Hi Jonathan,

Hope the microwave is OK - this CNC stuff can draw your concentration!

I still can't quite picture how you are using the spreadsheet, but if you are happy with your calcs then that's fine. If you have any more detailed dimensions and layouts then post them up and I'll try to help further if you like.

I briefly looked over those IGUS bearings. £21 and the low moment capability were concerns, but I'll study them a bit more and get back to you. Someone else might have used them and be able to comment? I'm a big fan of profile rail and over that short a span (400mm), and in say a 15mm size, are potentially affordable.

Drilling hardened rail - I'd worry about stress relief from the holes causing deflection of the nicely ground straight section. You'd have to switch to open bearing pillow blocks as well. Don't know if it's worth the effort, over buying the real thing. Anyone tried this?