JP6870336B2 - Drill - Google Patents

Description

The present invention relates to a drill having a first margin portion and a second margin portion on the outer periphery of the drill body.

Conventionally, double margin type drills as shown in Patent Documents 1 to 3 below are known, for example. These drills are provided with a first margin portion and a second margin portion on the outer periphery of the drill body.

Japanese Unexamined Patent Publication No. 2003-136317 Japanese Unexamined Patent Publication No. 2006-281407 Japanese Unexamined Patent Publication No. 2014-18883

However, the conventional drill has the following problems.
For example, when a work material made of a soft metal material or the like is drilled, the second margin portion may damage the inner peripheral surface of the machined hole of the work material, resulting in processing marks such as waviness patterns.

The present invention has been made in view of such circumstances, and even when a work material such as a soft metal material is drilled, the inner peripheral surface of the machined hole of the work material is damaged. It is an object of the present invention to provide a drill capable of suppressing the storage and improving the processed quality.

One aspect of the present invention is a drill body that has a shaft shape and is rotated in the drill rotation direction in the circumferential direction around the axis, and extends from the tip end in the axial direction toward the base end side on the outer periphery of the drill body. , A plurality of chip discharge grooves formed at intervals in the circumferential direction, and a cutting edge formed at an intersection ridge between the wall surface of the chip discharge groove facing the drill rotation direction and the tip surface of the drill body. A thinning surface formed between the tip surface and the chip discharge groove adjacent to the side opposite to the drill rotation direction of the tip surface, and the chip discharge grooves adjacent to each other in the circumferential direction on the outer periphery of the drill body. The land portion formed between the land portion, the first margin portion arranged adjacent to the wall surface of the land portion facing the drill rotation direction of the chip discharge groove, and the land portion in the drill rotation direction from the first margin portion. Is a drill provided with a second margin portion arranged on the opposite side, and the second margin portion is a front view of the drill when the drill body is viewed from the tip end side in the axial direction toward the base end side. Of the outer peripheral edge of the thinning surface, it is arranged at the rear end on the side opposite to the drill rotation direction, and in the cross-sectional view of the drill perpendicular to the axis of the drill body, the front end of the second margin portion in the drill rotation direction. The angle formed between the virtual straight line connecting and the rear end on the side opposite to the drill rotation direction and the extension line of the front wall surface of the margin adjacent to the drill rotation direction of the second margin portion in the land portion is , 30 ° or less, and the length of the line connecting the front end of the second margin portion in the drill rotation direction and the rear end on the side opposite to the drill rotation direction is the front end of the first margin portion in the drill rotation direction. It is characterized in that it is less than half the length of the line connecting the drill and the rear end on the opposite side of the drill rotation direction.

In the drill of the present invention, the second margin portion is arranged on the outer peripheral edge of the thinning surface in the front view of the drill (drill tip view) in which the tip surface of the drill body is viewed from the front. That is, the second margin portion is arranged not on the outer peripheral edge of the tip surface (tip relief surface) of the drill body, but on the outer peripheral edge of the thinning surface located on the side opposite to the drill rotation direction from the tip surface. Therefore, an intersecting ridgeline portion is formed between the second margin portion on the outer periphery of the drill body and the thinning surface, and no intersecting ridgeline portion is formed between the second margin portion and the tip surface.

Generally, the thinning surface has a larger clearance angle than the tip surface of the drill body. Therefore, unlike the case of the present invention, for example, as compared with the case where the intersecting ridge line portion is formed between the tip surface of the drill body and the second margin portion, the thinning surface of the drill body and the second margin portion are different from the case of the present invention. The crossed ridge line portion formed between the margin portion has a large displacement amount (that is, inclination) in the drill axis direction per unit length along the drill peripheral direction. Therefore, the intersecting ridge line portion of the second margin portion in the present invention is in a state of being inclined with respect to the inner peripheral surface of the machined hole of the work material (the twist angle is reduced), and the inside of the machined hole. It is less likely to affect the processed quality of the peripheral surface.

Specifically, in the present invention, the second margin portion is arranged at the rear end of the outer peripheral edge of the thinning surface in the drill rotation direction in the front view of the drill.
That is, as a result of intensive research on the drill and its second margin portion, the inventor of the present invention has the second margin portion at the rear end of the outer peripheral edge of the thinning surface of the drill body on the side opposite to the drill rotation direction. When arranged, the second margin portion is less likely to act as a cutting edge in combination with the action and effect of the special configuration of the present invention described later, and the accuracy of the inner peripheral surface of the machined hole of the work material is remarkably improved. We have come to the conclusion that it can be improved.

Although the detailed mechanism of the above test results is not known, as a result of evaluating the shape of the inner peripheral surface of the machined hole, when drilling a work material having low hardness, unlike the present invention, for example, the second margin portion Was provided at the center of the land portion in the circumferential direction, the second margin portion acted as a cutting edge, and the inner peripheral surface of the machined hole was damaged to generate a machined mark such as a waviness pattern.
On the other hand, as in the present invention, when the second margin portion is provided at the rear end portion of the land portion on the side opposite to the drill rotation direction (that is, the rear end portion of the outer peripheral edge of the thinning surface), the second margin portion is provided. The two-margin portion did not act as a cutting edge, that is, the inner peripheral surface of the machined hole was not damaged by the second margin part, and no machining marks such as waviness patterns were generated.

If the second margin portion is arranged at the rear end of the outer peripheral edge of the thinning surface of the drill body on the side opposite to the drill rotation direction, the first margin portion and the second margin portion are in the drill circumferential direction. Since it becomes easy to arrange the drills substantially evenly and it becomes easy to stabilize the circumferential balance of the drill at the time of drilling, it is possible to improve the accuracy of the machined surface by this action as well.

And the present invention has the following special configuration.
That is, in a cross-sectional view of the drill perpendicular to the axis of the drill body, a virtual straight line connecting the front end of the second margin portion in the drill rotation direction and the rear end on the side opposite to the drill rotation direction, and the second margin portion in the land portion. The angle formed between the extension line of the front wall surface of the margin adjacent to the drill rotation direction of the drill is 30 ° or less (see the angle θ in FIG. 6). In other words, since the front margin wall surface and the second margin portion intersect with each other so as to form a large obtuse angle (approximately 150 ° or more), the connection between the front wall surface of the margin and the second margin portion is provided. No edges are formed in the portion that act as a cutting edge.

Specifically, since the angle formed between the virtual straight line and the extension line of the front wall surface of the margin is 30 ° or less, the front wall surface of the margin is gently inclined with respect to the second margin portion and is gentle. Can be connected to. As a result, it is possible to reliably prevent the formation of a sharp edge at the connecting portion between the second margin portion and the front wall surface of the margin.
For this reason, it is possible to reliably prevent the connecting portion between the second margin portion and the front wall surface of the margin from being unintentionally cut into the inner peripheral surface of the machined hole of the work material and damaging it, thereby improving the processed quality. Can be done. In particular, according to the present invention, even when drilling a work material having a low hardness, it is possible to remarkably suppress the formation of machining marks such as waviness patterns on the inner peripheral surface of the drilled hole, and the machining is performed. Good surface accuracy can be maintained.

