JP3849993B2 - Throw-away drill tip - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a throw-away drill tip (hereinafter referred to as “drill tip”) that is detachably attached to a throw-away drill, and in particular, has improved the position of the cutting edge so as to improve chip disposal. Is.
[0002]
[Prior art]
Conventionally, this type of drill tip is disclosed in, for example, Japanese Patent Laid-Open No. 6-91416. This drill tip has a so-called all-round breaker shape in which a breaker is set substantially parallel to the cutting edge, and can also be used as an inner peripheral side cutting edge and an outer peripheral side cutting edge of a throw-away drill. Each edge of the rhomboid surface, which is the rake face of the drill tip, is adjacent to the apex that forms the acute angle of the rhombus surface, and forms a pair of side edge cutting edges, and the apex that forms the acute angle A pair of corner cutting edges shorter than the side edge cutting edges are formed in a V shape symmetrically with respect to the bisector of the top and having a crossing angle larger than the apex angle of the top. Forming. The breaker is formed with the same width on both the inner peripheral cutting edge and the outer peripheral cutting edge.
[0003]
Moreover, what was illustrated in FIG. 5 is known as a prior art. The schematic configuration of FIG. 5 will be described with reference to the drawings. The cutting blade lowering amounts Ha and Hb of the drill tip 1 are formed to be the same, and the breaker widths Wa and Wb are also formed to be the same in the center blade 1B and the outer peripheral blade 1A. . That is, there is a relationship of Ha = Hb and Wa = Wb. The shape of the breaker 5 is different from that of the concave curved surface breaker of the present invention, and is formed in a step shape. In the case of low-feed cutting, even with the drill tip 1 having such a configuration, there is no problem in chip disposal, but the processing is extremely inefficient.
[0004]
[Problems to be solved by the invention]
The problems of the prior art are described below. Problems that arise when using a throw-away drill include chip disposal troubles and missing center blades. There is a problem of chip disposal due to a difference in cutting speed at the bottom edge of the drill tip. When the tip of the drill is viewed from the drill axis direction, the cutting speed is proportional to the diameter of the drill, so it is greatest at the outer periphery of the drill and zero at the center of the drill. For this reason, chips are naturally easily curled on the center side of the drill, and there are few troubles due to the chip treatment, but on the outer periphery side of the drill, the chips are easily stretched, and troubles such as entanglement with the drill body may occur. Therefore, a breaker is provided on the cutting edge located on the outer peripheral side of the throw-away drill, and entanglement is avoided by curling the chips. However, when high-speed, high-feed cutting is performed, the chips may get over the breaker and become stretchable, causing troubles such as wrapping around the drill body again. Also on the drill center side, broken chips may be clogged in the breaker, increasing the thrust force and causing the center blade to be lost.
[0005]
Therefore, the subject of the present invention is that when a drill tip is used as a center blade of a throw-away drill, chips can be discharged smoothly without causing chip clogging, and as an outer peripheral blade. When used, it is possible to use both the center blade and the outer peripheral edge that can be broken shortly so that the chips do not wrap around the drill body, and prevent chipping of the center blade and chipping due to thrust force. An object of the present invention is to provide a drill tip that can be used.
[0006]
[Means for Solving the Problems]
The present invention has been made in view of the problems as described above. The drill tip is used as the center blade 1B constituting the central portion of the bottom blade and the outer peripheral blade 1A constituting the outer peripheral portion of the bottom blade. From the boss surface 7 which is detachably mounted on the outer peripheral side and the central side of the drill by screws 22 through a central mounting hole, and the outer peripheral blade 1A and the central blade 1B are arranged at the central portion of the upper surface of the throw-away drill tip. In the throw-away type drill tip 1 formed so as to be at a low position, the throw-away type drill tip 1 is a flat-type positive throw-type drill tip 1 having a substantially parallelogram shape , Among the opposing rotationally symmetric ends, the opposite ends in the longitudinal direction are formed with short side edge cutting edges 1a and corner cutting edges 1b that become the outer peripheral cutting edges 1A, A long side ridge edge cutting edge 1c and a corner edge cutting edge 1d, which are the central edge 1B, are formed on the other opposing end , and a concave curved surface breaker 5 is formed on the entire upper surface thereof. The breaker widths Wa and Wb of the outer peripheral blade 1A and the central blade 1B are in a relationship of Wa> Wb, and the cutting edge drop amount Ha from the boss surface 7 of the outer peripheral blade 1A and the central blade 1B is Ha. , Hb has a relationship of Ha> Hb.
