JP2006055915A - Small diameter drill for machining printed wiring board - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a small diameter drill which is for use in machining a small-diameter deep hole, and contributes to improvement in hole locational accuracy while preventing degradation of surface roughness on an inner wall surface of the machined hole due to degradation of chip disposal performance. <P>SOLUTION: According to the small diameter drill (1) for use in machining a printed wiring board, the thickness of a web (10) of a blade portion in the range from the tip of the blade portion (2) to a terminal (4a) of a chip discharging groove, is set to an almost predetermined thickness ranging from 32 to 54% of the diameter (D) of a cutting edge. Further, with respect to a blade cross section, provided that two straight lines in parallel with each other, each connecting between a front side edge (4d) and a rear side edge (4c) in a rotating direction (N) of a concave wall surface (4b) constituting the cutting chip discharging groove (4), are horizontally placed, a diameter (A) of a maximally inscribed circle in the concave wall surfaces (4b) is set to a dimension ranging from 30 to 65% of an interval (B) between the two straight lines. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

The present invention relates to a small diameter drill for processing a printed wiring board.

As the printed wiring board (hereinafter referred to as “wiring board”) becomes lighter, thinner, and smaller, the diameter of the processed hole is reduced, and further, there is an increasing demand for increasing the number of wiring boards to be stacked in order to improve the processing efficiency. Therefore, a small diameter drill for processing a printed wiring board (hereinafter referred to as “drill”) has a large ratio between the diameter of the cutting edge and the effective length of the chip discharge groove, so-called aspect ratio. On the other hand, the hole position accuracy of the processed hole and the surface roughness of the inner wall surface are also in high demand as before.

In order to meet such demands, various studies have been made so far regarding the specifications of drill shapes such as core thickness, groove width, and helix angle. FIG. 7 illustrates a cross-sectional view of a main part of this type of conventional drill. In this conventional drill, a taper gradient is applied to the core thickness portion so that the core thickness ratio (core thickness / cutting blade diameter) is 20 to 30% at the tip and 60 to 80% at the end of the chip discharge groove. The width ratio is 1.5 to 2.5: 1, and the twist angle of the blade groove (chip discharge groove) at the tip of the drill is 25 ° or more. And it has the structure which changes a torsion angle in steps or continuously so that it may become loose | gentle by the angle of 3-7 degrees per 3-5 times length of a drill diameter toward a drill rear part. (For example, see Patent Document 1)
Japanese Utility Model Publication No. 2-122712

However, in the above-described conventional drill, since the core thickness ratio increases as it approaches the rear part of the drill, the cross-sectional area of the chip discharge groove also decreases. For this reason, there is a problem that chip dischargeability when deep hole machining is reduced and the surface roughness of the inner wall surface of the machining hole is deteriorated.

The present invention has been made in view of the above circumstances, and its purpose is to prevent the deterioration of the surface roughness of the inner wall surface of the processed hole due to the deterioration of chip disposal in deep hole processing. An object of the present invention is to provide a drill with improved hole position accuracy.

In order to solve the above-mentioned problem, the present invention has a substantially round bar shape, and is constituted by a blade portion provided on the front end side in the rotation axis (O) direction and a shank portion connected to the rear end side of the blade portion, A pair of chip discharge grooves are formed on the outer peripheral surface of the blade part so as to sandwich the axis (O), and a cutting edge is provided at a cross ridge line part between the chip discharge groove and the tip surface of the blade part. The obtained small diameter drill for processing a printed wiring board has the following characteristic portions.

That is, in the first invention, the diameter (D) of the cutting edge is set to 0.03 mm or more and 1.00 mm or less, and in the range from the tip of the blade part to the terminal part of the chip discharge groove, the blade part The web thickness (S1) is set to a substantially constant thickness dimension in the range of 32% to 54% of the diameter (D) of the cutting edge, and each chip discharge groove is formed on the blade section. When two parallel straight lines connecting the front end and the rear end in the rotational direction (N) of the concave wall surface are horizontal, the diameter of the maximum inscribed circle ( A) is set to a diameter dimension in the range of 30% to 65% of the distance (B) between the two straight lines, and the length (L) from the tip of the blade portion to the end portion of the chip discharge groove Is a length in the range of 8 to 25 times the diameter (D) of the cutting edge And it is characterized in that it is set to law. The terminal portion of the chip discharge groove is a portion where the chip discharge groove starts to be cut up.

