Patent ID: 9687998
Date: 2017-06-27
CPC Classifications: B23B,B27G,Y10T

Claim:
1. A flat drill comprising: a handle part, and a flat blade part which is formed in a front part of the handle part, the front part of the flat blade part extending inward respectively from two side parts, forming two shoulders: a first shoulder and a second shoulder; the two shoulders continuing to extend in a direction away from the handle part and taper inward, forming two tapered parts respectively: a first tapered part and a second tapered part, and forming one pointed top at a top part; a first groove being formed on a blade part of the first shoulder toward an inside of the flat blade part, and an inner edge of the first groove inclining downward toward the side part of the blade part near the first shoulder, forming an angle of greater than 0 degree with respect to a horizontal line of the flat drill; a second groove is formed on a blade part of the first tapered part toward the inside of the flat blade part; wherein, a depth of the first groove is deeper than that of the second groove; the first groove is a smooth concave surface; the smooth concave surface of the first groove comprises a first camber surface starting from the blade part of the shoulder, and a second camber surface to the inner side part of the first groove, further comprises a third flat surface connecting the first camber surface and the second camber surface; the second groove is an arc surface starting from the blade part of the first tapered part and a surface between the arc surface and the inner part of the second groove.