JP3872451B2 - Throwaway drill - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a drill insert for drilling holes and a throw-away drill using the drill insert.
[0002]
[Prior art]
As a drill tool for drilling holes, a tool in which an outer peripheral outer blade insert and an inner peripheral inner blade insert are detachably mounted so that the rotational trajectories of the tool body intersect each other has been generally used. It was.
[0003]
FIG. 6 shows such a throw-away drill T.
[0004]
The drill insert 20 to be mounted on the throw-away drill T has a cutting edge formed on the ridge portion of the upper surface 21, and as shown in FIG. The blade insert 22 and the inner blade insert 23 are mounted with the upper surface 21 facing in the same rotational direction. Further, among the cutting blades formed on the outer blade insert 22 and the inner blade insert 23, the rotation trajectory of the cutting blade that becomes the bottom cutting blade 25 intersects and covers from the center axis T1 to the side surface T2 of the throw-away drill T. .
[0005]
On the other hand, in the case of machining a small-diameter hole of φ10 or less, the screw has to be very small, and such a shape could not be used because of its strength. One that attaches one piece to the front end has been used.
FIG. 7 shows such a throw-away drill S for small-diameter processing. As shown in FIG. 7, the thin plate-like insert 30 is wider than the holder diameter, and is formed on the upper and lower ridge sides of the front end. inner cutting edge and Gaisetsu blade were those cutting edge 31 that is integrated is formed.
[0006]
Some throwaway drills S for small diameter machining are fixed with two fixing bolts, but there is a problem that the mechanical strength is small and the machining area is very narrow. On the other hand, the one using a single fixing bolt was improved in terms of mechanical strength, but the fixing bolt was acting on the central axis of the holder. There was little space for discharging chips, and there was a big problem in chip discharge.
[0007]
[Problems to be solved by the invention]
In view of such a problem of the prior art, an object of the present invention is to improve chip discharging performance without sacrificing cutting performance, particularly in a throw-away drill used for drilling a small diameter hole.
[0008]
[Means for Solving the Problems]
In order to solve the above-mentioned problems, the present invention is such that a drill insert having both an inner cutting edge and an outer cutting edge is mounted with a single fixing bolt on a polygonal plate-like body at the front end of a holder. In throw-away drills, the center axis of the fixing bolt is displaced from the center axis of the holder in the direction of the outer cutting edge. Can be secured.
[0009]
As one means for making a throw-away drill with such a configuration, an inner cutting edge and an outer cutting edge are formed at substantially the same height at an intermediate position corresponding to the total thickness of the plate-like body, and the inner cutting edge is A drill insert bent in the direction of the back surface of the inner cutting blade having an insert width smaller than the diameter of the holder can be used.
[0010]
For example, when using the above-mentioned drill insert, the insert is mounted on the front end of the holder. At this time, if the drill insert is biased so that the corner of the outer cutting edge is at the outermost peripheral position, the center of the drill insert The axis shifts from the center axis of the holder toward the outer cutting edge. By bringing the bolt central axis of the drill insert on this central axis, a large chip discharging pocket can be secured on the inner cutting edge side.
[0011]
In addition, since the inner cutting edge is bent toward the back surface of the inner cutting edge , the pocket can be taken larger and the cutting property is also improved by the bent shape as described above.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0013]
FIGS. 1 and 2 show a drill insert 1 according to this embodiment, the drill support Creating 1, inner cutting edge 2 and the outer cutting the inner peripheral side of the machined hole on the front end of the plate-like body in which the polygonal shape a drill insert 1 formed by combine the Gaisetsu blade 3 for cutting, to form at approximately the same height as the inner cutting edge 2 and Gaisetsu blade 3 in an intermediate position of the total thickness L content of the plate-like body The rake faces 4 and 5 of the inner cutting edge 2 and the outer cutting edge 3 are respectively provided in a step-down manner.
Further, the inner cutting edge 2 is formed to bend in the back direction at an intermediate position.
[0014]
In addition, the outer cutting edge 3 of the drill insert 1 is provided with a pair of corner R portions 6 and 7 at its corners, thereby forming a protruding portion 8 slightly protruding forward.
[0015]
In the present invention, the corner R portions 6 and 7 are those in the range of 60 ° to 105 ° in which the angle formed by the straight line continuous to the curved portion is close to a right angle.
3 to 5 show a throw-away drill 10 to which the drill insert 1 is mounted. The throw-away drill (hereinafter abbreviated as a drill) 10 is inserted into the front end portion 12 of the holder 11 with the drill insert (hereinafter referred to as an insert). 1 is affixed with a single fixing bolt 13, the width of the insert 1 is made smaller than the diameter of the holder 11, and the central axis 13a of the fixing bolt 13 is shown in FIG. Is displaced in the direction of the outer cutting edge 3 from the central axis 11 a of the holder 11.
[0016]
Since the drill 10 is thus displaced in the direction of the outer cutting edge 3 in this way, a very large chip discharging pocket 14 is secured on the rotational direction side of the rake face 4 of the inner cutting edge 2. It becomes possible.
Moreover, since the inner cutting edge 2 is bent at a bending angle γ = 10 ° to 20 ° in the back direction of the inner cutting edge , the pocket 14 can be taken larger.
[0017]
In addition, when the bending angle γ is less than 10 °, the chip dischargeability may be deteriorated. In addition, the holder 3 can be removed by directing the composite force of the radial load, which will be described later, toward the outer cutting edge 3. There exists a possibility that the effect | action bent to the cutting blade 3 side may become weak.
