To provide a multi-stage drill which can efficiently form two or more through holes having different diameters or a through hole with a large diameter in lumber to be processed on a processing line by simple control without replacing a drill or installing an excess boring machine.
The multi-stage drill 10 fitted to a boring machine 12 for forming the through holes in the lumber 11 on the processing line includes at least two drill parts 17a, 17b, and 17c different in cutting diameter each having a length greater than the thickness t of the lumber 11. An axial center C is made coincide with the rear of the tip drill part 17a with the minimum cutting diameter, and the first rear drill part 17b and the second rear drill part 17c are joined/integrated to increase the cutting diameters stepwise.
| JPH07244 | [Name of device] Drill for cutting logs |
| WO/1996/036451 | CARBIDE SPADE-TYPE DRILL BIT |
Shuichi Maeda
Akihisa Iwamoto
Yoshiyuki Matsushima
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