JP6236851B2 - drill - Google Patents

Description

The present invention relates to a drill for drilling with high hole accuracy.

When drilling with high accuracy, it is required to widen the torsion groove in order to discharge chips efficiently and to increase the core thickness in order to maintain the rigidity of the tool. In addition, it is required to improve the centripetality by suppressing the core blur generated by cutting resistance and thrust resistance.

For example, Patent Document 1 discloses a drill having three or more twist grooves and a thinning blade formed at the tip of the drill so as to be smoothly connected to the concave main cutting edge. Furthermore, since the rake angle θ1 in the radial direction of the concave main cutting edge as viewed from the drill tip side is −20 ° ≦ θ1 <0 ° and has a negative negative angle portion, the feed amount per one rotation can be increased. High feed drilling exceeding 5% of the diameter D is possible. The rake angle in the radial direction of the concave main cutting edge is examined in the range of -25 ° to 5 ° in Patent Document 1, and if it is set to -25 °, the thrust resistance increases and the sharpness is poor, so it is not suitable for machining. It is said that there is.

In Patent Document 2, there is an outer peripheral blade portion including three sets of a concave main cutting edge and two auxiliary blades, and drilling (roughing) is performed with the concave main cutting edge. Intermediate finishing with the secondary blade and finishing with the second secondary blade. The radial rake angle θ1 of the concave main cutting edge is −25 ° ≦ θ1 ≦ −5 °, the radial rake angle θ2 of the first secondary blade is 0 ° <θ2 ≦ 20 °, and the radial rake angle of the second secondary blade. By making the angle θ3 in a range of −40 ° ≦ θ3 <0 °, a processed hole with good inner wall surface roughness is formed.

Note that the rake angle in the radial direction of the second sub-blade that is the finishing blade of the inner wall of the machined hole has been studied in the range of −42 ° to 0 °. However, the rake angle in the radial direction of the concave main cutting edge for drilling has been studied in the range of −27 ° to −3 °, and wear is normal at −27 °, but smaller than −25 °. Therefore, cutting resistance increases and vibration increases. For this reason, uncut parts and scratches generated when machining with a concave main cutting edge become large, and the inner wall roughness is not sufficient because the inner wall of the machining hole cannot be sufficiently finished with the first and second auxiliary blades. It is supposed to get worse.

International Publication No. 2010/038279 JP 2011-73129 A

However, although the drill disclosed in Patent Document 1 can perform high-feed drilling exceeding 5% of the drill diameter D, there is a problem that the accuracy of the drilled hole is not stable. Moreover, since the drill currently disclosed by patent document 2 forms two subblades other than a concave main cutting edge, there existed a problem that the manufacturing process of a drill became complicated.

Therefore, in view of the above-described problems in the present invention, it is an object to provide a drill that can improve drilling accuracy and can perform high-feed drilling with a long service life and low manufacturing cost. And

The inventors of the present invention have intensively studied the range of negative angles in which the radial rake angle of the concave main cutting edge, which has not been studied and suggested in Patent Documents 1 and 2, is greater than -25 °. As a result, the rake angle in the radial direction of the concave main cutting edge to be drilled is set to a negative angle further than -30 ° without forming the first sub-blade or the second sub-blade in Patent Document 2. I learned that the hole accuracy is improved.

Accordingly, in the present invention, in a drill having three torsion grooves, as viewed from the drill tip, a thinning having a corner radius and a thinning blade at the tip of the drill, a concave main cutting edge smoothly connected to the thinning, Radial rake angle that has a rake angle in the outer periphery of the cutting edge and a radial rake angle that recedes, a negative angle portion that forms a radial rake angle, and a margin along the twisted groove adjacent to the negative angle portion. The above-mentioned problems have been solved by providing a drill having a range of −45 ° to −30 °.

That is, by forming a negative angle portion on the outer periphery of the concave main cutting edge and setting the radial rake angle in the range of −45 ° to −30 °, cutting resistance is applied from the outer periphery of the drill toward the center. The position of the drill is stabilized, vibration during processing is reduced, and core blurring is suppressed. Further, as described later, the width of the negative corner portion (negative corner portion width) of the concave main cutting edge is set to a range of 0.04D ± 0.05 mm with respect to the diameter D of the drill.

