JPH11138320A - Drill - Google Patents

Abstract

PROBLEM TO BE SOLVED: To secure a stable size accuracy and a good finish surface coarseness, by improving the chip exhausting performance in a boring process. SOLUTION: At the outer peripheral corner of a front end cutting edge 4, a different level part guide surface 11 extending in the axial direction, and a step end face extending in the diameter direction are formed. A stepped cutting edge 5 is formed at the ridge line crossing the step end face and a grove side face 13 erecting a chip exhaust groove 9. The tip of a pressing part 6 at the front side in the rotating direction of the chip exhaust groove 9 is positioned by retreating to the rear side in the axial direction from the stepped cutting edge 5.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a drill for performing drilling with high precision.

[0002]

2. Description of the Related Art Reaming is a process in which the diameter is increased in accordance with a pilot hole previously formed by drilling, and is a finishing process for obtaining good dimensional accuracy and surface roughness. However, conventionally, there has been a problem that the depth of cut fluctuates depending on the quality of the prepared pilot hole diameter, and that machining cannot be performed to the expected accuracy. Further, the two processes of drilling and reaming have problems such as poor machining efficiency.

[0003] In order to solve these problems, a tool capable of simultaneously performing drilling and reaming has been developed and provided.

[0004] First, a drill shown in FIG. 7 has a cutting edge 20 opposed to a tip end of a drill body having an irregular cross section connected to a cylindrical shank and a rotating direction x connected to the cutting edge 20.
A rear slope 21 and a guide surface 22 extending axially rearward from an edge of the slope 21 are formed.

[0005] The cutting edge 20 has a constant cutting edge angle which retreats toward the rear end side as it goes radially outward from the axis of the front end portion. The vicinity of the axis of the cutting edge 20 is made of a cemented carbide, and the outer peripheral side is made of a diamond sintered body or the like fixed by brazing.

[0008] Next, as disclosed in Japanese Utility Model Publication No. 6-45287, as shown in FIG. 8, a small diameter portion 34 smaller than the maximum outer diameter of the drill body is provided at the tip of a cylindrical drill body connected to the shank. It is formed on the tip side from the step portion 33. A first cutting edge 31 that is inclined at a first cutting edge angle in a direction approaching the shank as it goes radially outward and extends radially outward is formed at the tip of the small diameter portion 34. The outer periphery of the distal end of the small-diameter portion in a direction orthogonal to the first cutting edge 31 has a second cutting edge inclined in a direction away from the shank as it goes radially outward.
Cutting edge 32 is formed.

[0007] Japanese Utility Model Publication No. 6-45287 discloses a drill body in which a plurality of reamer grooves extending in parallel along a central axis are provided in parallel on the outer periphery of a drill body. On the outer circumference of the tip end side of the drill body, a biting step portion is formed continuously in the reamer groove, and a surface extending in the radial direction of the drill body at the step portion is a rake face, and the rake face The angle between the drill and the center axis of the drill body is set to an angle equal to or less than a right angle, and a forward angle is provided on the rake face in the tool rotation direction. Further, a flank is provided on the outer periphery of the drill body connected to the rake face, and a finishing blade is provided on an intersection ridge line between the rake face and the flank.

[0008]

Here, the problems of the prior art will be described below. In the first prior art, a so-called drill blade and a reamer blade are integrally formed. When machining with this kind of tool, it is necessary to use it under conditions with a low feed amount. This is because when the feed amount is increased, the hole diameter tends to increase due to an increase in the cutting resistance and an increase in the amount of deposits on the cutting edge, and the finished surface roughness tends to deteriorate. In addition, the biting property in the initial stage of cutting is poor, and whirling may be induced at the tip of the drill body. In this case as well, the hole diameter may be increased or the finished surface roughness of the inner wall surface may be deteriorated. When the cutting edge is formed by a diamond sintered body, chipping or chipping may occur due to a variation in finishing margin, and sometimes cutting becomes impossible. This is because the diamond sintered body itself has a high hardness but is a brittle material.

Next, in the second prior art, the first cutting edge and the second cutting edge are arranged so as to intersect with the same axis of the drill body. A chip discharge groove is adjacent to the cutting edge. The second cutting edge as a finishing blade is configured so that a certain amount of margin can be secured, and the load on the cutting edge is reduced,
The dimensional accuracy and the finished surface roughness of the machined hole can be improved.

