clamping jaw especially in the area of the cutting edge i e in the front area as seen in the feed direction of the cutter plate optimal clamping can be achieved in addition the wear of the main body of the reamer is minimal because the chips always flow onto the clamping jaw because there are no edges in the area of the chip flow chip buildups are reduced to a minimum from the side view of fig4 it is evident that the thickness of the clamping jaw 5 as seen from the corner in which the opening 23 is provided decreases in the direction towards the edge 31 in other words the cross section of the clamping jaw is essentially triangular as is evident from fig2 the shape of the clamping jaw 5 corresponds to that of the recess 9 in the body of the reamer 1 so that the clamping jaw when mounted is virtually completely countersunk in the reamer in the area of the circular shaped wall 17 the length of the internal threads in the opening 23 corresponds to the thickness of the clamping jaw 5 this results in very high strength in this area so that strong clamping forces can be applied because the underside 33 of the clamping jaw 5 is shaped as a plane surface the mounting on the clamping surface of the cutter plate 3 or on the cutter lip is exact the lateral surfaces of the clamping jaws which act as guide surfaces 13 and 15 are perpendicular to the underside 33 just like.