[0008]
Further, on the upper surface of the throw-away type drill tip, a concave curved breaker is formed over the entire circumference, and a dimple continuous in a bead shape is formed on a part of the inner edge of the breaker, Alternatively, on the concave curved surface in the breaker, a plurality of concave grooves or ridges extending in a direction perpendicular to the side edge cutting edge are arranged in parallel.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0010]
1 to 3 show a first embodiment. FIG. 1 shows a state in which a drill tip 1 according to the present invention is incorporated in a drill body 20. A drill tip 1 that is also used as an outer peripheral blade 1 </ b> A and a central blade 1 </ b> B is fixed to a tip end of a rod-shaped throwaway drill by a screw 22 through a central attachment hole 21.
[0011]
The drill tip 1 according to the present invention is a positive type drill tip 1 having a substantially parallelogram flat plate shape in FIGS. 2 and 3, and a straight side at the ridge line portion of the rake face and the flank face. Ridge cutting edges 1a and 1c and corner cutting edges 1b and 1d are formed. Of the two opposing rotationally symmetric end portions, the opposite end portion in the longitudinal direction is formed with a short side edge cutting edge 1a and a corner portion cutting edge 1b, and the other opposite end portion has a long side. The side edge cutting edge 1c and the corner cutting edge 1d are formed. The side ridge part cutting edge 1a and the corner part cutting edge 1b, and the side ridge part cutting edge 1c and the corner part cutting edge 1d form a V-shaped cutting edge that intersects at an obtuse angle. A corner R blade 2 is formed at the intersection of adjacent corner cutting edges 1b and 1d.
[0012]
The cutting edge lengths C and D of the corner cutting edges 1b and 1d are different from each other, and the intersections of the edge cutting edge 1a and the corner cutting edge 1b, the edge cutting edge 1c and the corner cutting edge 1d. The V-shaped angles γ and δ are formed at different angles. The magnitude relationship between the cutting edge lengths C and D is given by C <D, and the magnitude relationship between the V-shaped angles γ and δ is given by γ <δ. Since the thrust force in the axial direction of the drill body acts strongly on the center blade 1B, the cutting edge length D is formed long so that the line load or the surface load can be reduced in consideration of the cutting edge defect.
[0013]
On the upper surface of the drill tip 1, a cutting edge land 4 adjacent to the cutting edge 3 and a breaker 5 having a concave curved surface are formed at positions separated from the cutting edge 3. The main role of the breaker 5 is chip processing such as curling the chips and smoothing out of the chips. However, the geometry of the breaker according to the present invention is determined in consideration of not only the chip treatment but also the balance with the cutting edge strength.
[0014]
The breaker 5 is formed over the entire circumference of the cutting edge 3, and the breaker width Wb on the long side is narrower than the breaker width Wa on the short side. That is, the breaker widths Wa and Wb have a relationship of Wa> Wb. Further, on the long side, following the end of the breaker, a gently sloping surface 6 that is gradually increased toward the center of the drill tip is continuously formed. Further, the breaker depth Db on the long side is shallower than the breaker depth Da on the short side and is engraved smoothly. The difference in the shape of the breaker between the long side and the short side is that one is for the purpose of maintaining the cutting edge strength of the central blade 1B where the thrust force acts strongly, and the other is the outer peripheral blade where the chip tends to extend. This is because of consideration for breaking the chips in 1B.
