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I want to build this thing, exactly.

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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.

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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.

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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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