| 摘要 |
<p>The present invention concerns a drill, in particular a deep hole drill, comprising a shaft (1) and a portion (2) which has flutes (6) and the length of which is more than three times the nominal diameter (D) and the front end of which is formed by a drill tip which is defined by main cutting edges (5) arranged in frontal relationship at the front end of the drill. In order to provide a drill having the above-mentioned features, which is capable in continuous operation of producing very deep drilled holes of more than 10 times to more than 20 times the nominal diameter and which in that respect is particularly economical in operation, it is proposed in accordance with the invention that the drill tip (3) and at least the region of the flutes (6) that adjoins the drill tip is coated with a hard material as far as a distance T from the tip of the drill, which at a maximum is three times the nominal diameter (D) while at least the flutes (6) are uncoated in the region which is spaced from the tip further than T, and wherein the drill core (4) in a region in the proximity of the drill tip is of a maximum diameter (K) which corresponds to at least 30%-55% of the nominal diameter, which narrows towards a region of the flute portion (2), that is closer towards the shaft (1), to a minimum diameter (k) of at most 20% to 50% of the nominal diameter, wherein the difference in the maximum core diameter (K) in the region of the tip in relation to the minimum core diameter (k) in the region closer towards the shaft (1) is at least 5% of the nominal diameter.</p> |