Moreover, in 2nd invention, the diameter (D) of a cutting blade is set to 0.03 mm or more and 1.00 mm or less, and the web of a blade part is the terminal end of the said chip discharge groove from the front end surface of the said blade part. A taper-shaped cross-section with a gradually increasing thickness dimension up to a portion, at a position spaced by a distance of 100% of the diameter (D) of the cutting edge from the leading edge to the trailing edge of the blade. The thickness (S2) is set to a thickness dimension in the range of 32% to 54% of the diameter (D) of the cutting edge, and the recesses forming the chip discharge grooves in the blade section at the position are provided. When two parallel lines connecting the front end and the rear end in the rotation direction (N) of the wall surface are horizontal, the diameter (A) of the maximum inscribed circle in each concave wall surface is 30% to 65% of the distance (B) between the two straight lines The length (L) from the tip of the blade portion to the end portion of the chip discharge groove is a length in the range of 8 to 25 times the diameter (D) of the cutting blade. It is characterized by being set to a size.

Moreover, in 3rd invention, the diameter (D) of a cutting blade is set to 0.03 mm or more and 1.00 mm or less, and the web of a blade part is the said cutting blade from the front end surface of the said blade part to a rear-end side. A first web formed over a range of 2 to 6 times the diameter (D) of the first web and a second web formed over a range from the first web to the end of the chip discharge groove, The first web has a constant-gradient tapered cross section in which the thickness dimension gradually increases from the front end side toward the rear end side, and the second web gradually increases in thickness dimension from the front end side toward the rear end side. The thickness of the web (S3) at a position having a tapered cross section with a smaller gradient than the first web and further spaced from the tip of the blade portion to the rear end by a distance of 100% of the diameter (D) of the cutting blade. ) Is the diameter of the cutting edge ( ) And a front end portion in the rotational direction (N) of the concave wall surface forming each of the chip discharge grooves in the blade section at the position. When two parallel straight lines connecting the rear end portions are horizontal, the diameter (A) of the maximum inscribed circle in each concave wall surface is 30% of the separation distance (B) of the two straight lines. The diameter dimension is set to a range of ˜65%, and the length (L) from the tip of the blade portion to the end portion of the chip discharge groove is a range of 8 to 25 times the diameter (D) of the cutting blade. It is characterized by being set to the length dimension.

In said 1st invention, since the thickness (S1) of the web of a blade part was set to the thickness dimension of the range of 32%-54% of the diameter (D) of a cutting blade, high blade part rigidity is obtained. Furthermore, in the blade section, two parallel straight lines connecting the front end and the rear end in the rotational direction (N) of the concave wall surface forming each of the chip discharge grooves are horizontal. Since the diameter (A) of the maximum inscribed circle in each of the concave wall surfaces is set to a diameter dimension in a range of 30% to 65% of the separation distance (B) of the two straight lines, the cross-sectional strength of the blade portion Further, the cross-sectional area sufficient for discharging chips and a suitable cross-sectional shape can be obtained in the chip discharge groove. The reason why the thickness (S1) of the web is limited to the above range is that when the thickness (S1) is less than 32% of the diameter (D) of the cutting edge, the rigidity of the blade portion is insufficient, so that the hole of the processed hole is formed. This is because the positional accuracy may be deteriorated, and when the thickness dimension exceeds 54%, the surface roughness of the inner wall surface of the processed hole may be deteriorated due to the reduction of chip dischargeability. Further, when the diameter (A) of the inscribed circle is less than 30% of the separation distance (B), the chip discharge property may be deteriorated. This is because the strength may decrease. As described above, since the rigidity of the blade portion is increased without reducing the chip discharging property, the hole position accuracy of the processed hole can be improved without deteriorating the surface roughness of the inner wall surface of the processed hole.

In said 2nd invention, it is set as the taper-shaped cross section which thickness increases uniformly toward the terminal part of a chip discharge | emission groove | channel from the front-end | tip of a blade part, and also from the front-end | tip of the said blade part to the rear end side Since the web thickness (S2) is limited to a thickness dimension in the range of 32% to 54% of the diameter (D) of the cutting edge at a position separated by a distance of 100% of the diameter (D) of the cutting edge, High blade rigidity, particularly high rigidity is obtained on the base side of the blade. Moreover, since the cutting edge shape with low cutting resistance is obtained, the sharpness is improved. In the blade section at the position, two parallel straight lines connecting the front end and the rear end in the rotational direction (N) of the concave wall surfaces forming the chip discharge grooves are horizontal. Since the diameter (A) of the maximum inscribed circle in each of the concave wall surfaces was set to a diameter dimension in a range of 30% to 65% of the two straight line separation distances (B), the cross section of the blade portion The strength is further increased, and a cross-sectional area sufficient for discharging chips in the chip discharge groove and a suitable cross-sectional shape are obtained. The reason why the thickness (S2) of the web is limited to the above range is that when the thickness (S2) is less than 32% of the diameter (D) of the cutting edge, the rigidity of the blade portion is insufficient, so that the hole of the processed hole is formed. This is because the positional accuracy may be deteriorated, and when the thickness dimension exceeds 54%, the surface roughness of the inner wall surface of the processed hole may be deteriorated due to the reduction of chip dischargeability. Further, when the diameter (A) of the inscribed circle is less than 30% of the separation distance (B), the chip discharge property may be deteriorated. This is because the strength may decrease. As described above, the rigidity of the blade part, notably the rigidity on the base side of the blade part, has been greatly increased and the sharpness has been further improved without deteriorating the chip discharge performance. It is possible to greatly improve the hole position accuracy of the processed holes without causing them.

