US Patent 9468981 Micro-drill and method for manufacturing the micro-drill

A micro-drill includes a first rake face, a first rear face, a second rake face, a second rear face, a first spiral groove extending from a drill point to a tail of the drill, a second spiral groove symmetrically arranged about the first spiral groove, and a biasing groove arranged in front of the drill point. Where the first rake face, the first rear face, the second rake face, and the second rear face are arranged on the drill point. The first spiral groove and the first rake face intersect to form a first cutting edge, and the second spiral groove and the second rake face intersect to form a second cutting edge. The biasing groove and the second rake face intersect to make a length of the second cutting edge be less than a length of the first cutting edge, and the biasing groove and the second spiral groove intersect each other.