Abstract: A system for fixing the mobile jaw on a conical head of a cone or giratory stone crusher, includes a bowl, with a feed hopper mounted thereon, a fixed truncated jaw mounted coaxially with the bowl, a crushing head mounted on a main shaft coaxial with the fixed jaw and a conical mobile jaw mounted on the head and clamped thereon by a locking element integral with the head and pressing on the top of the mobile jaw. The element has on its outer periphery notches radially oriented outwards and uniformly distributed on the periphery and the mobile jaw has, on its inner periphery, at its openings studs radially oriented inwards, uniformly distributed on the periphery and matching in number the notches, the studs penetrating when mounted in the notches so as to secure the locking element and the mobile jaw in rotation when the crusher is operating.