Twist drill

Abstract

The invention discloses a twist drill which comprises a cutting portion and a handle. The cutting portion comprises a drill tip and a spiral cutting edge, the spiral cutting edge comprises a first cutting edge and a second cutting edge, the first cutting edge comprises a first column edge and a first edge section, the second cutting edge comprises a fourth column edge, a third column edge and a second edge section, the second edge section is arranged between the fourth column edge and the third column edge, a first chip pocket is formed between the first column edge and the fourth column edge,a second chip pocket is formed between the first edge section and the third column edge, the intersection point of the central axis of the cutting portion and an optional plane which is perpendicularto the central axis of the cutting portion and intersects with the spiral cutting edge is denoted as O, the intersection point of the first column edge and the first chip pocket in the plane is denoted as A, the intersection point of the fourth column edge and the first chip pocket in the plane is denoted as D, the intersection point of the third column blade and the second chip pocket in the plane is denoted as C, the distances between the intersection points A, D, C and O are equal to one another, an angle AOC is denoted as beta, and the beta is larger than 150 degrees and is smaller than 180 degrees. The twist drill has the advantages that the twist drill can be automatically balanced, and holes machined by the aid of the twist drill are free of deviation.

Description

technical field [0001] The invention relates to a metal cutting tool, in particular to a twist drill. Background technique [0002] The known twist drill adopts a symmetrical design, and theoretically, its radial cutting force is balanced. However, in actual production, due to various reasons, such as the manufacturing error of the twist drill, the inhomogeneity of the workpiece material, the vibration of the machine tool, etc., there will be a random additional cutting force F' during the drilling process of the twist drill, so that As a result, the force of the twist drill is unbalanced, the drilled hole diameter is too large, and the hole wall is rough. [0003] In order to enhance the stability of drilling, double-margin or even multi-margin twist drills are often used. In the patent document 88205377.9, a four-margin twist drill is disclosed, which has four margin guides; in the patent document CN102389991A, a double-margin twist drill is disclosed, which also has fou...

AI Technical Summary

Problems solved by technology

At present, all multi-margin twist drills have a common problem. Theoretically, the four guide edges have the same diameter, that is, the four points are concentric. However, deviations are inevitable in the twist drill manufacturing process, and the four margins are not strictly concentric , and, as the main cutting edges, the two front guide edges are always in contact with the hole wall; while the two rear guide edges are constantly in contact with and separated from the hole wall. Prismatic

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