Patent ID: 8142115

Claim:
A tool for drilling countersunk holes comprising: a twist drill having a central longitudinal axis; said drill comprising a fluted portion and a shank portion; said fluted portion comprising: at least one helical chip flute; at least one helical land disposed adjacent said at least one chip flute; at least one helical cutting edge disposed adjacent said at least one chip flute; said at least one helical cutting edge being configured and disposed to define an angle relative to the central longitudinal axis of at most 25 degrees; a clamping ring being configured and disposed to surround a portion of said drill; said clamping ring comprising at least one fastening arrangement being configured and disposed to clamp said clamping ring to said drill; a cutting insert configured to make a countersink in a drilled hole; said clamping ring comprising a fastening arrangement being configured and disposed to fasten said cutting insert to said clamping ring; said drill comprising a flat bearing face being disposed along and on said at least one land, substantially parallel to and along the longitudinal axis of a substantial portion of said fluted portion of said drill; said flat bearing face having a width and a length greater than said width, and being configured and disposed to permit said cutting insert to abut and bear against said flat bearing face; said cutting insert being configured and disposed to bear against said flat bearing face and being slideable along said flat bearing face; said fastening arrangement being configured and disposed to press said cutting insert against said flat bearing face; said flat bearing face: being configured to permit said clamping ring to be moveably relocated longitudinally along said drill substantially parallel to the longitudinal axis; and having a sufficient width and a length to permit said cutting insert to be positioned at a plurality of locations along a substantial portion of the length of said fluted portion of said drill; said clamping ring being configured to be moved and fastened at a plurality of locations along a substantial portion of the length of said fluted portion of said drill; and said cutting insert and said flat bearing face being configured to permit substantial relative movement of said cutting insert along the length of said flat bearing face and to permit substantial relative movement between said clamping ring and said drill essentially without twisting or rotating said clamping ring on said drill.