The twist drill is a commonly used drilling tool with a simple structure. Sharpening the drill bit is very important for the processing of the workpiece, but it is not an easy task to actually sharpen it well. The key is to master the sharpening methods and techniques. Once you master the methods, coupled with the experience of multiple sharpenings, you can have a good grasp of the sharpening scale of the drill bit.

The vertex angle of twist diamonds is generally 118°, but it can also be treated as 120°. If you master the following 6 skills when sharpening drill bits, there will generally be no problems.

1. Before grinding the drill bit, first place the main cutting edge of the drill bit and the grinding wheel surface on a horizontal plane. In other words, ensure that when the cutting edge contacts the grinding wheel surface, the entire edge must be ground. This is the first step in determining the relative position of the drill bit and the grinding wheel. Once the position is set, slowly move it toward the grinding wheel surface.

2. This angle is the sharp angle of the drill bit. If the angle is wrong at this time, it will directly affect the size of the drill tip angle, the shape of the main cutting edge and the chisel edge bevel angle. This refers to the positional relationship between the axis of the drill bit and the surface of the grinding wheel. Just take 60°. This angle is generally more accurate. Here we should pay attention to the relative horizontal position and angular position of the drill bit before sharpening. Both should be taken into consideration. Do not neglect to set the angle in order to set the cutting edge, or neglect to set the cutting edge in order to set the angle.

3. After the cutting edge contacts the grinding wheel, it should be ground from the main cutting edge back, that is, the cutting edge of the drill bit first contacts the grinding wheel, and then slowly grinds downward along the entire flank surface. When cutting the drill bit, you can lightly touch the grinding wheel, perform a small amount of sharpening first, and pay attention to the uniformity of the sparks, adjust the pressure on your hands in time, and pay attention to the cooling of the drill bit, so as not to over-sharpen it, causing discoloration of the edge. , and then the edge is annealed. When the cutting edge temperature is found to be high, the drill bit must be cooled down in time.

4. This is a standard drill grinding action. The main cutting edge must swing up and down on the grinding wheel. That is, the hand holding the front of the drill bit must evenly swing the drill bit up and down on the grinding wheel surface. However, the hand holding the handle cannot swing, and the back handle must be prevented from tilting upward, that is, 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. This is the most critical step. Whether the drill bit is worn well or not has a lot to do with it. When it is almost polished, start from the edge of the blade and rub it gently toward the back corner to make the back of the blade smoother.

5. After grinding one edge, grind the other edge. Make sure that the edge is in the middle of the drill axis, and the edges on both sides must be symmetrical. An experienced master will look at the symmetry of the drill tip against a bright light and slowly polish it. The relief angle of the drill cutting edge is generally 10°-14°. If the relief angle is large, the cutting edge will be too thin, and the vibration will be severe during drilling. The hole will be triangular or pentagonal, and the chips will be needle-shaped; if the relief angle is small, the cutting edge will be too thin. When drilling, the axial force is very large, making it difficult to cut in. The cutting force increases, the temperature rises greatly, the drill head heats up seriously, and even drilling becomes impossible. The back angle is suitable for grinding, the sharp tip is centered, and the two edges are symmetrical. When drilling, the drill bit can remove chips quickly and without vibration, and the hole diameter will not expand.

6. After the two edges are sharpened, pay attention to sharpening the tip of the drill bit with a larger diameter.

After the two edges of the drill bit are sharpened, there will be a flat surface at the tips of the two edges, which affects the center positioning of the drill bit. It is necessary to chamfer the angle behind the edge and grind the flat surface of the edge as small as possible. The method is to stand the drill bit up, align it with the corner of the grinding wheel, and make a small groove at the root behind the blade toward the tip of the blade. This is also an important point for drill bit centering and light cutting. Note that when grinding the edge chamfer, it must not be ground onto the main cutting edge. This will make the rake angle of the main cutting edge larger and directly affect drilling.

There is no certain formula for sharpening drill bits. It requires accumulation of experience in actual operation, comparison, observation, repeated trials and groping, and a certain amount of human intuition to sharpen drill bits better.