I. Flat grinding wheel one.

Second, from the edge to the back of the grinding, to prevent the drill bit annealing, gradually depress the end of the drill, a rotary maneuver.

Three, the rear angle should not be too large

Four, the top angle of the drill 118 degrees, the two edges should be symmetrical.

No diagram, it is not good to say clearly, the rear angle is too large, the cross edge of the drill bit is certainly long, not conducive to cutting. And with a long cross blade, it must not look good when compared to a new drill. Without the back angle you can't drill in. The level of drill grinding is mainly reflected in the back angle.

There are many other ways to improve the standard twist drill, such as "Ni Zhifu drill".

Drills with a diameter of more than 5-6 millimeters can be ground by hand and are still relatively easy to master. If the drill is too small, you can only use a tool grinder to grind the drill, 0.2 millimeters of the drill, generally can not be seen, the hand can not be ground, can only be the use of tool grinder.