A surgical knife safety device (10 or 100) having (20 or 120), a blade (40 or 140) connected the handle, and a guard (30 or 130) carried by the handle for sliding movement between a retracted position in which the blade is exposed for use, and an extended position for covering the sharp cutting edge of the blade. In the retracted position, an enlarged guard (30 or 130) radius is provided at the distal end of the handle (20 or 120) to allow improved handle control and blade orientation. The enlarged guard radius is positioned to allow the user to firmly grip a large distal handle portion which is preferably molded as a single piece with the blade holder (26 or 126), preventing unwanted blade or handle movement due to guard mechanism tolerances. A spring, such as leaf spring or a cantilever beam (52 or 152), and a pair of detents (54, 56) or slots (154, 156) are provided to fix the guard (30 or 130) in the extended or retracted position and to provide resistance during movement between the two positions. Additionally, a pushback prevention mechanism, a user operable lock and a drop-force operable lock are provided to prevent accidental retraction of the ground from the fully extended and guarded position.
