JP2012187675A - Twist drill - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a work material from being pulled to the rear end side of a drill body when drilling a through-hole, or a drill from being drawn to the work material, or the work material from being pulled to the rear end side of the drill body upon pulling the tip end part of the drill body from the through hole, in the case where a twist drill is attached to a drilling machine or a hand held electric drill for drilling a through-hole in a plate material or the like.SOLUTION: Along the outer periphery of the tip end part of the drill body 1 which is made to rotate, in a direction of the drill's rotation, around the axis line O, a chip discharge groove 4 is formed that is twisted spirally around the axis line O, while a cutting blade 5 is formed at the tip end side ridge line part of the wall surface directed in a drill rotation direction of the chip discharge groove 4. In addition, a relieving surface 8 of the drill body 1 that extends from the outer peripheral side ridge line part M of the foregoing wall surface toward the rear side in the drill's rotation direction has a margin part 9 formed thereon, which, at its rear end part, has its width in the peripheral direction gradually reduced as it extends toward the rear end side in the direction of the axis line O, with the width being intended to be reduced to zero within the range where the chip discharge groove 4 is formed.

Description

  In the present invention, a chip discharge groove twisted in a spiral shape is formed on the outer periphery of the tip end portion of the drill body, and a cutting edge is formed on the tip side ridge line portion of the wall surface of the chip discharge groove facing the drill rotation direction. This invention relates to a twist drill in which a margin portion is formed on the second surface of the drill body extending from the outer peripheral side ridge line portion to the rear side in the drill rotation direction.

  When such a twist drill is attached to a drilling machine and a through hole is made in a relatively thin plate material, the plate material which is a work material is generally fixed to a vise or the like, but the vise itself may not be fixed. In such a case, when the drill penetrates the work material, the work material is likely to be drawn to the rear end side of the drill body along with the spiral chip discharge groove together with the vice. Moreover, when using it by attaching it to a hand-held electric drill, the drill may be drawn into the work material side.

  This is because in a general twist drill, the margin portion formed on the second face of the drill body is formed over the entire length of the chip discharge groove, that is, the cutting edge of the drill removes the work material. After drilling through, the drill and work material are only in contact with this margin, so usually the chip discharge groove and the margin that twist to the rear side in the drill rotation direction toward the rear end of the drill body As a result, the work material is drawn toward the rear end side of the drill body, or the drill is drawn into the work material side.

  Here, in such a twist drill, as described in Patent Documents 1 and 2, the outer diameter of the rear end is slightly higher than the outer diameter of the front end where the cutting edge of the drill body is formed. A so-called undercut type drill which is small is known. When such an undercut type drill is used for the drilling of the plate material as described above, a margin is formed on the second surface of the rear end portion when the tip portion having a large outer diameter comes out of the work material. Even if the portion is formed, it does not come into contact with the through hole, so that it is possible to prevent the work material from being drawn toward the rear end side of the drill body and the drill from being drawn into the work material side.

JP 2004-122288 A JP 2004-237375 A

  However, such an undercut type drill penetrates the work material because the rear end portion is formed with a step so as to make the outer diameter one step smaller than the large diameter tip portion as described above. When the front end of the drill body is pulled out from the through hole, there is a possibility that the step hits the work material and the work material is pulled together with the drill body toward the rear end. In particular, when drilling a through hole by attaching it to a hand-held electric drill, it is difficult to accurately pull out the drill body along its axis, so this situation is likely to occur.

  The present invention is made under such a background, and when the drill penetrates the work material when it is attached to a drilling machine or a hand held electric drill and a through hole is made in the work material such as a plate material, etc. Of course, the work material will not be pulled to the rear end side of the drill body and the drill will not be drawn to the work material side, so the tip of the drill body that penetrates the work material is pulled out from the through hole. In particular, it is an object of the present invention to provide a twist drill capable of preventing a situation in which a work material is drawn toward the rear end side of the drill body.

  In order to solve the above-mentioned problems and achieve such an object, the present invention provides a chip discharge groove that spirally twists around the axis on the outer periphery of the tip of the drill body that is rotated in the direction of drill rotation around the axis. And a cutting edge is formed on the tip side ridge line portion of the wall surface facing the drill rotation direction of the chip discharge groove, and the drill main body extends from the outer peripheral side ridge line portion of the wall surface to the rear side in the drill rotation direction. A margin portion is formed on the winding surface, and the margin portion gradually decreases in the circumferential direction toward the rear end side in the axial direction at the rear end portion, and the chip discharge groove is formed. In the range, the width is set to be zero.