In said 3rd invention, the 1st web which makes the taper-shaped cross section which thickness increases uniformly from the front-end | tip of a blade part to the predetermined position of a rotation axis (O) direction, and chip discharge | emission from this 1st web A second web having a tapered cross section whose thickness uniformly increases with a smaller gradient than the first web up to the terminal end of the groove, and further, the diameter of the cutting edge from the tip of the blade to the rear end ( Since the thickness (S3) of the web is limited to a thickness dimension in the range of 32% to 54% of the diameter (D) of the cutting edge at a position separated by a distance of 100% of D), a high blade rigidity, In particular, high rigidity is obtained on the root side of the blade portion, and a cutting edge shape with low cutting resistance is obtained, so that the sharpness is improved. Further, in the cross section of the blade portion at the position, two parallel straight lines connecting the front end and the rear end in the rotation direction (N) of the concave wall surfaces forming the chip discharge grooves become horizontal. When doing so, the diameter (A) of the maximum inscribed circle in each of the concave wall surfaces is set to a diameter dimension in the range of 30% to 65% of the separation distance (B) of the two straight lines. In addition, the cross-sectional strength and the cross-sectional area sufficient for discharging chips are obtained in the chip discharge groove. The reason for limiting the web thickness (S3) to the thickness dimension in the above range is that the rigidity of the blade portion is insufficient when the thickness (S3) is less than 32% of the diameter (D) of the cutting edge. This is because the hole position accuracy of the hole may be deteriorated, and when the thickness dimension exceeds 54%, the surface roughness of the inner wall surface of the processed hole may be deteriorated due to a decrease in chip dischargeability. Further, when the diameter (A) of the inscribed circle is less than 30% of the separation distance (B), the chip discharge property may be deteriorated. This is because the strength may decrease. In addition, the formation range (L1) of the first web in the axis (O) direction is set to a range of 2 to 6 times the diameter (D) of the cutting edge from the front end to the rear end side of the blade portion. It is preferable. If this is less than 2 times, the effect of increasing the rigidity of the tip of the blade portion on which the first web is formed may not be obtained. If it exceeds 6 times, the chip discharge groove at the end of the chip discharge groove This is because the cross-sectional area of the blade becomes small, or the thickness of the first web at the tip of the blade portion becomes small, which may cause a problem in either chip discharge performance or blade strength. As described above, the rigidity of the blade part, particularly the rigidity at the root side of the blade part, has been significantly increased without reducing the chip discharge performance, and the sharpness has been further improved. The hole position accuracy of the processed hole can be greatly improved without deteriorating.

In the second and third inventions in which the web has a tapered cross section, the taper gradient is preferably set in the following range. That is, in the second invention, the taper slope of the web section is preferably a constant slope within the range of 0.005 / 1 to 0.025 / 1. If the taper gradient is less than 0.05 / 1, the effect of improving the rigidity of the blade may not be obtained. If the taper gradient is greater than 0.025 / 1, the end portion of the chip discharge groove This is because there is a risk that the cross-sectional area at is insufficient and the chip discharge property is deteriorated. In the drill of the third invention, the taper slope of the first web section is a constant slope within the range of 0.025 / 1 to 0.045 / 1, and the taper slope of the second web section is 0.005. It is preferable to set a constant gradient within the range of / 1 to 0.025 / 1. This is because when the taper slope of the first web section is less than 0.025 / 1, the effect of improving the rigidity of the blade portion in the range where the first web is formed cannot be obtained, or the length of the cutting edge is shortened. (The chisel edge becomes longer) The sharpness may be deteriorated, and when it is larger than 0.045 / 1, the cross-sectional area of the chip discharge groove in the second web formed on the rear end side of the first web may be insufficient. Because there is. Moreover, when the taper gradient of the second web section is less than 0.005 / 1, the effect of improving the rigidity of the blade portion in the range where the second web is formed cannot be obtained, and when the taper gradient is larger than 0.025 / 1, chips are removed. This is because the cross-sectional area at the terminal end of the discharge groove is insufficient and the chip discharge property may be deteriorated.

According to the first to third inventions having the configuration described above, the diameter (D) of the cutting edge is 0.03 mm or more and 1.00 mm or less, and further, the chip discharge groove is formed from the tip of the blade part. For small diameter deep hole drills with a high aspect ratio of 8 to 25 times the diameter (D) of the cutting edge, the length to the end (L) is suitable for increasing the hole position accuracy of the processed holes. It can be demonstrated.