However, since the first cutting edge and the second cutting edge are arranged in different radial directions so as to cross each other in a cross-sectional view, it is necessary to discharge chips generated by the second cutting edge. The space of the drill must be shallow and narrow, and it becomes difficult to carry out the chips smoothly from the front end side to the rear end side of the drill body. If chips accumulate during machining, the cutting edge will bite the chips and cause chipping, or the chips will be trapped between the side surface of the drill body and the inner wall of the hole, causing scratches on the inner wall surface of the machined hole. Or attach it. Since the pressing portion is not formed on the outer periphery of the blade portion, it is inferior in centripetality and guideability, and may induce vibration. Further, since the cutting fluid is hard to penetrate, heat generation of the cutting edge may be caused, and abrasion of the cutting edge may be accelerated, or the surface roughness of the finished surface may be reduced due to generation of welded matter or deposits.

Although the third prior art can improve the dimensional accuracy of the machined hole and the roughness of the finished surface, and is quite useful in solving the above-mentioned problem, the third prior art does not.
In the same manner as in the prior art, the chips discharged by the finishing blade must be carried out through a narrow space called the reamer groove, so that the surface roughness of the finished surface may deteriorate due to contact between the chips and the inner wall surface of the machining hole. is there.

Although some of the above prior arts are quite useful in solving the problem, there has been a demand for the development of a drill that further improves the dimensional accuracy and the like in finishing. The present invention has been made from such a viewpoint, and an object of the present invention is to provide a tool capable of obtaining good dimensional accuracy and finished surface roughness by improving the configuration of a cutting edge.

[0013]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has a shank portion formed at one end of a cylindrical drill body and a chip discharge groove formed at the other end. An elongated blade portion is formed, and a pressing portion is formed on the outer periphery of the blade portion at least in front of the chip discharge groove in the rotation direction, and at the tip of the blade portion, the rotation of the chip discharge groove is formed. In a drill provided with a pair of tip cutting edges in the rear direction, the outer peripheral corner of the tip cutting edge is formed by a step guide surface extending in the axial direction and a step end surface extending in the radial direction. The stepped portion is notched, and a stepped cutting edge is formed at the intersection ridgeline between the stepped end surface and the rake face on which the chip discharge groove is erected, and a pressing portion located in front of the chip discharge groove in the rotation direction. Is located axially behind the step cutting edge. And characterized in that it retreat.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

FIGS. 1 and 2 show a drill according to the invention. The drill body 1 has a shank portion having a columnar shape and a blade portion 2 having an irregular cross section in which a part of a circle is notched in a fan shape.
It is schematically composed of A pair of chip discharging grooves 9 and a pressing portion 6 for carrying out chips are provided along the center axis of the drill body 1 on the outer periphery of the blade portion 2. Since the chip discharge groove 9 is formed deep and wide, chips generated during processing can be smoothly carried out from the front end side to the rear end side of the drill body 1 through these grooves. The pressing portion 6 is located forward of the chip discharge groove 9 in the rotational direction, and at the same time, its tip is located backward in the axial direction from a step cutting edge 5 described later. The outer peripheral side surface of the pressing portion 6 is formed in a curved arc shape that is the same as or slightly smaller than the curvature of the inner wall of the processing hole, thereby maintaining the finished surface roughness of the inner wall surface of the hole and vibration of the drill body 1. Is suppressed, and processing with good centripetality can be performed.

At the tip side of the blade portion 2, a tip cutting edge 4 for preparing a prepared hole and a step cutting edge 5 for performing a finishing process.
Are arranged via the step 3 of the outer peripheral corner. The step cutting edge 5 referred to here functions as a so-called finishing cutting edge for expanding a prepared hole to a desired processing diameter.

The tip cutting edge 4 has a chisel portion 16 including an axis.
A predetermined angle α in the direction from the tip to the outer peripheral side.
(Hereinafter referred to as “tip angle”). In a small area near the central axis of the tip cutting edge 4, a concave groove adjacent to the tip cutting edge 4 is formed (hereinafter simply referred to as "thinning"). Normally, this part forms a part of the tip part as a part that performs a pushing action rather than a cutting action.However, by forming thinning, it is also possible to apply this small area near the central axis where the cutting speed is low. A cutting action can be performed. As a result, the pushing force in the axial direction of the drill body is reduced, and it becomes possible to improve the centripetality, the biting property, the positioning accuracy, and the like.