  In the twist drill configured as described above, the margin portion formed on the second face is configured such that the circumferential width of the drill body is zero in a range where the chip discharge groove is formed, The margin part is interrupted in the middle of the entire length of the chip discharge groove, and the rear end side is a second surface having a smaller diameter than the outer diameter of the margin part. When the drill comes out of the through hole of the work material, the drill body does not come into contact with the work material. For this reason, when the drill penetrates the work material in this way, it is possible to prevent the work material from being drawn toward the rear end side of the drill body and the drill from being drawn into the work material side.

  On the other hand, the marginal portion gradually decreases in the circumferential direction toward the rear end side in the axial direction of the drill body at the rear end portion where the circumferential width becomes 0, and the width becomes 0. On the contrary, the width gradually increases from the position where the width becomes 0 toward the tip side. Therefore, when pulling out the drill that penetrates the work material, the position where the width becomes zero first makes point contact with the work material, and then the margin portion of the drill body gradually increases the contact width with the through hole. Since the tip portion is pulled out, it is possible to prevent the work material from being drawn toward the rear end side of the drill body as in the case where a step hits.

  As described above, according to the present invention, when the drill body penetrates the work material, the work material is prevented from being pulled toward the rear end side of the drill body and the drill is not pulled into the work material side. In this way, when pulling out a drill that penetrates the work material, it can be prevented that the work material hits the drill and is pulled to the rear end side, and can be attached to a drilling machine or a hand-held electric drill. When performing through-drilling, smooth and stable drilling can be promoted.

It is a side view which shows the 1st Embodiment of this invention. It is an enlarged side view of the drill main body front-end | tip part of embodiment shown in FIG. It is an enlarged front view of embodiment shown in FIG. It is an expanded side view of the drill main body front-end | tip part which shows the 2nd Embodiment of this invention. It is an expanded side view of the drill main body front-end | tip part which shows the 3rd Embodiment of this invention. It is an expanded side view of the drill main body front-end | tip part which shows the 4th Embodiment of this invention. It is an expanded side view of the drill main body front-end | tip part which shows the 5th Embodiment of this invention. It is an enlarged side view of the drill main body front-end | tip part which shows the 6th Embodiment of this invention. It is an expanded side view of the drill main body front-end | tip part which shows the 7th Embodiment of this invention.

  1 to 3 show a first embodiment of the present invention. In the present embodiment, the drill body 1 is integrally formed of a hard material such as high-speed tool steel or cemented carbide, and has a substantially cylindrical shaft shape with an axis O as the center, and a rear end portion (FIG. 1). The right shank portion 2 is a cylindrical shank portion 2, and the shank portion 2 is gripped by a chuck attached to a rotary shaft of a drilling machine or a hand-held electric drill so that the drill body 1 is rotated around the axis O. While being rotated in the drill rotation direction T, it is fed to the front end side in the axis O direction, and is used for drilling a work material by the blade portion 3 provided at the front end portion (left side portion in FIG. 1).

  In this blade portion 3, a pair of chip discharge grooves 4 that are spirally twisted around the axis O toward the rear side in the drill rotation direction T toward the rear end side in the axis O direction on the outer periphery of the tip of the drill body 1. Are formed symmetrically with respect to the axis O by 180 °, and a cutting edge 5 having a rake face at the tip end of the wall surface is formed at the tip ridge line portion of the wall surface facing the drill rotation direction T of the chip discharge groove 4. . The cutting edge 5 is provided with a tip angle so as to go to the rear end side in the axis O direction from the vicinity of the axis O on the inner circumference side toward the outer circumference, and the tip face of the blade section 3 (tip face of the drill body 1). Is a tip flank 6 provided with a clearance angle so as to go from the cutting edge 5 toward the rear side in the axis O direction as it goes backward in the drill rotation direction T.

  On the other hand, a portion between the chip discharge grooves 4 in the circumferential direction of the drill body 1 is a land portion 7, and the outer peripheral surface of the land portion 7, that is, the outer periphery of the wall surface facing the drill rotation direction T of the chip discharge groove 4. A portion extending from the side ridge line portion M to the rear side in the drill rotation direction T is a second picking surface (outer peripheral flank) 8. The outer surface of the second cutting surface 8 is made smaller than the outer diameter of the cutting blade 5 so as to be spaced from the inner periphery of the machining hole formed by the cutting blade 5. However, a margin 9 having an outer diameter equal to that of the cutting edge 5 is formed on the second picking surface 8 at the tip of the drill body 1 so as to protrude from the second picking surface 8 to the outer peripheral side. ing.

