Pithy formula 2: “drill the shaft obliquely to release the sharp angle.” This refers to the positional relationship between the axis line of the drill bit and the surface of the grinding wheel. “Sharp angle” is half of the top angle 118 ° ± 2O, which is about 60 °. This position is very important and directly affects the top angle of the drill bit, the shape of the main cutting edge and the inclined angle of the transverse edge. Students should be prompted to remember the angle of 60 ° in a commonly used 30 °, 60 ° and 90 ° triangular plate, which is easy for students to master. Pithy formula 1 and pithy formula 2 refer to the relative position of the drill bit before grinding. Both should be considered comprehensively. Do not neglect to set the bevel angle in order to set the edge, or ignore to set the inclined axis. These mistakes are often made in practice. At this time, the drill bit is ready to contact the grinding wheel when the position is correct.
Pithy formula 3: “grind the back from the blade.” This refers to grinding slowly along the whole flank from the edge of the drill bit. This facilitates heat dissipation and grinding. On the basis of stabilizing and consolidating Formula 1 and formula 2, at this time, the drill bit can gently contact the grinding wheel for a small amount of grinding. During grinding, observe the uniformity of sparks, adjust the pressure in time, and pay attention to the cooling of the drill bit. When the grinding is restarted after cooling, it is necessary to continue to set the position of formula one and formula two, which is often difficult to master at the beginning of learning, and often involuntarily change the correctness of its position.
Pithy formula 4: “swing up and down, don’t tilt your tail.” This action is also very important in the process of bit grinding. Some students often turn “up and down swing” into “up and down rotation” during grinding, so that the other main blade of the bit is damaged. At the same time, the tail of the drill bit shall not be higher than the horizontal centerline of the grinding wheel, otherwise the cutting edge will be blunt and cannot be cut.
( The former information please refer to passage Analysis of Twist Drill’s Knowledge and Methods Ⅰ)
Post time: Feb-20-2022