Accuracy in building a CNC router

[Darren]

Hi guys,

I've had lots of my questions answered and am back in building mode on my router. I have some questions about building the machine though. How are people ensuring good tolerances when these machines are being built? What is acceptable? I've never built anything like this before and have some really basic questions that I just don't know the answer to. I'll list them below:

1. when hanging my supported thomson rails how do I ensure they are perfectly parallel?

2. When cutting plate aluminum and large 80/20 pieces my chop saw is only so accurate. I have an engineers square and assume if it matches that I'm good. Is that good enough?

3. When bolting two pieces together, say the gantry sides to an 80/20 bridge do you leave enough play in each bolt hole on the gantry side so you can fudge it perfectly square as you torque them down?

I'm sure I'll have more but these will get me going. My machine and plans are described here: You opinion on my plan? Updated: DXF and Pics of parts included

Thanks for any answers or pointers to threads that cover any of my questions.

Darren

[ViperTX]

1. Secure one rail, have the cross piece that goes between the rails tighten down, move the cross piece from one end to the other, tighten the end of the 2nd rail as you move down the length of the rails. This assumed that you have leveled both rails and the cross piece.

2. Well, no, but that's as accurate as the tools you have, you'll need adjustability in the system.

3. Yes, that's correct.

[Darren]

Thanks again ViperTX. I'm hoping to begin assembling pretty soon. Still working out the plan but am getting close.