JPH06320316A - Drill - Google Patents

Abstract

PURPOSE:To perform cutting with small cutting resistance by breaking down a cutting chip from its part, produced by a cutting edge in the vicinity of a center part, producing a short cutting chip, and smoothly discharging the cutting chip. CONSTITUTION:A cutting edge is formed of a center cutting edge 43 extended in the peripheral direction from the center of rotation of a drill, intermediate cutting edge 41 extended in the peripheral direction from an outside end part of this center cutting edge and an external side cutting edge 4 extended from an outside end part of this intermediate cutting edge to a drill peripheral end, and a bent folding line is formed so as to protrude in the direction of rotation of the drill as viewed by plane in a connecting part to each other of each cutting edge. The first bottom surface 13 is formed in a point end part of the first cutting face 30 of the center cutting edge 43, the second bottom surface 14 is formed in a point end part of the second cutting face 31 of the intermediate cutting edge 41, the first ridge line 1 is formed between the second cutting face 31 and the first bottom surface 13, and the second ridge line 2 is formed between the second bottom surface 14 and a bottom surface of a cutting chip discharge groove 10.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a drill, and more particularly to improvement of the shape of a cutting edge near the center of the drill.

[0002]

2. Description of the Related Art In a conventional drill, a chip discharge groove is formed in a spiral shape on a shank, a pair of cutting blades is formed at the tip of the shank, and a chisel is formed at a center portion of the cutting edge. The chips generated by the cutting blade are configured to be discharged to the outside through the chip discharge groove. It has also been proposed to form a cutting edge on the part of the chisel so that the cutting edge is positively cut even at the center.

[0003]

In the above structure, the chips formed by the cutting blade are curled in a spiral shape having a continuous conical shape, and the chips are discharged through the chip discharge groove. Become. When chips continue in this way,
There is a problem that a great resistance is generated in passing through the chip discharge groove, and the chips discharged from the chip discharge groove are wound around the shank. For this reason, it was not possible to achieve continuous operation by unmanned drilling. Therefore, it is preferable to cut the chips as short as possible. However, with a conventional drill having a core thickness of about 15% of the diameter of the drill shank, even if the cutting blade is formed in the center, Chips were difficult to cut due to the small proportion.

The present invention has been made in order to solve the above-mentioned conventional drawbacks, and the chips are easily cut to generate short chips, the chips are smoothly discharged, and the cutting resistance is small. It is intended to provide a drill having a structure in which cutting is performed.

[0005]

SUMMARY OF THE INVENTION The present invention is directed to a central cutting edge that extends in the outer peripheral direction from the center of rotation of a drill, an intermediate cutting edge that extends in the outer peripheral direction from the outer end of the center cutting edge, and the intermediate cutting edge. The cutting edge of the drill is formed from the outer cutting edge extending from the outer end to the outer peripheral edge of the drill, and the center cutting edge, the intermediate cutting edge, and the outer cutting edge are connected to each other in the drill rotation direction in plan view. Forming a bent line or a curved line bent so as to project, the rake face of the outer cutting edge is formed in the axial direction of the drill by the extension face of the groove bottom face of the chip discharge groove,
A first rake face extending in the axial direction of the drill is formed on the central cutting edge, and a first rake face has a first rake face at the tip thereof.
A flat first bottom surface that is substantially orthogonal to the rake face is formed, and the first bottom surface is inclined with respect to the axial direction of the drill and the direction orthogonal to the axis, and the intermediate cutting edge has a second extending in the axial direction of the drill. A rake face is formed and at the tip of the second rake face, a second flat face that is substantially orthogonal to the second rake face is formed.
A bottom surface is formed, the second bottom surface is inclined with respect to the axial direction of the drill and the direction orthogonal to the axis, and the second rake surface is inclined with respect to the first bottom surface and the first rake surface, respectively. The second rake face and the second bottom face are connected so that a first ridgeline is formed between the face and the first bottom face.
The chips are connected so as to be inclined with respect to the bottom surface of the chip discharge groove and form a second ridgeline between the second bottom surface and the bottom surface of the chip discharge groove.

