The reason I went with using ball screws is the accuracy they give over the full length and their ease of use. The screws I bought are 1300mm long. I wanted a 4x4 working area and the 1300mm gives me 51 inches of travel take away the nut size @1.5 inches I get my 4 foot. For the table the extra foot provided by the rail will be used for the gantry off-set. On the gantry, I will mount the ball screw in the center and put 6' on each side. Thinking about this has me re thinking the mounts I built. Should one of the three be 6 inches +the 3" planed?
The third photo is one I found on the web. The information that was with it stated it needed 50 lb of force to make it slip and was printed. I would like to see more information on these.
If you have not seen or understand a Ball Screw vs Jack Screw. I'll try to help out. In reality they are the same. In the case of a ball screw the screw part is turning and in a jack screw the nut part is turning. Both have there uses. The one part that most sites forget about is the thrust bearing. This is the bearing that gets the real load.