  That is, the margin portion 9 is formed so that the outer peripheral surface thereof is located on a cylindrical surface having an outer diameter equal to that of the cutting edge 5, and the boundary from the outer peripheral surface to the second picking surface 8. As shown in FIG. 3, the portion 10 bends and intersects with the outer peripheral surface of the margin portion 9 at an obtuse angle and extends in a flat shape, a concave curved surface shape, a convex curved surface shape or a step shape so as to smoothly touch the second picking surface 8. Thus, the diameter from the axis O is gradually reduced. In order to reliably prevent the work material from being attracted when the drill body 1 is pulled out, the boundary portion 10 is preferably flat, concave, or convex. The margin portion 9 is formed so as to intersect the rake face and the tip flank 6 at the tip of the wall surface facing the drill rotation direction T of the chip discharge groove 4, and the rake face and the tip flank 6. , And the intersection with the outer peripheral surface of the margin portion 9 is the outer peripheral end of the cutting blade 5.

  As shown in FIGS. 1 and 2, the margin portion 9 has a range in which the circumferential width gradually decreases toward the rear end side in the axis O direction at the rear end portion, and the chip discharge groove 4 is formed. This width is set to zero. That is, the intersection ridge line L between the outer peripheral surface of the margin portion 9 and the boundary portion 10 between the outer peripheral surface and the second picking surface 8 extends on a plane perpendicular to the axis O at the rear end portion of the margin portion 9. Without extending at least the rear end side in the direction of the axis O, and intersecting the outer peripheral side ridge line portion M of the wall surface of the chip discharge groove 4 facing the drill rotation direction T.

  Here, in the first embodiment, the margin portion 9 intersects the tip flank 6 only at the portion of the tip flank 6 on the drill rotation direction T side (cutting blade 5 side). As described above, the width in the circumferential direction gradually decreases as described above from the front end edge intersecting the front end flank 6 toward the rear end side, and the cross ridge line L becomes the outer peripheral side ridge line portion M of the wall surface. This width is set to be 0 at the intersection point N that intersects with. Further, in the present embodiment, the intersecting ridge line L extends linearly substantially in parallel with the axis O over the entire length, and therefore the outer peripheral surface of the margin portion 9 in the present embodiment is substantially triangular as shown in FIG. Will be presented.

  The outer peripheral side ridge line portion M from the intersection N with the intersection ridge line L toward the rear end side is an axis line as an intersection ridge line between the boundary portion 10 and the wall surface facing the drill rotation direction T of the chip discharge groove 4. After extending in a substantially straight line shape, a concave curve shape, a convex curve shape or a step shape so that the diameter from O gradually decreases, the second picking surface 8 is used as an intersecting ridge line between the second picking surface 8 and the wall surface. It will extend spirally along the chip discharge groove 4 with the same diameter. In order to reliably prevent the work material from being drawn when the drill body 1 is pulled out in the same manner as described above, the outer peripheral side ridge line portion M from the intersection N toward the rear end side is linear or concave curved or It is desirable to extend in a convex curve shape.

  When the twist drill having such a structure is attached to a drilling machine or a hand-held electric drill as described above to make a through hole in a work material such as a plate material, the cutting blade 5 bites into the work material until it penetrates. Since the margin portion 9 having an outer diameter equal to that of the cutting blade 5 is in sliding contact with the inner periphery of the machining hole, the tip portion of the blade portion 3 is guided along the axis O, Machining holes with high roundness and straightness can be formed.

  Further, since the margin portion 9 is crushed because the circumferential width disappears in the range in which the chip discharge groove 4 is formed, the cutting blade 5 penetrates the work material and a through hole is formed. After passing through the through hole, a gap is generated between the through hole and the second surface 8 of the blade portion 3, and the drill body 1 and the work material are not in contact with each other. Therefore, the work material is not drawn toward the rear end side of the drill main body 1 along the chip discharge groove 4, or is not drawn into the work material side together with the drill main body 1 when a hand-held electric drill is used. .

  Further, when the drill body 1 is pulled out from the through hole after the margin portion 9 has passed through the through hole in this way, the margin portion 9 is gradually increased in the rear end portion as the circumferential width toward the rear end side. When the drill body 1 is pulled out in this way, the through-hole becomes a margin of the drill body 1 from the intersection N of the intersecting ridge line L and the outer peripheral ridge line part M when the width becomes 0. The portion 9 and the single second-handed surface 8 are brought into contact with each other at one point, and are gradually pulled out so that the circumferential contact width with the margin portion 9 becomes longer.

