I'll finish the computery softwary bit with a a few comments and suggestions for CAD / CAM software that will run or complement a small CNC setup such as this Raspberry Pi one I'm babbling on about.
So first up with CAD.
Well everybody has particular preferences and opinions about what is the best to use. There are plenty to choose from, some free, some not. I won't bother listing them all, just a couple of interest for reasons stated with each.
First up:
Librecad. Why, well it is free, it runs on a Raspberry Pi. It also runs on Windows, Mac, and most mainstream Linux systems. Does most general 2D CAD stuff. Here is a link for it.

Second up:
Heeks CAD/CAM. (3D) This one looks V interesting but I really have not spent enough time on it to make any objective comment. If anyone out there has had a good go on it, then please do let us know what it is good for. I might make further comment myself as, if and when...
Link Here

Third up:
Inkscape. Well its not CAD. It is a vector drawing system, which is CAD capable to a point. It can output in .DXF format and plain .SVG formats which makes it a handy editor / originator for all sorts of non technical drawings, pictures, photographs, sketches. So once a picture sketch etc has been imported at can be vectorised, stretched, squashed , resized. Whatever you like really. but the output is in a format that good CAM system can deal with. It also has limited ability to do a bit of CAM as well using a tool called "GcodeTools" I had pleasing but limited sucess with this. It can only realistically do outline or trace cuts. Gcode Tools is supposed to be able to do area cuts, but I did not have any joy with that.
So, it's good for more arty farty shapes and forms than the usual 2D CAD. It runs on a Raspberry Pi and Windows, Mac, mainstream Linux and is free.
Main Inkscape link here:

Quick "How to" Vectorise here:

Bit on Gcode Tools for Inkscape here:

Lastly, couldn't find anything remotely CAM useful to run on the Raspberry Pi. Couldn't find anything useful that would run on Linux ( Perhaps Heeks CAD/CAM....could do it?)

Did find this though.

You can take it for a test run for free. I was quite impressed with. So I bought a licence for it. Its Windows only. Full licence is $59
The bit that sold it for me which may interest the patten making casting fraternity is the ability to do good carves with a V bits so draft is created by the carve and also there is a text generator and a modest set of fonts that it will draw for you, even round curves. I think it is a rather good piece of software for the price. It can do all sorts of other things which I've not tried yet.
Take a look at the video manual, especially the ones on Carving and Texts

I'm now done on the software thing. I'll cover the mechanicals in the next exciting installment