# Radius on inside union

**URL:** <https://discourse.shapr3d.com/t/radius-on-inside-union/14536>\
**Category:** Modeling Questions\
**Created:** [August 22, 2021, 9:17pm UTC](https://discourse.shapr3d.com/t/radius-on-inside-union/14536 "2021-08-22T21:17:50Z")\
**Posts on this page:** 5\
**Page:** 1

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**Author:** ![Cpat39](https://avatars.discourse-cdn.com/v4/letter/c/e47774/32.png) [@Cpat39](https://discourse.shapr3d.com/u/Cpat39)\
**Post date:** [August 22, 2021, 9:17pm UTC](https://discourse.shapr3d.com/t/radius-on-inside-union/14536/1 "2021-08-22T21:17:50Z")

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I have a small knob that I would like to radius an inside 90 union or junction. When I try to use radius/chamfer tool it wants to perform the function on the flat not portion creating the opposite of what I am trying to accomplish.

 ![Screen Shot 2021-08-22 at 2.12.23 PM](https://us1.discourse-cdn.com/flex002/uploads/shapr3d/original/2X/8/8eb480d25d3fcecfece3808b35df5ca5675948c5.jpeg)  
Probably using wrong tool, but don’t see another tool that in my mind will work.

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**Author:** ![Rohan](https://sea2.discourse-cdn.com/flex002/user_avatar/discourse.shapr3d.com/rohan/32/15410_2.png) [@Rohan](https://discourse.shapr3d.com/u/Rohan)\
**Post date:** [August 23, 2021, 2:49am UTC](https://discourse.shapr3d.com/t/radius-on-inside-union/14536/2 "2021-08-23T02:49:40Z")

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Can you share a short video of what is the error.

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**Author:** ![Cpat39](https://avatars.discourse-cdn.com/v4/letter/c/e47774/32.png) [@Cpat39](https://discourse.shapr3d.com/u/Cpat39)\
**Post date:** [August 23, 2021, 3:26am UTC](https://discourse.shapr3d.com/t/radius-on-inside-union/14536/3 "2021-08-23T03:26:12Z")

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Attachment available until Sep 21, 2021

Hope this assists you to understand my issue

[Click to Download](https://www.icloud.com/attachment/?u=https%3A%2F%2Fcvws.icloud-content.com%2FB%2FAW37YS1O5Jp8xWF-OAN58Wu8S3veAXJ2AliGsQ_ZzenOkUPiY4dzEpzr%2F%24%7Bf%7D%3Fo%3DAvQtSbnuZ046vqDTqLkVeTjaM0K-jjGlmp1TLbvS7dct%26v%3D1%26x%3D3%26a%3DCAog91I2-qUR67L5ASkftX0IrN6UxdzCOH5wPIUozNbL5AkSdBD_pa2Ity8Y_7Wo3MAvIgEAKgkC6AMA_y_gh3BSBLxLe95aBHMSnOtqJLMWEjmR9L_Pz3kMyS6ILPIzBuwLV4uDPFwRACQ7tROPTObic3IknmD3SV5Tn1C-xZIDvEJ0S6WKiFEYSsdfhr8bxa-PsJCvMBD1%26e%3D1632281172%26fl%3D%26r%3DB1BD0278-ABE4-4F20-9962-E84F5029627E-1%26k%3D%24%7Buk%7D%26ckc%3Dcom.apple.largeattachment%26ckz%3DA0F288DD-2631-4165-916D-8E073EBD5377%26p%3D52%26s%3DI5LEPBlBwzkBDztmXWnHf3XFIic&uk=EwQAFCIbL_oEYTjWCVOZIQ&f=Screen%20Recording%202021-08-22%20at%208.11.15%20PM.mov&sz=440713191)

Screen Recording 2021-08-22 at 8.11.15 PM.mov  
440.7 MB

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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:** [August 23, 2021, 4:04am UTC](https://discourse.shapr3d.com/t/radius-on-inside-union/14536/4 "2021-08-23T04:04:18Z")

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From what I can tell, the problem is that your knob consists of more than one body. The cylinder wall is a separate body from the bottom. Do a **Union** first, then the fillet radius should work (unless you prefer to have a chamfer).

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<div class="post-metadata">

**Author:** ![Cpat39](https://avatars.discourse-cdn.com/v4/letter/c/e47774/32.png) [@Cpat39](https://discourse.shapr3d.com/u/Cpat39)\
**Post date:** [August 23, 2021, 6:07pm UTC](https://discourse.shapr3d.com/t/radius-on-inside-union/14536/5 "2021-08-23T18:07:59Z")

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Thank you, that fixed the issue.