When the chips flow out of the spiral groove, the surface in the spiral groove of the drill bit that contacts with the chips is called the front end of the drill bit.

2. The surface facing the bottom of the hole is called the back of the drill bit.

3. Suppose there is a plane perpendicular to the bottom of the hole, which is called the base plane.

4. The double-edged drill has two front faces, two rear faces and two bottom faces.

5. The included angle between the back of the drill bit and the bottom of the hole is called the relief angle.

6. The included angle between the front end of the drill bit and the base surface is called rake angle.

7. A double-edged drill has two sharp corners and two back corners.

8. The rake angle of the drill bit has been determined after the drill bit is made, and it is generally not ground.

9. When the drill bit is sharpened, the back corner of the drill bit is sharpened.

10. Due to the different manufacturing and grinding methods, the rake angle and rake angle of the same bit with different diameters are different. The rake angle of the blade tip is usually negative.

12. Boil and move to scrape the seeds of calcium-added abalone. In order to facilitate understanding, some names and definitions in the above viewpoints are not described according to the theory in this book. Please refer to the relevant materials to avoid misunderstanding.