When the angle formed between the virtual straight line and the extension line of the front wall surface of the margin is 5 ° or more, the front wall surface of the margin becomes too gentle with respect to the second margin portion, which is unintentional. It is preferable because it can prevent the function as a part of the margin. That is, in this case, the front wall surface of the margin surely functions as a part of the second taking surface, and the front wall surface of the margin slides with the inner peripheral surface of the machined hole of the work material together with the second margin portion. Can be prevented.

Therefore, for example, it is possible to prevent problems such as the front wall surface of the margin sliding in contact with the inner peripheral surface of the machined hole, affecting the desired margin function of the second margin portion, or increasing the cutting resistance. Then, it is possible to extend the life of the drill while maintaining good drilling accuracy.

Further, in the drill of the present invention, the length of the line segment connecting the front end in the drill rotation direction of the second margin portion and the rear end on the side opposite to the drill rotation direction in the cross-sectional view of the drill is the drill of the first margin portion. It is less than half the length of the line segment connecting the front end in the rotation direction and the rear end on the opposite side of the drill rotation direction. As a result, the length of the second margin portion in the drill circumferential direction (width of the second margin portion) is reduced, and the following excellent effects are obtained.
That is, since the surface area of the second margin portion is reduced, it is possible to prevent a problem that chips bite into the second margin portion and damage the inner peripheral surface of the machined hole. Specifically, for example, unlike the present invention, when the width of the second margin portion is set to be larger than half the width of the first margin portion, the surface area of the second margin portion is increased and the surface area of the second margin portion is increased. Fine chips are likely to be caught between the work material and the inner peripheral surface accuracy of the machined hole (surface roughness deteriorates). On the other hand, when the width of the second margin portion is set to half or less of the width of the first margin portion as in the present invention, the surface area of the second margin portion can be suppressed to a small size, and the margin surface and the work material can be suppressed. It becomes difficult for fine chips to get caught between the and, and the accuracy of the inner peripheral surface of the machined hole is maintained well (the surface roughness is improved).

Further, for example, unlike the present invention, when the width of the second margin portion is set to be larger than half the width of the first margin portion, the surface area of the second margin portion becomes large and the second margin portion becomes larger. Coolant (oil-based or water-soluble cutting liquid) becomes difficult to spread throughout, which also affects the accuracy of the inner peripheral surface of the machined hole. In particular, the second margin portion is arranged far away from the chip discharge groove in the direction opposite to the drill rotation direction as compared with the first margin portion arranged adjacent to the side opposite to the drill rotation direction of the chip discharge groove. Since it is a margin portion, it is difficult to distribute the coolant flowing in the chip discharge groove to the entire second margin portion. Therefore, when the width of the second margin portion is set to half or less of the width of the first margin portion as in the present invention, the surface area of the second margin portion can be suppressed to a small size, and the coolant is applied to the entire second margin portion. Can be easily distributed, the cutting resistance can be stably suppressed, the increase in cutting heat can be suppressed, and the accuracy of the inner peripheral surface of the machined hole can be stably improved.

In the present invention, even if the width of the second margin portion is less than half the width of the first margin portion as described above, the front wall surface of the margin having a gentle inclination in the drill rotation direction of the second margin portion is formed. By arranging them adjacent to each other, the wall thickness of the second margin portion is sufficiently secured and the rigidity is maintained high, so that damage or the like is prevented from occurring in the second margin portion. That is, in the conventional drill, an edge is formed at the connecting portion between the second margin portion and the front wall surface of the margin, and the front wall surface of the margin is inclined, so that the wall thickness of the second margin portion is insufficient. Therefore, the rigidity is not sufficient, and the impact on the edge is likely to act greatly during cutting. Therefore, if the width of the second margin portion is set to half or less of the width of the first margin portion, the second margin portion is damaged. Etc. may occur. In the present invention, such a problem can be prevented by combining the front wall surface of the margin having a gentle slope and the second margin portion having a narrow width, and the above-mentioned exceptionally remarkable effect can be obtained.

Further, during drilling, the drill body is sent toward the tip side in the axial direction with respect to the work material, and the intersecting ridge line portion between the front wall surface of the margin and the thinning surface is formed with respect to the machined hole of the work material. After being inserted, the second margin portion is inserted. This intersecting ridgeline portion forms an intersecting ridgeline between the front wall surface of the margin and the thinning surface, and gradually slopes outward in the radial direction of the drill toward the base end side in the axial direction and extends. At the time of drilling, the crossed ridge portion is first smoothly inserted into the drilled hole, and the second margin portion is inserted into the drilled hole so as to be guided by the crossed ridgeline portion. That is, the second margin portion is inserted into the machined hole in a state of being aligned with the machined hole.
Therefore, according to the drill of the present invention, it is possible to remarkably suppress a defect that the second margin portion damages the inner peripheral surface of the machined hole.

From the above, according to the drill of the present invention, even when drilling a work material such as a soft metal material, it is possible to prevent the inner peripheral surface of the machined hole of the work material from being damaged, and the work quality can be suppressed. Can be enhanced.

Further, in the drill, it is preferable that the length of the front wall surface of the margin in the circumferential direction is longer than the length of the second margin portion in the circumferential direction.

In this case, it becomes easier to connect the front wall surface of the margin to the second margin portion with a gentle inclination, and it becomes difficult for an edge to be formed at the connecting portion between the second margin portion and the front wall surface of the margin. The effect that the rigidity of the second margin portion is increased by the front wall surface of the margin becomes more remarkable.

In addition, since the length of the front wall surface of the margin in the circumferential direction is long, the depth (diameter) of the second surface (the part of the front wall other than the front wall of the margin) adjacent to the drill rotation direction of the front wall of the margin. A sufficient amount of dents toward the inside in the direction) can be secured, and various functions due to the second surface can be stabilized. Specifically, the various functions of the second take-up surface include, for example, a function of reliably separating the second take-up surface from the inner peripheral surface of the machined hole of the work material to reduce cutting resistance, and the inside of the machined hole. It has a function to prevent chips from getting caught between the peripheral surface and the second surface, and a function to distribute coolant through the second surface.

Further, in the drill, in the cross-sectional view of the drill, a virtual straight line connecting the front end of the second margin portion in the drill rotation direction and the rear end on the side opposite to the drill rotation direction, and an extension line of the margin front wall surface. The angle formed between the, is preferably 25 ° or less.

In this case, since the front margin wall surface and the second margin portion intersect with each other so as to form a larger obtuse angle (approximately 155 ° or more), the connecting portion between the front wall surface of the margin and the second margin portion. In the above, it is possible to make it more difficult to form an edge that acts as a cutting edge, and to remarkably improve the accuracy of the inner peripheral surface of the machined hole. In addition, the rigidity of the second margin portion can be further increased.

Further, in the above drill, the drill is a twist drill, and a pair of the tip surface and the thinning surface are formed on the drill body, and the drill body is viewed from the tip in the axial direction toward the base end side. When viewed from the front, the intersecting ridge line between the tip surface and the thinning surface is linear, and of the pair of the intersecting ridge lines, the extension line obtained by extending the first intersection ridge line toward the second intersection ridge line is , It is preferable that it is arranged on the second crossing ridge line or on the side opposite to the drill rotation direction from the second crossing ridge line.

