Abstract: An improved magnetic saw chuck includes a disc-shaped magnetic saw chuck plate, having a saw engaging surface at which a number of magnets are mounted, and a cylindrical arbor extending from the plate. A three-segment ring, mounted over the arbor adjacent the saw engaging surface, has an outer, saw eye engaging surface over which the saw is mounted. The segmented ring has a tapered inner surface which engages the tapered outer surface of a jam nut which is threaded onto the arbor. Tightening the jam nut against the segmented ring separates the segments to center the saw. The segmented ring includes an O-ring within a circular groove in the ring to keep the segments secured to the arbor when a saw is not mounted to the chuck. To prevent relative rotary motion of the ring segments, so the segments move only radially to aid centering the saw on the chuck, a guide pin is mounted to and extends from each segment and engages a complementary radial guide slot in the chuck plate.