thanks for the reply jonathan

firstly, im getting the screws machined free of charge, why pay if i dont need to?

as for pulleys, i will take your word for htd and give them preference so long as i can find a set to fit the cramped x axis

now, the bearing selection is an interesting predicament...
the largest id magneto bearing i could comfortably implement would be E5 (16mm od)
i can easily get 8x16x5 ball thrust bearings

so, do i turn 12mm ballscrews down to 5mm to use magnetos or 8mm and just use ball thrust bearings. or in other words is 5mm sufficient if i ever hope for this machine to cut steel?

and as for bellville washers, point taken