A diamond coated
drill capable of drilling holes in
fiber reinforced composite materials. The
drill is made from a
tungsten carbide (WC) substrate with cemented
cobalt (Co) in a range between about 3 to 10 wt. % and
a diamond coating having a thickness in a range between 3 to 20 microns. The
drill includes a shank, a longitudinal axis and includes two flutes at a
helix angle that is in a range between 25 and 35 degrees with respect to the axis. A margin width is maintained between about 5 to 10 percent of the drill
diameter. A body clearance
diameter is maintained at between about 92 to 96 percent of the drill
diameter. A web thickness before splitting is about 20 to 30 percent of the drill diameter. A clearance angle or lip relief angle is between about 10 and 20 degrees. A
chisel edge angle is between about 105 and 120 degrees. A
chisel edge length is up to about 0.035 mm. A splitting angle is between about 130 and 150 degrees. A notch angle is between about 30 and 40 degrees with respect to the drill axis. A notch
rake angle lies between about −5 and 10 degrees. A
split point angle is between about 70 and 100 degrees, and preferably about 90 degrees.