a little history for you, my machine was belt driven on the y and x axis and lead screw on z axis, i struggled to get the machine to travel the same measurement as the computer was telling it, it got worse the longer the travel,,, i new that the settings could be the issue and i new the belts were skipping...
i converted the x and y to acme lead screw, with the help of this group i was able to get the machine to move and measure the same regardless if it went 2 inches or 30 inches, this was big...
for the exact, with the limited tools i have, using a tape measure, i can tell the machine is exact, i know that in reality that is probably not a true statement but i do not have the ability to measure in mm, and at this point i am going to run with it and start cutting and make adjustments as i go... This was because of the help i received on this page...
I am working on the backlash work in progress, and yes i will be checking this as time goes on, on my machine the backlash will come with time because of the acme blocks i use and they will wear out in time....
any way, thanks again to everyone great help,,