JP2002239822A - Throw-away type drill - Google Patents

Abstract

PROBLEM TO BE SOLVED: To carry out certain and smooth drilling work by preventing sudden increase of cutting resistance at the time of deflection of a tool main body and contact of a cutting blade without requiring many chips or a large chip in the case of carrying out the large diametrical drilling work on a workpiece especially. SOLUTION: Throw-away chips 17, 17 positioned on the inner peripheral side in the diametrical direction out of a plural number of the throw-away chips 17... are mounted so that their cutting blades 18 are arranged on the head end side in the axis O direction of the cutting blade 18 of the throw-away chip 17 on the outer peripheral side on a throw-away type drill constituted by mounting a plural number of the throw-away chips 17... on a head end part 15 of the roughly columnar tool main body 11 to be rotated around an axis O free to connect and disconnect as they are slipped in the diametrical direction so that rotating tracks around the axis O of their respective cutting blades 18 continue in the diametrical direction.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a throw-away type drill to which a throw-away tip (hereinafter, referred to as a tip) having a cutting edge at a tip end of a tool body is detachably mounted, and in particular, to a workpiece. The present invention relates to a throw-away drill suitable for use in forming a large-diameter hole.

[0002]

2. Description of the Related Art When a large diameter hole of, for example, about 50 to 100 mm is drilled in a workpiece, a general solid twist drill causes breakage of the tool body due to insufficient rigidity. It is desirable to use an away drill. Here, in such a throw-away type drill, a pair of tips is provided at the tip of the tool body,
It is known that the cutting blade is mounted so as to be shifted in the radial direction so that the rotation trajectory of the cutting blade is continuous in the radial direction.However, when a large-diameter drilling process is performed with such a throw-away type drill, First, each tip must be enlarged to increase the cutting edge length, which is uneconomical and inefficient.

Therefore, as a throw-away type drill used for performing such a large-diameter drilling, for example, as shown in FIG. 4, an axis O of a tip end portion of a tool body 1 rotated around an axis O is used. (Two to four in FIG. 4) are mounted on opposite sides of each other so that the above-mentioned rotation trajectories of the cutting edges 3 are alternately continuous in the radial direction. Have been proposed to ensure the outer diameter D of the cutting blades 3. Also, apart from this,
For example, as shown in FIG. 5, a pilot drill 5 in the form of a solid twist drill is protruded from the center of the tip end of the tool body 4, and a plurality of pairs of tips 6 are arranged around the periphery thereof on the opposite side with respect to the axis O. Are mounted so that the rotational trajectories of the cutting edges 7 substantially coincide with each other and are continuous in the radial direction on both sides of the axis O.

[0004]

However, in the indexable drill shown in FIG. 4, first, like the indexable drill in which a pair of tips are attached to the tip of the tool body, the tips 2 are cut. The blades 3 are all arranged at the same position in the axis O direction. For this reason, when it is going to start drilling in a workpiece, all of these cutting blades 3... Come into contact with the workpiece at once, and the cutting resistance increases very sharply. The cutting blades 3 may not bite into the workpiece, or the tool body 1 may be largely shaken, and in some cases, drilling may not be possible.

In the indexable drilling tool shown in FIG. 5, the pilot drill 5 at the tip guides the tool body 4 by performing drilling in advance, so that the tool body 4 is less likely to run out. However, the chip 6 around it ...
Are also arranged at the same position in the direction of the axis O, so that when these cutting edges 7 come into contact with the workpiece, it is inevitable that the cutting resistance suddenly increases and drilling is not possible. May be possible. In addition, in this throw-away type drill, if the tool body 4 oscillates due to the drilling by the inserts 6, the solid twist drill-shaped pilot drill 5 protruding from the tip easily breaks. In order to balance the cutting resistance on both sides of the axis O as described above, the rotational trajectories of the cutting edges 7 of the plural pairs of tips 6 are matched with each other, and uncut portions are left on the bottom surface of the machined hole. The cutting blades 7 must be attached so as to be continuous in the radial direction on both sides of the axis O so that the large diameter hole having the same diameter is formed even if the outer diameter of the pilot drill 5 is considered. Requires more chips 6... Or the size of individual chips 6 must be increased.

The present invention has been made under such a background, and particularly when a large diameter hole is drilled in a workpiece, a large number of chips and a large number of chips are not required, and the tool body is not required. An object of the present invention is to provide a throw-away type drill capable of preventing a sharp increase in cutting resistance at the time of run-out or contact of a cutting blade, and capable of performing reliable and smooth drilling.

