JP3850000B2 - Drill - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a drill that performs drilling with high accuracy.
[0002]
[Prior art]
The reamer process is a process of expanding the diameter following a pilot hole previously drilled, and is a finishing process for obtaining a desired hole diameter and finished surface. However, the two-step machining by drilling and reamer machining has poor machining efficiency, and the amount of cutting varies depending on the quality of the drilled prepared hole diameter, and there are cases where machining cannot be performed with the expected accuracy.
[0003]
Therefore, in order to obtain the expected accuracy and to improve the machining efficiency, a tool capable of simultaneously performing drilling and reaming has been developed and provided.
[0004]
First, the drill shown in FIG. 7 has a cutting edge 20 facing each other at the tip of a drill body having an irregular cross section connected to a cylindrical shank, a slope 21 behind the cutting direction 20 in the rotational direction x, and an edge of the slope 21. And a guide surface 22 extending rearward in the axial direction. The cutting edge 20 has a constant cutting edge angle that recedes toward the rear end side as it goes radially outward from the axial center of the front end portion. The vicinity of the axis of the cutting edge 20 is made of cemented carbide, and the outer peripheral side is made of a diamond sintered body fixed by brazing.
[0005]
Next, as disclosed in Japanese Utility Model Publication No. 7-31926, as shown in FIG. 8, a small-diameter portion 30 smaller than the maximum outer diameter of the drill main body is provided from the stepped portion at the tip of the cylindrical drill main body connected to the shank. It is formed toward the tip side. A first cutting edge 31 that is inclined at a first cutting edge angle in a direction approaching the shank as it goes in the radially outward direction is formed at the tip of the small diameter portion 30. A second cutting edge 32 that is inclined with a second cutting edge angle in the direction away from the shank is formed on the outer periphery of the distal end of the small-diameter portion in the direction orthogonal to the first cutting edge 31 as viewed from the front end. Has been.
[0006]
[Problems to be solved by the invention]
Here, the problems of the prior art are described below.
[0007]
In the first prior art, in particular, since the biting property at the initial stage of cutting is poor, there is a case where a swinging motion is induced at the tip end portion of the drill body. The finished surface roughness may be deteriorated. In addition, although the outer peripheral blade is formed of a diamond sintered body to improve the processing accuracy, processing with a constant finishing allowance may cause chipping or chipping, which may make cutting impossible. This is because the diamond sintered body itself has a high hardness but is a brittle material.
[0008]
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 blade. Since the second cutting edge as the finishing blade is configured to ensure a certain amount of finishing allowance, the adverse effect of the first prior art is prevented, and the cutting stability, the dimensional accuracy / finishing of the machining hole are prevented. The surface roughness can be improved.
[0009]
However, when machining is performed with high efficiency by increasing the feed amount in the axial direction of the drill body, the burden on the cutting edge increases, which may induce chipping. In such a case, the diamond sintered body is particularly disadvantageous. In addition, the space for discharging chips generated by the second cutting edge, which is the finishing blade, must be shallow and narrow, and the chips can be smoothly moved from the distal end side to the proximal end side of the drill body. It becomes difficult to carry out. If chips remain during machining, the cutting blade bites the chips and induces chipping, or entrains chips between the side of the drill body and the inner wall of the hole, and scratches the inner wall of the processed hole. Sometimes it is attached. In addition, since the cutting fluid hardly penetrates, the cutting edge may generate heat, and the wear of the cutting edge may be accelerated, or the finish surface roughness may be reduced due to the formation of welds and deposits.
[0010]
Therefore, the present invention forms an intermediate blade between the main blade and the finishing blade, and prevents the cutting blade from being damaged by forming the finishing blade adjacent to the main chip discharge groove. The present invention provides a tool capable of improving accuracy and finished surface roughness.
[0011]
[Means for Solving the Problems]
The present invention has been made in view of the above-described problems. A shank portion is formed at one end of a cylindrical drill body, a blade portion is formed at the other end, and main chips are discharged on the outer periphery of the blade portion. A groove is provided, a pressing portion extending in parallel with the axial direction is provided in front of the main chip discharging groove in the rotation direction, and a pair of main blades 6 having a predetermined tip angle are provided at the tip of the blade portion. In the drill, a chamfered finishing blade made of a diamond sintered body is formed at the outer peripheral corner of the main blade, and is located at a position that is substantially 90 ° behind the rotation direction of the finishing blade. A chamfered intermediate blade having a predetermined cutting edge angle is formed on the outer periphery of the blade portion having a diameter larger than the radius and smaller than the radius of rotation of the finishing blade, and the outermost axis of the intermediate blade. Position in the direction between the outermost point of the main blade and the outermost point of the finishing blade Rutotomoni, the rotational locus is characterized by being arranged to protrude axially forward from the finishing blades.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
[0013]
1 to 3 show a drill according to the present invention. The drill main body 1 is roughly constituted by a shank portion having a cylindrical shape and a blade portion 2 having an irregular cross-section in which a part of a circle is cut out in a fan shape. A main chip discharge groove 3 and a sub chip discharge groove 4 for carrying out chips are arranged in parallel along the axial direction of the drill body 1 on the outer periphery of the blade portion 2, and the main chip A pressing portion 5 is disposed extending in the axial direction in front of the rotation direction x of the discharge groove 3.
