A cutting burr (10) that includes a pair of axially spaced diamond- shaped portions (18, 20) designed to be keyed into a spindle of a locking mechanism of a high speed surgical drilling instrument and adapted to fit into a single pawl thereof to lock said cutting burr in place so as to prevent axial movement thereof and provide concentric rotation of said cutting burr without any wobbling. The orientation of both portions may be identical with respect to a center plan and The diamond shape in the portion (18) at the proximal end (14) of the shank /16) of the cutting tool may be larger than the intermediately located diamond shape of the other portion (20). The apexes (32, 26) of the facets (34, 34a, 30, 30a) of the six-sided diamond shape may be disposed below the surface of the shank of the cutting burr.