In this case, the ratio of the thinning surface to the tip surface (tip flank surface) tends to be large, and since the thinning surface is formed large, the chip evacuation property is excellent and the cutting resistance is lowered.

Further, in the above drill, of the pair of the crossed ridges, the extension line obtained by extending the first crossed ridge toward the second crossed ridge is on the side opposite to the drill rotation direction from the second crossed ridge. It is preferable that the distance between the extension line and the second crossing ridge line along the circumferential direction is 0.08 mm or less.

In this case, it is possible to prevent the ratio of the thinning surface to be excessively large with respect to the tip surface (tip flank surface), and it is possible to maintain high rigidity of the drill.

According to the drill of the present invention, even when drilling a work material such as a soft metal material, it is possible to suppress damage to the inner peripheral surface of the machined hole of the work material and improve the work quality. be able to.

It is a front view of the drill which concerns on one Embodiment of this invention. It is a top view (side view) of the drill which concerns on one Embodiment of this invention. It is a perspective view of the drill which concerns on one Embodiment of this invention. It is a figure which shows the part A of FIG. 1 enlarged. It is sectional drawing of the drill which concerns on one Embodiment of this invention. It is a figure which shows the part B of FIG. 5 enlarged.

Hereinafter, the drill 10 according to the embodiment of the present invention will be described with reference to the drawings. It should be noted that the drawings used for explaining the embodiments of the present invention may be shown by enlarging or excerpting the main parts in order to make the features of the present invention easy to understand. The dimensional ratio is not always the same as the actual one.

As shown in FIGS. 1 to 3, the drill 10 of the present embodiment has a shaft-shaped drill body 1. The drill body 1 has a first end portion along the axis O direction as a blade portion, and a portion other than the first end portion including the second end portion along the axis O direction (that is, a portion other than the blade portion). ) Is a shank part (not shown).

The shank portion of the drill body 1 is detachably attached to, for example, a spindle or a drilling machine of a machine tool. The drill body 1 is rotated in the drill rotation direction T in the circumferential direction around the axis O with respect to the work material, is sent out in the axis O direction, and is cut into the work material by the blade portion to perform drilling.
The drill 10 of the present embodiment is particularly suitable for drilling a work material made of a soft metal material or the like.

The definition of the direction (direction) used in this embodiment is as follows.
The direction along the axis O of the drill body 1 (the direction in which the axis O extends) is referred to as the axis O direction. Of the axis O directions, the direction from the shank portion of the drill body 1 toward the blade portion (upper in FIG. 2) is referred to as the tip side, and the direction from the blade portion toward the shank portion (lower in FIG. 2) is referred to as the proximal end side. That is.
Further, the direction orthogonal to the axis O is called the radial direction. Of the radial directions, the direction approaching the axis O is referred to as the inside in the radial direction, and the direction away from the axis O is referred to as the outside in the radial direction.
Further, the direction of orbiting around the axis O is called the circumferential direction. Of the circumferential directions, the direction in which the drill body 1 is rotated during drilling is referred to as the drill rotation direction T, and the rotation direction opposite to this is referred to as the side opposite to the drill rotation direction T (anti-drill rotation direction).

A plurality of chip discharge grooves 2 extending from the tip end in the axis O direction toward the base end side are formed on the outer periphery of the drill body 1 at intervals in the circumferential direction. The chip discharge groove 2 opens at the tip of the drill body 1, and gradually twists toward the side opposite to the drill rotation direction T from the tip toward the base end side in the axis O direction, and extends spirally. ..

The plurality of chip discharge grooves 2 are arranged at equal intervals (at equal pitches) in the circumferential direction on the outer periphery of the drill body 1 so as to be rotationally symmetrical positions with respect to the axis O. As shown in FIG. 1, the chip discharge groove 2 has a concave curved surface on the inner circumference of the groove.
In the example of this embodiment, the drill 10 is a twist drill, and two chip discharge grooves 2 are formed on the outer periphery of the drill body 1. Along with this, two (pair each) of the tip surface 3, the cutting edge 4, the thinning surface 5, and the land portion 15 of the drill body 1, which will be described later, are also formed.

Although not particularly shown, the chip discharge groove 2 is cut off on the outer peripheral surface of the drill body 1 in the radial direction, for example, in a region located from the vicinity of the central portion in the axis O direction of the drill body 1 to the proximal end side. ing. In the drill body 1, the area where the chip discharge groove 2 along the axis O direction is formed is the blade portion, and the portion on the proximal end side of this range is the shank portion.

In FIGS. 1 to 3, the tip of the drill body 1 has a tip surface (tip relief surface) 3 facing the tip side (drill feed direction) of the drill 10 and a wall surface of the chip discharge groove 2 facing the drill rotation direction T. A cutting edge 4 formed at an intersecting ridge between 2a and the tip surface 3 and a chip discharge groove 2 adjacent to the tip surface 3 on the side opposite to the drill rotation direction T of the tip surface 3 are formed. A thinning surface 5 and the like are provided.

The tip surface (tip flank surface) 3 has a first tip flank surface 6 adjacent to the side opposite to the drill rotation direction T of the cutting edge 4 and a side opposite to the drill rotation direction T of the first tip flank surface 6. It is provided with a second tip flank surface 7 arranged adjacent to the surface.
The first tip flank surface 6 is gradually inclined toward the base end side in the axis O direction from the cutting edge 4 toward the side opposite to the drill rotation direction T. The second tip flank surface 7 is gradually inclined toward the base end side in the axis O direction from the first tip flank surface 6 toward the side opposite to the drill rotation direction T, and is more inclined from the first tip flank surface 6. Also has a large clearance angle. That is, the amount of displacement (inclination corresponding to the clearance angle) in the axis O direction per unit length along the drill circumferential direction on the second tip flank surface 7 is larger than the displacement amount on the first tip flank surface 6.

As shown in FIG. 1, in the front view of the drill when the drill body 1 is viewed from the tip in the axis O direction toward the proximal end side, the first tip flank surface 6 has a strip shape extending in the radial direction (long abbreviation in the radial direction). It has a square shape), and the second tip flank surface 7 has a fan shape.
In the example of the present embodiment, the tip surface 3 has two inclined surfaces (first tip relief surface 6 and second tip relief surface 7) that are different from each other, but the present invention is not limited to this. The tip surface 3 may be formed by a single inclined surface, or may have three or more inclined surfaces.

A coolant hole 8 is opened on the tip surface 3. The coolant hole 8 extends through the inside of the drill body 1 by twisting along the chip discharge groove 2, and is formed so as to penetrate the drill body 1 in the axis O direction. In the coolant hole 8, for example, a coolant (oil-based or water-soluble cutting liquid, compressed air, etc.) supplied through a spindle of a machine tool or the like flows. The coolant is discharged through the coolant hole 8 of the drill body 1 toward the tip (blade) of the drill body 1 and the machined portion of the work material.

