In a hard metal plate for insertion in to a seat formed at one end of a drill shaft of a rock drill, comprising a substantially rectangular base shape having two opposed long sides extending in the axial direction of the drill shaft which are at least partially covered by the seat, two opposed, substantially axial free short sides, a radial bottom side facing towards the seat and a cutting face facing away from the seat, both short sides are formed by an axial section having a purely axial direction component and a conical section inclined towards the axial direction, so that at the short side, the substantially rectangular plate tapers towards the bottom side.