Twist bit is the most commonly used cutting tool, twist bit to sharpen sharp, should pay attention to some points:
Twist bit for mechanical processing, it is a commonly used drilling tools. Although the structure is simple, it is not an easy thing to really sharpen it. The key is to master the method and skill of grinding, the method is mastered, the problem will be solved. Here I introduce the twist drill manual grinding skills.
Twist drill vertex Angle is 118° commonly, also can regard it as 120°. Grinding drill mainly master several skills:
1. The cutting edge should be leveled with the grinding wheel surface.
Before grinding the bit, place the main cutting edge of the bit on a horizontal plane with the grinding wheel surface, that is, ensure that the edge touches the grinding wheel surface and the whole edge is ground. This is the first step of the relative position between the drill bit and the grinding wheel.
2, the drill axis and grinding wheel surface oblique Angle of 60°.
This Angle is the edge Angle of the bit, and the wrong Angle will directly affect the size of the tip Angle of the bit and the shape of the main cutting edge and the bevel Angle of the cross edge. Here refers to the position relationship between the axis line of the drill bit and the grinding wheel surface, 60° is ok, this Angle is generally more accurate to see. Here, attention should be paid to the relative horizontal position and Angle position of the bit before grinding. Both should be taken into consideration. Do not ignore the alignment Angle in order to balance the edge, or ignore the alignment edge in order to balance the Angle.
3, from the edge of the back grinding behind.
After the cutting edge touches the grinding wheel, grind it backward from the main cutting edge, that is, from the cutting edge of the bit to touch the grinding wheel first, and then grind slowly down along the whole rear cutting surface. When the drill bit cuts in, it can gently contact the grinding wheel, and grind a small amount of grinding first, and pay attention to observe the uniformity of the spark, adjust the pressure on the hand in time, and pay attention to the cooling of the drill bit, so as not to overgrind, cause the edge to change color, and to the edge to annealing. When the temperature of the cutting edge is high, the bit should be cooled in time.
4. The edge of the drill bit should swing up and down, and the tail of the drill bit should not be warped.
This is a standard bit grinding action in which the main cutting edge swings up and down on the grinding wheel, i.e. the hand holding the front of the bit swings the bit evenly up and down on the grinding surface. The hand holding the handle can not swing, but also to prevent the rear handle to tilt up, that is, the tail of the drill can not tilt above the horizontal center line of the grinding wheel, otherwise it will make the edge blunt, unable to cut. This is the most critical step, drill grinding good and bad, and this has a great relationship. When it is almost finished, start with the edge and gently rub the back corner of the blade to make the back of the blade smoother.
5. Ensure that the blade tip is opposite to the axis, and repair symmetrically on both sides slowly.
After grinding one edge of the bit, grind the other edge again. It must be ensured that the edge is in the middle of the axis of the bit, and the edges on both sides should be symmetrical. Experienced master can inspect the symmetry of drill tip to light, undertake slowly repair grind. The rear Angle of the cutting edge of the drill bit is generally 10°-14°, the rear Angle is large, the cutting edge is too thin, the vibration is severe when drilling, the orifice is trilateral or pentagonal, the chip is needle-like; After the Angle is small, the axial force when drilling is very large, it is not easy to cut, the cutting force increases, the temperature rises, the bit heating is serious, and even can not be drilled. After the Angle grinding is suitable, the tip is in the center, the two edges are symmetrical, when drilling, the drill chip discharge is light, no vibration, the aperture will not expand.
6, after the two-edge grinding, the diameter of the larger bit also pay attention to grinding the bit tip.
After grinding the two edges of the bit, there will be a plane at the tip of the two edges, which will affect the center positioning of the bit. It is necessary to reverse the Angle behind the edge to make the plane of the tip of the edge as small as possible. The method is to erect the drill bit, align it with the Angle of the grinding wheel, and pour a small groove on the root behind the edge, facing the edge tip. This is also an important point for the bit to be centered and cutting briskly. Note that when trimming edge chamfering, do not grind to the main cutting edge, which will make the main cutting edge of the front Angle is too large, directly affect the drilling.
Of course, there is no definite formula for grinding drill bits. It is necessary to accumulate experience in practical operation. Through comparison, observation and repeated experiments, the drill bit will be ground better.