Safety core cutting knife

A knife for cutting honeycomb core and other materials with a combination of safety features to prevent or minimize injury to operator. The blade used has a hole through which a fastening device e.g. threaded screw, locks it to a handgrip. A safety guard covers the blade when not in use and automatically retracts as the blade is removed from the workpiece. The guard cannot be accidently displaced from the blade. It must be purposely unlocked by a manually triggered self-locking release assembly located in the handgrip which also automatically relocks the safety guard when retracted. The safety features consist of an automatically retractable guard attached to a safety handshield working in conjunction with the safety self-locking release assembly to prevent accidental release. Embodiments include (1) wherein the guard is opaque and has viewing ports and is hinged mechanically with springs, supports, and spacers, (2) wherein the guard is transparent eliminating the need for viewing ports, (3) wherein the guard and many other metal components are comprised of plastic, (4) wherein the guard is transparent and is hinged by an integrally molded component, (5) wherein the guard is hinged by a combination of mechanical (1) and integrally molded (4) means and (6) wherein a disposable blade is used.