The main features of group drilling are:
①The chisel edge is shortened and the rake angle is increased, which significantly reduces the adverse effect of the chisel edge. The axial force of the lathe can be reduced by 35% to 50%, thereby improving the cutting conditions, increasing the drawing amount and cutting speed, and improving the drilling efficiency.
②The cutting edge becomes sharp and the chip deformation is small, thus reducing the cutting heat, and the life of the drill can be increased by 3 to 5 times.
③The circular arc edge of the lathe cuts a convex ring on the cutting surface of the workpiece, which plays the role of centering, and the drill is not easy to yaw, which increases the stability of drilling, thereby improving the surface quality and machining accuracy of the hole.
@Chip divider acts as a chip divider. Conducive to chip removal and injection of cutting fluid.
Drilling operation
(1) Steps and methods of drilling operation 1) Clamp the straight shank or tapered shank of the twist drill in the drill chuck, special fixture or taper hole of the tailstock respectively, and adjust the relative position of the axis of the drill bit so that the center of the drill bit is aligned with the workpiece. The centers of rotation coincide.
2) According to the workpiece material and inner diameter, select a reasonable spindle speed.
3) Flatten the end face first. If necessary, it can be turned into a pit at the center of the end face, or centering with a center drill first, and then drilled with a twist drill, so that the inner hole of the lathe can obtain better coaxiality.
4) When the lathe is drilling small and deep inner holes, in order to prevent the drill from swinging, a copper rod or a hardwood rod can be clamped on the tool holder as a support, and lightly resist the cutting edge of the drill to make it align with the workpiece. Rotate the center, and try to feed the twist drill while the slide plate adjusts the support while moving. After the drill is centered, the support is withdrawn, as shown in Figure 6-25.
5) When drilling deep inner holes, if the chips cannot be discharged smoothly, the drill should be withdrawn frequently, and then continue to advance after removing the chips.
6) When the hole is about to be drilled, the axial resistance is reduced because the chisel edge is no longer involved in cutting. At this time, the feed amount should be reduced, and the tailstock handwheel should be held tightly to prevent the main cutting edge of the drill from protruding and being removed. Through the inner hole "bite"
7) In order to dissipate heat and cool the drill bit and reduce the friction between the drill bit and the workpiece and chips, sufficient cutting fluid should be added when drilling plastic materials.