machined ballscrews

[Jonathan]

ok it is in fact a silly question then as i had it in my head you could put a coupling straight on to a ball screw and attach it straight to the stepper.

One reason you can't do that is some bearings are required to resist the axial (parallel to the axis of the screw) and radial (to a lesser extent) forces on the ballscrew. The bearings in the stepper motor are very small and not the right type. The bearings in the BK/BF blocks you lined to are angular contact bearings which are used because they resist axial loads.

so with the mind set that i want to go for a straight motor to ballscrew i presume something like this is the kind of kit that would do everything

Yes and no - the bearing blocks are generally fine, but sometimes they need a bit of TLC to get running smoothly. However the coupling is a flexible type, which has relatively poor torsional stiffness and are not particularly strong. I know of at least one member on this forum who has had problems with that type of coupling snapping. You either want to get solid couplings (if the motor can be aligned accurately) or oldham couplings, since these are the types that will not introduce backlash.
You would be better of using a timing belt drive with two pulleys. This gives you the option to change the drive ratio between motor and ballscrew, to maximise either feedrate or resolution. In addition the timing belt has a damping effect which can help suppress resonant vibration, which ultimately leads to a smoother more stable system. Generally the most suitable belts and pulleys are 5M HTD (5mm pitch). Don't go below 15T for either pulley, ideally stick with more to prevent stressing the belt. Currently bearingstation is the cheapest place to buy belts and pulleys.

the above length is 547mm would this be the complete work length of that axis or do i need to take more out of that?

547mm is the overall length of the ballscrew including end-machining. So since the ballnut is 42mm long and the end machining is 44+12mm, that leaves 449mm travel. Realistically a little less due to the seals and stuff getting in the way. Here's the end machining drawing to help work things out:



Also, if you do decide to get pulleys I advise getting dimension F increased from 15mm to 25mm to make it easier to fit and align the pulleys.