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I want to build this thing, exactly.

enter image description here

I've created a cylinder and extrude it.

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How can I extrude the ring outwards exactly 7mm? Or Is this the complete wrong way to do this?

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  1. place a plane or other object exactly 7mm away from your cylinder
  2. extrude your ring of faces then scale them in the X/Y plane only with Snap to Vertex enabled and snap them to the object created in 1. Make sure the vertex is what's exactly 7mm away from the cylinder.

enter image description here

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Another way to do this is to first create a one-sided cross-section with the object origin in the middle. That way you can extrude with numerical input or even set the locations in the transform panel.

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when all edge lengths and positions match, just use the Screw Modifier or the Spin tool to create the cylinder.

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To me, this method is the most transparent. I have full overview over the shape and dimensions. I usually take my calipers and make a quick drawing on paper to have a reference instead of switching back and forth between object and computer.

It also liberates from the pretty much relative nature of extrusion. I could just measure the distance between the two rims and SHIFT-D the verts that distance apart. Lots of possibilities.

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    $\begingroup$ +1 for suggesting an alternate workflow which in this case (an object which is almost entirely a SoR) might be a much easier approach $\endgroup$ – A C Feb 21 '18 at 17:01
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Calculate scale factor from dimensions

Consider you have a cylinder with diameter 20cm (200mm).

enter image description here To extrude the selection about centre point, and to have a new diameter of 214mm ES1 The 1 is arbitrary we can fix in the operator panel

The required scale factor is 214 / 200 or 1.07. Can set the x, y and z scale factor in panel. (Or ES1.07 and reset z to 1.

Notice you can type arithmetic, 214 / 200 directly into the property.

enter image description here

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Alt+E >Extrude Region (Vertex normals)

Type "0.007" or "=7mm", Enter

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  • $\begingroup$ Could you please explain how extrusion is kept in the XY plane? I get 45 degree vertex normals on ngon edge verts. pasteall.org/pic/show.php?id=128580 $\endgroup$ – batFINGER Feb 21 '18 at 11:51
  • $\begingroup$ Extrude Region (Vertex normals) is just Blender way to say "Extrude along face normals), I think. $\endgroup$ – JuhaW Feb 21 '18 at 11:57
  • $\begingroup$ @batFINGER Extrude scale shift Z would work too on a circular faceloop. $\endgroup$ – Haunt_House Feb 21 '18 at 22:18

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