JP2002205213A - Drill - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve hole position precision and to improve inner wall surface coarseness of a drilled hole. SOLUTION: One chip discharge groove 12 twisted around the periphery of an rotary axis O is formed in the peripheral surface of a blade edge part 11 throughout its whole length and one finishing edged groove 13 being the same as the chip discharge groove 12 and twisted at a specified twist angle βis formed. A blade angle θ of a finishing blade 15 of the finishing edged groove 13 is set to a range of 80 deg.<=θ<=120 deg.. The core thickness ratio of the blade edge part 11 is set to 60% or more. The groove depth ratio of the finishing edged groove 13 is set to 5% or more and a groove width ratio to 10% or more. A maximum outside diameter D of the blade edge part 11 is set to 1 mm or less and a ratio between an effective blade length L and the maximum outside diameter D is set to 5 or more.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a drill used for drilling a work material. For example, a drill having a small diameter and a deep hole is drilled in a work material such as a printed circuit board, minute metal parts, or plastic. To a small drill used to do

[0002]

2. Description of the Related Art Generally, a small drill has an extremely small hole to be drilled. For example, a small-diameter rod-shaped cutting edge having a diameter of about 0.05 to 3.175 mm is provided at the front end of the drill body, and at the rear end. A relatively large-diameter shank portion for gripping the drill body on the rotating shaft of the machine tool is provided integrally with the cutting edge portion or connected by brazing or interference fitting. The material of the cutting edge portion is usually a cemented carbide, and the shank portion is made of a cemented carbide or a steel material such as steel.

[0003] In the conventional small drill, two chips discharge grooves twisted around the rotation axis from the tip of the blade to the base end face the peripheral surface of the cutting edge of the small drill rotated about the rotation axis. It is formed. In such a conventional small drill provided with such two chip discharge grooves, the core thickness is reduced by the two chip discharge grooves and the rigidity of the drill is reduced, so that the hole diameter is particularly 1 mm or less and the hole depth is small. In the case of processing a small-diameter deep hole whose ratio to the hole diameter is 5 or more, the hole position accuracy is reduced due to the bending of the hole, and the cutting edge is broken.

In order to solve the above problems, US Pat.
There is a small drill as disclosed in P55884617. FIG. 17 is a side view showing the cutting edge of such a small drill, and FIG. 18 is a sectional view of the cutting edge of the small drill. This small drill 1 is provided with a cutting edge 2 and a shank, and the cutting edge 2 has a single chip discharge groove 3 twisted around the rotation axis O from the tip to the base end as shown in FIG. The feature is that the torsion angle γ of the chip discharge groove 3 is continuously increased from the tip of the cutting edge portion 1 toward the base end, thereby improving the chip discharge processing.

In the cross section of the cutting edge 2, as shown in FIG. 18, the outer peripheral surface of the cutting edge 2 excluding the chip discharge groove 3 is formed by a margin 4, and when drilling a work material, The margin 4 comes into contact with the inner wall surface of the machined hole to obtain the straightness of the drill. In the conventional small drill 1 having such a configuration, since the chip discharge groove 3 is only one, the rigidity can be kept high without reducing the core thickness d of the blade edge portion 2 and the hole position. Accuracy can be improved.

[0006]

However, the chips generated during drilling of the work material are not carried to the base end side of the cutting edge portion 2 by the chip discharge grooves 3 and the margins 4 contact each other. The chip may enter between the inner wall surface of the machined hole and the chip may adhere to the inner wall surface of the machined hole as it is, or the chip may rub against the inner wall, resulting in the inside of the machined hole. Problems such as reducing wall roughness often occur. Such a phenomenon,
This is more likely to occur in the case of small-diameter deep hole processing in which the hole diameter of the hole to be drilled is 1 mm or less, and the ratio of the hole depth to the hole diameter is 5 or more, which has been a serious problem.

[0007] In particular, when a printed circuit board is drilled as a work material, a deposit called smear is generated on the inner wall surface of the drilled hole. If the smear remains in the drilled drilled hole, a plating process or the like is performed. Therefore, a step of mechanically removing smear is required. As a result, the smear not only lowers the roughness of the inner wall surface of the machined hole, but also causes a large decrease in the product yield.

Further, in the small drill 1 provided with the above-described one chip discharge groove 3, since the drill rigidity is high, the feed rate of the small drill 1 at the time of drilling can be increased to perform highly efficient machining. Although it becomes possible, there is a problem that burrs are generated in the processing holes and the inner wall surface roughness is reduced as a disadvantage of increasing the feed speed, and it has been difficult to achieve both high efficiency and high precision processing at the same time. .

SUMMARY OF THE INVENTION In view of the above problems, an object of the present invention is to provide a drill capable of maintaining high drill rigidity, having high hole position accuracy, and improving the inner wall surface roughness of a machined hole.

[0010]

Means for Solving the Problems To solve the above problems,
In order to achieve such an object, according to the present invention, a chip discharge groove that is twisted around a rotation axis from a tip of the blade portion toward a base end side is formed on a peripheral surface of the blade edge portion, and rotation of the chip discharge groove is performed. In a drill in which a tip side region of a wall surface facing in the direction is a rake face and a cutting edge is formed at an intersection ridge portion of the rake face and a tip flank, a chip discharge groove formed on a peripheral surface of the cutting edge portion is 1. And a groove having a finishing blade having a twist angle of 0 ° or more from the tip of the blade toward the base end side is formed on the peripheral surface of the blade.
With such a configuration, since only one chip discharge groove is provided in the cutting edge portion, the core thickness becomes larger and higher than that of a conventional drill in which the cutting edge portion has two chip discharge grooves. Rigidity can be obtained. Further, since a groove with a finishing blade is formed in a portion where a margin for rubbing the inner wall surface of the processing hole is formed, chips entering between the margin and the inner wall surface of the processing hole are subjected to the finishing blade groove. And discharge, and the inner wall surface of the machined hole can be cut again by the finishing blade for finishing.
The accuracy of the inner wall surface can be improved.

