JP2599549B2 - Drill - Google Patents

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 an improvement in 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 spirally in a shank, a pair of cutting blades is formed at a tip of the shank, and a chisel is formed at a center portion corresponding to a core thickness. 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 that a cutting edge is formed in the chisel portion so that cutting is actively performed at the center even by the cutting edge.

[0003]

In the above configuration, the chips formed by the cutting blade are curled in a spiral shape having a continuous conical shape and are generated, and are discharged through the chip discharge groove. Become. If the chips are continuous like this,
There is a problem in that a large resistance is generated when passing through the chip discharge groove, and chips discharged from the chip discharge groove are wound around the shank. For this reason, continuous drilling cannot be performed by unmanned drilling. Therefore, it is preferable to cut the chips as short as possible. However, in a conventional drill having a core thickness of about 15% of the diameter of the drill shank, even if the cutting edge is formed at the center, the cutting edge at the center having a large curvature is formed. Due to the small proportion, chips were difficult to cut.

SUMMARY OF THE INVENTION The present invention has been made to solve such a conventional drawback. Chips are easily cut, short chips are generated, and the chips are discharged smoothly. It is an object of the present invention to provide a drill having a structure in which cutting is performed.

[0005]

SUMMARY OF THE INVENTION The present invention provides a center cutting edge extending from the center of rotation of a drill in an outer circumferential direction, an intermediate cutting edge extending in an outer circumferential direction from an outer end of the center cutting edge, and a center cutting edge. A cutting edge of the drill is formed from an outer cutting edge extending from the outer end to the outer peripheral end of the drill, and the center cutting edge, the intermediate cutting edge, and the outer cutting edge are connected to each other in a drill rotation direction in a plan view. Form a bent line or a curved line bent so as to protrude, 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 of the chip discharge groove,
A first rake face extending in the axial direction of the drill is formed on the center cutting edge, and a first rake face is provided at a tip end of the first rake face.
A flat first bottom surface substantially perpendicular to the rake face is formed, and the first bottom surface is inclined with respect to the axial direction and the direction perpendicular to the axis of the drill, respectively, and the intermediate cutting edge has a second surface extending in the axial direction of the drill. A rake face is formed, and a flat second substantially orthogonal to the second rake face is provided at the tip of the second rake face.
A bottom surface is formed, and a second bottom surface is inclined with respect to the axial direction of the drill and a direction orthogonal to the axis, respectively, and the second rake surface is inclined with respect to the first bottom surface and the first rake surface, respectively. Connected so that a first ridgeline is formed between the surface and the first bottom surface, the second rake surface and the second bottom surface are:
It is connected so that the second ridgeline is formed between the second bottom surface and the bottom surface of the chip discharge groove so as to be inclined with respect to the bottom surface of the chip discharge groove.

[0006] The center cutting edge, the intermediate cutting edge, and the outer cutting edge are:
It is preferable that each is formed in a straight line in plan view.

[0007]

In the above construction, the center 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. The tip of the chip is stopped by contact with the first bottom surface near the center of rotation of the drill, while the chip outside of the tip continues to extend, so that the tip of the chip contacts the first ridge line. A bending moment is received with the point as a fulcrum, whereby a chip at a portion closer to the center than the ridge line receives a force to separate from the first cutting edge to form a cut portion.

Further, the chips are extended and their tips are stopped by abutting against the second bottom surface, while the chips on the outer side continue to extend, so that the tips of the chips abut the second ridge line. A bending moment is received with the point as a fulcrum, so that a chip at a portion closer to the center than the ridge line receives a force to separate the chip from the second cutting edge. Therefore, even if the chip is not cut short due to the bending moment at the first ridge line, the chip is reliably cut by the force due to the bending moment at the second ridge line, whereby the chip is cut short and the chip discharge groove. Smoothly sent inside. Therefore, cutting is performed with a small cutting resistance. In addition, in this configuration, since the chip is smoothly discharged, conventionally, the diameter of the drill is 3 mm.
Instead of being able to machine only twice the depth in one step, it has become possible to perform drilling in one step to a depth of at least five times the diameter of the drill.

