When you have a rectangular plane, extrude it and then scale, it will scale in or out according to the lengths of the edges. How do I avoid this? I want it to scale, so that the new inset rectangles edges are all the same distance from the outer rectangles edges. Imagine creating the walls of a rectangular room etc. Can this be dont in one go? Or do I always have to manually scale two axes separatly
You’re doing it all wrong, Blender’s doing all correctly 
Scaling is done by a value/percentage.
If your quad is 12 units long and 6 units high and you scale it down 50% it scales the dimensions down, obviously to 6 by 3, leaving you with 3 units border at the top, 1.5 units at the sides.
What you are looking for is to press “i” instead of “s” for “inset”, which does exactly what you’re looking for
Oooooo! Thanks much
Hmmm. You scaled that mesh in Object Mode and forgot to apply the scale (CTRL-A)?
That’s because you have scaled your plane object in Object Mode at some point, and due to this your scale is not 1.0 on the X/Y/Z axis, by example here i scaled an object on the X axis in Object Mode if i press N and look at the scale values you can see the X is not 1.0 anymore :
scales that are not all 1.0 in X/Y/Z axis will impact several tools in Edit Mode, as you just experienced with the inset.
To fix this problem, in Object Mode select your plane object and press CTRL+A -> Scale to apply the scale transformation, and get it to 1.0 again.
Then you can redo the inset and it will deliver the result you wanted.
edit : too slow
Ah ha, thank you! That’s not the first time I’ve been stumped by forgetting to apply a transformation. I need to be better at keeping that in mind.
Is there a way to do this with edge loops?
there is an addon “offset edges” works quite well