[0015]
In the outer peripheral blade 1A, since the chip becomes easy to extend, a breaker having an appropriate shape for curling the chip is necessary, and the breaker width Wa and the breaker depth Da are sufficiently secured. Furthermore, by setting a large height difference between the cutting edge 3 and the boss surface 7 (hereinafter referred to as “cutting edge drop amount”), the bending effect on the chips can be further improved, and the curvature radius can be made smaller. It can be curled and cut into short pieces. On the other hand, since the cutting speed difference is large in the center blade 1B, the chips are naturally curled and rarely cause a problem in the chip processing, and it is a problem to avoid an increase in cutting resistance due to chip clogging. In particular, this tendency becomes prominent at high feed rates. However, it is difficult to widen the breaker width Wb of the center blade 1B because of consideration on the cutting edge strength and restrictions on the shape of the drill tip. Therefore, by making the cutting edge drop amount Hb of the central blade 1B smaller than the cutting edge drop amount Ha of the outer peripheral blade 1A, overbreaking can be avoided and smooth chip discharge can be promoted. That is, the cutting edge drop amounts Ha and Hb are given by the relationship Ha> Hb. Normally, the center blade 1B is formed with a large cutting edge drop amount Hb in consideration of cutting edge loss, but the drill tip 1 of the present invention maintains a balance between cutting edge strength and chip discharge. It is an improvement.
[0016]
A plurality of concave grooves 9 and a plurality of protrusions 8 for reducing contact friction are provided on the rake face of the drill tip 1. Both the concave groove 9 and the protrusion 8 have an effect of reducing the contact area with the chip on the rake face and suppressing an increase in cutting resistance and an increase in cutting heat.
[0017]
The concave groove 9 is formed in the breaker 5 on the long side for guiding chips cut by the center blade 1A, and starts from the rear of the cutting edge land 4 and extends in a direction away from the cutting edge 3. End at the inner edge. In order to enhance the above-described effect, it is preferable to arrange the concave grooves 9 in the direction of chip discharge. In the present embodiment, a plurality of grooves 9 are arranged in a row substantially perpendicular to the long side edge cutting edge 1c. Yes. Taking such a configuration is effective on the long side where the breaker depth Db is shallow and the chips easily come into contact with the bottom of the breaker, and the chip is effectively discharged without causing clogging or staying of the chips. Can be promoted. In particular, it is effective for processing of stainless steel or the like that easily causes chip adhesion. Note that the concave groove 9 is not necessarily required, and a convex portion such as the protrusion 8 may be formed as long as the contact area with the chip can be reduced.
[0018]
The protrusion 8 is formed in the short-side breaker 5 that guides the chips cut by the outer peripheral blade 1B, starts behind the cutting edge land 4, and extends in a direction away from the cutting edge 3. End at the inner edge of the breaker. Similar to the concave groove 9, a plurality of protrusions 8 are also arranged in parallel substantially perpendicularly to the short side edge cutting edge 1 a. Since the breaker depth Da is deep on the short side, chips do not come into contact with the breaker bottom. The protrusion 8 is for avoiding that the chip collides with the breaker rising wall surface and becomes overcurled. By providing the ridge 8, the chip is limited to a narrow range of contact centered on the top of the ridge 8, and smooth machining with low cutting resistance can be performed without deteriorating the chip processing function. it can.
