Patent application number | Description | Published |
20100232899 | Drill - A drill includes a pair of main cutting edges extending from a distal portion of the drill to a position close to a proximal end of the drill to entirely define a two-edge configuration, and a pair of auxiliary cutting edges extending between positions at the distal and proximal sides of a maximum diameter position to partly define a four-edge configuration. A ridgeline of each auxiliary cutting edge is located within an angle smaller than 90° from a ridgeline of the corresponding main cutting edge toward the rear in a rotation direction of the drill. The point angle of the auxiliary cutting edges increases at a higher rate than the point angle of the main cutting edges in a predetermined range from the maximum diameter position toward a distal end of the drill. | 09-16-2010 |
20120251253 | CUTTING TOOL - Disclosed is a cutting tool, including: a cutting edge including a coating from a rake face to a flank face, and has a relief angle of not less than 15 degrees, a material of the coating having a higher wear resistance than a base material of the cutting edge, and during cutting of a work, an edge of the coating on the rake face at a top of the cutting edge is worn by friction with the work; with a progress of a wear inward in a radial direction, an edge of the coating on the flank face at the top of the cutting edge is removed by friction with the work to expose the base material thereunder; and the exposed base material is worn by friction with the work to retract the flank face inward in the radial direction. | 10-04-2012 |
20120321403 | DRILL BIT - Provided is a step-shaped drill bit including at least two stepped cutting edges that are axially provided. A cutting edge of a first step from a tip is formed so as to satisfy at least one of the following conditions. That is, a number of blades is smaller, a point angle of the cutting edge is larger, or a clearance angle of the cutting edge is larger than that of cutting edges of a second and subsequent step(s). As a result, a thrust resistance during a perforation can be reduced compared with a case in which the first step cutting edge is formed such that the number of blades, the point angle of the cutting edge and the clearance angle of the cutting edge are the same as those of the second and subsequent step(s). | 12-20-2012 |