I also have a Millrite. There were 2 different types of gibs installed on them, a tapered one that is adjustable from the ends, or a parallel gib that requires the table to be removed from the saddle to adjust it. Regardless, if the mill has been neglected, first take it apart and clean everything up. You cannot do a good job of adjusting it without clean and freshly lubricated parts. Wear is always an issue. Most users leave their chuck in only one position along the table, and so the wear mostly accumulates in that area, which tends to make the table loose in the middle, and tight at the ends of the travel. If you just adjust the gib to be snug in the middle, the table will lock up before reaching the ends. The only cure to that is refitting the gib to the table, and requires possibly machining and definitely scraping the parts in to fit each other properly. Those are required skills that come after training and practice, no quick and dirty shortcuts if you want a good job that will last. I regularly move my vise to different positions along the table, which helps to even out the wear. Keeping everything clean and properly lubed is also required if you want the mill to turn out accurate work, and without chatter.
The above also applies to other machines besides Millrite mills. Figure out how they work, keep them clean and well lubricated, and use different portions of the various axes travels to help keep the inevitable wear even along the entire axis.