[0019]
FIG. 4 shows a second embodiment of the present invention. The same parts are denoted by the same reference numerals. As in the first embodiment, the drill tip 1 is configured such that the cutting edge drop amounts Ha and Hb are different between the central blade 1B and the outer peripheral blade 1A. That is, the cutting edge drop amounts Ha and Hb have a relationship of Ha> Hb. Further, the breaker width Wb on the long side is formed so that the breaker width Wa on the short side becomes narrower, and the breaker widths Wa and Wb have a relationship of Wa> Wb. Further, the breaker 5 on the long side is carved shallower than the breaker 5 on the short side, and the breaker depths Da and Db have a relationship of Da> Db. In addition, the gentle inclined surface 6 which becomes gradually high following the concave groove 9 and the protrusion 8 and the breaker 5 on the long side shown in the first embodiment is not formed. Instead, a dimple 10 continuous in a bead shape is formed on a part of the inner edge of the breaker 5. The dimple 10 can also reduce the contact area with the chips and improve the chip discharge performance.
[0020]
【The invention's effect】
As described above, according to the present invention, it is possible to avoid a chip disposal trouble particularly under high speed and high feed conditions. When using one of the cutting edges of the drill tip as the center cutting edge of the indexable drill smoothly can chip removal, Rutotomoni can avoid chip packing constraints chip shape for the drill It is possible to maintain the cutting edge strength of the central blade 1A, which makes it difficult to increase the width of the breaker, and to prevent the cutting edge from being lost. It is possible to prevent chips from being wound around the drill body.
[Brief description of the drawings]
1A is a front view of a tip portion of a throw-away drill, FIG. 1B is a rear view of FIG. 1A, and FIG. 2 is a perspective view of a drill tip according to a first embodiment of the present invention. (A) Plan view of the drill tip shown in FIG. 2 (b) Enlarged section taken along line AA in FIG. 3 (c) Enlarged section taken along line BB in FIG. 3 (a) FIG. 4A is a plan view of a drill tip showing a second embodiment of the present invention. FIG. 4B is an enlarged cross-sectional view taken along line AA in FIG. 4A. FIG. FIG. 5A is a plan view of a drill tip showing the prior art. FIG. 5B is an enlarged cross-sectional view taken along the line AA in FIG. a) Cross-sectional enlarged view along line BB in a) [Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Tip for drill 8 Projection 9 Groove 10 Dimple 1A Peripheral blade 1B Center blade Wa, Wb Breaker width Ha, Hb Cutting blade fall amount Da, Db Breaker depth

Claims (2)

The drill tip is also used as the center blade 1B constituting the center portion of the bottom blade and the outer peripheral blade 1A constituting the outer periphery portion of the bottom blade, and is screwed through the center mounting holes on the outer periphery side and the center side of the throw-away drill. The throw-away drill tip 1 is detachably mounted by 22 and is formed such that the outer peripheral blade 1A and the central blade 1B are positioned lower than the boss surface 7 disposed at the center of the upper surface of the throw-away drill tip. The throw-away drill tip 1 is a flat plate-type positive throw-type drill tip 1 having a substantially parallelogram shape, and is a longitudinally opposed end of two opposing rotationally symmetrical ends. The edge is formed with a short side edge cutting edge 1a and a corner edge cutting edge 1b to be the outer peripheral edge 1A, and the other opposite end is a long side edge to be the central edge 1B. A ridge cutting edge 1c and a corner cutting edge 1d are formed , and a concave curved circuit breaker 5 is formed on the entire upper surface of the edge cutting edge 1c, and the breaker width Wa of the outer peripheral cutting edge 1A and the central cutting edge 1B, Wb is in a relationship of Wa> Wb, and the cutting edge drop amounts Ha and Hb of the outer peripheral blade 1A and the central blade 1B from the boss surface 7 are in a relationship of Ha> Hb. Type drill tip.  A concave curved breaker 5 is formed on the entire upper surface of the throw-away drill tip 1 and a dimple 10 continuous in a bead shape is formed on a part of the inner edge of the breaker 5. Alternatively, on the concave curved surface in the breaker 5, a plurality of concave grooves 9 or ridges 8 extending in a direction perpendicular to the side edge cutting edges 1a and 1c are arranged in parallel. The throw-away type drill tip according to claim 1.

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