hey guys which type of rail would be better for a wood CNC
video 1
Video 2
or the one from the picture
hi Bijil,
all are ok, is a question how exactly you like to build… and the cost! 
http://www.hiwin.de/de/HGL-Produkte?co_id=4276&art_id=22183
Certainly depend on your budget and your engineering limits. The simple wood block with some bearing pairs on the square rail looks cheap and effective. But that still requires some precision placement of those holes to get the exact spacing correct. Also presumably those tracks need to be mounted on the corners which could be tricky. The two that use extruded aluminium profile to form the runners both look nice if you can afford that. Again looks like some pretty accurate machining required to get beating placement just right. and I’m not sure how expensive those d-bearings are compared to standard 608 skateboard bearings. My current design just uses threaded rod and bolts to position 608 bearings on each side of square section rail. It has some disadvantages, but it is adjustable, fairly cheap and didn’t need me to machine anything to a high degree of accuracy.
@Hermann_Platschka these are really expensive i am looking for cheaper alternative
The 2 photos show parts sold by http://cncrouterparts.com . That uses a steel rail, and by all reports is well made. I expect it or the vbearings will work absolutely fine. The one in “building a CNC machine part 3” looks workable, but my knee-jerk is that you’re putting all the contact on the sides of the bearings, not the centre, if you follow me. I imagine that would lead to fast wear on the bearings.
@Richard_Betel thanks i was thinking of using v baring but i dont know if proper v baring would be available. i am using 40mmx40mm aluminum extrusion with curved edges