Abstract: The clamping mechanism and companion cutting insert disclosed are designed for use in a milling cutter intended to be ganged with other like cutters on a common rotational axis for the simultaneous milling of multiple slots or grooves. The axially movable clamp for the on-edge inserts employed in the cutter is operated indirectly by an adjusting screw accessible radially from the outside of the ganged cutter bodies without requiring disassembly of the individual cutters to index or replace the cutting inserts. In each of several clamping mechanisms disclosed, the ultimate clamping element or detent takes the form of an arm which is rocked into engagement with the insert at the site of a blind depression in the face of the insert, being drawn in the axial direction by inward adjustment of a radially accessible adjusting screw, and rockable in the reverse direction by a return spring to release the insert as the adjusting screw is backed off.