Homebrew PCBs

> Bad idea,
> 
> You will have no control over the force - with a spring, you would 
> simply get a single feedrate for everything.  Believe me, a .010" 
> diameter drill requires a much different feedrate than a .125" 
> diameter drill.

Why? If I compress the spring a little more, I'll have more strength.
Or so I think. So I can put a screw to adjust the spring tension for
the different bits (I use .75 and 1mm bits anyway...)

> There is no quick and easy answer on motor sizing,  
Well, I'll be making my machine with whatever I have handy. I can't
seem to find a supplier of ball screws for my country (I'm sure there
are, but anyway the price will be too high), so I'd have to build it
with a regular threaded and nuts. I don't mind the efficiency either,
I don't care if it's a little oversized. I ask this as I have
absolutely no idea about stepper motors.

hjf