| 摘要 |
PURPOSE:To smoothly discharge chips and execute excellent boring by providing the plural number of chip discharge grooves along the periphery on the bottom of a surrounding wall of a cylindrical body provided for boring action of a core drill by which a hole of a large diameter is drilled in rigid metallic material. CONSTITUTION:The plural number of chip discharge grooves 5 are provided at intervals along a surrounding wall 1b on the bottom of a cylindrical body 1 of a core drill. Cutter pieces 7 of cutting body parts 6 are laid in the lowermost angular parts formed between discharge grooves 5 in such a manner as exterior cutting edges 7a and interior cutting edges 7b are arranged alternately. The exterior of the discharge groove of the interior cutting edges 7b is chamfered and the breadth of the chip is narrowed. Since each chip is discharged through an individual discharge groove, it is smoothly discharged without stagnating in a cutter piece area, and a good as well as deep hole can be bored. |