Moreover, it was set as the drill which has a chamfer of a negative angle part in the intersection formed by the flank and margin of a negative angle part. In other words, by having negative chamfering at the intersection formed by the flank and margin of the negative corner, the strength against the cutting resistance and thrust resistance of the outer periphery and peripheral corner of the drill is improved, and chipping and wear are prevented. Less likely to occur.

Furthermore, in invention of Claim 2 , it is set as the drill whose chamfering width of a negative angle part chamfering exists in the range of 0.03 mm-0.05 mm. In other words, by providing a range for the chamfer width, the resistance to cutting and thrust resistance of the outer periphery and peripheral corner of the drill is improved, and chipping and wear are less likely to occur, and at the same time, the sharpness of the main cutting edge is ensured without deterioration. Is done .

In the present invention, in a drill having three torsion grooves, the outer periphery of the concave main cutting edge has a negative corner, and the rake angle in the radial direction is within a range of −45 ° to −30 °. Since the position of the drill is stabilized and vibration during machining is reduced and core blurring is suppressed, centripetality is increased and machining hole accuracy is improved. Moreover, since an increase in excessive cutting resistance can be prevented by providing a margin, stable drilling can be performed.

Further, in the invention according to claim 2, by having the chamfered negative corner portion, the strength of the drill outer periphery and the outer periphery corner with respect to cutting resistance and thrust resistance is improved, and chipping and wear are less likely to occur. Long-life high-feed drilling is now possible.

Furthermore, in the invention described in claim 3, by making the chamfer width of the chamfer of the negative angle portion within a range of 0.03 mm to 0.05 mm, chipping and wear are less likely to occur, and the sharpness does not deteriorate. Therefore, vibration during machining is suppressed, machining hole accuracy is improved, and high feed drilling with a long service life can be performed.

It is a front view of drill 1 which is an example of an embodiment of the invention. It is a side view of FIG. It is an enlarged view of the front-end | tip part of FIG. It is an expansion perspective view of the front-end | tip part of FIG. It is the sectional view on the AA line of FIG.

Embodiments of the present invention will be described with reference to the drawings. 1 is a front view of a drill 1 as an example of an embodiment of the present invention, FIG. 2 is a side view of FIG. 1, FIG. 3 is an enlarged view of a tip portion of FIG. 2, and FIG. FIG. 5 is a sectional view taken along line AA in FIG.

As shown in FIG. 1, the drill 1 of the present invention includes a corner radius 4 and a thinning blade 5 at the tip of an axis O as seen from the tip of the drill 1 in a drill 1 having three twisted grooves 2, 2, 2. A thinning 3 is provided. Further, the concave main cutting edge 6 is smoothly connected to the thinning 3. On the outer periphery of the concave main cutting edge 6, there are provided a radial rake angle α that recedes in the rotational direction and a negative angle portion 7 in which the radial rake angle α is formed. Further, the intersection formed by the margin 9 along the twisted groove 2 adjacent to the negative corner 7 and the relief surface 10 of the negative corner 7 and the margin 9 has a negative corner chamfer 8. . The rake angle α in the radial direction of the negative corner portion 7 is in the range of −45 ° to −30 °, and the chamfer width C of the negative corner portion chamfer 8 is in the range of 0.03 mm to 0.05 mm.

The reason for providing a range in the radial rake angle α is that the core blur of the drill 1 is suppressed by the load applied from the outer periphery of the drill 1 to the center due to the cutting resistance, so that the hole accuracy can be improved in drilling. . When the rake angle α in the radial direction becomes a negative angle further than −45 °, the cutting resistance applied to the drill 1 increases, and the core blur cannot be suppressed. Further, when the angle is closer to -30 °, chipping or chipping occurs at the outer corner of the drill 1. Therefore, it is desirable to set the rake angle α in the radial direction within a range of −45 ° to −30 °.

