Method Step 1: First remove the drill bit from the drill chuck, and don't grind the drill bit with a pistol drill. Hold the top of the drill bit with the right hand and the tail of the drill bit with the left hand. Let the upper edge of the drill be parallel to the grinding wheel of the grinder, and then grind it against the grinding wheel. When grinding, keep the drilling position with your right hand, hold the drill tail with your left hand and move it up and down slightly. Grind one knife edge and then rotate 18 degrees to grind the other knife edge.

The second step of the method: hand grinding the drill depends entirely on practice, and you will gradually understand it in practice. Prepare a small pot of water and don't grind it too hard. If it is hot, it will invade the water to cool down. Grind from the back of the drill bit (the cutting part of the drill bit is divided into transverse edge, main cutting edge, auxiliary cutting edge, rake face and flank face) to the main cutting edge gradually.

Pay attention to the observation that the cross blade should not be too long, otherwise the axial force will increase. The two main cutting edges should be symmetrical and equal in length. Otherwise, the aperture becomes larger. The included angle between the two main blades is greater than or less than 1 18 degrees (tool tip angle). The cutting edge is not a straight line but an arc. The sharpening of self-centering drill is best to use tool grinding, such as hand grinding, which is very difficult.

Now the grinding wheel will cut off the edges and corners, and the two sides of the horizontal edge of the drill will be ground into cutting edges, and the cutting edges will be close to the middle and intersect at one point. You will master a lot if you practice slowly, and you can change the tool angle appropriately according to different processing materials.