OK, so I'm thinking about building a new CNC. I can do some searches and find out whether rack and pinon or ballscrews would be the best option, but while I'm researching this what do I look at for rack and pinon to know if they are the right components? Meaning I can buy a rack and gear off of McMaster Carr but do all their sets mate without any backlash? I'm more familiar with ballscrews so backlash might not be the correct term. And as far as using let's say servos to move the cnc what size, pitch etc... should I look at for a 6' long table by 3' wide? Thanks.