Further, when the drill 1 is manufactured, the linear negative angle portion 7 is formed after forming the twisted groove 2 using one grindstone, and in order to give a sharpness, the aim of the radial rake angle α is aimed. The value is -37 ° and the tolerance is ± 3 °. By doing so, it becomes possible to manufacture the drill 1 whose drill diameter D is in the range of several mm to several tens of mm. Therefore, it is more desirable to set the rake angle α in the radial direction within a range of −40 ° to −34 °.

As shown in FIG. 2 to FIG. 4, the strength of the outer periphery of the drill 1 with respect to cutting resistance and thrust resistance is obtained by having the negative corner chamfer 8 at the intersection formed by the relief surface 10 of the negative corner 7 and the margin 9. As a result, chipping and wear are less likely to occur, and core blurring is suppressed. Therefore, the hole accuracy is improved in drilling, and the tool life is extended.

Further, the chamfer width C of the negative angle chamfer 8 is set within a range of 0.03 mm to 0.05 mm. The reason for providing a range for the chamfer width C of the negative corner chamfer 8 is that if it is smaller than 0.03 mm, the strength is not improved and chipping or wear occurs. Further, if the thickness exceeds 0.05 mm, the sharpness of the concave main cutting edge 6 deteriorates and the centripetality is impaired. Therefore, the chamfering width C of the negative corner chamfer 8 is set within a range of 0.03 mm to 0.05 mm. It is desirable to do.

By performing the thinning 3 so as to form a corner radius 4 at the tip of the axis O of the drill 1, the discharge performance of thin chips generated at the axis O of the drill 1 is improved. Further, by providing the thinning blade 5, the centripetality is increased, the cutting resistance and the thrust resistance are lowered, and the core blur is hardly generated, and the machining hole accuracy can be increased.

The thinning blade 5 is provided so as to be smoothly connected to the concave main cutting edge 6, and the rake angle β of the thinning blade 5 is set within a range of −1 ° to 1 °. The reason for providing a range for the rake angle β of the thinning blade 5 is that if it is less than −1 °, the thickness of the thinning blade 5 is increased, and the chip dischargeability at the tip of the drill 1 is lowered. Further, if it exceeds 1 °, the blade thickness is thin, and chipping and chipping are likely to occur due to thrust resistance, and the centripetality of the drill 1 is impaired. Therefore, it is set within the range of −1 ° to 1 °.

When the negative angle portion width N in which the negative angle portion 7 of the concave main cutting edge 6 is formed becomes small, the cutting resistance applied from the outer periphery of the drill 1 toward the center tends to be small, so that the core blur tends to increase. On the other hand, when the negative angle portion width N is increased, the sharpness of the concave main cutting edge 6 is deteriorated, the cutting resistance applied to the drill 1 is increased, exceeds the rigidity of the tool and breaks, and therefore 0.04D ± 0. Set within the range of 0.05 mm (D: drill diameter).

As shown in FIG. 5, when the core thickness W of the drill 1 is decreased, the rigidity of the tool and the strength of the blade are impaired. On the other hand, when the core thickness W is increased, the chip dischargeability is impaired. 0.29D to 0.31D (D : Drill diameter).

The ratio of the groove width angle δ to the land width angle γ (groove width ratio: δ / γ) is set within the range of 1.4 to 2.0. The reason for setting the range for the groove width ratio (δ / γ) is that the cutting thickness can be suppressed and the core thickness W that can withstand the load applied to the drill 1 and the chip dischargeability can be secured in a balanced manner. is there. When the land width angle γ is smaller than the groove width angle δ, the rigidity of the tool and the strength of the blade are impaired. However, when the land width angle γ is increased, chip dischargeability is impaired. Set in.