In the example of the present embodiment, the coolant hole 8 is opened on the second tip flank surface 7 of the tip surface 3. Alternatively or in conjunction with this, the coolant hole 8 may be opened in the first tip flank surface 6 or the thinning surface 5.

The cutting edge 4 is formed at the intersecting ridge line portion of the tip portion of the wall surface 2a of the chip discharge groove 2 facing the drill rotation direction T and the first tip relief surface 6 of the tip surface 3. The cutting edge 4 is formed with the wall surface 2a as a rake face and the tip surface 3 (first tip flank surface 6) as a flank surface. The cutting edge 4 may be paraphrased as a tip blade, a bottom blade, a main cutting edge, or the like.

Of the blade length (total length) of the cutting edge 4, the portion located at the inner end in the radial direction is the thinning blade 9. The thinning blade 9 is formed at an intersecting ridge line portion between the thinning wall surface (thinning rake surface) shown by reference numeral 14 in FIG. 2 and the tip surface 3 (first tip flank surface 6).

In FIG. 1, the thinning surface 5 is formed from the wall surface 2b of the tip of the drill body 1 facing the side opposite to the drill rotation direction T of the chip discharge groove 2 to the groove bottom (most radially inward of the chip discharge groove 2). It is formed in a portion located between the region extending to the deepest portion where the region is located) and the tip surface 3 adjacent to the drill rotation direction T in the region. The thinning surface 5 has a flat shape inclined so as to face the tip side in the axis O direction and the side opposite to the drill rotation direction T.

The thinning surface 5 has a larger clearance angle than the tip surface 3 (first tip flank surface 6 and second tip flank surface 7). That is, the displacement amount (inclination corresponding to the clearance angle) in the axis O direction per unit length along the drill circumferential direction on the thinning surface 5 is larger than the displacement amount on the tip surface (tip relief surface) 3.

In FIGS. 1 to 3 and 5, a land portion 15 is formed between the chip discharge grooves 2 adjacent to each other in the circumferential direction in the outer circumference of the drill body 1.
The land portion 15 has a first margin portion 11 arranged adjacent to the wall surface 2a facing the drill rotation direction T of the chip discharge groove 2 on the side opposite to the drill rotation direction T, and a drill rotation direction T than the first margin portion 11. It is provided with a second margin portion 12 arranged on the opposite side to the above. That is, the drill 10 of the present embodiment is a double margin type drill.
Further, the portion of the land portion 15 other than the first margin portion 11 and the second margin portion 12 is a second surface that is retracted radially inward from these margin portions 11 and 12.

A leading edge (outer peripheral blade) is formed at least at the tip of the intersecting ridge line portion between the wall surface 2a of the chip discharge groove 2 facing the drill rotation direction T and the first margin portion 11 in the axis O direction. In the example of the present embodiment, the outer diameter of the blade portion of the drill body 1 is gradually reduced from the tip end in the axis O direction toward the base end side, and a back taper is provided. Correspondingly, the outer diameter of the leading edge is also gradually reduced from the tip end side of the drill body 1 toward the base end side. However, the present invention is not limited to this, and the blade portion of the drill body 1 may not be provided with a back taper. That is, the outer peripheral blade of the drill body 1 may have a constant outer diameter along the axis O direction.

In the land portion 15, the first margin portion 11 has an outer diameter substantially equal to the outermost diameter of the cutting edge 4 (the diameter of the circle of the rotation locus formed by rotating the outer end of the cutting edge 4 in the radial direction around the axis O). It is formed so as to be located on a virtual cylindrical surface centered on an axis O having a diameter. The first margin portion 11 gradually extends from the tip in the axis O direction toward the base end side as the chip discharge groove 2 spirally twists and extends toward the side opposite to the drill rotation direction T. It is twisted and extends in a spiral.

In the front view of the drill shown in FIG. 1 and the cross-sectional view perpendicular to the axis O of the drill body 1 shown in FIG. 5 (cross-sectional view of the drill), the first margin portion 11 has an arc shape (centered on the axis O). It has an arc shape that is convex toward the outside in the radial direction). Further, in the front view of the drill of FIG. 1, the first margin portion 11 is arranged on the outer peripheral edge of the tip surface 3 (first tip relief surface 6). Therefore, the tip of the first margin portion 11 in the axis O direction is connected to the tip surface 3.

As shown in FIGS. 1 and 5, in the land portion 15, the second margin portion 12 is arranged so as to be separated from the first margin portion 11 on the side opposite to the drill rotation direction T. In FIGS. 2 and 3, the second margin portion 12 is gradually twisted toward the side opposite to the drill rotation direction T from the tip end in the axis O direction toward the base end side, and extends spirally. Further, the second margin portion 12 extends substantially parallel to the first margin portion 11.
In the front view of the drill shown in FIG. 1 and the cross-sectional view of the drill shown in FIG. 5, the second margin portion 12 has an arc shape centered on the axis O (an arc shape that is convex outward in the radial direction). ing.

Then, as shown in FIGS. 1 and 4, the second margin portion 12 is the outer peripheral edge of the thinning surface 5 in the front view of the drill when the drill body 1 is viewed from the tip end side in the axis O direction toward the base end side. Of these, it is arranged at the rear end 5b (corresponding to the heel) on the side opposite to the drill rotation direction T. That is, in this front view of the drill, the entire second margin portion 12 (total length of the arc) is located on the outer peripheral edge of the thinning surface 5. Therefore, the tip of the second margin portion 12 in the axis O direction is connected only to the thinning surface 5, not to the tip surface 3.

Further, in the front view of the drill shown in FIG. 1, the second margin portion 12 is arranged on the outer peripheral edge of the thinning surface 5 so as to be separated from the front end 5a of the drill rotation direction T on the side opposite to the drill rotation direction T. Has been done. That is, in this front view of the drill, the second margin portion 12 is arranged at the end portion of the outer peripheral edge of the thinning surface 5 opposite to the drill rotation direction T.

Further, in the front view of the drill shown in FIGS. 1 and 4, the front end 12a of the second margin portion 12 in the drill rotation direction T is the front end 5a and the rear end 5b of the drill rotation direction T of the outer peripheral edge of the thinning surface 5. It is located between the midpoint of and the rear end 5b. Further, in this front view of the drill, the rear end 12b of the second margin portion 12 on the side opposite to the drill rotation direction T coincides with the rear end 5b of the outer peripheral edge of the thinning surface 5 on the side opposite to the drill rotation direction T. Have been made to.

Then, in the cross-sectional view of the drill perpendicular to the axis O of the drill body 1 shown in FIGS. 5 and 6, the front end 12a of the second margin portion 12 in the drill rotation direction T and the rear end on the side opposite to the drill rotation direction T. The angle formed between the virtual straight line VL connecting 12b and the extension line L of the margin front wall surface (second margin front wall surface) 16 adjacent to the drill rotation direction T of the second margin portion 12 in the land portion 15. θ is 30 ° or less.
Specifically, the front margin wall surface 16 is located radially inside the rotation locus (virtual cylindrical surface VC described later) around the axis O of the second margin portion 12 (see FIGS. 1 and 4). In the embodiment, the angle θ is more than 0 ° (preferably 5 ° or more) and 30 ° or less. More preferably, the angle θ is 10 ° or more and 25 ° or less.

