At the moment nothing is stopping the whole gantry from lifting up and it will only have a worktop/surface spanning the 2 uprights holding the X axis rails, so in actual fact the only thing that will hold it from lifting will be the threaded rod when its connected to the bottom of the gantry and obviously this will be connected to the stepper motor one ened and the other end will float within the bearing at the other end. At the moment it is bothering me but I might even fit a fixture which will hold a bearing so it rides under the table but also be pressing down on the gantry which will stop the lifting if it occurs.
John sure could use your expertise on this one bro ?