.com/davorin/32/12827_2.png) [@davorin](https://discourse.shapr3d.com/u/davorin)\
**Post date:** [January 13, 2022, 7:03pm UTC](https://discourse.shapr3d.com/t/add-construction-plane-on-inner-surface/16869/4 "2022-01-13T19:03:03Z")

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Okay Mike…

Seems your solution is much better of course 🙂

Especially as I can precisely define the thickness between the nut at the back and the front plane…

Very much appreciated your short video 😉

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**Author:** ![TigerMike](https://sea2.discourse-cdn.com/flex002/user_avatar/discourse.shapr3d.com/tigermike/32/32650_2.png) [@TigerMike](https://discourse.shapr3d.com/u/TigerMike)\
**Post date:** [January 13, 2022, 7:07pm UTC](https://discourse.shapr3d.com/t/add-construction-plane-on-inner-surface/16869/5 "2022-01-13T19:07:30Z")

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Glad to help.  
BTW, nice Pug!

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**Author:** ![davorin](https://sea2.discourse-cdn.com/flex002/user_avatar/discourse.shapr3d.com/davorin/32/12827_2.png) [@davorin](https://discourse.shapr3d.com/u/davorin)\
**Post date:** [January 13, 2022, 8:54pm UTC](https://discourse.shapr3d.com/t/add-construction-plane-on-inner-surface/16869/6 "2022-01-13T20:54:19Z")

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Yes she makes us laugh every day 😉

Hmm…tried now on my iPad your solution…

1. Select body and click “align” and select inner circle of the nut front and the screw hole in the body…aligns fine…

2. When I reselect the nut and do a transform it can be only moved in xyz axis…not at the angle of the nut…

So I have to position the nut before I click “finish” for the align process…but in your video I see that you do a regular move command which is done at the right angle…guess I’m missing something here…

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**Author:** ![davorin](https://sea2.discourse-cdn.com/flex002/user_avatar/discourse.shapr3d.com/davorin/32/12827_2.png) [@davorin](https://discourse.shapr3d.com/u/davorin)\
**Post date:** [January 13, 2022, 9:13pm UTC](https://discourse.shapr3d.com/t/add-construction-plane-on-inner-surface/16869/7 "2022-01-13T21:13:18Z")

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Ah got it now (o;

I have to select the move point and drag it to the inner circle…so it knows then in which axis it has to move…brilliant (o;

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**Author:** ![TigerMike](https://sea2.discourse-cdn.com/flex002/user_avatar/discourse.shapr3d.com/tigermike/32/32650_2.png) [@TigerMike](https://discourse.shapr3d.com/u/TigerMike)\
**Post date:** [January 13, 2022, 9:24pm UTC](https://discourse.shapr3d.com/t/add-construction-plane-on-inner-surface/16869/8 "2022-01-13T21:24:31Z")

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You answered your own question. BTW, you don’t have to align with the inner circle, you can re-align the **Move/Rotate** point at other surfaces of the body you wish to move provided they point to the desired local XYZ (versus true XYZ).

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<div class="post-metadata">

**Author:** ![davorin](https://sea2.discourse-cdn.com/flex002/user_avatar/discourse.shapr3d.com/davorin/32/12827_2.png) [@davorin](https://discourse.shapr3d.com/u/davorin)\
**Post date:** [January 14, 2022, 1:07pm UTC](https://discourse.shapr3d.com/t/add-construction-plane-on-inner-surface/16869/9 "2022-01-14T13:07:42Z")

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Tried something different now…from the assembly point of view it should be anyway better (o;

Sketched the real size of the nut plus some few 0.1mm to adjust the 3D printing errors…and then extruded it sideways so I could subtract it from the body.

That way I can slide in the nuts from the side:

 ![Bildschirmfoto 2022-01-14 um 14.03.51](https://us1.discourse-cdn.com/flex002/uploads/shapr3d/original/2X/7/7b8b285e7020d711ed3dd4d2e64de30778978204.jpeg)

The little circular extrusion in the nut is just for aligning with the screw hole cutout…