[0011] Further, in the groove with a finishing blade, the chip discharge groove is formed to be longer than a length that makes one revolution around the peripheral surface of the blade edge portion. With such a configuration, it is possible to obtain a groove with a finishing blade having a sufficient length for finishing the inner wall surface of the processing hole. Here, if the length of the groove with the finishing blade is shorter than the length of the chip discharge groove making one revolution around the peripheral surface of the blade edge, the uncut portion easily occurs, and the inner wall surface accuracy of the machined hole is reduced. The effect of improvement cannot be obtained.

Further, the blade angle θ formed by the finishing blade of the groove with a finishing blade is set in a range of 80 ° ≦ θ ≦ 120 °. By adopting such a configuration, it is possible to ensure the chipping resistance of the finishing blade and to ensure good sharpness. Here, when the blade angle θ formed by the finishing blade of the groove with the finishing blade becomes smaller than 80 °,
The cutting resistance applied to the finishing blade increases, and the cutting edge becomes more susceptible to chipping. On the other hand, when the blade angle θ is larger than 120 °, the sharpness of the finishing blade decreases, and the effect of improving the accuracy of the inner wall surface of the processing hole is obtained. Will be gone.

A ratio d / D (hereinafter referred to as a core thickness ratio) of a diameter d of a maximum circle inscribed in a cross section of the cutting edge to a maximum outer diameter D of the cutting edge is 60% or more. It is characterized by being. With such a configuration, the core thickness of the cutting edge portion can be sufficiently ensured, the drill rigidity can be kept high, and the size of the groove with the finishing blade is not increased more than necessary. Here, the core thickness ratio d / D is 60%.
If it is smaller, the core thickness of the cutting edge portion becomes thin, and it becomes impossible to maintain sufficient drill rigidity.

Further, a ratio a / D (hereinafter, referred to as “a / D”) of the groove depth a of the groove with the finishing blade with respect to the maximum outer diameter D of the cutting edge portion.
It is called the groove depth ratio. ) Is 5% or more,
The groove width b of the groove with the finishing blade is the maximum outer diameter D of the cutting edge.
B / D (hereinafter referred to as groove width ratio)
Is 10% or more. With such a configuration, chips that enter between the margin and the inner wall surface of the processing hole and are removed by the groove with a finishing blade,
Alternatively, a sufficient space for releasing chips generated by the finishing processing of the finishing blade can be secured. Note that the groove depth ratio a / D is set to be smaller than 5% or the groove width ratio b
If / D is set to be smaller than 10%, a sufficient space for the groove with a finishing blade cannot be secured, and the efficiency of removing chips by the groove with a finishing blade deteriorates.

The maximum outer diameter D of the cutting edge is 1 mm or less, and the ratio L / D of the effective cutting length L of the cutting edge to the maximum outer diameter D of the cutting edge is 5 or more. I do. By adopting such a configuration, the present invention can be effectively used particularly when drilling a hole of a small-diameter deep hole in which problems such as a decrease in hole position accuracy and a decrease in hole inner wall surface accuracy are likely to occur.

[0016]

Embodiments of the present invention will be described below with reference to the accompanying drawings. 1 is a side view of a cutting edge of the small drill according to the first embodiment of the present invention, FIG. 2 is a sectional view of the cutting edge of the small drill, FIG. 3 is an enlarged view of a main part in FIG. 2, and FIG. FIG. 5 is an enlarged view of a main part, and FIG. 5 is an explanatory view of a cross section of a cutting edge of the small drill.

Small drill 1 according to the first embodiment of the present invention
Reference numeral 0 denotes a blade edge portion 11 and a shank portion.
As shown in FIG. 1, reference numeral 1 denotes a straight type having the same outer diameter D from the distal end to the proximal end. That is, the outer diameter D of the cutting edge 11 is set to the maximum outer diameter D.

The tip 11 has a single chip discharge groove 12 which is helically twisted around the rotation axis O at a constant helix angle α from the tip to the base end, and opens to the outer peripheral surface.
Is provided. This chip discharge groove 12 is
Is formed so as to make about three and a half turns around the outer peripheral surface from the distal end to the proximal end of the base member, and has a constant groove depth and a constant groove width. Thereby, the diameter d of the largest circle inscribed in the cross section of the cutting edge portion 11 (so-called core thickness d of the cutting edge portion 11) is made constant from the tip to the base end of the cutting edge portion 11.

Further, similarly from the tip of the cutting edge portion 11 toward the base end side, a single groove 13 with a finishing blade is formed on the outer peripheral surface of the cutting edge portion 11 around the rotation axis O in a spiral shape. And twisted at a constant twist angle β in the same direction. At this time, if the torsion angle α of the chip discharge groove 12 is a positive angle, the torsion angle β of the finishing blade groove 13 is set to an angle of 0 ° or more. The helix angle β of the groove 13 with the blade is the chip discharge groove 1
2 is the same positive angle as the torsion angle α.

As shown in FIG. 2, the groove 13 with a finishing blade is located at a predetermined distance from the chip discharge groove 12 on the rear side in the drill rotation direction T, and is recessed toward the rotation axis O. It is formed in a concave groove shape by the wall surface 14 forming a concave curved surface. Further, in the first embodiment, the groove 13 with the finishing blade is formed from the tip to the base end of the cutting edge portion 11, in other words, the groove 13 with the finishing blade is the chip discharging groove 1
2 is formed up to a position where it is about three and a half turns around the outer peripheral surface of the blade edge portion 11 (the same length as the chip discharge groove 12).

Also, as shown in FIG.
The tip side region of the wall surface of the small drill 10 facing the rotation direction T is a rake face, and a cutting edge 17 is formed at the intersection ridge line between the rake face and the tip flank 16 of the cutting edge portion 11.
The tip flank 16 is a first flank 16a located immediately behind the cutting edge 17 in the rotation direction T, a second flank 16b connected to the first flank 16a and located rearward in the rotation direction T,
Further, it is constituted by a third flank 16c which is connected to the second flank 16b and located on the rear side in the rotation direction T.

