I'm making some technical drawings in Inkscape to be laser cut through ponoko.com. I'm having trouble getting exact dimensions for the objects of the drawing when I change line strokes. The laser cutter requires line widths of 0.01mm, but lines that small are hard to see and work with. I'd like to use thicker lines to draw and then change the stroke width at the end, but doing so changes the dimensions of the object. Is there any way to keep the dimensions constant when changing the line width? Or to have Inkscape measure object dimensions from the center of the line, rather than the outside edge as it seems to? Also, Inkscape often changes the dimensional value slightly when its first entered (i.e. 3mm goes to 2.999mm, or 4.508mm goes to 4.510mm). Entering it again often solves the problem. Is this just a bug or is there a way to fix it? Thanks!

You can set up geometric bounding box instead of the default visual bounding box in the preferences (Ctrl+Shift+P) -the very fitst setting.
Note the select tool's tool control icon that makes strokes scale with the objects or not.
http://tavmjong.free.fr/INKSCAPE/MANUAL/html/Attributes-Stroke.html.
Also, you can draw in outlines only display mode (Ctrl+5 twice on the numpad).

Good luck!

When making drawings for laser-cutters or cnc, I usually set stroke and fill to none, and use Menu: View>Display mode>Outline.

Kerf is different for each machine/material, so I would discuss that with the service provider.

Hello,
It is really neccesary to draw your designs in Inkscape?
Because, there is an importer/exporter for dxf format.

http://tavmjong.free.fr/INKSCAPE/MANUAL ... mport.html