OM154-26-3/16'' Piloted Microstop Countersink Cutter 7/16'' x 100 x 3/16'' | EUMRO Aircraft Tools
3" Extended Microstop Countersink, Depth Stop Accurate to 0.001", for deburring and Countersinking Holes in Aircraft and Automotive Applications. - Amazon.com
Micro Stop Countersink Cutters set of 3 #21,30,40 HSS 1/2" Body Dia 100 degree | eBay