As shown in FIG. 2, the outer peripheral surface of the cutting edge portion 11 except for the chip discharge groove 12 and the groove 13 with a finishing blade is formed by a margin 18. The groove 13 is divided into two parts by providing the groove 13 with the opening on the surface. In other words, on the outer peripheral surface of the cutting edge 11, the groove 13 with the finish Is formed. Further, the margin 18 is
Like the chip discharge groove 12, the small drill 10 is formed in a spiral shape by being twisted rearward in the rotation direction T of the small drill 10 from the tip of the blade tip portion 11 toward the base end side. It is formed over.

As shown in FIG. 2 and FIG. 3, the rake face 1 is located on the rear side of the wall 14 forming the groove 13 with the finishing blade in the drill rotation direction T and facing the rotation direction T.
4a, a finishing blade 15 (cutting blade) is formed at the intersection ridge line between the rake face 14a and the margin 18. Also,
The blade angle θ formed by the finishing blade 15 is set in a range of 80 ° ≦ θ ≦ 120 °, and in the first embodiment, for example, θ
= 100 °. Here, the blade angle θ of the finishing blade 15 is defined as a rake face 14a in a cross-sectional view of the blade edge portion 11 on an imaginary circle whose center is the rotation axis O and whose margin 18 is an arc. At the intersection X with the tangent A direction.

Further, a front side wall surface 14 located in a region on the front side in the rotation direction T of the wall surface 14 constituting the groove 13 with the finishing blades.
As shown in FIG. 3, b is an angle φ formed with the margin 18 (in a cross-sectional view of the cutting edge portion 11, the front side wall surface 14 b is on the front side on an imaginary circle whose center is the rotation axis O and whose margin 18 is an arc). The angle formed by the tangent B direction at the point Y where the wall surface 14b and the margin 18 intersect is set to 120 ° or more. In the first embodiment, for example, φ = 16
It is set to 0 °. More specifically, as shown in the enlarged cross-sectional view of FIG. 4, the connecting portion between the margin 18 and the front side wall surface 14b (that is, the front side wall surface 14b
(In the vicinity of the point Y where the margin 18 intersects with the margin 18) forms a smooth convex curved surface. In addition, this connection part does not need to be connected smoothly, and may be formed so that it may have multiple steps.

Further, a groove depth a of the groove 13 with a finishing blade (that is, a virtual circle having the margin 18 as an arc centered on the rotation axis O in the sectional view of the blade edge portion 11 in FIG. The ratio a / D (groove depth ratio a / D) of the maximum outer diameter D of the cutting edge portion 11 with respect to the diameter r of the circle r concentric with the groove 13 with the finishing blade groove 13 is 5% or more. Further, the groove width b of the groove 13 with a finishing blade (that is, the wall surface 14 constituting the groove 13 with a finishing blade in the cross-sectional view of the blade edge portion 11 in FIG. The ratio b / D (groove width ratio b / D) is 10% with respect to the maximum outer diameter D of the blade edge portion 11.
That is all.

The maximum outer diameter D of the cutting edge 11 (in the first embodiment, the rotation axis O
, The diameter of a virtual circle having a margin 18 as an arc) is 1 mm or less, and the effective blade length L of the blade edge portion 11
The cutting edge portion 11 is formed such that the ratio L / D between the cutting edge 11 and the maximum outer diameter D is 5 or more.

Further, as shown in FIG. 2, the diameter d of the largest circle inscribed in the cross section of the cutting edge portion 11 (so-called cutting edge portion 1).
The ratio d / D (core thickness ratio d / D) made by the core thickness d) of 1 with respect to the maximum outer diameter D of the cutting edge portion 11 is set to 60% or more. Here, in the first embodiment, as shown in FIG. 2, a circle inscribed in the margin 18 and the chip discharge groove 12 has a maximum diameter d, and the core thickness ratio d / D is, for example, 65.
%, And is constant from the distal end to the proximal end of the blade edge portion 11.

At this time, since the core thickness ratio d / D is set to 60% or more, the groove 13
5 is limited, and the space in which the groove 13 with the finished blade can be secured is the maximum, but as shown in FIG. 5, the largest circle inscribed in the cross section of the blade edge portion 11 (core thickness d is (Circle shown). For this reason, the groove 13 with the finishing blade is sufficiently smaller than the size of the chip discharge groove 12, and the groove 13 with the finishing blade does not easily lower the drill rigidity.

The small drill 10 constructed as described above
Is formed with a single chip discharge groove 12 and a single finishing blade groove 13 in its blade edge portion 11, and the chip discharging groove 12 secures a space secured by the finishing blade groove 13. Because it is sufficiently smaller than the space, the cutting edge 11
The core thickness can be sufficiently secured, and the drill rigidity is overwhelmingly higher than that of a conventional small drill provided with two chips discharge grooves.

Moreover, the margin 1 for rubbing the inner wall surface of the processing hole
Since the grooves 13 with the finishing blades are formed in the workpiece 8, the chips entering between the margin 18 and the inner wall surface of the machining hole are removed by the grooves 13 with the finishing blades when the work material is drilled. And finish the inner wall of the hole
5, it is possible to cut and finish the work again, and it is possible to improve the wall surface accuracy in the hole.

Since the rigidity of the drill can be kept high, even if the feed speed of the small drill 10 is increased during drilling of a work material, bending of the hole and breakage of the cutting edge 11 do not occur. Efficiency drilling can be performed, and the problem of burrs and reduced inner wall surface roughness in the machined holes, which is an adverse effect of high feed,
Such a problem can be solved by cutting the inner wall surface of the machining hole again by the finishing blade 15 of the groove 13 with the finishing blade. As a result, it is possible to perform drilling with higher efficiency than a conventional small drill in which two chip discharge grooves are formed, while maintaining the inner wall surface roughness of the processed hole satisfactorily.

Although the groove 13 with a finishing blade has a certain effect even if it is adopted in a conventional small drill provided with two chip discharge grooves, considering the problem of the drill stiffness, the groove 13 has a small diameter. As in the present invention, by employing the small drill 10 in which the single chip discharge groove 12 is formed in the cutting edge 11, both high-efficiency drilling and high-precision drilling can be achieved at the same time. .

