Z-axis design - help sizing materials please!

[Jonathan]

As far as I know thats for friction bearings like the igus or dovetails like a mill/lathe. and is to stop/reduce binding, not for resisting the cutting force.....

I've just checked the Igus datasheet and that is indeed the case.

The other point is that it will only be as good as the weakest bit....theres no point in have expensive powerful motors and drives and then using unsupported rail... it just dosnt make sense.

I've already got the expensive powerful motors and drivers on my milling machine. I intending to use those motors on the router and put some 1 Nm ones I've got lying around on the router.

I hope I dont seem negative or put you off but rather offered some pointers to another route.

On the contrary - you're not putting me off, yet!