Drilling tool comprises web, ending in point, with standard part and widened part, near point, with first and second truncated portions

摘要

The tool comprises a web (12) ending in a point (14). The web has a standard part (20) of external diameter DD and a widened part (22) near the point. The widened part comprises a first truncated portion (26) whose top is directed towards the point and whose diameter increases from DD to a diameter D1 greater than DD and a second truncated portion (24) whose top is located in the direction opposite to the point and whose diameter decreases from D1 to DD. A first blade (28) has a first part surrounding the first truncated portion with an external diameter increasing from D2 greater than DD to D3 greater than D1. A second part around the second truncated portion has an external diameter which decreases from D3 to D4 and a third part surrounding the blade standard part has an external diameter equal to D4.