That is disappointing. Have you tried putting Elmer's School glue on the screw and then tightening? That may work to hold the screw until needed to put in new blade. I did this with one of my Olfa cutters. That screw kept coming loose after a couple of cuts. It didn't take much effort to unscrew with the glue but it held the screw tight. After I thought I got my money's worth using it I tossed it.