Behind the tip cutting edge 4 in the rotational direction x, a tip flank 7 is formed which inclines rearward in the axial direction as going outward in the radial direction. An oil hole can be formed in the flank face 7 at the tip end. Further, an outer peripheral flank 8 extending along the central axis is formed axially rearward of the drill body 1 so as to be continuous with the distal flank 7. By forming the front end flank 7 and the outer peripheral flank 8, it is possible to prevent portions other than the cutting edge from interfering with the inner wall surface of the processing hole during processing.

In the preparation of a pre-drilled hole, ie, drilling, a cutting force in the direction of the central axis of the drill body 1 (hereinafter referred to as "thrust").
Since the cutting force in the rotation direction x simultaneously acts on the tip cutting edge 4, it is necessary for the drill body 1 itself to have excellent mechanical properties in both rigidity and cutting edge strength. In particular, the vicinity of the axial center of the tip cutting edge 4 is a place where the thrust acts most strongly, so that consideration must be given to the cutting edge loss.
Therefore, it is advantageous in terms of strength that the tip cutting edge 4 is integrally formed of the same material as the drill body 1. By configuring the drill body 1 with an appropriate tool material, it is possible to maximize the performance inherent in the tool.

The outer peripheral corner of the tip cutting edge 4 has a surface 11 (hereinafter, appropriately referred to as a “step guide surface”) extending rearward in the axial direction of the drill body 1 and a surface 12 extending radially outward.
(Hereinafter referred to as “step end face” as appropriate) is cut out. According to FIG. 3, the step portion 3 is
It is recessed axially rearward and radially inward, and the amount of axial dent is set to 1/2 or more of the feed amount, and the amount of dent in the radial direction is set in consideration of the amount of cutting of the step cutting edge 5 described later. Is done.

First, the step guide surface 11 is formed so as to be inclined so as to have a smaller diameter as it goes from the front end to the rear end of the drill body 1, and has an inclination angle β (hereinafter simply referred to as “inclination”) with respect to the center axis of the drill body 1. The angle is set to 0 ° to 30 °. If the inclination angle β is smaller than 0 °, a cutting action occurs on the intersection ridge line between the groove side surface 13 where the chip discharge groove 9 is erected and the step guide surface 11, which is not preferable. If the inclination angle β is larger than 30 °, the strength of the corner portion of the tip cutting edge 4 is reduced, which may cause cutting edge chipping.

Next, the step end face 12 is formed so as to be inclined forward in the axial direction as going outward in the radial direction, and is inclined at an angle γ (hereinafter referred to as “cutting edge angle”) that is inclined with respect to a section perpendicular to the axis of the drill body 1. Is set to 0 ° to 45 °. As a result, the direction of inclination of the leading edge cutting edge 4 and the direction of inclination of the stepped cutting edge 5 are opposite to each other.
4 are different from each other, so that the chips 14 can be reliably separated.

FIGS. 4 (a) and 4 (b) show that the chip outflow direction is different depending on the inclination of the stepped cutting edge 5. FIG. As shown in FIG. 4A, when the tip cutting edge 4 and the step cutting edge 5 are inclined in the same direction, the direction in which the chips 14 flow out is also substantially the same. On the other hand, as shown in FIG. 4B, when the tip cutting edge 4 and the step cutting edge 5 are inclined in opposite directions, the direction in which the chips 14 flow out is also opposite. In the former case, if the feed in the axial direction of the drill body 1 is small, the chip 3
If the chips are divided into stages, but the feed is large, the chips 14 may be discharged integrally without being divided into two stages. In the latter case, the chips 14 are surely divided into two stages and discharged, so that stable cutting can be maintained and the finished surface is not deteriorated.

The cutting edge angle γ also has a very important effect on the cutting action of the step cutting edge 5 formed at the intersection ridgeline between the groove end face 13 of the chip discharge groove 9 and the step end face 12. As shown in FIGS. 5A and 5B, since the welded material 15 tends to be generated in a direction perpendicular to the cutting edge, the cutting edge corner portion projects radially outward due to the welded material 15. In this case, the over-cutting not only increases the hole diameter but also deteriorates the finished surface roughness. As the amount of feed forward in the axial direction per rotation (hereinafter, simply referred to as “feed”) increases, the amount of deposit 15 increases, the amount of increase in the hole diameter further increases, and the surface roughness of the inner wall surface of the hole increases. It gets even worse. Chipping may occur on the cutting edge due to the formation and detachment of the deposit 15. FIG. 5A shows a case where a conventional drill is used, in which an overcut c is generated by the welded material 15. FIG. 5B shows a case where the drill of the present invention is used, and shows that the overcut amount c decreases.