In the first to third inventions, it is preferable to set the twist angle (θ) of the chip discharge groove to a twist angle in the range of 38 ° to 56 ° in terms of chip discharge performance and hole position accuracy of the processed hole. . This is because when the twist angle (θ) is less than 38 °, the chip dischargeability may decrease or the hole position accuracy of the processed hole may decrease due to the decrease in sharpness, and the twist angle (θ) may be 56. This is because if the angle exceeds 60 °, the rigidity of the blade portion is lowered, so that the hole position accuracy of the processed hole may be lowered or the drill may be broken.

In the first to third aspects of the invention, it is preferable to set the groove width ratio of the drill in the range of 0.8 to 1.5 from the viewpoints of chip dischargeability and blade rigidity. This is because when the groove width ratio is less than 0.8, the volume of the chip discharge groove cannot be secured sufficiently, and the chip discharge property may be deteriorated. When the groove width ratio exceeds 1.5, the blade portion This is because the rigidity of the hole cannot be sufficiently secured, and the hole position accuracy of the processed hole may be deteriorated.

Embodiments to which the present invention is applied will be described below with reference to FIGS. 1A and 1B are diagrams showing a drill according to a first embodiment, wherein FIG. 1A is a front view, and FIG. 1B is a partial front sectional view of an essential part. 2 is an enlarged side view of the drill shown in FIG. 1, FIG. 3 is an enlarged cross-sectional view taken along line AA of the drill shown in FIG. 1, and (a) is a diagram showing the drill of the present embodiment. And (b) and (c) are diagrams conceptually showing a drill outside the scope of the present invention. The basic configuration of the drill (1) will be described below. As shown in FIGS. 1 and 2, the drill (1) has a substantially round bar shape, and has a blade portion (2) provided on the tip side in the direction of the rotation axis (O), and the blade portion (2). The shank portion (3) is connected to the rear end side, and a pair of chip discharge grooves (4) are formed on the outer peripheral surface of the blade portion (2) so as to face each other with the axis (O) interposed therebetween. ing. A cutting blade (5) is formed at the intersecting ridge line portion between the chip discharge groove (4) and the tip end surface (2a) of the blade portion. The web (10) formed by the groove bottom of the chip discharge groove (4) is formed in a range from the tip of the blade part to the terminal part (4a) of the chip discharge groove. The diameter (D) of the cutting edge is set to 0.03 mm or more and 1.00 mm or less, and the length (L) from the tip of the blade part (2) to the terminal end part (4a) of the chip discharge groove is the cutting edge. And a length in the range of 8 to 25 times the diameter (D). The end portion (4a) of the chip discharge groove is a portion where the chip discharge groove starts to be cut, and the length (L) is the chip discharge groove (4) in another expression. Is the effective length.

Next, a characteristic configuration will be described below. As shown in FIG. 1B, the thickness (S1) of the web (10) is formed to have a substantially constant thickness dimension from the tip of the blade (2) to the end (4a) of the chip discharge groove. The And the said thickness (S1) is set to the thickness dimension of the range of 32%-54% of the diameter (D) of a cutting blade, and the rigidity of a blade part (2) is fully improved. The thickness (S1) is limited to the above range because when the thickness (S1) is less than 32% of the diameter (D) of the cutting edge, the rigidity of the blade (2) is insufficient, so that the processing hole is formed. This is because the hole position accuracy may be deteriorated, and when the thickness exceeds 54%, the surface roughness of the inner wall surface of the processed hole may be deteriorated due to a decrease in chip dischargeability.

Further, as shown in FIG. 3 (a), in the cross section obtained by cutting the blade portion (2) along a plane orthogonal to the rotational axis (O), each chip discharge groove is centered on the axis (O). The diameter (A) of the inscribed circle that is inscribed in the concave wall surface (4b) that constitutes the front end portion (4d) and the rear end portion in the rotational direction (N) of the drill (1) in each concave wall surface The diameter is limited to a range of 30% to 65% of the distance (B) between two parallel lines connecting (4c). By doing so, the cross-sectional strength of the blade portion (2) can be further increased, and the cross-sectional shape of the chip discharge groove (4) sufficient for discharging chips can be obtained. When the diameter of the inscribed circle (A) is less than 30% of the distance (B), the rotational direction of the concave wall surface (4b) as shown in the conceptual diagram of FIG. Since the front end part (4d) and the rear end part (4c) of (N) are close to each other, the cross-sectional shape of the chip discharge groove is reduced in cross-sectional area and the radius of curvature of the concave wall surface (4b). Therefore, the cross-sectional shape becomes unfavorable for chip discharge. On the other hand, when the diameter (A) of the inscribed circle exceeds 65% of the separation distance (B), the land portion (8) becomes narrow as shown in the conceptual diagram of FIG. Therefore, sufficient rigidity of the blade (2) cannot be ensured.

