JPS6216765B2 - - Google Patents

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 resistance when chips pass through the spiral or linear chip evacuation groove formed in the shank, the drilling depth that can be drilled at the maximum capacity of the drill is approximately three times the drill diameter. It was at its limit.

This invention was made to solve these conventional drawbacks, and it creates a difference between the area near the cutting edge where chips are formed and the cross-sectional area of the discharge groove, thereby improving chip discharge. This allows for smooth passage through the groove. That is, in the present invention, the pair of cutting edges have their starting ends near the center of rotation, are arranged approximately point-symmetrically with respect to each other when viewed from the tip in the axial direction of the drill, and each cutting edge forms a curved line that is convex with respect to the direction of rotation. , and 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. The rake face of the cutting blade is formed at the tip of the chip evacuation groove to protrude inside the chip evacuation groove, and the inner wall of the chip passage formed by the rake face of the cutting blade and the chip evacuation groove is free from chips from other parts. It is curved to a larger curvature than the inner wall of the discharge groove.

Embodiments of the present invention will be described below with reference to the drawings. In FIGS. 1 to 3, 1 is a shank of a drill, and 2 is a tip. The tip 2 is attached to the head of the shank 1 by means such as brazing. A cutting edge 3 is formed on each of the chips 2, and this cutting edge 3 forms a curve convex in the direction of rotation when viewed from the tip in the axial direction, has a constant large curvature at the center, and becomes almost straight at the outer periphery. There is. 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 3 is formed point-symmetrically with respect to the center point 4 which is the apex thereof. The center point 4 may be eccentric to the extent of a manufacturing error, and the point symmetry is not strictly defined; it is sufficient that it is substantially point symmetric.
Furthermore, both cutting edges may be discontinuous at the center point.
Note that a supply port 50 for cooling oil during cutting is formed in the land portion 5 for receiving the force acting on the cutting edge 3.

The rake face 7 of each cutting edge 3 is formed continuously from the center to the outer periphery. And at the outer periphery,
As shown in FIG. 1, the edge 70 of the rake face 7 is formed to protrude inward from the rotational direction rear edge 11 of the groove 10. 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 30 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 with the above drill, the chips 8 generated by the cutting edge 3 grow in a fan shape in the inner circumferential direction of the groove 10 and form a conical shape, as shown in FIG. The cutting material is curled into a transitional shape and is discharged along the length of the groove 10 as chips in the form of a transition break. During the process of chip generation, since the cross-sectional area of the rake face 7 of the cutting edge 3 and the part of the groove 10 that faces it is smaller than the other part of the groove 10, the chips 8 formed in this part cut into the groove 10. It is ejected without resistance as it passes through. In contrast, in conventional drills, the cross-sectional area of the groove of the chip generating part and the passage part are the same, as shown by the imaginary line 30, so the chips 9 generated are
When the material is discharged, the inner wall 80 of the groove and the machined hole
will interfere with Therefore, the chips 9 are removed from the groove 10.
Even while it is rising, it is rubbed against the inner wall 80 of the machined hole and the bottom wall of the groove 10, creating a large resistance to ejection. For this reason, not only does the load on the cutting edge increase, but when the machined hole becomes deep, chips become clogged in the groove and cannot be discharged, resulting in chipping of the cutting edge. For this reason, it was not possible to machine very deep holes. However, if the cross-sectional area of the groove where chips are formed is made smaller than the cross-sectional area of the discharge groove as described above, the chips 8 can easily pass through the groove 10, which makes the chip much smaller than before. In addition to being able to cut with torque, it is also possible to easily machine deep holes that were previously considered impossible, and the surface roughness of the machined holes is significantly improved.

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 circumferential 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, FIG. 2 is a side view thereof, and FIG. 3 is a bottom view thereof.
FIG. 4 is a sectional view taken along the line -- in FIG. 2. 1...shank, 2...chip, 3...cutting blade,
8... Chips, 10... Chip discharge groove.

Claims (1)

[Claims] 1 The starting end of the pair of cutting blades is near the center of rotation, and they are arranged approximately point symmetrically to each other when viewed from the tip in the axial direction of the drill, and each cutting blade forms a curve that is convex with respect to the rotation direction, and The cutting edge curve at the center has a larger curvature than the cutting edge curve, and the chip discharge groove corresponding to each cutting edge is formed in a spiral shape in the shank, and the rake face of each cutting edge near the outer periphery is formed in a spiral shape. is formed at the tip of the chip discharge groove so as to protrude inside the chip discharge groove, and the inner wall of the chip passage formed by the rake face of the cutting edge and the chip discharge groove is smaller than the inner wall of the other part of the chip discharge groove. A drill characterized by being curved with a large curvature.