I've been fixing up an older Atlas/Craftsman 12" and noticed today that when the tool post is about midrange the two end gib screws are not pressing the gib against the dovetail. For about 3/4-inch of travel the two outer screws are just "floating" off the ends and the only gib screw with a bearing is the center one:
This permits a little slop unless that center gib screw is snugged right up. It seems like two more intermediate gib screws would be a good idea, but mine can't be the only one like this, right? Am I fussing too much? Maybe I should just shut up and cut some metal.