[0007]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems and to achieve such an object, the present invention provides a plurality of chips at a tip end of a substantially cylindrical tool body rotated about an axis. Is a throw-away type drill which is detachably attached by being shifted in the radial direction so that the rotation trajectories of the cutting edges around the axis are continuous in the radial direction. The tip located on the inner peripheral side in the radial direction is characterized in that its cutting edge is arranged closer to the tip side in the axial direction than the cutting edge of the outer peripheral tip.
Therefore, in such a throw-away type drill, the cutting edge of the tip arranged on the inner peripheral side of the tool body tip portion makes a hole in the workpiece in advance, and then the cutting edge of the outer peripheral side defines the predetermined cutting edge. Since the large-diameter machining hole is formed, the cutting edge does not contact the workpiece at once, and it is possible to prevent a sharp increase in the cutting resistance. Like the drill, the tool body can be guided to suppress the occurrence of runout.

[0008] Here, a plurality of pairs of the chips are attached to the tip end of the tool body on opposite sides with respect to the axis so that the rotation trajectories of the cutting edges are alternately continuous in the radial direction. Of these, if the cutting blades of the pair of tips located on the inner peripheral side in the radial direction are arranged closer to the distal end in the axial direction than the cutting blades of the outer peripheral tip, the inner peripheral side of the distal end portion of the tool body In the above, the above-mentioned pair of tips will adopt a configuration similar to a conventionally known throw-away type drill for normal drilling in which the pair of tips is shifted in the radial direction. In addition to reducing run-out, the radially offset cutting edge of the outer tip prevents breakage like a conventional pilot drill even if the cutting resistance is not balanced on both sides of the axis. Can . Also, on the outer periphery of the tip of the tool body,
If a guide pad extending in the axial direction is provided,
The straightness of the tool body can be improved to further prevent runout.

[0009]

FIG. 1 and FIG. 3 show an embodiment of the present invention. In the present embodiment, the tool body 11 has a substantially multi-stage cylindrical shape with the axis O as the center,
A shank portion 13 for gripping the tool main body 11 on the main shaft of the machine tool is formed at a rear end portion thereof through a flange portion 12 formed in a flange shape. the outer peripheral portion, twisted from the distal end surface of the flange portion 12 to the tip face of the tool body 11, the spiral axis O toward the rear side in the rotation direction T of the tool body 11 toward the rear side a pair of chip discharge flutes 1
4 and 14 are formed on opposite sides of the axis O. In particular, the chip discharge grooves 14 and 14 have a substantially L-shaped cross section orthogonal to the axis O at the tip end portion 15 of the tool body 11. Is formed.

Further, in the distal end portion 15 of the tool body 11, an inner peripheral end portion 15A on the inner peripheral side protrudes one step distal end side from the outer peripheral end portion 15B on the outer peripheral side, and the axis O is formed. The chip discharge grooves 14, 14 are formed so as to have a substantially disk shape with the center at the center so that the depth of the chips at the front end portion 15 reaches the inner peripheral portion 15A at the front end. And, these chip discharge grooves 14, 1
The tip mounting seats 16 are formed at the tip end inner peripheral portion 15A and the tip outer peripheral portion 15B of the wall surface facing the tool rotation direction T side of No. 4, and the chip mounting seats 16 have the tips 17 mounted thereon. Then, the cutting blade 18 is slightly projected from the distal end surface of the tool body 11 at the distal inner peripheral portion 15A and the distal outer peripheral portion 15B, and the
Are detachably attached. That is, in the present embodiment, a pair of four tip mounting seats 16 are formed on the distal end inner peripheral portion 15A and the distal end outer peripheral portion 15B on opposite sides with respect to the axis O. Are mounted in the same arrangement as above, and the cutting edges 18 thereof are the cutting edges 18, 18 of the pair of tips 17, 17 mounted on the inner peripheral portion 15A.
Are a pair of chips 1 attached to the outer peripheral portion 15B of the tip.
And thus arranged in the direction of the axis O frontward of the 7 and 17.

In the present embodiment, the chips 17 are formed of a hard material such as a cemented carbide in the shape of a substantially rhombic flat plate of the same shape and size. The cutting edge 1 which is a rake face and which is bent at an obtuse angle and is outwardly convex at four side ridges of the rake face.
8 are formed respectively, toward the first cutting edge 18 to the distal end side as the bending point is at the forefront, it is attached to the chip mounting seat 16. In the pair of tips 17 attached to the distal end inner peripheral portion 15A and the distal end outer peripheral portion 15B, the positions of the bending points of the cutting blades 18. Have been equal.

