drill

Abstract

When viewed along the central axis, the start phase of the first discharge groove is located in a range of +10° to +90° relative to the central blade, the end phase of the first discharge groove is located in a range of -40° to 0° relative to the central blade, the start phase of the second discharge groove is located in a range of +10° to +90° relative to the peripheral blade, and the end phase of the second discharge groove is located in a range of -40° to 0° relative to the peripheral blade. The first discharge groove has a first front groove portion and a first rear groove portion connected to the first front groove portion. The second discharge groove has a second front groove portion and a second rear groove portion connected to the second front groove portion. The twist angle of the first front groove portion monotonically decreases toward the first rear groove portion. The twist angle of the second front groove portion monotonically decreases toward the second rear groove portion. The twist angle of each of the first rear groove portion and the second rear groove portion is 0°.