Six skills of hand sharpening of drilling tool fri

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Six skills of hand sharpening of drilling tool fried dough twist drill

fried dough twist drill is a commonly used drilling tool. Although its structure is simple, it is not easy to sharpen it well. The key lies in mastering the grinding methods and skills. Once the methods are mastered, the problem will be solved. Here is an introduction to the manual sharpening skills for the fried dough twist drill when carrying out the tensile test according to astmd638 and iso527

the vertex angle of fried dough twist drill is generally 118 °, which can also be regarded as 120 °. There are several skills to master in sharpening drill bit:

1. The cutting edge should be leveled with the grinding wheel surface

before grinding the drill bit, first place the main cutting edge of the drill bit on a horizontal plane with the grinding wheel surface, that is, ensure that when the edge contacts the grinding wheel surface, the whole edge must be ground. This is the first step for the relative position of the drill bit and the grinding wheel. After the position is set, slowly lean against the grinding wheel surface

2. The axis of the drill bit shall be inclined at an angle of 60 ° with the grinding wheel surface

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 top angle of the drill bit, the shape of the main cutting edge and the oblique angle of the transverse edge. Here, it refers to the positional relationship between the drill bit axis and the grinding wheel surface. Take 60 ° as the position. This angle is generally accurate. Here, pay attention to the relative horizontal position and angular position of the drill before grinding. Both should be taken into account. Do not neglect to set the angle in order to set the edge, or ignore to set the edge in order to set the angle

3. Grind back from the edge

after the cutting edge contacts the grinding wheel, it is necessary to grind from the main cutting edge to the back surface, that is, first contact the grinding wheel from the cutting edge of the drill bit, and then slowly grind down along the whole back surface. When the drill bit cuts in, it can gently contact the grinding wheel, perform a small amount of grinding first, observe the uniformity of sparks, adjust the pressure on the hand in time, and pay attention to the cooling of the drill bit. It is not allowed to over grind it, causing the edge to change color, until the edge is annealed. When the cutting edge temperature is found to be high, the drill bit shall be cooled in time

4. The cutting edge of the drill shall swing up and down, and the tail of the drill shall not be warped

this is a standard drill bit grinding action. The main cutting edge should swing up and down on the grinding wheel, that is, the hand holding the front of the drill bit should swing the drill bit up and down evenly on the grinding wheel surface. However, the hand holding the handle shall not swing, and the back handle shall not be upturned, that is, the tail of the drill bit shall not be upturned above the horizontal center line of the grinding wheel, otherwise the cutting edge will be blunt and the sharp cooling and cutting will not be possible. This is the most critical step. The good or bad grinding of the drill has a lot to do with it. When the grinding is about the same, you should start from the edge of the blade and gently rub the back corner to make the back of the blade more smooth

5. Ensure that the blade tip is aligned with the axis, and the two sides are symmetrical and slowly repaired

after grinding one edge, grind the other edge. Make sure that the edge is in the middle of the drill axis and that the edges on both sides are symmetrical. An experienced master will observe the symmetry of the drill point against the light and grind it slowly. The back angle of the cutting edge of the bit is generally 10 ° -14 °. If the back angle is large, the cutting edge is too thin, and the vibration is severe during drilling. The orifice is trilateral or pentagonal, and the chips are needle shaped; When the back angle is small, the axial force is very large during drilling, so it is difficult to cut in. The cutting force increases, the temperature rises greatly, and the drill bit heats seriously, even unable to drill. The back angle grinding is suitable, the sharp point is centered, and the two edges are symmetrical. During drilling, the bit removes chips quickly, without vibration, and the hole diameter will not be expanded

6. After the two edges are grinded, the bit tip with larger diameter shall be grinded

after the two edges of the drill are grinded, there will be a plane at the sharp points of the two edges, which will affect the center positioning of the drill. It is necessary to turn an angle behind the edge and grind the plane of the tip as small as possible. The method is to erect the drill bit, align it with the angle of the grinding wheel, and remove the extensometer); At the root behind the blade, pour a small groove against the blade tip. This is also an important point for the centering of the drill bit and the lightness of cutting. Note that when grinding the chamfer of the edge tip, do not grind it onto the main cutting edge, which will make the rake angle of the main cutting edge too large and directly affect the drilling

of course, there is no definite formula for grinding the drill bit. It is necessary to accumulate experience in actual operation. Through comparison, observation and repeated tests, the drill bit will be grinded better


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