Homebrew PCBs

> and made by Milford instruments. The "data sheet" is in fact the
instructions
> to build.
> 
> Milford instruments' own site is
> 
> http://www.milinst.com/


That machine has been around a few years, and often pops up as an example of
a simple one to build.

The assembly manual is here:
http://www.milinst.co.uk/shop/RA/pdf/5_300mnl.pdf, you could use that as a
guide.  A couple of interesting points is it's made from laminated chipboard
(not MDF), not that it matters much (both are fairly stable), and the drive
is done by cable, not screws.

The cable is wound around the stepper shaft and tensioned, it's a fairly
common method seen in things like photocopiers etc.  It explains why you
can't see the motors, and the resolution.  

Since the cable is wound around the shaft, one rotation moves the axis the
circumference of the shaft, so a 1/4" shaft gives 6.35mm x 3.14, so 20mm.
Dividing that by 200 steps gives your 0.1mm resolution.  Good enough for
drilling PCBs which seems to its main goal.

It's well worth building something like that from junk as a learning
experience.  CNC is more than just the machine; you need to get your head
around the software as well, in that case a clunky machine is better than
nothing.

Tony