Tip 1: "The blade is leveled by the wheel surface." This is the first step in the relative position of the drill bit and the grinding wheel. Often students start sharpening by leaning on the grinding wheel before the cutting edge is leveled. This is definitely not good for grinding. The "edge" here is the main cutting edge, and "leveling" means that the main cutting edge of the sharpened part is in a horizontal position. "Wheel face" refers to the surface of the grinding wheel. "Lean" means to move closer slowly. The drill bit cannot yet contact the grinding wheel at this time.

Tip 2: "The drill shaft is tilted to release the sharp angle." This refers to the positional relationship between the drill bit axis line and the grinding wheel surface. The "sharp angle" is half of the top angle of 118°±2?0?2, which is about 60°. This position is very important and directly affects the size of the drill's top angle, the shape of the main cutting edge and the chisel edge bevel angle. Students should be prompted to memorize the 60° angle in a commonly used 30°, 60°, and 90° triangle, so that students can easily master it. Tips 1 and 2 both refer to the relative position of the drill bit before sharpening. Both should be taken into consideration. Do not neglect to set the bevel angle in order to set the cutting edge, or neglect to set the cutting edge in order to set the bevel axis. These errors often occur in actual operations. At this point the drill bit is in the correct position and ready to contact the grinding wheel.

Tip 3: "Grind the back from the edge to the back." This means slowly sharpening from the edge of the drill bit along the entire flank surface. This facilitates heat dissipation and sharpening. On the basis of stabilizing and consolidating formulas 1 and 2, at this time, the drill bit can lightly contact the grinding wheel and perform a smaller amount of sharpening. During sharpening, the uniformity of sparks must be observed, the pressure must be adjusted in time, and the cooling of the drill bit must be paid attention to. When you restart sharpening after cooling, you must continue to place the positions of formulas 1 and 2. This is often not easy to grasp when you first learn, and you will often change the correctness of its position involuntarily.

Tip 4: "Swing the tail up and down and don't tilt the tail." This action is also very important in the process of sharpening the drill. Students often change "swinging up and down" into "turning up and down" during sharpening. The other main cutting edge of the drill bit is destroyed. At the same time, the tail of the drill bit cannot be raised above the horizontal center line of the grinding wheel, otherwise the cutting edge will be blunted and cutting will be impossible.

Based on the basic grasp of the essentials of the movements in the above four sentences, students should be reminded in time to pay full attention to the back angle of the drill bit and not to grind it too large or too small. You can use a drill bit with too large a relief angle and another drill bit with too small a relief angle for students to test drill on the bench drill. Students will find that when drilling with a drill bit with too large a relief angle, the hole opening will be three-sided or pentagonal, vibrate violently, and the chips will be needle-shaped; while a drill bit with an excessively small relief angle will have a large axial force during drilling, making it difficult to cut in. , the drill is too hot and cannot drill. Through comparison, observation, repeated "grind less and see more" test drilling and appropriate grinding of the chisel edge, students can quickly master the correct sharpening method of twist drills and better control the size of the corner. When test drilling, if the drill bit removes chips quickly, without vibration, and the hole diameter does not expand, it can be better transferred to the sharpening practice of other types of drill bits.