Thus, according to the drill (1) according to the first embodiment, the diameter (D) of the cutting edge is set to 0.03 mm or more and 1.00 mm or less, and the tip of the blade part (2) In a high aspect ratio drill in which the length (L) from the tip to the end portion (4a) of the chip discharge groove is set to a range of 8 to 25 times the diameter (D) of the cutting edge, chip discharge performance is reduced. Since the rigidity of the blade part (2) is improved without any problem, the hole position accuracy of the processed hole can be improved without deteriorating the surface roughness of the inner wall surface of the processed hole.

Next, a drill according to a second embodiment to which the present invention is applied will be described with reference to FIGS. 4, 2, and 3. 4A and 4B are views showing the drill, in which FIG. 4A is a front view and FIG. 4B is a partial front sectional view of a main part. 4 and FIG. 3 are substantially the same as those in the first embodiment, and the side view of the drill shown in FIG. Since the basic configuration of the drill (1) is the same as that of the drill (1) according to the first embodiment described above, it will be omitted and only the characteristic configuration will be described below.

As shown in FIG. 4B, the web (10) of the blade part (2) has a tapered shape in which the thickness dimension gradually increases uniformly from the tip of the blade part to the end part (4a) of the chip discharge groove. Presents a cross section. Specifically, the taper gradient of the cross section of the web (10) is preferably constant within a range of 0.005 / 1 to 0.025 / 1. If the taper gradient is less than 0.05 / 1, there is a possibility that the effect of improving the rigidity of the blade part (2), particularly the rigidity of the root part of the blade part (2), may not be obtained. This is because the cross-sectional area of the end portion (4a) of the chip discharge groove is insufficient in the cross section perpendicular to the rotation axis (O), and the chip discharge performance may be deteriorated. Then, in the cross section of the blade part (2) cut by a plane perpendicular to the rotation axis (O) at a position separated by a distance substantially equal to the diameter (D) of the cutting edge from the front end to the rear end side of the blade part (2), The thickness (S2) of the web (10) is formed in a thickness dimension in the range of 32% to 54% of the diameter (D) of the cutting edge. Then, the strength of the blade portion (2), particularly high rigidity on the root side of the blade portion (2) can be obtained, and as can be seen from FIG. 2, the tip portion of the blade portion (2) where the web thickness decreases. In this case, since the length of the chisel edge (6) extending from the vicinity of the rotation axis (O) to the cutting edge (5) is shortened, a cutting edge shape with reduced cutting resistance and improved sharpness is obtained. Position accuracy is greatly improved. The reason why the thickness (S2) of the web (10) in the cross section of the blade part (2) is limited to the above range is that when the thickness (S2) is less than 32% of the diameter (D) of the cutting edge, Since the rigidity of the part (2) is insufficient, the hole position accuracy of the processed hole may be deteriorated. When the thickness dimension exceeds 54%, the surface roughness of the inner wall surface of the processed hole is deteriorated due to the reduction of chip dischargeability. Because there is a fear.

Further, in the cross section of the blade part (2), referring to the cross sectional view shown in FIG. 3A, the drill (1) in the concave wall surface (4b) constituting each chip discharge groove (4). ) In the rotational direction (N) when the two parallel straight lines connecting the front end (4d) and the rear end (4c) are horizontal, the maximum in each concave wall surface (4b) The diameter (A) of the inscribed circle is limited to a diameter dimension in the range of 30% to 65% of the distance (B) between the two straight lines. If it does so, while the cross-sectional intensity | strength of a blade part (2) is further raised, sufficient cross-sectional area and suitable cross-sectional shape to discharge a chip in the cross-sectional shape of a chip discharge groove (4) are obtained. The reason for limiting to the above range is the same as in the first embodiment described above. The diameter (A) of the inscribed circle is set to a diameter of approximately 1.03 to 1.06 times the thickness of the web at the tip of the blade (2), that is, the so-called core thickness.

Thus, according to the drill (1) according to the second embodiment, in the drill having a small diameter and a high aspect ratio, the rigidity of the blade (2), in particular, the blade, without reducing the chip discharge performance. Since the rigidity of the root side of (2) is increased and the sharpness is further improved, the hole position accuracy of the processed hole can be greatly improved without deteriorating the surface roughness of the inner wall surface of the processed hole.

Next, a drill according to a third embodiment to which the present invention is applied will be described with reference to FIGS. FIG. 5 is a view showing this drill, in which (a) is a front view and (b) is a partial front sectional view of a main part. 4 and FIG. 3 are substantially the same as those in the first embodiment, and the side view of the drill shown in FIG. Since the basic configuration of the drill (1) is the same as that of the drill (1) according to the first embodiment described above, it will be omitted and only the characteristic configuration will be described below.