Moreover, in the small drill 10 according to the first embodiment, the maximum outer diameter D of the cutting edge 11 is 1 mm or less, and the ratio L / D between the maximum outer diameter D of the cutting edge 11 and the effective blade length L is 5 mm. As described above, the present invention can be effectively used particularly when drilling a hole portion of a small-diameter deep hole in which problems such as a decrease in hole position accuracy and a decrease in hole inner wall surface accuracy are likely to occur. Further, even when smear or the like adheres to the inner wall surface of the processing hole, such as when a small-diameter deep hole is formed in a printed circuit board or the like as a work material, a groove 13 with a finishing blade is required. Can remove the smear, finish the inner wall surface with the finishing blade 15, and the like, thereby improving the inner wall surface roughness of the machined hole. For this reason, it is possible not only to prevent the deterioration of the inner wall surface due to the smear which has been a problem in the past, but also to keep the yield of the product high because the step of removing the smear is not required.

The groove 13 with a finishing blade has a length sufficient for finishing the inner wall surface of the hole because the chip discharge groove 12 is formed to be longer than the length of one revolution of the cutting edge 11. Can be formed, and stable finishing of the inner wall surface of the processing hole can be performed. Here, if the length in which the groove 13 with the finishing blade is formed is shorter than the length in which the chip discharge groove 12 makes one revolution around the outer peripheral surface of the cutting edge portion 11, uncut portions are likely to occur, and The effect of improving the wall accuracy cannot be sufficiently obtained.

Further, the finishing blade 15 of the groove 13 with a finishing blade
By setting the blade angle θ to be in the range of 80 ° ≦ θ ≦ 120 °, it is possible to ensure the chipping resistance of the finishing blade 15 and to ensure good sharpness. Here, if the blade angle θ formed by the finishing blade 15 is smaller than 80 °, the cutting resistance applied to the finishing blade 15 increases, and the cutting blade tends to be chipped. On the other hand, if the blade angle θ becomes larger than 120 °, the finishing blade 15 The sharpness is reduced, and the effect of finishing the inner wall surface of the processing hole to improve the surface roughness cannot be obtained. The blade angle θ formed by the finishing blade 15 is preferably set in the range of 80 ° ≦ θ ≦ 90 ° in order to further ensure the above-described effects.

Further, since the core thickness ratio d / D is set to 60% or more over the entire length of the cutting edge portion 11, the cutting edge portion 11
The core thickness can be sufficiently secured, the drill rigidity can be kept high, and the space in which the groove 13 with the finishing blade is formed is not unnecessarily increased. Here, if the core thickness ratio d / D is smaller than 60%, the core thickness of the blade edge portion 11 becomes thin, and it becomes impossible to maintain sufficient drill rigidity.

Further, since the groove depth ratio a / D is set to 5% or more and the groove width ratio b / D is set to 10% or more, the groove enters between the margin 18 and the inner wall surface of the machined hole. Thus, it is possible to secure a sufficient space for the chips removed by the finishing blade groove 13 and the chips generated by the cutting by the finishing blade 15 to escape. The groove depth ratio a / D
Is set to less than 5%, or the groove width ratio b / D is 10
%, The groove 1 with the finishing blade for releasing the chips entering between the margin 18 and the inner wall surface of the machined hole and the chips generated by the cutting by the finishing blade 15.
3 will not be able to secure a sufficient space.

In the above-described first embodiment of the present invention, the twist angle β of the groove 13 with the finishing blade is set to the same positive angle as the twist angle α of the chip discharge groove 12, but is always the same. It is not necessary, and the torsion angle β of the groove 13
May be different as long as 0 ° or more. A small drill in such a case will be described as second to sixth embodiments of the present invention. In addition, these 2nd-6th embodiment are the blade edge parts 1
Only the configuration of the groove 13 with a finishing blade formed on the outer peripheral surface (margin 18) of the first embodiment differs from that of the first embodiment.

FIG. 6 is a side view of the cutting edge of the small drill according to the second embodiment of the present invention, and FIG. 7 is a side view of the cutting edge of the small drill according to the third embodiment. As shown in FIG. 6, the small drill 20 according to the second embodiment has one finishing blade that opens on the outer peripheral surface of the cutting edge 11 around the rotation axis O from the tip of the cutting edge 11 toward the base end side. The groove 13 is spirally formed with a constant helix angle β, and the helix angle β of the finishing blade groove 13 is set to a positive angle smaller than the helix angle α of the chip discharge groove 12, At a position where the discharge groove 12 has a length that makes a circumference of the outer peripheral surface of the cutting edge portion 11 by about two turns, the groove 13 with a finishing blade merges with the chip discharge groove 12.

Also, the small drill 30 according to the third embodiment
As shown in FIG. 7, a single groove 13 with a finished blade spirally opening in the outer peripheral surface of the blade edge portion 11 centering on the rotation axis O from the tip of the blade edge portion 11 toward the base end side is fixed. The groove 13 is formed by twisting at a twist angle β.
Is set to a positive angle larger than the torsion angle α of the chip discharge groove 12 and the chip discharge groove 12 has a length that makes the outer circumference of the cutting edge portion 11 rotate about one and a half turns. The groove 13 joins the chip discharge groove 12.

Next, FIG. 8 shows a side view of a cutting edge of a small drill according to a fourth embodiment of the present invention. As shown in FIG. 8, the small drill 40 according to the fourth embodiment is configured such that the cutting edge 11 extends around the rotation axis O from the tip of the cutting edge 11 toward the base end.
Is formed so as to be parallel to the rotation axis O, that is, the torsion angle β of the finishing blade groove 13 is set to 0 °. is there. At this time, the groove 13 with the finishing blade is formed up to a position where the chip discharge groove 12 turns about one and a half turns around the outer peripheral surface of the cutting edge portion 11, and the chip discharge groove 1 is formed at that portion.
2, but the middle part is divided by the chip discharge groove 12.

