JPS597509A - Drill - Google Patents

Abstract

PURPOSE:To enable chips to smoothly pass through chip discharge flutes by a structure wherein the difference in cross-sectional area is provided between the part, where the chip is formed near a cutting edge, and the discharge flute. CONSTITUTION:The parts near the outer periphery of respective cutting edges are formed protruding beyond the extension line of chip discharge flutes to the inside of grooves. The chip 8 produced at the cutting edge 3 grows itself in the inner peripheral direction of the flute 10 in a fan shape and curls in a cone shape and is discharged along the longitudinal direction of the flute 10 in a transition fracture type chip. Because the cross-sectional area between the rake face 7 of the cutting edge 3 and the flute 10 opposing to the rake face 7 is smaller than that of the remaining part of the flute 10 during the chip producing process, the chip 8 is discharged without resistance in passing through the chip discharge flute 10.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a drill suitable for reducing cutting power, improving machined surface roughness, and drilling deep holes.

Recently, a new type of drill has been proposed in which the shape of the cutting edge of the drill has been changed to eliminate the chisel part, eliminate the unreasonable cutting process of the chisel part cutting edge, and increase the core thickness to improve cutting performance. However, even with this drill, due to the resistance when chips pass through the spiral or linear chip evacuation groove formed on the shank, the hole that can be drilled at its maximum capacity is approximately 6 times the drill diameter. was the limit.

This invention was made to solve these conventional drawbacks, and it creates a difference between the area near the cutting edge where chips can be formed and the cross-sectional area of the discharge groove, thereby making the chip discharge groove smoother.・It was designed so that it can be passed through. That is, in this invention, the vicinity of the outer periphery of each cutting edge is formed to protrude inward from the extension line of the chip discharge groove.

Embodiments of the present invention will be described below with reference to the drawings. 1st
In Figures 1 to 6, 1 is a drill shank, 2 is a tip, and the tip 2 is attached to the head of the shank 1 by brazing or other means. A cutting edge 6 is formed on each of the tips 2, and the cutting edge 6 has a curved line convex in the direction of rotation when viewed from the bottom, has a constant large curvature at the center, and has a straight line at the outer periphery. Ideally, the cutting edge 3 has a spiral curve in which the curvature increases from the outer periphery toward the center. Further, the head of the shank 1 is formed into a conical shape, and each cutting edge 6 is formed point-symmetrically with respect to the center point 4 which is the apex thereof. This center point 4 may be eccentric to the extent of a manufacturing error, and the point symmetry is not strictly defined, as long as it is substantially point symmetrical. Furthermore, both cutting edges may be discontinuous at the center point. Note that the rake face 7 of each cutting edge 3 is formed continuously from the center to the outer periphery of the cutting edge B. In the outer peripheral portion, as shown in FIG. 1, the edge 70 of the rake face 7 is formed so as to protrude more than the rear edge 11 of the groove 10 in the direction of rotation. In the conventional drill, the cutting edge and its outer circumferential edge were formed on the extension line of the groove 10, as shown by the imaginary line 60 in FIGS. are formed to protrude inward of the groove 10. Although there is a step between the rake surface 7 and the bottom surface of the groove 10 as shown in FIG. 1, this step may be eliminated so that both surfaces are continuous.

When drilling is performed using the drill, as shown in FIG. 4, the chips 8 generated by the cutting blade 6 grow in a fan shape in the inner peripheral direction of the groove 10 and are curled into a conical shape. The chips are ejected along the length of the groove 10 as transition-shaped chips. A cross section of the rake face 7 of the cutting edge 6 and the groove 10 facing it in the process of chip generation.

Since the product is smaller than that in other parts of the groove 10, the chips 8 formed in this part are ejected without resistance when passing through the groove 10. In contrast, when conventional birds are ejected,
This will interfere with the groove and the inner wall 80 of the machined hole. For this reason, even when the chips 9 are moving up the groove 1D, they are rubbed against the inner wall 80 of the machined hole and the bottom wall of the groove 10, and there is great resistance to ejection.

This not only increases the load on the cutting edge, but also
If the machined hole becomes deep, chips will get stuck in the groove and cannot be removed, resulting in chipping of the cutting edge. For this reason, very deep holes could not be machined. However, it is possible to pass through the groove 10 easily, and therefore cutting can be performed with much lower torque than before, and it is also possible to easily machine deep holes, which were previously considered impossible, and to improve the surface roughness of the machined hole. It also improves significantly.

As explained above, the present invention prevents chips from interfering with the inner wall of the discharge groove when discharging chips by forming the cutting edge to protrude inward from the extension line of the outer peripheral line of the chip discharge groove of the shank in side view. It has low chip evacuation resistance and is particularly suitable for drilling deep holes.

[Brief explanation of the drawing]

Fig. 1 is a front view of a drill showing an embodiment of the present invention;
The figure is a side view, FIG. 6 is a bottom view, and the fourth helmet is a sectional view taken along the line IV--IV in FIG. 2. 1...shank, 2...tip, 6...cutting blade,
8... Chips, 10... Chip discharge groove. Figure 1 Figure 2' Figure 3/V Figure 4

Claims (1)

[Claims] 1. When viewed from the bottom of the drill, the pair of cutting edges have their starting ends near the center of rotation and are arranged symmetrically with respect to the drilling point, and each cutting edge has a convex shape and a curved line that is a combination of a convex and concave shape in the direction of rotation. The cutting edge curve at the center has a larger curvature than the cutting edge curve at the outer periphery, and the chip discharge groove corresponding to each cutting edge is formed in a spiral shape on the shank. A drill characterized in that an outer peripheral portion of a nearby rake face is formed to protrude inward from an extension line of the chip discharge groove.