As shown in FIG. 5B, the web (10) of the blade part (2) has a constant gradient in which the thickness dimension gradually increases from the front end of the blade part (2) to a predetermined position toward the rear end side. The first web (10A) having a tapered cross section, and the second web having a taper-shaped cross section having a constant gradient in which the thickness dimension gradually increases from the first web (10A) to the end portion (4a) of the chip discharge groove. (10B). The cross-sectional shapes of the first web (10A) and the second web (10B) have different taper slopes, and the taper slope of the first web (10A) is set to be larger than that of the second web (10B). The taper gradient of the first web (10A) cross section is constant within the range of 0.025 / 1 to 0.045 / 1, and the taper gradient of the second web (10B) cross section is 0.005 / 1 to 0.005 / 1. It is preferable to make it constant within a range of 0.025 / 1. If the taper gradient of the cross section of the first web (10A) is less than 0.025 / 1, the effect of improving the rigidity of the blade portion (2) in the range where the first web (10A) is formed is not obtained. Or, as shown in FIG. 2, it becomes difficult to obtain the effect of improving the sharpness by shortening the length of the chisel edge (6) at the tip of the blade (2) where the thickness of the first web decreases. This is because if it exceeds 0.045 / 1, the cross-sectional area of the chip discharge groove (4) in the range where the second web (10B) is formed may be insufficient. Moreover, when the taper gradient of the cross section of the second web (10B) is less than 0.005 / 1, the rigidity of the blade portion (2) in the range where the second web (10B) is formed, particularly the root side of the blade portion (2). This is because the effect of improving the rigidity cannot be obtained, and if it exceeds 0.025 / 1, the cross-sectional area at the end portion (4a) of the chip discharge groove is insufficient, and the chip discharge property may be deteriorated. And the formation range (L1) of the 1st web (10A) in the said axis (O) direction is the range of 2-6 times the diameter (D) of a cutting blade from the front-end | tip side of a blade part (2) to a rear-end side. Is preferably set. If this is less than twice, there is a risk that the effect of increasing the rigidity of the tip of the blade part (2) on which the first web (10A) is formed may not be obtained. The cross-sectional area of the chip discharge groove (4) in the part (4a) is reduced, or the thickness of the first web (10A) at the tip of the blade part (2) is reduced. This is because a problem may occur in either of the strengths.

Furthermore, in the cross section of the blade part (2) cut by a plane perpendicular to the rotation axis (O) at a position separated by a distance substantially equal to the diameter (D) of the cutting edge from the front end to the rear end side of the blade part (2), The thickness (S3) of the web (10) is formed in a thickness dimension ranging from 32% to 54% of the diameter (D) of the cutting edge. Then, the strength of the blade portion (2), in particular, high rigidity is obtained on the root side of the blade portion (2), and at the tip portion of the blade portion (2) where the thickness of the web is reduced, the rotation axis (O ) Since the length of the chisel edge (6) extending from the vicinity to the cutting edge (5) is shortened, a cutting edge shape with reduced cutting resistance and improved sharpness is obtained, and the hole position accuracy of the processed hole is greatly improved. . The reason why the thickness (S3) of the web (10) in the cross section of the blade part (2) is limited to the above range is that when the thickness (S3) is less than 32% of the diameter (D) of the cutting edge. Since the rigidity of the part (2) is insufficient, the hole position accuracy of the processed hole may be deteriorated. When the thickness dimension exceeds 54%, the surface roughness of the inner wall surface of the processed hole is deteriorated due to the reduction of chip dischargeability. Because there is a fear.

Furthermore, in the section of the blade part (2), referring to the sectional view shown in FIG. 3, the direction of rotation of the drill (1) on the concave wall surface (4b) constituting each chip discharge groove (4) ( N) When the two parallel straight lines connecting the front end portion (4d) and the rear end portion (4c) are horizontal, the diameter of the maximum inscribed circle in each concave wall surface (4b) (A) is limited to a diameter dimension in the range of 30% to 65% of the distance (B) between the two straight lines. By doing so, the cross-sectional strength of the blade portion (2) can be further increased, and the cross-sectional shape of the chip discharge groove (4) sufficient for discharging chips can be obtained. The reason for limiting to the above range is the same as in the first embodiment described above. The diameter (A) of the inscribed circle is set to a diameter of approximately 1.05 to 1.08 times the thickness of the web at the tip of the blade (2), that is, the so-called core thickness.

Thus, according to the drill (1) according to the third embodiment, in the drill having a small diameter and a high aspect ratio, the rigidity of the blade (2), in particular, the blade, without reducing the chip discharge performance. Since the rigidity on the base side of (2) is increased and the sharpness is further increased, the hole position accuracy of the processed hole can be improved without deteriorating the surface roughness of the inner wall surface of the processed hole.

