Stepper motor sizing

My XYZ router 'to be' i.e. my dream machine !! only needs to cut 0.9mm aluminium and up to 2mm ABS/styrene sheet and I need to know what size stepper motor i need to choose if actual speed of travel is not critical to me.
NEMA 24 or 34 or anything around 200oz? comments please. Am I likely to retrieve any suitable sized steppers out of old photocopiers for this task?
Must admit that all I have seen have seemed physically far too small.
What about those polished round 0.5inch guide rails that most of them use, are they any use for say the Z axis?
Raynor Johnston