Abstract: A grinding mill requiring one or more new grinding balls is adapted so that they can be passed into the mill through spider-guide apertures. The spider-guide apertures provide anchors for spider-guide mountings, by means of which a spider used to grip an upper ring is restrained against rotation. There may be provided two mounting frames between the spider-guide mounting, and the mill. Frame is secured to the mill and has a large opening, able to pass a grinding ball. Frame is secured to frame and has a smaller opening, and provides a mounting location for the spider-guide mounting. The arrangement means that mill disassembly and lifting then lowering grinding balls is no longer needed.