The margin front wall surface 16 is formed on the second surface of the land portion 15 and is arranged adjacent to the drill rotation direction T of the second margin portion 12. The margin front wall surface 16 is formed so as to gradually incline outward in the radial direction toward the side opposite to the drill rotation direction T. Therefore, the extension line L of the front wall surface 16 of the margin also gradually inclines and extends outward in the radial direction toward the side opposite to the drill rotation direction T. The angle θ refers to the acute angle of the acute angle and the obtuse angle formed by the intersection of the extension line L and the virtual straight line VL.

In FIGS. 1, 4 and 5, reference numeral VC represents a virtual cylindrical surface formed by rotating the second margin portion 12 around the axis O. The margin front wall surface 16 is gently inclined so as to gradually approach the virtual cylindrical surface VC toward the side opposite to the drill rotation direction T (as it approaches the second margin portion 12 along the drill circumferential direction). It is extending.

In the example of the present embodiment, in the cross-sectional view of the drill shown in FIGS. 5 and 6, the front wall surface 16 of the margin has a convex curve shape or a straight line shape that bulges outward in the radial direction. The front margin wall surface 16 is gently connected so as to be in contact with the front end 12a of the second margin portion 12, that is, so as not to form an edge with the second margin portion 12. The front wall surface 16 of the margin may have a concave curved shape in the cross-sectional view of the drill. However, it is preferable that at least the connecting portion of the front wall surface 16 of the margin to the second margin portion 12 is formed in a convex curved shape or a straight line that is convex outward in the radial direction in the cross-sectional view of the drill. Desirably, the entire margin front wall surface 16 is formed in a convex curved shape or a straight line that is convex outward in the radial direction in the cross-sectional view of the drill.

In the example of the present embodiment, in the cross-sectional view of the drill shown in FIG. 6, the wall surfaces of the land portion 15 at the front end 16a of the drill rotation direction T of the margin front wall surface 16 before and after the drill rotation direction T have large obtuse angles with each other. They intersect to form (approximately 150 ° to 180 °). That is, in FIG. 6, the margin front wall surface 16 and the wall surface portion 19 located in the drill rotation direction T from the front end 16a of the margin front wall surface 16 are gently connected to each other so as to form the obtuse angle between them. There is. As a result, the connecting portion (near the front end 16a) between the front wall surface 16 of the margin and the wall surface portion 19 is formed to be concave or flat. When viewed from the inside of the drill body 1, the wall surfaces before and after the drill rotation direction T of the front end 16a of the drill rotation direction T of the margin front wall surface 16 intersect (connect) at an angle of approximately 180 ° to 210 °. It can be said that it is doing.

In the front view of the drill shown in FIG. 4, the front end 16a of the margin front wall surface 16 in the drill rotation direction T is located on the outer peripheral edge of the thinning surface 5. In the example of the present embodiment, the front end 16a of the margin front wall surface 16 is arranged near the intermediate point between the front end 5a and the rear end 5b of the outer peripheral edge of the thinning surface 5 in the front view of the drill. Is located slightly opposite to the drill rotation direction T from this midpoint.

As shown in FIGS. 1 and 5, in the example of the present embodiment, the margin front wall surface 16 of the second drilling surface located between the first margin portion 11 and the second margin portion 12 of the land portion 15 The second depth of the part excluding the above is set to be substantially constant along the circumferential direction of the drill.

Then, in the cross-sectional view of the drill shown in FIGS. 5 and 6, a line segment (virtual line) connecting the front end 12a of the second margin portion 12 in the drill rotation direction T and the rear end 12b on the side opposite to the drill rotation direction T. Minutes) is less than half the length of the line segment (virtual line segment) connecting the front end 11a of the first margin portion 11 in the drill rotation direction T and the rear end 11b on the opposite side of the drill rotation direction T. is there. In other words, in the cross-sectional view of the drill, the second margin portion 12 with respect to the length of the line segment connecting the front end 11a of the first margin portion 11 in the drill rotation direction T and the rear end 11b on the side opposite to the drill rotation direction T. The ratio P of the length of the line segment connecting the front end 12a of the drill rotation direction T and the rear end 12b on the opposite side of the drill rotation direction T is 50% or less.
The ratio P is 25% or more. More preferably, the ratio P is 30% or more and 45% or less.

Further, the length of the front wall surface 16 of the margin in the circumferential direction is longer than the length of the second margin portion 12 in the circumferential direction. In the example of the present embodiment, the length of the front wall surface 16 of the margin in the circumferential direction is twice or more, specifically, three times or more with respect to the length of the second margin portion 12 in the circumferential direction.

In the front view of the drill shown in FIG. 1, the intersecting ridge line R between the tip surface 3 (the second tip flank surface 7) and the thinning surface 5 is linear. In the front view of the drill, of the pair of crossed ridges R, the extension line extending the first crossed ridge (one crossed ridge) R1 toward the second crossed ridge (the other crossed ridge) R2 is the first. It is arranged so as to coincide with the crossing ridge line R2 of 2 or to be adjacent to the second crossing ridge line R2 on the side opposite to the drill rotation direction T.

In the present embodiment, of the two crossed ridges R1 and R2, the extension line extending the first crossed ridge R1 toward the second crossed ridge R2 is in the drill rotation direction as compared with the second crossed ridge R2. It is arranged on the opposite side of T, and the distance (width Y) along the circumferential direction between this extension line and the second crossing ridge line R2 is 0.08 mm or less. In particular, when the diameter (blade diameter) of the drill 10 is small, it is preferable to make the width Y smaller to improve the processing quality. Specifically, for example, in a drill 10 having a diameter of 10 mm or less, the width Y is preferably 0.05 mm or less.

In the drill 10 of the present embodiment described above, the second margin portion 12 is arranged on the outer peripheral edge of the thinning surface 5 in the front view of the drill (drill tip view) in which the tip surface 3 of the drill body 1 is viewed from the front. There is. That is, the second margin portion 12 is not the outer peripheral edge of the tip surface (tip relief surface) 3 of the drill body 1, but the outer peripheral edge of the thinning surface 5 located on the side opposite to the drill rotation direction T from the tip surface 3. Is located in. Therefore, an intersecting ridge line portion is formed between the second margin portion 12 on the outer periphery of the drill body 1 and the thinning surface 5, and no intersecting ridge line portion is formed between the second margin portion 12 and the tip surface 3. ..

As shown in FIGS. 2 and 3, the thinning surface 5 has a larger clearance angle than the tip surface 3 of the drill body 1. Therefore, unlike the case of the present embodiment, for example, as compared with the case where the intersecting ridge line portion is formed between the tip surface 3 of the drill body 1 and the second margin portion 12, the drill body 1 is different from the case of the present embodiment. The crossed ridge line portion formed between the thinning surface 5 and the second margin portion 12 has a large displacement amount (that is, inclination) in the drill axis O direction per unit length along the drill peripheral direction. Therefore, the crossed ridge line portion of the second margin portion 12 in the present embodiment is processed so as to be inclined with respect to the inner peripheral surface of the machined hole of the work material (the twist angle is reduced). It is less likely to affect the processing quality of the inner peripheral surface of the hole.