[0018]
On the other hand, when the bending angle γ exceeds 20 °, the lower thickness of the inner cutting edge 2 is reduced, and as a result, the mechanical strength may be reduced.
[0019]
Moreover, since the thickness of the insert 1 will become large if the height of the outer cutting edge 3 and the inner cutting edge 2 differs greatly, there exists a possibility that the mechanical strength of the holder 11 may fall.
[0020]
By the way, the drill 10 is provided with the protrusion 8 of the outer cutting edge 3 on the outermost peripheral side. Although this protrusion 8 is provided with a pair of said corner R parts 6 and 7, this has the effect | action which changes the direction of the radial load of the outer cutting blade 3 to the rotation direction side. As a result, the combined force direction of the radial load of the inner cutting edge 2 and the radial load of the outer cutting edge 3 is directed toward the outer cutting edge 3 from the center axis 11a of the holder, and the holder 11 is moved to the outer cutting edge 3 side. Bend. Accordingly, the machining diameter becomes large, and when the drill 10 is pulled out from the machining hole, the outer cutting blade 3 and the hole wall can be pulled out without contact, so that the machining surface can be improved. The inner cutting edge 2 is bent in the radial direction at the intermediate portion. However, the radial load of the inner cutting edge 2 can be somewhat directed toward the outer cutting edge 3 by this bending, and the protrusion 8 Reinforce the action of.
[0021]
Moreover, the said protrusion part 8 has the effect | action which divides a chip | tip finely. When cutting, chips from the bottom of the hole on the outer peripheral side have a property that the discharge speed is high and difficult-to-cut materials such as stainless steel can be easily stretched and entangled with the holder 11. However, the chips are finely divided and discharged well without entanglement. Is done. On the other hand, according to the inner cutting edge 2, the chip discharge speed is slow, but since the pocket 14 is large, chips can be discharged without being retained.
[0022]
As mentioned above, although embodiment of this invention was illustrated with the figure, this invention is not limited to the above-mentioned embodiment, It cannot be overemphasized that it can be set as arbitrary forms, unless it deviates from the objective of invention.
[0023]
【The invention's effect】
As described above, according to the present invention, a drill insert having both an inner cutting edge and an outer cutting edge is mounted on a front end portion of a holder on a polygonal plate with a single fixing bolt. In throw-away drills, the center axis of the fixing bolt is displaced from the center axis of the holder in the direction of the outer cutting edge. Can be secured.
[0024]
Further, a drill insert in which the inner cutting edge and the outer cutting edge are provided at substantially the same height at an intermediate position corresponding to the entire thickness of the plate-like body and the inner cutting edge is bent in the radial direction is used as such a throw-away drill. In particular, the following excellent effects can be obtained.
[0025]
That is, when the drill insert is biased so that the width of the drill insert is smaller than the holder diameter and the corner of the outer cutting edge is at the outermost peripheral position, the center axis of the drill insert is cut off from the center axis of the holder. Shift to the side of the blade.
By bringing the bolt central axis of the drill insert on this central axis, a large chip discharging pocket can be secured on the inner cutting edge side.
In addition, since the inner cutting edge is bent toward the back surface of the inner cutting edge , the pocket can be taken larger and the cutting property is also improved by the bent shape as described above.
[Brief description of the drawings]
FIG. 1 is a perspective view of a drill insert according to the present invention.
FIG. 2 is a perspective view of the drill insert of the present invention.
FIG. 3 is a perspective view of a throw-away drill according to the present invention.
FIG. 4 is a perspective view of a throw-away drill according to the present invention.
FIG. 5 is a plan view of the throw-away drill of FIGS. 3 to 4;
FIG. 6 is a plan view of a conventional throw-away drill equipped with two inserts.
FIG. 7 is a plan view of a conventional throw-away drill for small-diameter machining equipped with one insert.
[Explanation of symbols]
1 .... Drill insert, 2 .... Inner cutting blade, 3 .... Outer cutting blade, 4, 5 .... Rake face, 6, 7 .... Corner R part, 8 .... Projection part, 10 .... Throw away drill, 11 ·· Holder 11a ·· Center shaft, 12 ·· Front end, 13 ·· Fixing bolt, 13a ·· Center shaft, 14 ·· Pocket, L ··· Thickness, γ ·· Bending angle

Claims (3)

The front end of the the plate-like body polygonal shape with two main surfaces on the back of each other, independently of cutting the outer circumferential side to the inner cutting edge and the inner cutting edge for cutting the inner peripheral side of the machined hole A throw-away drill in which a drill insert combined with an outer cutting blade is attached to the front end of the holder with a single fixing bolt ,
The drill insert, the provided with a stepped down-like rake face from the seat and the seat surface on each of the two major surfaces, arranged alternately on the back relationship the two seat surface, and,
One rake face forms the rake face of the inner cutting edge, and the other rake face forms the rake face of the outer cutting edge ,
Above the rake face of the inner cutting blade has a chip discharge pocket,
The throw-away drill characterized in that the width of the drill insert is made smaller than the diameter of the holder, and the center axis of the fixing bolt is displaced from the center axis of the holder toward the outer cutting edge. The throw-away drill according to claim 1, wherein the inner cutting edge is bent in a back surface direction of the inner cutting edge . The throw-away drill according to claim 2, wherein the inner cutting blade is bent in the back direction at an intermediate portion of the inner cutting blade.

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