The center cutting edge, the intermediate cutting edge and the outer cutting edge are
It is preferable that each of them is formed into a straight line in a plan view.

[0007]

In the above structure, the central cutting edge, the intermediate cutting edge and the outer cutting edge each generate chips, and the chips grow in the axial direction of the drill along the rake face of each cutting edge. Then, the tip of the chip is stopped by abutting the first bottom surface near the center of rotation of the drill, while the chip on the outer side continues to extend, so that the tip of the chip abuts the first ridge. A bending moment is received around the point as a fulcrum, and thereby a chip in a portion on the center side of the ridge line receives a force of peeling from the first cutting edge to form a cut portion.

The chip further extends and its tip is stopped by abutting against the second bottom surface, while the chip on the outer side continues to extend, so that the tip of the chip abuts the second ridge. A bending moment is received by using the point as a fulcrum, and as a result, the chip in the portion closer to the center than the ridge receives a force that causes it to separate from the second cutting edge. Therefore, even if the chip is not cut short due to the bending moment at the first ridge, the chip is reliably cut due to the force due to the bending moment at the second ridge, whereby the chip is cut short and the chip discharge groove. It is sent smoothly inside. Therefore, cutting is performed with a small cutting resistance. Moreover, in this configuration, since chips are discharged smoothly, conventionally, the diameter of the drill is 3 mm.
Although it was possible to machine only a depth of about twice in one step, it became possible to machine a hole to a depth of 5 times the diameter of the drill or more in one step.

[0009]

1 and 2, a pair of cutting blades are formed point-symmetrically with respect to each other at a tip portion of a shank 100 forming a drill, and a chip discharging groove corresponding to each cutting blade is formed on an outer peripheral portion of the shank 100. 10 are formed. The cutting edge is a central cutting edge 43 extending from the rotation center O of the drill in the outer peripheral direction,
It is formed of an intermediate cutting edge 41 extending from the outer end of the central cutting edge 43 in the outer peripheral direction, and an outer cutting edge 4 extending from the outer end of the intermediate cutting edge 41 to the outer peripheral edge of the drill. The central cutting edge 43, the intermediate cutting edge 41, and the outer cutting edge 4 are each formed in a substantially straight line in a plan view, and form a fold line bent so as to project in the drill rotation direction in a plan view at a mutual connection portion. , The rake face of the outer cutting edge 4 (3rd
The rake surface 32 is formed in the axial direction of the drill by the extension surface of the groove bottom surface of the chip discharge groove 10.

As shown in FIGS. 3 to 5 which are sectional views taken along the lines AA, BB and CC of FIG. 2, the central cutting edge 43 extends in the axial direction of the drill. First rake face 30
And a flat first bottom surface 13 that is substantially orthogonal to the first rake surface 30 is formed at the tip end portion of the first rake surface 30 via the square wire 12. The first bottom surface 13 is inclined with respect to the axial direction of the drill and the direction orthogonal to the axis. A second rake face 31 extending in the axial direction of the drill is formed on the intermediate cutting edge 41, and
A flat second bottom surface 14 that is substantially orthogonal to the rake surface 31 is formed via a square line 22. The second bottom surface 14 is inclined with respect to the axial direction of the drill and the direction orthogonal to the axis.

The second rake face 31 is inclined with respect to the first bottom face 13 and the first rake face 30, respectively, and the first ridge line 1 is formed between the second rake face 31 and the first bottom face 13, and The ridge line 11 is connected between the first and second rake faces 31 and 30. Further, the second rake face 31 and the second bottom face 14 are respectively inclined with respect to the bottom face of the chip discharge groove 10, and the second ridge line 2 is formed between the second bottom face 14 and the bottom face of the chip discharge groove 10, and the second ridge line 2 is formed. Rake face 3
1 and the bottom surface of the chip discharge groove 10 are connected so that a ridge line 21 is formed.