The groove 1 with a finishing blade as in the fourth embodiment.
3 is 0 ° or close to 0 °,
In order to form the groove with a finishing blade 13 longer than the length in which the chip discharge groove 12 makes one revolution around the outer peripheral surface of the blade edge portion 11, the groove with the finishing blade 13 is divided by the chip discharge groove 12. However, there is no adverse effect on the effects of the present invention.

Next, FIG. 9 shows a side view of a cutting edge of a small drill according to a fifth embodiment of the present invention, and FIG. 10 shows a side view of a cutting edge of a small drill according to the sixth embodiment. As shown in FIG. 9, the small drill 50 according to the fifth embodiment has
A groove 13 with a finishing blade is formed in the outer peripheral surface of the cutting edge 11 around the rotation axis O from the distal end toward the base end of the cutting blade 1 in a spiral shape.
3 is the same as the torsion angle α of the chip discharge groove 12 at the tip of the cutting edge 11,
1 at a position where the size of the chip discharge groove 12 becomes continuously smaller as it goes toward the base end side and the length of the chip discharge groove 12 is about one and a half turn around the outer peripheral surface of the cutting edge portion 11. It is designed to join.

Also, the small drill 60 according to the sixth embodiment
As shown in FIG. 10, a single groove 13 with a finished blade spirally opening on the outer peripheral surface of the blade edge portion 11 around the rotation axis O from the distal end of the blade edge portion 11 toward the base end side is spirally twisted. The torsion angle β of the groove 13 with a finishing blade is
At the tip end of the cutting edge 11, the torsion angle α of the chip discharge groove 12 is the same, but increases continuously toward the base end side of the cutting edge 11, so that the chip discharge groove 12 The groove 13 with the finishing blade merges with the chip discharge groove 12 at a position where the outer peripheral surface has a length of about one and a half turn around the outer peripheral surface.

The second to second aspects of the present invention having the above-described configuration.
Small drills 20, 30, 40, 5 according to the sixth embodiment
Reference numerals 0 and 60 denote the grooves 13 with the finishing blades because the grooves 13 with the finishing blades formed in the respective blade edge portions 11 are formed so that the chip discharge grooves 12 are longer than the length of one rotation of the outer peripheral surface of the blade edge portion 11. The present invention has the same advantages as the first embodiment of the present invention described above. Furthermore, since the groove 13 with a finishing blade is formed so as to merge with the chip discharge groove 12,
The chips discharged by the grooves 13 with the finishing blades can be discharged so as to be merged with the chip discharging grooves 12 having a large space for allowing the chips to escape. Can be kept.

In the first to sixth embodiments, the straight type small drill in which the outer diameter D of the cutting edge 11 is constant from the distal end to the proximal end has been described. However, the present invention is not limited to this. A small drill having a back taper that gradually becomes smaller as the outer diameter of the cutting edge portion 11 goes from the distal end toward the proximal end side may be used. In this case, the outer diameter of the tip side portion of the cutting edge 11 is the maximum outer diameter D.

Further, small straight type drills 10, 20, 3 as in the first to sixth embodiments described above.
The drill is not limited to 0, 40, 50, and 60, and may be an undercut type drill in which only the tip of the cutting edge 11 is enlarged by one step. In such a case, a small drill may be used according to the seventh to eleventh aspects of the present invention. This will be described as an embodiment. In the seventh to eleventh embodiments, the shape of the cutting edge 11 and the cutting edge 11
Only the configuration of the groove 13 with a finishing blade formed on the outer peripheral surface (margin 18) is different, and the same parts as those in the above-described first embodiment are denoted by the same reference numerals and description thereof is omitted.

First, FIG. 11 shows a side view of a cutting edge of a small drill according to a seventh embodiment of the present invention. As shown in FIG. 11, the small drill 70 according to the seventh embodiment
1 is a first cutting edge 11A located at the tip thereof, and a second cutting edge 11B having an outer diameter smaller than the outer diameter D of the first cutting edge 11A, located on the rear end side of the first cutting edge 11A. And undercut type. At this time, the outer diameter D of the first cutting edge portion 11A becomes the maximum outer diameter D of the cutting edge portion 11, and the margin 18 for rubbing the inner wall surface of the machining hole is formed on the outer peripheral surface of the first cutting edge portion 11A. . Note that the chip discharge groove 12 is formed at a constant twist angle α from the tip to the base end of the cutting edge 11 and turns around the outer peripheral surface of the cutting edge 11 by about three and a half turns. The discharge groove 12 makes the outer peripheral surface of the blade edge 11 approximately 1
The first cutting edge 11A is up to the position where the length of rotation is half a revolution.
It has been.

Small drill 70 according to the seventh embodiment
As shown in FIG. 11, a single groove 13 with a finishing blade spirally opening in the outer peripheral surface of the cutting edge portion 11 centering on the rotation axis O from the tip end of the cutting edge portion 11 toward the base end side, discharges chips in a spiral shape. Groove 1
2 and is twisted at a constant twist angle β. Further, the groove 13 with the finishing blade is formed from the tip to the base end of the blade edge portion 11 with its twist angle β set to the same positive angle as the twist angle α of the chip discharge groove 12, in other words The chip discharge groove 12 makes the outer peripheral surface of the
It is formed up to a position where the length of rotation is half a revolution (the same length as the chip discharge groove 12).

The small drill 70 according to the seventh embodiment, which is of the undercut type as described above, has the same effect as the small drill 10 according to the first embodiment described above. Since the second cutting edge portion 11B whose outer diameter is reduced by one step is formed on the side portion, although the drill rigidity is somewhat lost, the area of the margin 18 that contacts the inner wall surface of the machined hole is reduced. hand,
It is possible to further improve the accuracy of the inner wall surface of the processing hole.

In the case of the small drill of the undercut type, the groove 13 with the finishing blade is formed by the first cutting edge 11A.
(A portion where the margin 18 is formed) is sufficient.
It is not necessary to form up to the base end of 1B. Such a case is referred to as an eighth embodiment of the present invention, and a side view of the cutting edge portion of the small drill is shown in FIG.

