I would be grateful if someone can advise a free guide for building a home-made cnc router machine
I read alot about the router machines but I just need a step by step guide if possible
There is a tremendous amount of free info here but you have to do the work and dig it out. Everything you need to know has probably been discussed already. Do a search for the topic you are interested in and read eveything.
Take a look at the JGRO design. There are even free plans available, on this site.
Thoroughly tested, and proven -- and well designed.
If you don't mind paying (a fair price) for some plans, David Steel's SolSylva planset seems particularly promising. It has some interesting refinements, like the fully supported rails that will prevent sagging.