A land 17 is formed on the rear side of the flank 40 of each of the cutting edges 43, 41, 4 in the direction of rotation through a ridge line 44 between the land 17 and the flank 40, and further on the rear side of the land 17. In the vicinity of the center of the drill, the first bottom surface 13 is continuous via a ridge line 15, and on the outer peripheral side thereof, the second bottom surface 14 and land portion 19 are formed via a ridge line 16. The land portion 19 is connected to the bottom surface of the chip discharge groove 10 via the ridge line 18.

When drilling is performed with the drill having the above-mentioned structure, the central cutting edge 43, the intermediate cutting edge 41 and the outer cutting edge 4
Are cut into the work material 9 to generate chips 90. The chips 90 are rake faces of each cutting edge, that is, the first rake face 30, the second rake face 31, and the third rake face 32.
Along the axial direction of the drill. That is, in the planar shape, as shown in FIG. 2, each cutting edge and the rake face are bent so as to project in the rotation direction of the drill,
The chips 90 also grow in the axial direction of the drill while being bent along the shape thereof. Then, as shown in FIG. 3, the tip of the chip 90 is stopped by abutting the first bottom surface 13 in the vicinity of the center of rotation of the drill, while the chip 90 on the outer side continues to extend and the chip 90 on the outer side continues. A bending moment M is generated by the chips with the tip 91 of the chips 90 abutting against the first ridge line 1 as a fulcrum, whereby the chips 90 on the center side of the ridge line 11 are removed by the first cutting blades 4.
It will receive the force to peel from 3. As a result, in the process in which the conical chips 90 as shown in FIG. 6 are continuously generated in a spiral shape, a cutting portion (tearing portion) 93 is generated in the portion generated from the first cutting edge 43.

Further, the chips 90 further extend, and the tip end thereof is the second
It is stopped by abutting on the bottom surface 14, while the chips 90 on the outer side continue to extend, so that the bending moment N is about the point 92 at which the tip of the chip 90 abuts the second ridge 2 as a fulcrum. The chips 90 on the center side of the ridge line 21 are generated by this, and receive a force in the direction of separating from the second cutting blade 41. Therefore, the bending moment M causes the cutting portion 93 to generate in the chip 90, and the cutting portion 93 cuts along the cutting line 94 indicated by a broken line (so-called transition cutting occurs) starting from this, and as a result, short chips are formed. Further, when the chip 90 is a viscous material and transition cutting does not occur, the bending moment N that continues occurs
Further, a similar tearing force is given by the above, and cutting is performed along the cutting line 94. The short chips pass through the chip discharge groove 10 and are smoothly discharged.
By applying a bending moment in two steps in this way, chips can be cut reliably regardless of the type of material, and even in drills with a small core thickness that are difficult to cut, chips can be shortened reliably. It became possible to disconnect.

In the above embodiment, the first cutting edge 43, the second cutting edge 41, and the third cutting edge 4 are each formed in a straight line in a plan view, and between the first rake face 30 and the second rake face 31. An example in which the ridge line 1 is formed and the ridge line 21 is formed between the second rake face 31 and the third rake face 32 has been shown.
Each of 1 and 4 may be formed into a curved line in a plan view. However, when each cutting edge 43, 41, 4 is formed in a straight line as in the above embodiment, there is an advantage that the rake face of each cutting edge can be easily processed. Further, when each cutting edge is formed into a straight line, the ridge line 11 and the ridge line 2 between the rake faces are formed.
1 is sharply formed, and the chip 90 extending along each rake face receives a bending moment by these ridges, and the force exerted thereby causes the chip to be separated from the cutting edge. There is. This force, together with the force due to the bending moment acting on the ridge lines 1 and 2, promotes separation of chips from the cutting edge near the center of rotation.

