Ha yeah thats a monster.

I decided to make it 2000x1900mm I'll just have to get it trailered away if I ever need to move it. 1900 will just squeeze through the garage door lol. And I think i'll probably make it only 500mm Z travel. The raising bed will make up for it I think. One thing I can envision needing todo in the future is deep pockets, where the length of the cutting tool and the width of the spindle would be the limiting factor, maybe make a super thin spindle if it becomes a problem.

I see what your saying about the accuracy but I may aswell do everything I can to make it better. If I get the poor quality screws thats just another inaccuracy to add on. I can't do anything about those other inaccuracies but I can about this and it wont cost much more so why not?

Not sure about locking it, maybe once i've got the machine built I can use it to make some locking devices. I've no way to make them especially with any accuracy at the moment. Not sure it will be a big issue to be honest, the weight of the bed will take up the ballnut backlash. I guess the main benefit would be reduced power consumption you'd get from turning off the motors. I could also use double ballnuts which would probably be a much simpler solution, the ballnuts I should be able to get cheap from fred.

I had a question about the gantry design though, need to get it designed so you lot can see, I've been trying to learn how to use fusion 360,solidworks and sketchup but I just can't get along with any of them. Give me AutoCAD 2000 any day of the week over these, I don't know how they can take a program thats so simple and works so well and thoroughly ruin it.