Hi Steve,

Thanks for the advices. Of course I will make the drilling as you suggested. I got the 15 m of this 50x50 extrusion for 80 EUR, so I don't have bad feeling using them all to build a solid machine.
I intend to mill wood, plastic and alu, but not the harder metals.
It seems that ZAPP has quite good prices for ballscrews&nuts, it's very likely that I will order from there. I have used ball screws, but they are heavy weight really: 40x12 in three sizes 400mm/10000mm/1080mm. I don't know if I will use them ever, because I don't want to waste so much power to move the gantry with these brutal screws. But if someone has good ideas how to utilize them .....