As shown in FIG. 12, the small drill 80 according to the eighth embodiment has substantially the same configuration as that of the above-described seventh embodiment, except that only the length in which the groove 13 with the finishing blade is formed is provided. Is different, and the groove 13 with the finishing blade is
From the front end of the blade 11 to a position where the chip discharge groove 12 has a length of about two turns around the outer peripheral surface of the blade edge portion 11, in other words, the groove 13 with a finishing blade is formed at a substantially central portion of the second blade edge portion 11B. Is formed up to. The small drill 80 having such a configuration also has the same effect as the small drill 70 according to the seventh embodiment.

Further, the finishing blade 15 of the groove 13 with the finishing blade is provided.
Is sufficient if it is provided over the entire length of the first cutting edge portion 11A in which the margin 18 is formed. As in the case of the small drills 70 and 80 in the seventh and eighth embodiments, the groove 13 with a finishing blade is sufficient. Is formed from the tip of the first cutting edge portion 11A to the second cutting edge portion 11B, the finishing blade 15 is formed in a portion of the groove 13 with a finishing blade located at the second cutting edge portion 11B. It is not necessary.

Next, FIG. 13 is a side view of the cutting edge of the small drill according to the ninth embodiment of the present invention, and FIG. 14 is a side view of the cutting edge of the small drill according to the tenth embodiment. As shown in FIG. 13, the small drill 90 according to the ninth embodiment is of an undercut type including a first cutting edge 11 </ b> A and a second cutting edge 11 </ b> B. A single groove 13 with a finishing blade is formed on the outer peripheral surface of the cutting edge portion 11 around the rotation axis O and is spirally formed with a constant helix angle β.
3 is set to a positive angle smaller than the twist angle α of the chip discharge groove 12, and the chip discharge groove 12 is
The groove 13 with a finishing blade merges with the chip discharge groove 12 at a position where the length thereof is about one and a half turn around the outer peripheral surface of the chip. In addition, the groove 13 with the finishing blade is the first cutting edge 11A.
Is formed over the entire length.

The small drill 100 according to the tenth embodiment is
As shown in FIG. 14, the undercut type is also provided with a first cutting edge portion 11A and a second cutting edge portion 11B, and extends from the tip of the cutting edge portion 11 to the base end side about the rotation axis O. 1 groove with finishing blades opening on the outer peripheral surface
3 is spirally formed at a constant helix angle β, the helix angle β of the finishing blade groove 13 is set to a positive angle larger than the helix angle α of the chip discharge groove 12, and the chip discharge is performed. At a position where the groove 12 has a length that makes a one-turn and a half turn around the outer peripheral surface of the blade edge portion 11, the groove 13 with the finishing blade merges with the chip discharge groove 12. The groove 13 with a finishing blade is formed over the entire length of the first cutting edge 11A.

Next, FIG. 15 shows a side view of the cutting edge of the small drill according to the eleventh embodiment of the present invention. As shown in FIG. 15, the small drill 110 according to the eleventh embodiment is of an undercut type including a first cutting edge 11 </ b> A and a second cutting edge 11 </ b> B. A single groove 13 with a finished blade is formed so as to be open to the outer peripheral surface of the cutting edge 11 around the rotation axis O so as to be parallel to the rotation axis O, that is, the torsion angle of the groove 13 with the finished blade. β is set to 0 °.
At this time, the groove 13 with the finishing blade is formed up to a position where the chip discharge groove 12 has a length (about the entire length of the first blade edge portion 11A) that makes the outer circumference of the blade edge portion 11 make about one rotation and a half revolution. At that portion, it merges with the chip discharge groove 12, but the middle part is divided by the chip discharge groove 12.

The ninth to ninth aspects of the present invention configured as described above.
Small drills 90, 100, 110 according to the eleventh embodiment
The groove 13 with a finishing blade formed in each blade edge 11 is longer than the length of the chip discharge groove 12 making one revolution around the outer peripheral surface of the blade edge 11, and is formed over the entire length of the first blade edge 11A. Therefore, the length of the groove 13 with the finishing blade can be ensured as necessary and sufficient.
The present invention has the same effect as the seventh embodiment of the present invention described above.

Although not shown, in the undercut type small drill as in the seventh to eleventh embodiments, the torsion angle of the groove 13 with the finishing blade is directed toward the base end side of the cutting edge 11. It may be formed so as to be continuously increased or decreased. Even in such a case, the groove 13 with the finishing blade is formed such that the chip discharge groove 12 is formed from the tip of the blade edge portion 11 to be longer than the length of one revolution around the outer peripheral surface of the blade edge portion 11, or the margin 18 is formed. It is preferably formed over the entire length of the first cutting edge 11A.

In this embodiment, the cutting edge 11
The outer peripheral surface excluding the chip discharge groove 12 and the groove 13 with the finishing blade is constituted only by the margin 18, but is not limited thereto. For example, as shown in FIG.
The outer peripheral surface excluding the chip discharge groove 12 and the groove 13 with the finishing blade is the margin 18 and the drill rotation direction T of the margin 18.
A second take-up surface 19 having a certain second take-up depth c located on the rear side may be used.

Further, the chip discharge groove 1 of the cutting edge 11
2 and the outer peripheral surface excluding the groove 13 with a finishing blade have a margin 18
And a second take-up surface 19, and the margin 18 is 2
For example, it is divided into two by the numbering surface 19, and 2
The groove 13 with a finishing blade may be formed in at least one of the divided margins 18.

In this embodiment, the cutting edge 11
Although only one groove 13 with a finishing blade is provided on the outer peripheral surface of the above, there is no limitation to this, and a plurality of grooves 13 with a finishing blade may be provided.

In the present embodiment, the core thickness ratio d
/ D is constant from the distal end to the proximal end of the cutting edge portion 11, but is not limited to this, and the core thickness ratio d / D is gradually increased from the distal end of the cutting edge portion 11 toward the proximal end side. You may make it larger.