Further, the distal end inner peripheral portion 15A and the distal end outer peripheral portion 15A
B, the chips 17, 17 attached to the chip mounting seats 16, 16 formed in one of the chip discharge grooves 14 (the upper chip discharge groove 14 in FIG. 3) have their cutting edges 18, 18 inside. While being arranged to be biased to the circumferential side,
Cutting 18, 18 of the chip 17, 17 is attached to the chip mounting seat 16 and 16 (the chip discharge groove 14 of the lower side in FIG. 3) the other chip discharge groove 14 in the reverse is arranged disproportionately on the outer peripheral side, Moreover, these cutting blades 18 are arranged so that their rotation locus around the axis O is continuous in the radial direction with respect to the axis O. The cutting edge 18 of the tip 17 attached to the tip inner peripheral portion 15A of the one chip discharge groove 14 located on the innermost side has an inner peripheral end exceeding the axis O and the other chip discharge groove 14 side. to be so as to be slightly over-center, also the rotation diameter of the axis O of the outer circumference end of the cutting edge 18 of the other chips 17 mounted on the distal outer peripheral portion 15B of the chip discharge groove 14 located on the outermost peripheral side , The outer diameter D of the indexable drill of the present embodiment.

Furthermore, in the present embodiment, the outer peripheral surface of the tool body 11, a substantially central portion between the pair of chip discharge grooves 14 and 14 in the circumferential direction, across the axis O a pair of grooves 20, 20 again Are formed on the opposite sides in parallel with the axis O. Brass guide pads 21 and 21 are detachably attached to these grooves 20 and 20 by pad fixing screws 22. The outer peripheral surfaces of the guide pads 21 and 21 slightly protrude from the outer peripheral surface of the distal end portion of the tool main body 11 so that the outer diameter is slightly smaller than the outer diameter D and forms an arc surface around the axis O. It is. In the direction of the axis O, the grooves 20, 20 spirally extend parallel to the axis O from a position slightly retracted from the distal end surface of the tool body 11 at the distal end outer peripheral portion 15B. Chip discharge grooves 14, 1
4 is formed just before crossing, thus guide pads 21 and 21 the tool body 1 is also in the direction of the axis O
It is arranged only within the range of one tip side.

[0014] However, when performing drilling by the thus constructed throw-away drill, first cutting edge 18, 18 of a pair of chips 17, 17 attached to the distal end inner circumferential portion 15A is preceded Then, the cutting edge 18 of the pair of tips 17, 17 attached to the distal end outer periphery 15B is formed after forming a processing hole by making a hole protruding from the outer peripheral end 15B. , 18
As a result, the processing hole is widened, and a processing hole having a predetermined inner diameter equal to the outer diameter D is formed. Therefore, even if the same four tips 17 are attached, the cutting edges 18 of the four tips 17 do not come into contact with the workpiece at one time unlike the throw-away type drill shown in FIGS. For,
At the time of this contact, the cutting resistance does not increase at a stretch, and drilling is not impossible due to such a sharp increase in the cutting resistance. On the other hand, the cutting blades 17 are radially displaced from each other at the distal end inner peripheral portion 15A and the distal end outer peripheral portion 15B, and their rotation trajectories are continuous. If the lengths are the same,
Insert 1 less than indexable drill shown in Figure 1
8, a large outer diameter D can be secured, and it is economical and efficient even when a large-diameter drilling process is performed.

Moreover, the cutting edges 18, 18 of the tips 17, 17 attached to the inner peripheral portion 15A of the distal end in this manner are located closer to the distal end than the cutting edges 18, 18 of the tips 17, 17 of the outer peripheral portion 15B of the distal end. Then, the inner peripheral portion 15A of the distal end moves the tool main body 11 along its axis O.
The tool body 11 does not run out even when the cutting edges 18, 18 of the tips 17, 17 at the outer peripheral portion 15B of the tip come into contact with the workpiece. even it is possible to form a high linearity machined hole. In addition, in this embodiment, the guide pad 2 is provided on the outer peripheral surface of the tool body 11.
The guide pads 21 and 21 are attached to the tool body 11 while slidingly contacting the inner periphery of the machining hole.
Order but to advance, not only the guidance of a tool tip side by the tip inner circumferential portion 15A, so as to go straight along the tool body 11 in the axis O in the rear end side of the tool tip 15 provided with the cutting edge 18, 18 , And it is possible to ensure a high straightness even when the machined hole is pulled out.