More specifically, when the cutting edge angle γ is smaller than 0 °, the deposited material 15 at the cutting edge corner portion accumulates.
Over-cutting may occur, causing the hole diameter to increase or the surface roughness to deteriorate. However, when the cutting edge angle γ exceeds 45 °, the angle of the cutting edge corner portion becomes too acute, and the cutting edge strength is reduced, which is not a preferable configuration. Therefore, the present invention sets the cutting edge angle γ from 0 ° to 4 °
The angle is set to 5 ° to improve the dimensional accuracy of the machined hole and the roughness of the finished surface.

Regarding the geometric configuration of the step end face 12,
This will be described in detail with reference to FIGS. 6A and 6B in which the step portion 3 is schematically enlarged. The direction in which the step end surface 12 inclines is
The drill body 1 may be inclined rearward in the central axis direction as it goes backward in the rotation direction x, or it may incline forward in the central axis direction as it goes backward in the rotation direction.
FIG. 6A shows a case where the angle of inclination δ of the drill body 1 with respect to the section perpendicular to the axis is positive, and FIG. 6B shows the angle of inclination δ of the drill body 1 with respect to the section perpendicular to the axis (hereinafter referred to as “bite”). Angle) is negative.

If the bite angle δ is positive, the step end surface 12
The crossing ridgeline between the cutting edge 9 and the groove side surface 13 becomes the step cutting edge 5, and the tip cutting edge 4 and the step cutting edge 5 are arranged in the same radial direction when viewed from the front. Therefore, each cutting edge uses the groove side surface 13 of the chip discharge groove 9 as a common rake face, and discharges the chips 14 by passing over the rake face. This configuration is particularly advantageous for chip evacuation.

On the other hand, when the biting angle δ is negative, the intersection of the outer peripheral flank 8 extending rearward in the rotational direction x adjacent to the step end face 12 and extending rearward in the axial direction and the step end face 12. The ridge line becomes the step cutting edge 5. In this case, the rake face of the step cutting edge 5 becomes the step end face 12, which is different from the above configuration, but the chips 14 passing over the step section 12 are discharged by the chip discharge grooves 9. You. Also in this case, similarly to the above, the tip cutting edge 4 and the step cutting edge 5 are configured to share the chip discharge groove 9, and the chip 14
It is possible to prevent the finished surface from being deteriorated due to the discharge of water.

When the bite angle δ is negative, the greater the bite angle δ, the thinner the chip in the direction perpendicular to the cutting edge, which is more effective in preventing welding. However, as the bite angle δ increases, the step cutting edge 5
Approaches the tip cutting edge 4 and the bite angle δ exceeds −60 °, it becomes difficult to separate the chips 14 into two steps, and the effect of improving the finished surface roughness and the like is reduced. Therefore, in order to prevent such an adverse effect, the bite angle δ is set to −
It is preferable that the angle is 5 ° to -60 °.

The processing by the step cutting edge 5 is performed by the tip cutting edge 4.
Is performed subsequent to the preparation of the prepared hole, thereby eliminating the trouble of controlling the prepared hole diameter and continuously performing the processing of a predetermined finishing margin. The cutting amount of the step cutting edge 5 is given as a radius difference a between the step cutting edge 5 and the tip cutting edge 4. The radius difference a needs to be set so that a flaw or the like on the inner wall of the processing hole formed by the tip cutting edge 4 can be removed. Radius difference a is 0.0
If it is less than 1 mm, it becomes difficult to completely remove the uncut portion of the leading edge cutting edge 4 with the stepped cutting edge 5, and it is not possible to improve the finished surface roughness. On the other hand, 2.00
If it exceeds mm, the load on the step cutting edge 5 increases, and the finished surface may be deteriorated. Therefore, the radius difference a is preferably set to 0.01 mm to 2.00 mm.

