The two edges of the two blades will have a plane at the edge of the blade, which will affect…
The drill is used for cutting its head, and its cutting edge and the transverse blade act as the cutting tools. In order to make the tapered surface of the cutting part not touching the workpiece, the value of the rear angle and back angle should be selected according to the material of the workpiece.
1, horizontal blade
The sharpness of the cross edge is very poor. A large diameter drill bit made relatively coarse, chisel edge is big, in addition, the chisel edge grinding to drill in heavy grinding, the horizontal edge will become big. In order to increase sharpness, or restore the same sharpness at the beginning of grinding, it is necessary to perform horizontal grinding.
2, the blade is oriented in the machined hole wall, so that the machining can be carried out correctly. However, if the friction between the hole and the wall is large, the drill will overheat and the power consumption will be too large. So, usually from the head of the drill to the handle with a very small taper, called it the inverted cone, about every 100 millimeters for 0.04 to 0.1 mm or so.
3, spiral groove
It is set to discharge the chip, and its size shall discharge the chip smoothly and shall have a screw angle. The spiral angle of the groove varies with the material of the workpiece. For hard materials, the angle should be small, and the angle of the soft material should be large. An ordinary drill for iron and steel with a helix angle of about 30 degrees.
4, the vertex angle of the drill
Although the cutting edge is longer, the required power is increased, the front angle of the cutting edge is reduced, and the service life is shortened. Therefore, the tip bit is used in the drilling of soft material. Usually on the general steel material, the vertex angle of about 120 degrees.