In this embodiment, the rotation axis O
The torsion angle α of the chip discharge groove 12 twisted around the blade tip 1
Although the torsion angle α is constant from the distal end to the proximal end, the twist angle α may be changed continuously from the distal end toward the proximal end.

Further, in this embodiment, the maximum outer diameter D of the cutting edge is 1 mm or less, and the effective blade length L and the maximum outer diameter D
A small drill having a ratio L / D of 5 or more has been described. However, the present invention is not limited to this range, and a drill having a larger maximum outer diameter D or a drill having an L / D smaller than 5 can be used. I do not care.

[0065]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A small drill according to an embodiment of the present invention is shown in FIGS.
The drilling test was performed on the work material using small drills having various configurations (Comparative Examples 1 to 4 and Conventional Examples 1 to 3).

In Examples 1 to 17 and Comparative Examples 1 to 4, the tip 11 has a single chip discharge groove 12 and a single finishing groove 13 with the same torsion angle. In Examples 1 to 17, the core thickness ratio d / D of the blade edge portion 11 and the blade angle θ formed by the finishing blade 15 of the groove 13 with a finishing blade are within the range of the present invention (60% ≦ d /
D, 80 ° ≦ θ ≦ 120 °)
In Comparative Examples 1 and 2, the ratio d / D of the core thickness of the cutting edge portion 11 is set to be smaller than the range of the present invention, and in Comparative Examples 3 and 4, the blade angle θ formed by the finishing blade 15 of the groove 13 with the finishing blade. Are set larger than the scope of the present invention. Further, in Conventional Examples 1 to 3, the single chip discharge groove 3 is formed in the blade edge portion 2, but the groove 13 with a finishing blade is not formed.

Examples 1 to 17 and Comparative Examples 1 to 4
The torsion angle α of the chip discharge groove 12 is set to a constant 40 ° from the tip to the base end of the cutting edge portion 11, whereas in the conventional examples 1 to 3, the torsion angle γ of the chip discharge groove 3 is It is set to 30 ° at the tip of the part 2, and as it goes toward the base end,
The torsion angle γ continuously increases and is set to 60 ° at the base end portion. Small drill as described above (Examples 1-1
Table 1 shows the test conditions and results of the drilling test performed using 7, Comparative Examples 1 to 4 and Conventional Examples 1 to 3.

[0068]

[Table 1]

Examples 1 to 17, Comparative Examples 1 to 4 and Conventional Examples 1 to 3 are common and the outer diameter D of the cutting edge 11 is
1 is a straight type with a constant 0.1 mm from the distal end to the proximal end, and the effective blade length L is 1.2 mm (L / D =
12). Further, the grooves 13 with finished blades formed on the blade edge portions 11 of Examples 1 to 17 and Comparative Examples 1 to 4 have a groove depth a of 10 μm (a groove depth ratio a / D is 10%) and a groove width. b is 20 μm (the groove width ratio b / D is 20%).

A small drill having such a configuration (Examples 1 to 5)
17, using Comparative Examples 1 to 4 and Conventional Examples 1 to 3), a plate (0.2 mm thick BT resin on which two double-sided plates are stacked) is used as a work material. LE40
0) and a bottom plate (a bakelite resin plate having a thickness of 1.6 mm), and a drilling test was performed. Drill speed is 160
000 min ^-1 (rpm), feed rate is 12.5 μm /
As rev., the work material is drilled without step feed, and the maximum surface roughness of the inner wall of the machined hole after machining 7000 holes, and the average hole position accuracy of the 100th hole of the 6901 to 7000th hole ( The average value of the deviation of each hole position from the target hole position of the substrate located in the lowermost layer in the stacked substrates was measured.

As shown in Table 1, in Examples 1 to 17, which are examples of the present invention, the roughness of the inner wall surface of each of the drilled holes is smaller than 13 μm, and the average hole position accuracy is all lower. The value was smaller than 49 μm, and the result that the inner wall surface accuracy of the machined hole and the average hole position accuracy were good was obtained.

Further, the core thickness ratio d / D in the blade edge portion 11
Are 45% and 50%, which are smaller than the range of the present invention. In Comparative Examples 1 and 2, the inner wall surface roughness of the machined hole was as good as 12 μm and 14 μm, but the core thickness was Since the ratio d / D is small, the rigidity of the drill cannot be kept high, the straightness of the drill cannot be obtained, and the average hole position accuracy is 71 μm and 65 μm. As a result, the result that the hole position accuracy was poor was obtained.

Further, the finishing blade 15 of the groove 13 with a finishing blade
In Comparative Examples 3 and 4, in which the blade angles θ of the are set to 140 ° and 150 ° and larger than the range of the present invention, the average hole position accuracy was as good as 49 μm and 47 μm. Since the blade angle θ of the blade 15 is large and the sharpness is poor, the inner wall surface of the processing hole cannot be satisfactorily finished, and the inner wall surface roughness becomes 26 μm or 25 μm, which is an example of the present invention. The result that the inner wall surface roughness was inferior to Examples 1 to 17 was obtained.

Further, a groove 13 with a finishing blade is formed in the blade edge portion 11.
In the conventional examples 1 to 3 where no is formed, the average hole position accuracy was 12 μm or less, which was good. However, since the finishing with the finishing blade 15 was not possible, the inner wall surface roughness was all about 32 μm. As compared with Examples 1 to 17, good inner wall surface roughness could not be obtained.

As described above, Examples 1 to 1 according to the present invention were used.
7 is a machined hole compared to Comparative Examples 1 to 4 and Conventional Examples 1 to 3 in which the ratio d / D of the core thickness in the blade edge portion 11 and the blade angle θ of the finishing blade 15 are out of the range of the present invention. It was found that the accuracy of the inner wall surface was particularly good, and that the accuracy of the hole position was also good.