Specifically, in the present embodiment, the second margin portion 12 is arranged at the rear end 5b of the outer peripheral edge of the thinning surface 5 in the drill rotation direction T in the front view of the drill.
That is, as a result of intensive research on the drill 10 and its second margin portion 12, the inventor of the present invention finds that the second margin portion 12 is the outer peripheral edge of the thinning surface 5 of the drill body 1 in the drill rotation direction T. If it is arranged at the rear end 5b on the opposite side, the second margin portion 12 is less likely to act as a cutting edge in combination with the action and effect of the special configuration of the present embodiment described later, and the work material is processed. We have come to the conclusion that the accuracy of the inner peripheral surface of the hole can be significantly improved.

Although the detailed mechanism of the above test results is not known, as a result of evaluating the shape of the inner peripheral surface of the machined hole, when drilling a work material having low hardness, unlike the present embodiment, for example, a second margin When the portion 12 is provided at the central portion in the circumferential direction of the land portion 15, the second margin portion 12 acts as a cutting edge and damages the inner peripheral surface of the machined hole to generate a machined mark such as a waviness pattern. ..
On the other hand, as in the present embodiment, the second margin portion 12 is provided at the rear end portion (that is, the rear end 5b portion of the outer peripheral edge of the thinning surface 5) of the land portion 15 on the side opposite to the drill rotation direction T. In that case, the second margin portion 12 did not act as a cutting edge, that is, the inner peripheral surface of the machined hole was not damaged by the second margin part 12, and no machining marks such as waviness patterns were generated.

If the second margin portion 12 is arranged at the rear end 5b of the outer peripheral edge of the thinning surface 5 of the drill body 1 on the side opposite to the drill rotation direction T, the first margin portion 11 and the second margin portion 11 Since 12 and 12 are easily arranged substantially evenly in the circumferential direction of the drill, and the balance in the circumferential direction of the drill 10 during drilling is easily stabilized, the accuracy of the machined surface can be improved by this action as well.

The drill 10 of the present embodiment has the following special configuration.
That is, in a cross-sectional view of the drill perpendicular to the axis O of the drill body 1, a virtual straight line VL connecting the front end 12a of the second margin portion 12 in the drill rotation direction T and the rear end 12b on the side opposite to the drill rotation direction T. The angle θ formed between the land portion 15 and the extension line L of the margin front wall surface 16 adjacent to the drill rotation direction T of the second margin portion 12 is 30 ° or less (the angle θ in FIG. 6 is defined as reference). In other words, since the front margin wall surface 16 and the second margin portion 12 intersect with each other so as to form a large obtuse angle (approximately 150 ° or more), the front wall surface 16 of these margins and the second margin portion 12 At the connecting portion with 12, an edge that acts as a cutting edge is not formed.

Specifically, since the angle θ formed between the virtual straight line VL and the extension line L of the margin front wall surface 16 is 30 ° or less, the margin front wall surface 16 is gently set with respect to the second margin portion 12. It can be connected gently while tilting. As a result, it is possible to reliably prevent the formation of a sharp edge at the connecting portion between the second margin portion 12 and the margin front wall surface 16.
For this reason, it is possible to reliably prevent the connecting portion between the second margin portion 12 and the front wall surface 16 of the margin from being unintentionally cut into the inner peripheral surface of the machined hole of the work material and damaging it, thereby improving the processed quality. Can be enhanced. In particular, according to the present embodiment, even when drilling a work material having a low hardness, it is possible to remarkably suppress the formation of machining marks such as waviness patterns on the inner peripheral surface of the machined hole. Good machined surface accuracy can be maintained.

When the angle θ formed between the virtual straight line VL and the extension line L of the margin front wall surface 16 is 5 ° or more, the margin front wall surface 16 has a gentle inclination with respect to the second margin portion 12. It is preferable because it can prevent it from unintentionally functioning as a part of the margin. That is, when the angle θ is 5 ° or more, the margin front wall surface 16 surely functions as a part of the second taking surface, and the margin front wall surface 16 together with the second margin portion 12 is inside the machined hole of the work material. It is possible to prevent sliding contact with the peripheral surface.

Therefore, for example, it is possible to prevent problems such as the front wall surface 16 of the margin sliding in contact with the inner peripheral surface of the machined hole, affecting the desired margin function of the second margin portion 12, or increasing the cutting resistance. .. Then, the life of the drill 10 can be extended while maintaining good drilling accuracy.

Further, in the drill 10 of the present embodiment, in the cross-sectional view of the drill, the length of the line segment connecting the front end 12a of the second margin portion 12 in the drill rotation direction T and the rear end 12b on the side opposite to the drill rotation direction T is , It is less than half the length of the line segment connecting the front end 11a of the first margin portion 11 in the drill rotation direction T and the rear end 11b on the side opposite to the drill rotation direction T. As a result, the length of the second margin portion 12 in the drill circumferential direction (width of the second margin portion 12) is reduced, and the following excellent effects are obtained.
That is, since the surface area of the second margin portion 12 is reduced, it is possible to prevent a problem that chips bite into the second margin portion 12 and damage the inner peripheral surface of the machined hole. Specifically, for example, unlike the present embodiment, when the width of the second margin portion 12 is set to be larger than half the width of the first margin portion 11, the surface area of the second margin portion 12 becomes larger. , Fine chips are easily caught between the margin surface and the work material, which affects the accuracy of the inner peripheral surface of the machined hole (surface roughness deteriorates). On the other hand, when the width of the second margin portion 12 is set to half or less of the width of the first margin portion 11 as in the present embodiment, the surface area of the second margin portion 12 can be suppressed to a small size and the margin surface can be suppressed. Fine chips are less likely to get caught between the work material and the work material, and the inner peripheral surface accuracy of the machined hole is maintained well (surface roughness is improved).

Further, for example, unlike the present embodiment, when the width of the second margin portion 12 is set to be larger than half the width of the first margin portion 11, the surface area of the second margin portion 12 is increased and the surface area of the second margin portion 12 is increased. It becomes difficult for the coolant (oil-based or water-soluble cutting liquid) to spread over the entire second margin portion 12, which also affects the accuracy of the inner peripheral surface of the machined hole. In particular, the second margin portion 12 is located adjacent to the first margin portion 11 of the chip discharge groove 2 on the side opposite to the drill rotation direction T, from the chip discharge groove 2 to the side opposite to the drill rotation direction T. Since the margin portions are arranged at a large distance from each other, it is difficult to distribute the coolant flowing in the chip discharge groove 2 to the entire second margin portion 12. Therefore, when the width of the second margin portion 12 is set to half or less of the width of the first margin portion 11 as in the present embodiment, the surface area of the second margin portion 12 can be suppressed to a small size and the second margin The coolant can be easily distributed throughout the portion 12, the cutting resistance can be stably suppressed, the increase in cutting heat can be suppressed, and the accuracy of the inner peripheral surface of the machined hole can be stably improved.

