An improved fuze for a submunition grenade designed to be launched from a cargo projectile comprising a fuze, a charge and a casing; the improved fuze comprising a fuze housing; a threaded firing pin having a pointed tip, oriented coaxially with the submunition grenade, and threadedly engageable to a threaded hole in a weighted insert that is able to reciprocate within the fuze housing; a slider slidingly moveable in a substantially radial plane tangential to the axis of the firing pin, between a safe position and an armed position; the firing pin being able to rotatably reciprocate forwards and backwards by rotation of the firing pin with respect to the weighted insert along the threadedly engaged screw threads; the fuze further comprising a fully mechanical inertial releasable safety apparatus for preventing swiveling of the swivel mounted striker, to prevention initiation of the time delay detonator ignition system.