v bearing or small square linear rails?

[GrahamWhite]

So I started a build on an 8x4 router and the first comments I have had said V bearings are a no no.
Would using small '15' square linear rails be a preference to V bearings?
Cost is a huge factor for me so no 'go get Hiwin 25 rails 'please!
cheap 15 rails are £120 for 2x1500mm so need 2 sets for my y axis ?
any thoughts?

[JAZZCNC]

There's massive difference even with 15mm but that said have you checked out prices from China rather than UK. You'll get them lot cheaper than in UK.
Also if your budget is tight look for supported round rail. It's good compromise and still light years ahead of v bearings.

[Web Goblin]

Stay away from v bearings. They are a pain in the bum. Seen them fitted to a few machines I used to work on in the past and they were always needing adjusted to work properly.

[m_c]

You'll most likely find 15mm linear rail has a higher load rating than V bearings.
15mm rail is more than capable of handling most CNC machines, it's just larger rail is a bit easier to mount (15mm typically needs M4 bolts, which require more care than M5 or M6).

I've just checked the load rating for some 15mm rail, and it is around 10kN depending on the carriage used. That's roughly the same as sitting a tonne on each carriage. Off course that relies on the rails being suitably mounted.