In the present embodiment, even if the width of the second margin portion 12 is less than half the width of the first margin portion 11 as described above, the inclination of the second margin portion 12 is gentle in the drill rotation direction T. By arranging the front wall surfaces 16 of the margins adjacent to each other, the wall thickness of the second margin portion 12 is sufficiently secured and the rigidity is maintained high, so that the second margin portion 12 may be damaged or the like. It is prevented. That is, in the conventional drill, an edge is formed at the connecting portion between the second margin portion and the front wall surface of the margin, and the front wall surface of the margin is inclined, so that the wall thickness of the second margin portion is insufficient. Therefore, the rigidity is not sufficient, and the impact on the edge is likely to act greatly during cutting. Therefore, if the width of the second margin portion is set to half or less of the width of the first margin portion, the second margin portion is damaged. Etc. may occur. In the present embodiment, such a problem can be prevented by combining the gently sloping margin front wall surface 16 and the narrow second margin portion 12, and the above-mentioned exceptionally remarkable effect can be obtained. ..

Further, in FIGS. 2 to 4, at the time of drilling, the drill body 1 is sent toward the tip side in the axis O direction with respect to the work material, and the margin front wall surface 16 with respect to the machined hole of the work material. After the intersection ridge line portion 17 with the thinning surface 5 is inserted, the second margin portion 12 is inserted. The intersecting ridge line portion 17 forms an intersecting ridge line between the front wall surface 16 of the margin and the thinning surface 5, and gradually inclines and extends outward in the radial direction of the drill toward the base end side in the axis O direction. ing. At the time of drilling, the intersecting ridge line portion 17 is first smoothly inserted into the machined hole, and the second margin portion 12 is inserted into the machined hole so as to be guided by the crossed ridge line portion 17. That is, the second margin portion 12 is inserted into the machined hole in a state of being aligned with the machined hole.
Therefore, according to the drill 10 of the present embodiment, it is possible to remarkably suppress a defect that the second margin portion 12 damages the inner peripheral surface of the machined hole.

From the above, according to the drill 10 of the present embodiment, even when a work material such as a soft metal material is drilled, it is possible to prevent the inner peripheral surface of the machined hole of the work material from being damaged. The processed quality can be improved.

Further, in the present embodiment, since the length of the front wall surface 16 of the margin in the circumferential direction is longer than the length of the second margin portion 12 in the circumferential direction, the following effects are obtained.
That is, in this case, it becomes easy to connect the margin front wall surface 16 to the second margin portion 12 with a gentle inclination, and it becomes difficult for an edge to be formed at the connecting portion between the second margin portion 12 and the margin front wall surface 16. The effect of improving the accuracy and the effect of increasing the rigidity of the second margin portion 12 by the margin front wall surface 16 become more remarkable.

Further, since the length of the front wall surface 16 in the circumferential direction is long, the portion of the second facing surface adjacent to the drill rotation direction T of the front wall surface 16 of the margin (the portion of the front wall surface other than the front wall surface 16 of the margin). It is possible to secure a sufficient depth (amount of dent toward the inside in the radial direction) in the portion 19 and the like, and to stabilize various functions by the second drilling surface. Specifically, the various functions of the second take-up surface include, for example, a function of reliably separating the second take-up surface from the inner peripheral surface of the machined hole of the work material to reduce cutting resistance, and the inside of the machined hole. It has a function to prevent chips from getting caught between the peripheral surface and the second surface, and a function to distribute coolant through the second surface.

Further, in the present embodiment, in the cross-sectional view of the drill, a virtual straight line VL connecting the front end 12a of the second margin portion 12 in the drill rotation direction T and the rear end 12b on the side opposite to the drill rotation direction T, and the margin front wall surface 16 Since the angle θ formed between the extension line L and the extension line L is 25 ° or less, the following effects are obtained.
That is, in this case, since the margin front wall surface 16 and the second margin portion 12 intersect with each other so as to form a larger obtuse angle (approximately 155 ° or more), the margin front wall surface 16 and the second margin portion 12 are formed. At the connection portion with 12, it is possible to make it more difficult to form an edge that acts as a cutting edge, and it is possible to remarkably improve the accuracy of the inner peripheral surface of the machined hole. In addition, the rigidity of the second margin portion 12 can be further increased.

Further, the drill 10 of the present embodiment is a twist drill, and a pair of a tip surface 3 and a thinning surface 5 are formed on the drill body 1, and the drill body 1 is viewed from the tip in the axis O direction toward the base end side. When viewed from the front of the drill, the intersecting ridge line R between the tip surface 3 and the thinning surface 5 is linear, and the first intersection ridge line R1 of the pair of intersection ridge lines R is extended toward the second intersection ridge line R2. Since the extension line coincides with the second crossing ridge line R2 or is arranged on the side opposite to the drill rotation direction T from the second crossing ridge line R2, the following effects are exhibited.

That is, in this case, the ratio of the thinning surface 5 to the tip surface (tip flank surface) 3 tends to be large, and since the thinning surface 5 is formed large, the chip evacuation property is excellent and the cutting resistance is lowered.

Further, in the present embodiment, of the pair of crossed ridges R, the extension line extending the first crossed ridge R1 toward the second crossed ridge R2 is the drill rotation direction T more than the second crossed ridge R2. Is arranged on the opposite side, and the distance along the circumferential direction between the extension line and the second crossing ridge line R2 is 0.08 mm or less, so that the following effects are exhibited.

That is, in this case, it is possible to prevent the ratio of the thinning surface 5 to become too large with respect to the tip surface (tip flank surface) 3, secure the wall thickness of the tip portion of the drill body 1, and maintain the rigidity of the drill 10 high. be able to.

The present invention is not limited to the above-described embodiment, and as described below, various modifications can be made without departing from the spirit of the present invention.

The drill 10 described in the above-described embodiment is a two-flute twist drill, but the present invention is not limited thereto. That is, the drill 10 may be a drill with three or more blades.

In addition, each configuration (component) described in the above-described embodiments, modifications, reference examples, and notes may be combined as long as it does not deviate from the gist of the present invention, and the configurations may be added, omitted, or replaced. , Other changes are possible. Further, the present invention is not limited by the above-described embodiments, but is limited only by the scope of claims.

Hereinafter, the present invention will be specifically described with reference to Examples. However, the present invention is not limited to this embodiment.

[Drilling test 1]
The work material S50C (A) was drilled and evaluated using a coated oil hole twist drill made of cemented carbide. In the drilling test 1, the drill 10 described in the above-described embodiment is used as the basic shape, and in the cross-sectional view of the drill, the front end 12a of the second margin portion 12 in the drill rotation direction T and the rear end on the side opposite to the drill rotation direction T are used. The angle θ (°) formed between the virtual straight line VL connecting the ends 12b and the extension line L of the margin front wall surface 16 adjacent to the drill rotation direction T of the second margin portion 12 in the land portion 15 is set. The evaluation is based on Example 1 having a temperature of 25 ° and Comparative Example 1 having a temperature of 35 °. Then, 500 holes were machined in each, and the damage form of the second margin portion was evaluated. The dimensions of the drill were outer diameter φ6 mm × groove length 47 mm × total length 100 mm in both Examples and Comparative Examples.