In the first to third embodiments, the twist angle (θ) of the chip discharge groove is preferably set in the range of 38 ° to 56 °. If it does so, the rigidity of a blade part (2) can be improved further, without reducing a chip discharge | emission property. The above range is limited because when the twist angle (θ) is less than 38 °, there is a possibility that the chip discharge property may be reduced or the hole position accuracy of the processed hole may be reduced due to a decrease in sharpness. This is because if the twist angle (θ) exceeds 56 °, the rigidity of the blade portion (2) is lowered, so that the hole position accuracy of the processed hole may be lowered or the drill may be broken.

Similarly, it is preferable to set the groove width ratio in the range of 0.8 to 1.5 from the viewpoint of increasing the rigidity of the blade portion (2). The reason for this limitation is that if the groove width ratio is less than 0.8, the chip discharge groove (4) cannot have a sufficient volume and the chip discharge property may be deteriorated. This is because if the width ratio exceeds 1.5, the rigidity of the blade portion (2) cannot be sufficiently secured, and the hole position accuracy of the processed hole may be deteriorated.

Next, a small diameter deep hole drilling test using the drill (1) according to the second embodiment will be described below. FIG. 6 shows a side view of a drill used for the test, a sectional view of a blade part, and a dimension list. The product of the present invention in FIG. 6 is a drill according to a second embodiment to which the present invention is applied, and the conventional product is a drill outside the scope of the present invention. In both the product of the present invention and the conventional product, the blade part (2) and the shank part (3) are made of cemented carbide, the diameter (D) of the cutting edge, the aspect ratio (L / D), the twist angle of the chip discharge groove ( θ), the leading edge angle (α) of the cutting edge, and the clearance angle of the leading edge surface (2a) of the cutting edge are the same. The conventional product has a ratio A / B shown in FIG. 6, that is, a cross section of the blade part (2) at a position spaced from the tip of the blade part (2) to the rear end side by a distance substantially equal to the diameter (D) of the cutting edge. , The front end portion (4d) and the rear end portion (4c) in the rotational direction (N) of the drill (1) in the concave wall surface (4b) constituting each chip discharge groove (4) are connected. When two straight lines parallel to each other are horizontal, the ratio A / B between the diameter (A) of the maximum inscribed circle in each concave wall surface (4b) and the separation distance (B) of the two straight lines is It is outside the scope of the present invention. Using these drills, three printed wiring boards having a thickness of 0.8 mm were stacked and drilled. The processing conditions are the two conditions shown in (a) of Table 1. Under each condition, the processing of 3000 holes was repeated 3 times with different drills. Table 1 (b) shows the average value (Avg), the maximum value (Max), and the standard deviation (σ) obtained from the measured values of the deviations of the hole positions of the processed holes. Also, the surface roughness (Ry) of the inner wall surface of the processed hole in 3000 holes is shown in the same table.

As can be seen from (b) of Table 1, in both of the processing conditions (1) and (2), the product of the present invention has greatly improved the hole position accuracy of the processed holes over the conventional product. The average value (Avg) of the deviation amount of the hole position was improved by about 20 to 40%, and the standard deviation (σ) was improved by about 10 to 20%. As described above, the rigidity of the blade portion (2) is greatly increased by setting the web thickness (S2) and the ratio A / B within the range of the present invention, and the web having a tapered cross section. This is because the sharpness was good. Moreover, the surface roughness of the inner wall surface of the processed hole is not deteriorated, but rather is better than the conventional product. This is because the contact around the processed hole is improved by the high rigidity and good sharpness of the blade part (2). Although not shown in Table 1, similar results were obtained with a drill having the web thickness (S2) and the above ratio A / B as the upper and lower limits of the present invention. In addition, the drills according to the first and third embodiments not shown in Table 1 also showed a significant improvement in hole position accuracy over the conventional product.

It is a figure which shows the drill which concerns on 1st Embodiment, (a) is a front view, (b) is a partial front sectional view of the principal part. FIG. 2 is an enlarged side view of the drill shown in FIG. It is the sectional view on the AA line in FIG. 1, (a) is a figure which shows the drill of 1st Embodiment, (b) And (c) is a drill outside the scope of the present invention conceptually. FIG. It is a figure which shows the drill which concerns on 2nd Embodiment, (a) is a front view, (b) is a partial front sectional view of the principal part. It is a figure which shows the drill which concerns on 3rd Embodiment, (a) is a front view, (b) is a partial front sectional view of the principal part. It is a tip view side view, blade part sectional view, and dimension list of the drill used for the test. It is principal part sectional drawing of the conventional drill.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Drill 2 Blade part 2a Tip part surface 3 of a blade part 4 Shank part 4 Chip discharge groove 4a End part 4b of a chip discharge groove Recessed wall surface 4c which comprises a chip discharge groove Rotation direction of the concave wall surface which comprises a chip discharge groove (N) Rear end 4d Rotation direction of concave wall surface constituting chip discharge groove (N) Front end 5 Cutting edge 6 Chisel edge 10 Web 10A First web 10B Second web S1, S2, S3 Web Thickness O Rotation axis N Drill rotation direction D Cutting edge diameter L Length from the tip of the blade to the end of the chip discharge groove (effective length)
A Diameter of the maximum inscribed circle in contact with the concave wall surface constituting the chip discharge groove B Distance between two straight lines connecting both end portions of the concave wall surface constituting the chip discharge groove

