Development of high-efficiency new drill type special sharpening machine (2)

The new drill type has the following main advantages: 1) The chip is divided into three or five segments in the width direction of the main cutting edge, and the cutting speed difference between the outer end and the inner end of each cutting edge is significantly reduced, reducing the cutting torque and reducing the bit. Wear and chip additional deformation; 2) The chip is thick and narrow at the outer edge, and the chip is easy to remove. After the arc blade is shortened, the amount of curled chips is reduced, which reduces the risk of chip clogging, so the chip removal The situation is better than the standard group drill; 3) If the cutting edge on both sides has a slight height error during the sharpening, it will not cause the change of the cutting load on both sides and affect the change of the radial force, but only the radial force at the moment of drilling, and The radial force is balanced during the drilling process, which is unmatched by other drill bits; 4) the sharpening is convenient.

2. Sharpening of the new drill bit

This type of drill requires grinding of the cutting edge, the arc edge, the chisel edge and the flank face. To complete the grinding of a drill bit, the height of the center of the grinding wheel must be three heights relative to the center height of the drill bit to ensure a certain back angle. When sharpening, the spiral flank of the drill bit is simplified into a plane, which is convenient for sharpening. The adjustment principle during the grinding process is shown in Fig. 2.

For the knife, the cutting edge is leveled, and the outer edge and the arc edge are ground. Adjust the height of the grinding wheel to ensure that the first back angle b1=12°, a1=b1, then the center of the grinding wheel is higher than the center of the bit H1H1=Rsina1(1)

R is the radius of the grinding wheel, and then the side of the blade is shaped by the feed in the X and Y directions, and then the drill bit is rotated by 180° in a straight line, and then the other side is sharpened.

The secondary flank is ground to ensure that the second relief angle b2 is 20°. This is to reduce the flank and avoid the flank involved in cutting while drilling, while ensuring the strength of the drill. A2=b2=20°, the grinding wheel needs to be raised H2H2=Rsin20°+B-H1(2)

B is the width of the first flank after grinding, which is about 3 mm.

Grind the chisel edge and raise the grinding wheel again so that a3 is equal to 55°, then the grinding wheel needs to be raised again H3H3=Rsin55°-H2-H1(3)

Under the condition of ensuring the strength of the chisel edge, it is beneficial to reduce the axial force by increasing the rake angle of the inner blade as much as possible. Taking 55° a3 is a comprehensive consideration of these two aspects.

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