If attention is paid only to the tip inner peripheral portion 15A which comes into contact with the workpiece in advance, a pair of chips 17, 17 are provided on the tip inner peripheral portion 15A,
18 are arranged so as to be shifted in the radial direction so that the rotation trajectories 18 are continuous, that is, the structure of the tip of a conventionally known throw-away type drill for performing medium and small diameter drilling. . However, such a throw-away type drill has higher rigidity than the solid twist drill as described above, that is, higher rigidity than the pilot drill 5 shown in FIG.
The outer diameter of the cutting edge 18 at 18A (the axis O of the cutting edge 18 of the tip 17 attached to the other chip discharge groove 14 side)
Even by increasing the rotational diameter) d around the, does not tip the peripheral portion 15A is easily or breakage. Moreover,
As described above, the outer diameter d of the cutting blades 18, 18 of the inner peripheral portion 15A at the distal end is obtained.
Is increased, the distance from the axis O increases, so that the cutting amount increases.
It is also possible to balance the cutting amounts of the cutting blades 7 and 17 with the cutting blades 18 and 18.

The throw-away type drill having such a configuration is suitable for drilling a large-diameter hole as described above, that is, for performing medium- and small-diameter drilling, the individual chips 17. However, when a hole having an extremely large diameter is to be drilled, it is more efficient to use, for example, a BTA tool or a trepanning tool. For this reason, it is appropriate to use the above-mentioned throw-away type drill for drilling a hole having an inner diameter in the range of about 50 to 100 mm.
It is also desirable to set this in accordance with this. Also, the ratio d / D of the outer diameter d to the outer diameter D is too small,
If the distance L in the direction of the axis O between the cutting edge 18 disposed on the front end side and the cutting edge 18 disposed on the rear end side is too large, how rigid the throw-away drill structure is such that the distal end inner peripheral portion 15A has high rigidity. However, if the ratio d / D is too large or the distance L is too small, the effect of arranging the inner cutting edge 18 on the distal end side from the outer peripheral side can be obtained. There is a risk that the response will not be sufficient. Therefore, it is desirable that the ratio d / D is set in the range of 0.4 to 0.8, and the distance L is set in the range of 5 mm or more and d / 2 or less.

[0018]

As described above, according to the present invention,
In indexable drills for drilling large diameter holes,
Without requiring a lot of chips and large chip, moreover or cutting resistance increases rapidly when these chips comes into contact with the workpiece, no shake the tool body or occur during processing, large it is possible to perform the drilling reliably and smoothly.

[Brief description of the drawings]

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

FIG. 2 is an enlarged side view of a tool tip 15 of the embodiment shown in FIG.

3 is a front view of the embodiment shown in FIG. 2 as viewed from a tool tip side.

FIG. 4 is a side view showing a conventional indexable drill.

FIG. 5 is a side view showing another conventional indexable drill.

[Explanation of symbols]

 Reference Signs List 11 Tool body 14 Chip discharge groove 15 Tip part of tool body 11 15A Tip inner peripheral part 15B Tip outer peripheral part 17 Throw-away tip 18 Cutting blade 21 Guide pad O Axis line of tool main body 11 Tool rotation direction

Claims (3)

[Claims] 1. A plurality of indexable inserts are provided at the tip of a substantially cylindrical tool body that is rotated about an axis such that rotation trajectories of the cutting blades about the axis are continuous in the radial direction. A throw-away drill that is detachably attached by being displaced in the direction, and among the plurality of throw-away tips, the throw-away tip that is located on the inner peripheral side in the radial direction has a cutting edge whose outer periphery is Characterized in that the drill is disposed closer to the tip end in the axial direction than the cutting edge of the indexable insert on the side. 2. A plurality of pairs of the indexable inserts, which are opposite to each other with respect to the axis, at the tip end of the tool body, so that the rotational trajectories of the cutting edges are alternately continued in the radial direction. It is characterized in that the cutting blades of the pair of throw-away tips located on the inner peripheral side in the radial direction are disposed more axially distal than the cutting edges of the throw-away tips on the outer peripheral side. Claim 1
A throw-away drill according to item 1. Wherein the distal end outer periphery of the tool body, indexable drill according to claim 1 or claim 2, characterized in that the guide pad extends toward the axis direction is provided.