Abstract: A kind of sawtooth structure with reversed cutting function and its drill series are presented in this invention. This invention is suitable for drilling low-damage holes on carbon fiber reinforced polymers (CFRP). The sawtooth structure is comprised of sawteeth and grooves located on the cutting edges of drill. And the sawtooth structure is helically arranged with a specific helix angle around the axis of the drill. It can be classified as the left-hand helix sawtooth structure and the right-hand helix sawtooth structure based on the helix angle value. The bottom edges of the left-hand helix sawtooth structure are the cutting edges, and the rake angles are positive; while the top edges of the right-hand helix sawtooth are the cutting edge with the positive rake angles. The sawtooth structure can be applied to various drilling tools, which proves to be universal. And it can effectively reduce delamination at both hole entrance and hole exit as well as burrs defects.

Abstract: A kind of sawtooth structure with reversed cutting function and its drill series are specifically fitted for drilling carbon fiber reinforced polymers (CFRP). The sawtooth structure is constructed by sawteeth and grooves located on the cutting edges of drill. And the sawtooth structure is helically arranged with a large helix angle around the axis of the drill. It can be divided into left-hand sawtooth structure and right-hand sawtooth structure by the helix angle. The bottom edges of the left-hand sawtooth function as cutting edges, and the rake angles are positive, while the top edges of the right-hand sawtooth are ground as positive rake angles. The sawtooth structure can be applied into multiple drilling tools, which proves to be universal. And it can effectively reduce delamination at both hole entry and hole exit as well as burrs defects. The series of drilling tools are double point angle drill, twist drill and stepped drill with sawtooth structure on the cutting edges.