As described above, it is important to consider the wear and welding of the cutting edge in order to secure desired dimensional accuracy and surface roughness by the step cutting edge 5. Deposit 15
Is also affected by the type of workpiece, the constituent material of the cutting edge, etc., especially when aluminum alloy is used as the workpiece,
Care must be taken because the generation and detachment of the welded material 15 and the constituent cutting edges are continuously repeated. In this regard, the configuration of the step cutting edge 5 according to the present invention can avoid the above-mentioned inconvenience.

Further, in the processing of an aluminum alloy, it is extremely advantageous to employ a diamond sintered body tool. This is because a diamond sintered body has high welding resistance, and particularly has an extremely low affinity for an aluminum alloy.
In addition, it is excellent in abrasion resistance, and by maintaining a sharp cutting edge shape, it is possible to avoid scuffing and digging of the finished surface. Although a diamond sintered body is a suitable choice, a cemented carbide or another hard sintered body may be used if similar functions and effects can be expected. The cutting edge shape of the drill and the constituent material thereof can complement and complement each other to exhibit the performance, and from this viewpoint, the optimal selection of the constituent material is extremely important.

[0033]

As described above, according to the drill of the present invention in which the tip cutting edge and the step cutting edge are arranged in a position that shares the chip discharge groove, the chip discharged by the step cutting edge is retained. It is possible to discharge smoothly without any problem, to improve the dimensional accuracy and the roughness of the finished surface, and to satisfactorily finish the inner wall surface of the machined hole.

[Brief description of the drawings]

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

FIG. 2 is a front view of FIG.

FIG. 3 is an enlarged view of an outer corner of FIG. 1;

4A and 4B are diagrams illustrating a relationship between a cutting edge shape and a chip outflow direction, in which FIG. 4A is a diagram in a case where a leading edge cutting edge and a step cutting edge are inclined in the same direction, and FIG. FIG. 7 is a view showing a case in which a step cutting edge and a step cutting edge are inclined in opposite directions.

5A and 5B are schematic diagrams of a conventional drill, and FIG. 5B is a schematic diagram of a drill according to the present invention, illustrating a relationship between a cutting edge shape and a welded material in an outer peripheral corner.

6A and 6B are perspective views of the outer peripheral corner, illustrating the relationship between the step portion of the blade portion and the biting angle. FIG. 6A is a schematic diagram when the biting angle δ is positive, and FIG. FIG. 9 is a schematic diagram when the angle of incidence δ is negative.

7A is a front view showing a first conventional example, and FIG.
It is an enlarged side view of the outer peripheral corner.

8A is a front view showing a second conventional example, and FIG.
It is an enlarged side view of the outer peripheral corner.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Drill main body 3 Step part 4 Tip cutting edge 5 Step cutting edge 9 Chip discharge groove 11 Step guide surface 12 Step end face β Incline angle γ Cutting angle δ Biting angle

Claims (4)

[Claims] 1. One end of a cylindrical drill body 1 is
A shank portion is formed, and the other end is formed with a blade portion 2 provided with a chip discharge groove 9. On the outer periphery of the blade portion 2, a pressing portion 6 is provided at least forward of the chip discharge groove 9 in the rotation direction. Is formed, and a drill having a pair of tip cutting edges 4 at the tip of the blade portion 2 in the rotation direction of the chip discharge groove 9 is provided. The step 3 formed by the step guide surface 11 extending in the axial direction and the step end face 12 extending in the radial direction is cut out, and the step end face 12 and the chip discharge groove 9 are erected. The stepped cutting edge 5 is formed at the intersection ridgeline with the groove side surface 13 to be formed, and the tip of the pressing portion 6 located in front of the chip discharge groove 9 in the rotation direction is retracted axially rearward from the stepped cutting edge 5. A drill characterized in that: 2. The drill according to claim 1, wherein the step end face 12 has a bite angle δ of −5 ° to −60 ° with respect to a section perpendicular to the axis. 3. The step guide surface 11 is formed so as to be inclined so as to have a smaller diameter from the front end to the rear end of the drill body 1 and has an inclination angle β with respect to the center axis of the drill body 1 of 0 ° or more. The step end surface 12 is formed so as to be inclined forward in the axial direction as it goes radially outward, and the cutting edge angle γ with respect to a cross section perpendicular to the axis of the drill body is 0 °. The drill according to claim 1, wherein the angle is set to 45 °. 4. The radius difference a between the outermost point of the step cutting edge 5 and the outermost point of the tip cutting edge 4 is 0.01 mm to 2.00.
The drill according to any one of claims 1 to 3, wherein the drill is set to mm.