Observe or visualize the condition of the drill when drilling:

When the chips flow out of the spiral groove, the face in the spiral groove of the drill that is in contact with the chips is called the front of the drill.

2. The face that faces the bottom of the hole is called the back of the bit.

3. It is assumed that there is a face perpendicular to the bottom face of the hole, called the base face.

4. A double-edged drill has two fronts, two backs and two base faces.

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

6. The angle between the front of the drill bit and the base face is called the front angle.

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

8. The front angle of a drill is determined after the drill is made and is usually not sharpened.

9. The back angle of a drill is sharpened when the drill is sharpened.

10. The values of the leading and trailing angles of the same drill at different diameters vary due to differences in manufacturing and sharpening methods. The front angle at the tip of the blade is generally negative.

12. open Ding move scraping calcium planting state water Bao shock in order to facilitate the understanding of some of the above ideas in the name, definition, not according to the theory of the book. After understanding, please consult the relevant information to avoid misunderstanding.