I attaching the tool assembly to the X axis base and then threaded the base bearings onto the x axis supporting bars . For the first time I had a picture of what the final project would look like.
This also allowed me to check how easily the tool assembly would slide across the gantry. I found there was some problems as the tool assembly reached the far ends of the gantry and the bearing were grating along with resistance when the assembly was pushed. I measured the separation of the X-axis bars at both ends and found that they were out by a two millimetres. Thermal/moisture contraction / expansion of the porous MDF material, bad workmanship or a combination of the both were to blame. Time to rebuild in a acrylic.