[0014]
The chip discharge groove is for smoothly carrying out chips generated during machining from the distal end side of the drill body 1 to the proximal end side through the grooves together with the cutting fluid. However, the chip discharge performance varies depending on the depth and width of the chip discharge groove. In this respect, the deep and wide main chip discharge groove 3 can discharge chips smoothly.
[0015]
The pressing portion 5 is for suppressing vibration of the drill body 1 and performing processing with good centripetality. The tip of the pressing portion 5 is positioned away from the tip of the drill body 1 and retracted in the axial direction. The outer peripheral side surface of the pressing portion 5 is formed in a curved arc shape that is the same as or slightly smaller than the curvature of the inner wall of the processed hole, and thereby the finished surface roughness of the inner surface of the processed hole is improved.
[0016]
As shown in FIG. 1, a main blade 6 for drilling a pilot hole is provided on the inner peripheral side of the tip of the blade portion 2, and an intermediate blade for expanding the diameter of the pilot hole on the outer peripheral side of the tip of the blade portion 2. 7 and a finishing blade 8 are provided. When viewed from the front end, the main blade 6 and the finishing blade 8 are arranged on the same plane, and the intermediate blade 7 is positioned away from them in the rotational direction x rearward. The positional relationship in the radial direction of the outermost point of each cutting edge is such that the main blade 6, the intermediate blade 7, and the finishing blade 8 have a larger diameter in this order.
[0017]
First, the main blade 6 extends to the front of the outer periphery of the blade portion at a predetermined angle α (hereinafter referred to as “tip angle”) in a direction from the tip toward the outer peripheral side following the chisel portion 9 including the shaft center. Is formed. A concave groove adjacent to the main blade 6 is formed in a small region near the central axis o of the main blade 6 (hereinafter simply referred to as “thinning”). Normally, this part forms part of the tip as a part that performs a pushing action rather than a cutting action. However, by forming a thinning, this part is also located in the vicinity of the central axis o 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 main body is reduced, and it becomes possible to improve centripetality, biting property, positioning accuracy, and the like.
[0018]
At the rear of the main blade 6 in the rotational direction x, there is formed a tip flank 10 that is inclined axially rearward as it goes radially outward. An oil hole may be formed in the tip flank 10. Further, an outer peripheral flank 11 extending in parallel with the axial direction of the drill body 1 is formed continuously with the tip flank 10. By forming these flank faces, portions other than the cutting edge are prevented from interfering with the inner wall surface of the machining hole during machining.
[0019]
Next, the intermediate blade 7 is located at a position where the phase of the main blade 6 and the finishing blade 8 to be described later are substantially 90 ° behind the rotational direction x and has a diameter larger than the rotation radius R1 of the main blade 6 and the finishing blade. A chamfered cutting edge having a cutting edge angle β is formed on the outer periphery of the blade portion 2 having a rotation radius R2 smaller than the rotation radius R3. From FIG. 3, the outermost point of the intermediate blade 7 is the outermost point of the main blade 6 extending radially outward at the tip angle α and the outermost point of the finishing blade 8 on the outermost diameter of the blade portion 2. In addition to being positioned in the middle, the rotation locus is positioned so as to protrude forward in the axial direction from the finishing blade 8. As a result, the intermediate blade 7 contributes to reducing the burden on the subsequent finishing blade 8, improving the working efficiency, improving the rotational balance of the drill body 1, and the like.
[0020]
That is, the intermediate finishing edge 8 and the finishing edge 8 divide the original finishing allowance δ into ε1 and ε2 in two stages, and processing with a good balance of low cutting resistance is performed. Further, the feed amount in the axial direction can be increased, and high-efficiency machining can be performed. The cutting allowance ε2 is set to such an extent that scratches on the finished surface and minute irregularities can be removed. This is because if the machining allowance ε2 is excessively increased, the significance of sharing the machining allowance δ in two steps is reduced, leading to an increase in cutting resistance.
[0021]
The finishing blade 8 is connected to the main blade 6 having a tip angle α, and is formed into a chamfered cutting blade having a predetermined cutting angle γ. The cutting edge angle γ is determined in consideration of the balance between cutting edge strength and sharpness. In this configuration, the cutting edge strength is given priority. Further, the finishing blade 8 is formed adjacent to the deep and wide main chip discharge groove 3, and the chip is formed between the inner wall of the machining hole and the cutting edge or between the inner wall of the machining hole and the side surface of the drill body 1. There is no problem of entering and leaving streak-like scratches on the inner wall of the processed hole. Therefore, it is possible to ensure a good finished surface roughness as described above.
[0022]
Furthermore, in order to obtain desired hole diameter accuracy and finished surface roughness by the finishing blade 8, consideration must be given to wear and welding of the cutting blade.