[0076]

As described above, according to the drill of the present invention, since there is only one chip discharge groove provided in the cutting edge portion, high drill rigidity can be obtained without reducing the core thickness. Furthermore, apart from the chip discharge groove, a groove with a finishing blade that is twisted at a helix angle of 0 ° or more is formed in a portion that is a margin of the peripheral surface of the cutting edge, so that the margin and the inner wall surface of the machined hole are formed. The chips that have entered the gap are removed by the grooves with finishing blades and discharged, and the inner wall surface of the machined hole can be cut again by the finishing blade, so that the accuracy of the inner wall surface of the hole can be improved.

Further, since high drill stiffness can be obtained, high efficiency processing can be performed by increasing the feed rate of the drill when drilling a work material. Can be solved by the finishing blade of the groove with a finishing blade, and both high-efficiency processing and high-precision processing can be achieved at the same time.

Further, since the chip discharge groove is formed to be longer than the length of one turn of the cutting edge, the finishing blade groove has a sufficient length for finishing the inner wall surface of the processing hole. Can be secured. Also, the blade angle θ formed by the finishing blade of the groove with a finishing blade is 80 ° ≦ θ ≦ 120.
By being set to the range of ゜, the chipping resistance and sharpness of the finishing blade can be ensured.

Further, the core thickness ratio d / D is not less than 60%, whereby the core thickness of the cutting edge can be sufficiently ensured, and the drill rigidity can be kept high.
The space formed by the groove with a finishing blade is not made unnecessarily large. When the groove depth ratio a / D is 5% or more and the groove width ratio b / D is 10% or more, the groove enters between the margin and the inner wall surface of the processing hole, and the groove with a finishing blade is formed. A sufficient space for relieving chips removed by the cutting process and chips generated by cutting by the finishing blade can be secured.

Further, the maximum outer diameter D of the cutting edge is 1 mm or less,
And the ratio L / D of the maximum outer diameter D of the blade tip to the effective blade length L is 5
By being characterized as described above, the present invention can be effectively used particularly when drilling a small-diameter deep hole in which a problem such as a decrease in hole position accuracy or a decrease in inner wall surface accuracy is likely to occur. Furthermore, smears, which are problematic when drilling small-diameter deep holes in printed circuit boards, etc., are effectively removed to maintain good inner wall surface accuracy, and the smear removal process is not required, thereby improving productivity. Can be planned.

[Brief description of the drawings]

FIG. 1 is a side view showing a cutting edge portion of a small drill according to a first embodiment of the present invention.

FIG. 2 is a sectional view of a cutting edge portion of the small drill according to the first embodiment of the present invention.

FIG. 3 is an enlarged view of a main part in FIG. 2;

FIG. 4 is an enlarged view of a main part in FIG. 3;

FIG. 5 is an explanatory view showing a cross section of a cutting edge of the small drill according to the first embodiment of the present invention.

FIG. 6 is a side view showing a cutting edge of a small drill according to a second embodiment of the present invention.

FIG. 7 is a side view showing a cutting edge of a small drill according to a third embodiment of the present invention.

FIG. 8 is a side view showing a cutting edge of a small drill according to a fourth embodiment of the present invention.

FIG. 9 is a side view showing a cutting edge of a small drill according to a fifth embodiment of the present invention.

FIG. 10 is a side view showing a cutting edge of a small drill according to a sixth embodiment of the present invention.

FIG. 11 is a side view showing a cutting edge portion of a small drill according to a seventh embodiment of the present invention.

FIG. 12 is a side view showing a cutting edge of a small drill according to an eighth embodiment of the present invention.

FIG. 13 is a side view showing a cutting edge of a small drill according to a ninth embodiment of the present invention.

FIG. 14 is a side view showing a cutting edge of a small drill according to a tenth embodiment of the present invention.

FIG. 15 is a side view showing the cutting edge of the small drill according to the eleventh embodiment of the present invention.

FIG. 16 is an explanatory view showing a cross section of a cutting edge portion of the small drill according to the embodiment of the present invention.

FIG. 17 is a side view showing a cutting edge of a conventional small drill.

FIG. 18 is a sectional view of a cutting edge of the small drill in FIG.

[Explanation of symbols]

10,20,30,40,50,60,70,80,9
0, 100, 110 Small drill 11 Blade tip 12 Chip discharge groove 13 Groove with finishing blade 14 Wall 15 Finishing blade 16 Tip flank 17 Cutting blade 18 Margin a Groove depth b Groove width d The largest inscribed in the cross section of the blade tip Diameter of circle D Maximum outer diameter of cutting edge L Effective blade length T Rotation direction α Helix angle β Helix angle θ Tool angle

Claims (6)

[Claims] 1. A chip discharge groove which is twisted around a rotation axis from a tip end of the cutting edge portion toward a base end side is formed on a peripheral surface of the cutting edge portion. In a drill having a rake face and a cutting edge formed at an intersection ridge line between the rake face and the flank of the tip, there is only one chip discharge groove formed on a peripheral surface of the cutting edge portion. A drill having a groove with a finishing blade having a twist angle of 0 ° or more from the distal end of the cutting edge portion toward the base end side on a peripheral surface of the portion. 2. The drill according to claim 1, wherein the groove with a finishing blade is formed such that the chip discharge groove is longer than a length of one turn around the peripheral surface of the cutting edge. . 3. The drill according to claim 1, wherein a blade angle θ formed by a finishing blade of the groove with a finishing blade is set in a range of 80 ° ≦ θ ≦ 120 °. Drill to do. 4. The drill according to claim 1, wherein a diameter d of a maximum circle inscribed in a cross section of the cutting edge portion is formed with a maximum outer diameter D of the cutting edge portion. A drill characterized in that / D is 60% or more. 5. The drill according to claim 1, wherein a ratio a / D of a groove depth a of the groove with a finishing blade to a maximum outer diameter D of the cutting edge is 5 or more. % Or more, and the groove width b of the groove with the finishing blade is the maximum outer diameter D of the cutting edge portion.
Characterized in that the ratio b / D of the drill is 10% or more. 6. The drill according to claim 1, wherein a maximum outer diameter D of the cutting edge is 1 mm or less, and an effective blade length L of the cutting edge and a maximum outer diameter of the cutting edge. A drill having a ratio L / D to D of 5 or more.