The processing conditions were as follows.
Cutting speed Vc: 80m / min
Rotation speed n: 4246min ^-1
Feed amount f: 0.18 mm / rev
Feed rate Vf: 764 mm / min
Processing depth: 30 mm
Cooling method: Mist cooling

In Example 1 in which the angle θ was reduced to 30 ° or less, the second margin portion 12 showed a stable wear form without being damaged, and there were few machining marks such as machined hole waviness patterns, and the machining quality was good. On the other hand, in Comparative Example 1 in which the angle θ is larger than 30 °, the second margin portion is largely missing, and many machining marks such as waviness patterns are observed on the inner peripheral surface of the machined hole.

[Drilling test 2]
In the drilling test 2, in the cross-sectional view of the drill, the length of the line segment connecting the front end 11a of the first margin portion 11 in the drill rotation direction T and the rear end 11b on the side opposite to the drill rotation direction T is the second. Example 2 has a length ratio P (%) of a line segment connecting the front end 12a of the margin portion 12 in the drill rotation direction T and the rear end 12b on the opposite side of the drill rotation direction T to 50% or less. The evaluation is based on Comparative Example 2 in which more than 50% is used.
Then, the hole accuracy (maximum height roughness Rz defined in JIS B 0601: 2013, maximum cross-sectional height Pt of the cross-sectional curve) of each machined hole after 300 holes were machined was measured, and the machined quality was evaluated. The dimensions of the drill and other processing conditions were the same as in the drilling test 1 described above. The results are shown in Table 2.

Under the machining conditions of the drilling test 2, both Example 2 and Comparative Example 2 have few machining marks such as waviness patterns on the inner peripheral surface of the drilled hole, and the machining quality is excellent. In Example 2 in which the width was reduced to 50% or less of the width of the first margin portion 11, the maximum height roughness Rz and the maximum cross-sectional height Pt of the cross-sectional curve were both suppressed to be smaller, resulting in excellent processed quality. became.

[Drilling test 3]
In the drilling test 3, the drill 10 used in the second embodiment was used as a base, and the following configuration was further made. That is, in the front view of the drill when the drill body 1 is viewed from the tip in the axis O direction toward the base end side, the cross ridge line R between the tip surface 3 and the thinning surface 5 is linear, and a pair of cross ridge lines R. Of these, an extension line extending the first crossing ridge line R1 toward the second crossing ridge line R2 is arranged so as to be adjacent to the second crossing ridge line R2 on the side opposite to the drill rotation direction T. Evaluation that the distance (width Y) along the circumferential direction between the extension line and the second crossing ridge line R2 is 0.08 mm or less is defined as Example 3, and that it exceeds 0.08 mm is defined as Example 4. Is.
Then, the roundness and the hole accuracy of the machined holes after 100 holes were machined were evaluated. The dimensions of the drill were an outer diameter of φ6 mm, a groove length of 47 mm, and a total length of 100 mm.

The processing conditions were as follows.
Cutting speed Vc: 120m / min
Rotation speed n: 6369min ^-1
Feed amount f: 0.20 mm / rev
Feed rate Vf: 1274 mm / min
Processing depth: 30 mm
Cooling method: Water-soluble coolant

In both Example 3 and Example 4, the roundness and hole accuracy of the machined holes were satisfactorily ensured. In particular, in Example 3 in which the width Y was reduced to 0.08 mm or less, the maximum height roughness Rz and the maximum cross-sectional height Pt of the cross-sectional curve were suppressed to be smaller, resulting in excellent processed quality.

The drill of the present invention can suppress damage to the inner peripheral surface of the machined hole of the work material even when drilling a work material such as a soft metal material, and can improve the work quality. it can. Therefore, it has industrial applicability.

1 Drill body 2 Chip discharge groove 2a Wall surface 3 Tip surface (tip escape surface)
4 Cutting edge 5 Thinning surface 5b Rear end 10 Drill 11 1st margin part 11a Front end 11b Rear end 12 2nd margin part 12a Front end 12b Rear end 15 Land part 16 Margin front wall surface L Extension line O Axis line R Crossed ridge line R1 1st Crossed ridge (one crossed ridge)
R2 Second crossing ridge (the other crossing ridge)
T drill rotation direction VL virtual straight line θ angle

Claims (5)

A drill body that has a shaft shape and can be rotated in the direction of rotation of the drill in the circumferential direction around the axis.
A plurality of chip discharge grooves extending from the tip in the axial direction toward the base end side and formed at intervals in the circumferential direction on the outer circumference of the drill body.
A cutting edge formed at the intersection ridge between the wall surface of the chip discharge groove facing the drill rotation direction and the tip surface of the drill body, and
A thinning surface formed between the tip surface and the chip discharge groove adjacent to the tip surface on the side opposite to the drill rotation direction,
A land portion formed between the chip discharge grooves adjacent to each other in the circumferential direction on the outer circumference of the drill body, and a land portion.
A first margin portion arranged adjacent to a wall surface of the land portion facing the drill rotation direction of the chip discharge groove, and a first margin portion.
A drill having a second margin portion arranged on the land portion on the side opposite to the drill rotation direction from the first margin portion.
In front view of the drill when the drill body is viewed from the tip in the axial direction toward the base end side, the second margin portion is arranged at the rear end of the outer peripheral edge of the thinning surface on the side opposite to the drill rotation direction. Has been done
In the cross-sectional view of the drill perpendicular to the axis of the drill body,
A virtual straight line connecting the front end of the second margin portion in the drill rotation direction and the rear end on the side opposite to the drill rotation direction, and an extension of the margin front wall surface of the land portion adjacent to the drill rotation direction of the second margin portion. The angle formed between the line and the line is 30 ° or less,
The length of the line segment connecting the front end of the second margin portion in the drill rotation direction and the rear end on the side opposite to the drill rotation direction is opposite to the front end of the first margin portion in the drill rotation direction and the drill rotation direction. A drill characterized in that it is less than half the length of the line segment connecting the rear end of the side. The drill according to claim 1.
A drill characterized in that the length of the front wall surface of the margin in the circumferential direction is longer than the length of the second margin portion in the circumferential direction. The drill according to claim 1 or 2.
In the cross-sectional view of the drill
The angle formed between the virtual straight line connecting the front end of the second margin portion in the drill rotation direction and the rear end on the side opposite to the drill rotation direction and the extension line of the front wall surface of the margin is 25 ° or less. A drill characterized by being. The drill according to any one of claims 1 to 3.
The drill is a twist drill, and a pair of the tip surface and the thinning surface are formed on the drill body.
In front view of the drill when the drill body is viewed from the tip in the axial direction toward the base end side.
The intersecting ridgeline between the tip surface and the thinning surface is a straight line.
Of the pair of the crossed ridges, the extension line extending the first crossed ridge toward the second crossed ridge coincides with the second crossed ridge or is drilled more than the second crossed ridge. A drill characterized by being placed on the opposite side of the direction. The drill according to claim 4.
Of the pair of the crossed ridges, the extension line extending the first crossed ridge toward the second crossed ridge is arranged on the side opposite to the drill rotation direction from the second crossed ridge.
A drill characterized in that the distance along the circumferential direction between the extension line and the second crossing ridge line is 0.08 mm or less.

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