[0009]

1 and 2, a pair of cutting edges are formed symmetrically at the tip of a shank 100 forming a drill, and a chip discharge groove corresponding to each cutting edge is formed on the outer periphery of the shank 100. 10 are formed. A center cutting edge 43 extending in the outer peripheral direction from the rotation center O of the drill,
An intermediate cutting edge 41 extending from the outer end of the center 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 end of the drill are formed. The center cutting edge 43, the intermediate cutting edge 41, and the outer cutting edge 4 are each formed substantially linearly in plan view, and form a bent line at a connection portion thereof so as to protrude in the drill rotation direction in plan view. Rake face of the outer cutting edge 4 (third face)
The rake face 32 is formed in the axial direction of the drill by an extension of the bottom surface of the chip discharge groove 10.

As shown in FIGS. 3 to 5 which are sectional views taken along lines AA, BB and CC of FIG. 2, the center cutting edge 43 extends in the axial direction of the drill. First rake face 30
Is formed, and a flat first bottom surface 13 that is substantially perpendicular to the first rake surface 30 is formed at the front end of the first rake surface 30 via the square line 12. The first bottom surface 13 is inclined with respect to the axial direction of the drill and the direction perpendicular to the axis. The intermediate cutting edge 41 has a second rake face 31 extending in the axial direction of the drill.
A flat second bottom surface 14 that is substantially perpendicular to the rake face 31 is formed through 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, so that the first ridge line 1 is provided between the second rake face 31 and the first bottom face 13, The first rake face 31 and the first rake face 30 are connected so that the ridge 11 is formed. 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 so that the second ridge line 2 is formed between the second bottom face 14 and the bottom face of the chip discharge groove 10, Rake face 3
1 and the bottom surface of the chip discharge groove 10 are connected so that a ridgeline 21 is formed.

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

When drilling is performed by the drill having the above configuration, the center cutting edge 43, the intermediate cutting edge 41 and the outer cutting edge 4 are formed.
Are cut into the work material 9 to generate chips 90. The chips 90 are provided on the rake face of each cutting edge, that is, the first rake face 30, the second rake face 31, and the third rake face 32.
Grow along the axis 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 protrude in the rotation direction of the drill.
The chips 90 also grow in the drill axis direction while being bent along the shape. Then, as shown in FIG. 3, the tip of the chip 90 is stopped by abutting on the first bottom surface 13 near 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 to extend. The bending moment M is generated by the chip around the point 91 at which the tip end of the chip 90 abuts the first ridgeline 1, and the chip 90 on the center side of the ridgeline 11 receives the first cutting edge 4.
3 will be subjected to such a force as to be peeled off. As a result, in a process in which the conical chips 90 as shown in FIG. 6 are continuously generated in a spiral shape, a cut portion (tearing portion) 93 is generated in a portion generated from the first cutting edge 43.

Further, a chip 90 extends, and the tip thereof is
The chip 90 is stopped by abutting the bottom surface 14, while the chip 90 in the outer portion continues to extend, so that the bending moment N is reduced about the point 92 where the tip of the chip 90 abuts the second ridge 2. As a result, the chips 90 in the portion closer to the center than the ridge line 21 receive a force in the direction of peeling from the second cutting blade 41. Therefore, a cutting portion 93 is generated in the chip 90 due to the bending moment M, and the chip is cut along a cutting line 94 indicated by a broken line (a so-called transition cutting occurs) from the starting point, thereby forming a short chip. When the chip 90 is a sticky material and no transition cutting occurs, the bending moment N
Thus, a similar tearing force is applied, and the sheet is cut along the cutting line 94. The short chips are smoothly discharged through the chip discharge groove 10.
By applying the bending moment in two stages in this way, chips can be reliably cut regardless of the type of material, and even with a drill with a small core thickness, which is difficult to cut chips, the chips can be reliably shortened. It became possible to cut.

