Joo Baik Kim

US Patent:

42092752, Jun 24, 1980

Filed:

Oct 30, 1978

Appl. No.:

5/955650

Inventors:

Joo B. Kim - Pasco WA

International Classification:

B23B 5102

US Classification:

408211

Abstract:

A twist drill for producing or enlarging holes in a metal workpiece includes a point with peripheral cutting shoulders and concave cutting lips leading inwardly from the shoulders to a central chisel point. The cutting shoulders are spaced slightly toward the shank end of the drill from the chisel point along the axis of the drill. The cutting lips are longitudinally convex so that points along the bases thereof will be spaced axially toward the drill shank from the cutting shoulders. The concave configuration along with the smooth curvature of the cutting lips facilitates quick removal of metal while causing minimal wear along the actual cutting surfaces. Chips are directed inwardly from the cutting shoulders and outwardly from the chisel point. The oppositely flowing chips converge within the drill flutes and are carried outward of the hole along the drill axis.