Hole exit damage and tool wear during the drilling of CFRP with a double-point angle drill

The control of hole exit damage and hole wall quality poses a considerable challenge during the drilling of carbon fiber-reinforced plastic (CFRP). This study aims to study the effect of the cutting edge type on the aforementioned issues. First, a comparative study between hole exit damage caused by a twist drill and a double-point angle drill was conducted to investigate the influences of the chisel, principal, and secondary cutting edges on hole exit damage. The maximum damage ring caused by the double-point angle drill is smaller than that caused by the twist drill because the drop speed of the cutting force in the secondary cutting edge drill during the exit stage of the double-point angle drill is less than that of the twist drill. Then, the double-point angle drill was used to determine the effects of tool wear on thrust force and hole wall damage. Outer corner wear and flank wear were investigated, and hole wall damage mechanisms were discussed. The damage of missing fibers does not worsen with an increase in tool wear, but the damage of fiber pullout becomes more serious due to increased cutting force. Consequently, a double-point angle drill bit is preferable for drilling holes on CFRP.