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 plan view, and the first rake face 30 and the second rake face 31 are provided between the first rake face 30 and the second rake face 31. The 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 described.
Each of 1 and 4 may be formed as a curve in plan view. However, when each of the cutting blades 43, 41, 4 is formed in a straight line as in the above embodiment, there is an advantage that machining of the rake face of each of the cutting blades is easy. Further, when each cutting edge is formed in a straight line, the ridge line 11 and the ridge line 2 between the rake faces are formed.
1 is formed sharply, and the chips 90 extending along each rake face are subjected to a bending moment by these ridges, and the force exerted by the forces to cause the chips to separate from the cutting edge is applied. There is. This force, together with the force due to the bending moment exerted by the ridgelines 1 and 2, promotes the separation of chips from the cutting edge near the center of rotation.

[0016]

As described above, according to the present invention, the center cutting edge, the intermediate cutting edge and the outer cutting edge respectively generate chips, and the chips are formed along the rake face of each cutting edge in the axial direction of the drill. To grow. Then, the tip of the chip is stopped by abutting on the first bottom surface near the center of rotation of the drill, while the chip on the outer portion continues to extend,
For this reason, a bending moment is received with the point where the tip of the chip abuts on the first ridge line as a fulcrum, whereby the chip on the center side of the ridge line receives a force to separate from the first cutting blade, and the cut portion is subjected to the bending moment. Will be formed.

Further chips extend and are stopped by their tips abutting the second bottom surface, while the chips on the outer side continue to extend, so that the tips of the chips abut the second ridgeline. A bending moment is received with the point as a fulcrum, so that a chip at a portion closer to the center than the ridge line receives a force to separate the chip from the second cutting edge. Therefore, even if the chip is not cut short due to the bending moment at the first ridge line, the chip is reliably cut by the force due to the bending moment at the second ridge line, whereby the chip is cut short and the chip discharge groove. Smoothly sent inside. Therefore, cutting is performed with a small cutting resistance. In addition, in this configuration, since the chip is smoothly discharged, conventionally, the diameter of the drill is 3 mm.
Instead of being able to machine only twice the depth in one step, it has become possible to perform drilling in one step to a depth of at least five times the diameter of the drill.

[Brief description of the 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.

FIG. 3 is a sectional view taken along line AA of FIG. 2;

FIG. 4 is a sectional view taken along line BB of FIG. 2;

FIG. 5 is a sectional view taken along line CC of FIG. 2;

FIG. 6 is an explanatory diagram of chips.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 1st ridgeline 2 2nd ridgeline 4 Outer cutting edge 10 Chip discharge groove 13 1st bottom surface 14 2nd bottom surface 17 Land part 30 1st rake surface 31 2nd rake surface 32 3rd rake surface 40 Flank 90 90 Chip 93 Cutting part 100 Drill shank

Claims (2)

(57) [Claims] 1. A central cutting edge extending in the outer peripheral direction from the center of rotation of a drill, an intermediate cutting edge extending in an outer peripheral direction from an outer end of the central cutting edge, and a distance from the outer end of the intermediate cutting edge to an outer peripheral end of the drill. The cutting edge of the drill is formed from the outer cutting edge that extends, and the center cutting edge, the intermediate cutting edge, and the outer cutting edge are bent at a connection portion of each other so as to protrude 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 an extension of the groove bottom face of the chip discharge groove, and the first rake face extending in the axial direction of the drill is formed on the central cutting edge. And a flat first bottom surface substantially perpendicular 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 perpendicular to the axis. The above-mentioned intermediate cutting edge has a drill shaft A second rake face extending in the direction of the drill is formed, and a flat second bottom face substantially orthogonal to the second rake face is formed at the tip of the second rake face, and the second bottom face is formed in the axial direction and the axis of the drill. And the second rake face is respectively inclined with respect to the first bottom face and the first rake face to form a first ridge line between the second rake face and the first bottom face. And the second rake face and the second bottom face are respectively inclined with respect to the bottom face of the chip discharge groove so that the second rake face and the second bottom face are located between the second bottom face and the bottom face of the chip discharge groove.
A drill, which is connected so as to form a ridge. 2. The drill according to claim 1, wherein the center cutting edge, the intermediate cutting edge, and the outer cutting edge are each formed linearly in a plan view.