Beginner FreeCAD question on axes when sketching I am a raw beginner at FreeCAD and 3D draughting. Watched some tutorials and designed 2-3 simple items. Aiming to use it for 3D printing.
My question relates to 2D sketching. As I understand the workflow, one draws 2D items that one can then extrude, cut etc. So one picks the drawing axes (eg X and Y), and the sketch is then at Z axis zero. After extruding, one can place another sketch on a face for further extruding etc.
But the sketch is always at relative Z/3rd axis zero.
Consider a fairly large block extruded 10 mm thick. Say I want (example only, never mind  why) to cut a 20 mm disk from the interior, 3 mm deep, 5 mm from the bottom surface therefore 2 mm from the top.
If I place a sketch on the top surface, make a 20 mm circle and use that to cut a hole, the cut will always start at the top surface - but I want it to start 2 mm down. I.e. it seems to me I need to be able to offset the sketch from local Z/3rd axis zero, in this case to -2 mm.
Can one do that, or have I missed the point somewhere?
This answer assumes you're working in the Part Design workbench.
So you want to adjust the starting height of a pad or pocket. There are two ways I can think of to do this easily.

Adjust the Z attachment value of the sketch to lower the sketch below the surface.
Use the &quot;two dimensions&quot; option in the pad/pocket operation and set the second value negative.

By the way, it is highly suggested not to attach a sketch to a surface. The current development version (0.19) and previous versions have an issue (&quot;topographical naming&quot;) where editing a previous feature can change the internal name of a face causing the attachment to break. There is a solution under development but it doesn't loom like it will get in earlier than 0.20. You should instead simply adjust the Z attachment value to match the face you want.
Also, there is a very active (and very helpful) forum here. I'd suggest asking further FreeCAD questions there.