| 摘要 |
PROBLEM TO BE SOLVED: To solve the problem that a conventional throwaway type drill may decrease drill durability under a resultant force of a cutting load generated by an inner cutting blade with a cutting load generated by an outer cutting blade.SOLUTION: A throwaway type drill based on one aspect has a rod-like body part extending along the rotation center shaft, a first cutting insert having an inner cutting blade, and first and second land faces positioned between first and second chip discharge grooves, where the width of the first land face at a rear end part is larger than that of the second land face at a rear end part with the rear end part of the first land face positioned at an extension of a virtual straight line extending from the rotation center shaft toward the outer peripheral side end part of the inner cutting blade when the body part is viewed through from the tip.SELECTED DRAWING: Figure 1 |
