BRL-CAD is a free, open-source alternative to AutoCAD

http://www.webupd8.org/2009/10/free-...ternative.html

RKK, never heard of BRL-CAD.

to the OP;
Before using BRL-CAD to do what you have in mind, make sure it exports to a vector program like Illustrator either directly or via PDF. Have someone with Illustrator check your art. Do not use a .eps export.

Also
RULE #1:
LOGOS DESIGNED IN AUTOCAD NEED TO BE CREATED USING CLOSED POLYLINES.
let me say that again:
LOGOS DESIGNED IN AUTOCAD NEED TO BE CREATED USING CLOSED POLYLINES.
If you don't follow that rule any logo you create will not be usable in the real world.

Rule #2:
BEWARE OF FILLS
fills and hatches in CAD programs create a separate shape under the main outline that does not correspond to the main outline. If you are using colors, have the result checked in outline view in Illustrator.

Rule #3
WATCH YOUR CURVES.
On export to .eps most CAD programs will facet curves, especially in text/fonts, into a mass of straight lines and points, which are also no good. This also sometimes happens in PDF. Have your art checked.

Rule #4
WATCH YOUR LAYERS.
CAD programs are notorious for creating multiple stacked outlines on shapes. You only want one outline.

Rule #5
WATCH YOUR COLORS
Logos in the real world use PMS colors and CMYK equivalents that are standardized. CAD programs don't generally have these available.

If you have Illustrator there is a plug-in called CADTools from Hotdoor software that does what you need it to do. I can't stress enough that CAD programs for logo creation have a lot of pitfalls that unless you are versed in how logos are made (and even most designers aren't) you can really mess things up.

I don't use any CAD programs .. I had just heard that this was a free alternative.

So if it's no good ... I take no responsibility lol

Thank you very much for the replies

RKK I will take a look at that program and update this thread with my findings!

Print Driver, thanks for the warnings - I predicted that CAD programs would have a huge number of limitations and obstacles in being used for art so it was helpful seeing exactly what these were. I found the last point about CADTools particularly interesting but unfortunately, I don't have illustrator. What I can afford however, is free software so I am currently looking for some CAD-style inkscape plugins of which I have found a couple of developments. I wouldn't have thought of this without the suggestion! Cheers!

So do either of you know how designers actually make logos to be precise shapes? Or are they not precise at all, and just happen to look that way?

By using the transform panel, and guides and grids, in Illustrator. I believe the transform panel is accurate to .001".