[0016]

As described above, according to the present invention, the central cutting edge, the intermediate cutting edge, and the outer cutting edge each generate chips, which are along the rake face of each cutting edge in the axial direction of the drill. Grow to. Then, the tip of the chip is stopped by coming into contact with the first bottom surface in the vicinity of the center of rotation of the drill, while the chip on the outer side continues to extend,
Therefore, the tip of the chip receives a bending moment with the point of contact with the first ridge line as a fulcrum, whereby the chips in the part closer to the center of the ridge line receive a force such that they are separated from the first cutting edge and the cutting part is separated. Will be formed.

The chip further extends and its tip is stopped by abutting against the second bottom surface, while the chip on the outer side continues to extend, so that the tip of the chip abuts the second ridge. A bending moment is received by using the point as a fulcrum, and as a result, the chip in the portion closer to the center than the ridge receives a force that causes it to separate from the second cutting edge. Therefore, even if the chips are not cut short due to the bending moment at the first ridge, the chips are reliably cut by the force due to the bending moment at the second ridge, whereby the chips are cut short and the chip discharge groove is cut. It is sent smoothly inside. Therefore, cutting is performed with a small cutting resistance. Moreover, in this configuration, since chips are discharged smoothly, conventionally, the diameter of the drill is 3 mm.
Although it was possible to machine only a depth of about twice in one step, it became possible to machine a hole to a depth of 5 times the diameter of the drill or more in one step.

[Brief description of drawings]

FIG. 1 is a side view of a drill showing an embodiment of the present invention.

FIG. 2 is a plan view of FIG.

3 is a cross-sectional view taken along the line AA of FIG.

FIG. 4 is a sectional view taken along line BB in FIG.

5 is a cross-sectional view taken along line CC of FIG.

FIG. 6 is an explanatory diagram of chips.

[Explanation of symbols]

 1 1st ridge line 2 2nd ridge line 4 Outer cutting edge 10 Chip discharge groove 13 1st bottom face 14 2nd bottom face 17 Land part 30 1st rake face 31 2nd rake face 32 3rd rake face 40 Flank face 90 Chips 93 Cutting part 100 Drill shank

Claims (2)

[Claims] 1. A central cutting edge extending from a rotation center of a drill in an outer peripheral direction, an intermediate cutting edge extending in an outer peripheral direction from an outer end of the central cutting edge, and an outer end of the intermediate cutting edge to an outer peripheral end of the drill. A cutting edge of a drill is formed from an extending outer cutting edge, and the center cutting edge, the intermediate cutting edge and the outer cutting edge are bent at a connecting portion of each other so as to project in the drill rotation direction in a plan view or A curved line is formed, the rake face of the outer cutting edge is formed in the axial direction of the drill by the extension surface of the groove bottom surface of the chip discharge groove, and the central cutting edge is formed with a first rake face extending in the axial direction of the drill. In addition, a flat first bottom surface that is substantially orthogonal to the first rake surface is formed at the tip of the first rake surface, and the first bottom surface is inclined with respect to the axial direction of the drill and the direction orthogonal to the axis. , The intermediate cutting edge has a drill shaft A second rake face extending in a direction is formed, and a flat second bottom face that is substantially orthogonal to the second rake face is formed at the tip end of the second rake face, and the second bottom face is in the axial direction and the axis of the drill. And the second rake face is inclined respectively with respect to the first bottom face and the first rake face, and a first ridge line is formed between the second rake face and the first bottom face. And the second rake face and the second bottom face are inclined respectively with respect to the bottom face of the chip discharge groove, and the second rake face and the second bottom face are inclined between the second bottom face and the bottom face of the chip discharge groove.
A drill characterized by being connected so that a ridgeline is formed. 2. The drill according to claim 1, wherein the central cutting edge, the intermediate cutting edge, and the outer cutting edge are each formed in a straight line in a plan view.