Quote Originally Posted by dudz View Post
Seeing all my rails are 25mm round (unsupported) do I really need to replace them with supported rails ?
Yes, if you are not satisfied with the current rigidity of the machine. Even 12mm supported is likely to be stronger than 25mm unsupported over a reasonable distance, but that doesn't meant you should use 12mm:
http://www.mycncuk.com/forums/faqs-p...ted-rails.html

Quote Originally Posted by dudz View Post
I see that most machines of this size only have 16 or 20mm supported rails.
For much of history most people believed the earth was flat, but that didn't make it flat!