Jonathon, Jonathon... How on gods green do I even start thinking about making something of that caliber? they really are amazing. But I am a realist as much as I could probably make one, if I set my mind to it. The other 7 just wouldnt be the 'same'. :-D Just looking at them, their accuracy makes me feel sick. Its one of these situations where I need to see them before I know what Im doing... For example you have mentioned seals, Ive heard circlips mentioned. All of this is assumed knowlege that you guys have gathered from building a mk1 machine first. And I think ultimately this is what I am going to have to do.

An example, if I need 1500mm of drivable screw. (inside the supports) then how do I calculate how much 'extra' I need at either end to go through the housing (your suggesting I do not buy from the same supplier), and also through the support on the other side and through a pulley that I also havent bought!. This is why (I guess) for me it may be easier to just buy the supported bearing housings from the china supplier and if necessary re-make them based on the design on the ones that come with the screw? (can you see my thought pattern?) On previous threads on here I noticed your original build thread for your first machine. This machine was significantly different to your present one, and I guess you learnt from your mistakes on that build to gain the knowlege you have today?


You say i should upgrade my X axis rails, they are already SBR20... what is an upgrade to them?

So, taking on board your comments, a modification to the shopping list would be

(X Axis)
* 2 x RM1610 (1500mm) screws (machined at both ends, one side will need to be machined to fit through the BF bearing and also so I can fit a driven pulley, and the other needs to be machined simply to fit the BF bearing. Im assuming I just let Chai know that I want to fit a pulley so he leaves enough shaft after the bearing housing. then I just by a piloted pulley and bore it to fit the machined end of the screw?
* 4 x BF bearing with supported block mouting
* 1 x ballscrew nut (as above re housing)
* 2 x SBR20 fully supported rail (1600mm) (with 4 bearing blocks) I assume SBR20UU


Y Axis
*1 x RM1610 Screw (1000mm) (same question as above)
* 2 x BF bearing with supported block mouting
* 1 x ballscrew nut (as above re housing)
* 2 x SBR20 fully supported rail (1000mm) (with 4 bearing blocks)

Z Axis
* 1 x RM1605 Screw (300mm)
* 2 x BF bearing with supported block mouting
* 1 x ballscrew nut (as above re housing)
* 1 x SBR20 fully supported rail (300mm) (with 4 bearing blocks)

Although your comments re-pulleys is useful. Its another answer that fills my head with more questions... I think il put off buying pulleys until I have stuff on the workshop floor I can bite.

I genuinely really appreciate your thoughts, Im absorbing as much as I can. Your clearly an immensly clever lad but Im just a normal bloke!. The entire point of me building a machine is to be able to get to a point where I can make 'things' more accurate, Its a chicken and egg situation. If I had a rig, this rig build would be as easy as you make it sound!