[0023]
The so-called scraping wear is a wear form in which the wear amount increases in proportion to the cutting distance, that is, the wear amount becomes larger on the outer peripheral side than on the inner peripheral side of the blade portion 2. Therefore, for the finishing blade 8 positioned on the outer peripheral side of the blade portion 2, a material having high hardness such as a diamond sintered body is more preferable than a material having high toughness, and a shape in which a cutting edge angle γ is disposed. So it covers the decrease in strength. On the other hand, a material having higher toughness than a material having high hardness is suitable for the main blade 6 located on the inner peripheral side of the blade portion 2.
[0024]
Welding is easily affected by the type of workpiece, the constituent material of the cutting edge, and the like. In particular, when an aluminum alloy is used as a workpiece, the generation of welds and constituent cutting edges becomes a problem. The diamond sintered body has high welding resistance, is suitable for cutting aluminum alloys and the like, and has high wear resistance, so that a sharp cutting edge shape can be maintained, and peeling and digging of the finished surface can be avoided.
[0025]
Accordingly, a diamond sintered body is a more preferable choice for the finishing blade 8 in order to suppress wear of the cutting edge and avoid welding.
[0026]
4 to 6 show a second embodiment of the present invention. The same components as those in the first embodiment are denoted by the same reference numerals, and detailed description thereof is omitted.
[0027]
The outer peripheral corner of the main blade 6 has a surface 12 extending rearward in the axial direction of the drill body 1 (hereinafter referred to as “step guide surface” as appropriate) and a surface 13 extending outward in the radial direction (hereinafter referred to as “step portion” as appropriate). The step portion 14 formed by “the end face” is cut out and formed. The finishing blade 8 is formed on the intersecting ridge line between the groove side surface 15 where the main chip discharge groove 3 is erected and the stepped end surface 13. Further, unlike the first embodiment, the finishing blade 8 is formed separately from the main blade 6.
[0028]
When the stepped guide surface 12 is formed so as to be inclined in the axial direction, that is, when it is formed to have a smaller diameter from the distal end of the drill body 1 toward the proximal end, the configuration is advantageous for chip breaking. . On the other hand, in the opposite case, a cutting action is generated on the intersecting ridgeline between the groove side surface 15 where the main chip discharge groove 3 is erected and the step guide surface 12, which is not preferable.
[0029]
The stepped end face 13 is formed extending in a direction perpendicular to the central axis o. Here, when the stepped end face 13 is formed so as to approach the distal end side of the drill body 1 as it goes radially outward, the so-called sharpness is improved and the inclination direction of the main blade 6 and the inclination of the finishing blade 8 are improved. Since the direction is opposite to the direction, the flow direction of chips from each cutting edge is different, which is advantageous for chip breaking.
[0030]
【The invention's effect】
As described above, since the finishing allowance of the original finishing blade is shared by the intermediate blade and the finishing blade in two stages, the cutting resistance can be reduced and damage to the cutting blade can be prevented. Furthermore, by disposing the finishing blade adjacent to the main chip discharge groove, it becomes possible to discharge the chips smoothly without retaining them, and it is possible to maintain good dimensional accuracy and finished surface roughness. it can.
[Brief description of the drawings]
FIG. 1 is a front view of a drill showing a first embodiment of the present invention.
FIG. 2 is a side view of FIG.
FIG. 3 is an enlarged view of the outer edge of the blade part of FIG. 2;
FIG. 4 is a front view of a drill showing a second embodiment of the present invention.
FIG. 5 is a side view of FIG. 4;
6 is an enlarged view of the outer edge of the blade portion of FIG.
FIG. 7 is a front view showing an example of a conventional drill.
FIG. 8 is a front view showing another example of a conventional drill.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Drill main body 2 Blade part 3 Main chip discharge groove 6 Main blade 7 Intermediate blade 8 Finishing blade 14 Step part

Claims (1)

A shank portion is formed at one end of a cylindrical drill body 1, a blade portion 2 is formed at the other end, a main chip discharge groove 3 is provided on the outer periphery of the blade portion 2, and a main chip discharge groove 3 is provided. In a drill provided with a pair of main blades 6 having a tip angle α at the front end of the blade portion 2 provided with a pressing portion 5 extending in parallel along the axial direction in front of the rotation direction x of
A chamfered finishing blade 8 made of a diamond sintered body is formed at the outer peripheral corner of the main blade 6, and the main blade 6 is located at a position that is substantially 90 ° behind the rotational direction x of the finishing blade 8. A chamfered intermediate blade 7 having a cutting edge angle β is formed on the outer periphery of the blade portion 2 having a rotation radius R2 larger than the rotation radius R1 and smaller than the rotation radius R3 of the finishing blade 8. The axial position of the outermost point of the blade 7 is arranged between the outermost point of the main blade 6 and the outermost point of the finishing blade 8, and in the rotational path, it is axially forward of the finishing blade 8. A drill characterized in that it is arranged to project.

Images