Using a drill according to the present invention (hereinafter referred to as the present product) and a conventional drill (hereinafter referred to as a conventional product), a cutting test is performed under the following processing conditions. Wall roughness and perpendicularity were measured. The common specification is that the material of the present invention and the conventional product used in the cutting test are cemented carbide and the drill diameter D is 12 mm. Further, the product of the present invention has a rake angle in the radial direction of −37 °, and a negative angle chamfer is applied to the intersection formed by the flank and the margin of the negative angle part. On the other hand, the conventional product has a rake angle of −20 ° in the radial direction.
・ Work material: SCM440H
・ Cutting oil: Water-soluble oil agent ・ Cutting speed: 75 m / min
・ Feed amount: 0.48mm / rev
・ Feeding speed: 955mm / min
・ Rotation speed: 1990 min ^-1
・ Processing depth: 60mm (5D)

Table 1 shows the results of measuring the hole expansion amount, roundness, inner wall surface roughness, and squareness after the cutting test in order to evaluate the accuracy of the drilled hole for SCM440H. As shown in Table 1, the product of the present invention has a hole expansion amount of 4.0 μm, roundness of 2.9 μm, inner wall roughness of 1.3 μm, and squareness of 38.0 μm smaller than the conventional product. Yes. From this result, it can be seen that the machined hole accuracy of the product of the present invention is improved over the conventional product.

This is because the product according to the present invention has a rake angle in the radial direction that is more negative than −30 ° compared to the conventional product, and further, the chamfered negative corner portion is formed at the intersection formed by the relief surface and the margin of the negative corner portion. This is because vibration during processing is suppressed.

Using a drill according to the present invention (hereinafter referred to as the present product) and a conventional drill (hereinafter referred to as a conventional product), a cutting test was performed under the following processing conditions. The common specification is that the material of the present invention and the conventional product used in the cutting test are cemented carbide and the drill diameter D is 6 mm. Further, the product of the present invention has a rake angle in the radial direction of −37 °, and a negative angle chamfer is applied to the intersection formed by the flank and the margin of the negative angle part. On the other hand, the conventional product has a rake angle of −20 ° in the radial direction.
・ Work material: S50C, SCM440H
Cutting oil: water-soluble oil agent Cutting speed: 120 m / min, 75 m / min
・ Feed amount: 0.24mm / rev
・ Feeding speed: 1530mm / min, 955mm / min
・ Rotational speed: 6370 min ⁻¹ , 3980 min ⁻¹
・ Processing depth: 30mm (5D)

Table 2 shows the results of the number of holes processed when a cutting test is performed until the end of the life due to breakage or wear in order to evaluate the durability against S50C and SCM440H. As shown in Table 2, the product of the present invention is 1.4 times or more in the S50C and 1.3 times or more in the SCM440H compared to the conventional product, and the number of machining holes is increased. I understand that.

This is because the product according to the present invention has a rake angle in the radial direction that is more negative than −30 ° compared to the conventional product, and further, the chamfered negative corner portion is formed at the intersection formed by the relief surface and the margin of the negative corner portion. This is because the core blur was suppressed. In addition, the strength of the outer periphery and outer periphery of the drill against cutting resistance and thrust resistance is improved, so that chipping and wear are less likely to occur, drilling accuracy is improved, and drilling with a long life and high feed becomes possible. This is because.

DESCRIPTION OF SYMBOLS 1 Drill 2 Twist groove | channel 3 Thinning 4 Corner radius 5 Thinning blade 6 Concave main cutting edge 7 Negative corner 8 Negative corner chamfer 9 Margin 10 Negative corner relief O Drill shaft center C Chamfer width α Radial rake angle

Claims (2)

A thinning having a corner are and a thinning blade at a chisel edge of the drill as viewed from the tip of the drill in a drill having three twist grooves, a concave main cutting edge smoothly connected to the thinning, and the main cutting edge A radial rake angle that recedes in the rotational direction on the outer periphery of the rim, a negative angle portion where the radial rake angle is formed, and a margin along the torsion groove adjacent to the negative angle portion,
The radial rake angle is within a range of −45 ° to −30 °, and the negative corner width N of the concave main cutting edge is 0.04D ± when the diameter of the drill is D. A drill having a chamfered negative corner at an intersecting line formed by the flank of the negative corner and the margin within a range of 0.05 mm . The drill according to claim 1, wherein a chamfering width of the negative corner portion chamfering is in a range of 0.03 mm to 0.05 mm .

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