Claims (5)

It has a substantially round bar shape and is composed of a blade portion provided on the front end side in the rotation axis (O) direction and a shank portion connected to the rear end side of the blade portion, and the axis (O ) With a pair of chip discharge grooves facing each other, and a small-diameter drill for processing a printed wiring board in which a cutting edge is provided at the intersection ridge line portion between the chip discharge groove and the tip end surface of the blade part. The diameter (D) of the cutting edge is set to 0.03 mm or more and 1.00 mm or less, and in the range from the tip of the blade part to the end part of the chip discharge groove, the web of the blade part The thickness (S1) is set to a substantially constant thickness dimension in the range of 32% to 54% of the diameter (D) of the cutting edge, and further, each of the chip discharge grooves is configured in the blade section. Connecting the front end and the rear end in the rotational direction (N) of the concave wall surface When two parallel straight lines are horizontal, the diameter (A) of the maximum inscribed circle in each concave wall surface is in the range of 30% to 65% of the separation distance (B) of the two straight lines. The length (L) from the tip of the blade to the end of the chip discharge groove is set to a diameter of 8 to 25 times the diameter (D) of the cutting blade. A small-diameter drill for processing printed wiring boards characterized by being set. It has a substantially round bar shape and is composed of a blade portion provided on the front end side in the rotation axis (O) direction and a shank portion connected to the rear end side of the blade portion, and the axis (O ) With a pair of chip discharge grooves facing each other, and a small-diameter drill for processing a printed wiring board in which a cutting edge is provided at the intersection ridge line portion between the chip discharge groove and the tip end surface of the blade part. The diameter (D) of the cutting edge is set to 0.03 mm or more and 1.00 mm or less, and the web of the blade portion gradually increases from the tip of the blade portion to the end portion of the chip discharge groove. The web thickness (S2) is at a position having a taper-shaped cross section with a constant gradient of increasing dimensions and spaced from the tip end to the rear end side by a distance of 100% of the diameter (D) of the cutting edge. The thickness dimension is in the range of 32% to 54% of the diameter (D) of the cutting edge. Furthermore, two parallel straight lines connecting the front end and the rear end in the rotational direction (N) of the concave wall surface forming each chip discharge groove in the cross section of the blade portion at the position are defined. When set to be horizontal, the diameter (A) of the maximum inscribed circle in each concave wall surface is set to a diameter dimension in a range of 30% to 65% of the separation distance (B) of the two straight lines, and The length (L) from the tip of the blade portion to the end portion of the chip discharge groove is set to a length dimension in the range of 8 to 25 times the diameter (D) of the cutting blade. A small diameter drill for processing printed wiring boards. It has a substantially round bar shape and is composed of a blade portion provided on the front end side in the rotation axis (O) direction and a shank portion connected to the rear end side of the blade portion, and the axis (O ) With a pair of chip discharge grooves facing each other, and a small-diameter drill for processing a printed wiring board in which a cutting edge is provided at the intersection ridge line portion between the chip discharge groove and the tip end surface of the blade part. The diameter (D) of the cutting edge is set to 0.03 mm or more and 1.00 mm or less, and the web of the cutting edge is formed from the leading edge of the cutting edge to the rear end side. ) And a second web formed over a range from the first web to the end portion of the chip discharge groove, the first web comprising: A constant gradient in which the thickness dimension gradually increases from the front end to the rear end The second web has a taper-shaped cross section with a gradually increasing thickness dimension from the front end side toward the rear end side and a smaller gradient than the first web, and further, the tip of the blade portion The web thickness (S3) is in the range of 32% to 54% of the diameter (D) of the cutting edge at a position separated from the rear edge by a distance of 100% of the diameter (D) of the cutting edge. 2 in parallel to each other connecting the front end and the rear end in the rotational direction (N) of the concave wall surface constituting each chip discharge groove in the blade section at the position. When the straight line is horizontal, the diameter (A) of the maximum inscribed circle in each of the concave wall surfaces is set to a diameter dimension in a range of 30% to 65% of the separation distance (B) of the two straight lines. And the chip from the tip of the blade portion. A small-diameter drill for processing printed wiring boards, characterized in that the length (L) to the end portion of the exit groove is set to a length dimension in the range of 8 to 25 times the diameter (D) of the cutting edge. . The small-diameter drill for processing a printed wiring board according to any one of claims 1 to 3, wherein a twist angle (θ) of the chip discharge groove is in a range of 38 ° to 56 °. The groove diameter ratio is in a range of 0.8 to 1.3, and the small-diameter drill for processing a printed wiring board according to any one of claims 1 to 4.

Images