  For this reason, a step extending on a plane perpendicular to the axis of the drill body, as in the case of pulling out the undercut type drill described above, comes into contact with the work material at a stretch and causes a catch at the periphery of the opening of the through hole. In the case of drilling with a drilling machine, the work material is lifted when the drill body 1 is pulled out, or in the case of drilling work with a hand-held drill, the work material is drawn to the operator side. Can be prevented. Therefore, according to the twist drill having the above-described configuration, it is possible to perform such a through-hole drilling process smoothly and stably.

  The length A of the margin portion 9 formed in this way in the direction of the axis O shown in FIG. 2, that is, the outer peripheral surface of the margin portion 9 serving as the outer peripheral end of the cutting blade 5, the tip flank 6 and the drill rotation of the chip discharge groove 4 The distance in the direction of the axis O between the intersection with the wall surface facing the direction T and the intersection N between the outer peripheral ridge line portion M and the intersection ridge line L of the wall surface is too long depending on the thickness of the work material. Since the work material may be drawn toward the rear end side in the axis O direction after the blade portion 3 penetrates the work material, the length is set to about 2 × D with respect to the outer diameter D of the cutting blade 5. Is desirable.

  On the other hand, if the marginal portion 9 has a maximum circumferential width that is too small, the blade 3 can be guided straight between the cutting edge 5 biting into the work material and penetrating as described above. Since there is a possibility that it cannot be performed, as shown in FIG. 3, both ends in the circumferential direction of the outer peripheral surface of the margin portion 9 when viewed from the front in the direction of the axis O It is desirable that the included angle α of the straight line connecting the axis line O and the axis O is 25 ° or more.

  Furthermore, in the present embodiment, the intersecting ridge line L extends in parallel to the axis O, that is, as shown in FIG. 2, the intersecting ridge line L intersecting with the intersecting point N at the rear end of the margin portion 9 and chip discharge. The intersection angle β of the wall surface of the groove 4 facing the drill rotation direction T with the outer peripheral ridge line portion M is substantially equal to the twist angle θ of the chip discharge groove 4 shown in FIG. 1, but this intersection angle β is small. If it is too large, the circumferential width of the margin portion 9 becomes too small before the intersection N of the rear end portion of the margin portion 9, so that the blade portion 3 cannot be guided straight or the strength of the margin portion 9 is impaired. There is a risk.

  On the other hand, if this crossing angle β is too large, for example, the crossing ridge line L extends from the crossing point N toward the front end side with a large inclination toward the rear side of the drill rotation direction T, When pulling out the tip of the blade portion 3 penetrating the material, the boundary portion 10 between the margin portion 9 and the second picking surface 8 is easily caught on the periphery of the opening portion of the through hole, as in the case of the undercut type drill. There is a possibility that the work material is drawn toward the rear end side of the drill body 1. For this reason, it is desirable that the crossing angle β is in a range of about θ-10 ° to θ + 50 ° with respect to the twist angle θ (°) of the chip discharge groove 4.

  Next, FIGS. 4 to 9 show the second to seventh embodiments of the present invention, respectively, and the same reference numerals are assigned to the same components as those of the first embodiment, and the description will be simplified. Turn into. Among these, first, in the second embodiment shown in FIG. 4, the width in the circumferential direction of the margin portion 9 on the distal end side of the drill body 1 is made longer than that in the first embodiment. A wall surface facing the rear side in the drill rotation direction T of the chip discharge groove 4 on the heel side of the land portion 7, with the entire length of the intersecting ridge line portion with the chamfering surface 8 being the entire rim line that is an intersection ridgeline with the margin portion 9 Also, the margin portion 9 intersects, and the cross ridge line L of the one chip discharge groove 4 adjacent to the circumferential direction extends from the outer peripheral side ridge line portion of the wall surface facing the rear side in the drill rotation direction T of the other chip discharge groove 4. It extends over the outer peripheral side ridge line portion M of the wall surface facing the drill rotation direction T.

  Further, in the second embodiment and the first embodiment, the intersecting ridge line L between the outer peripheral surface of the margin portion 9 and the boundary portion 10 extending from the outer peripheral surface to the second picking surface 8 is a straight line parallel to the axis O. On the other hand, in the third to seventh embodiments shown in FIGS. 5 to 9, the intersecting ridge line L is a polygonal line as shown in these drawings. Of these, in the third to sixth embodiments shown in FIGS. 5 to 8, the margin portion 9 is located on the drill rotation direction T side (cutting blade 5 side) of the tip flank 6 as in the first embodiment. Only the portion intersects the tip flank 6.

  Furthermore, in the third and fourth embodiments shown in FIGS. 5 and 6, after the intersecting ridge line L extends from the intersection with the tip flank 6 in a straight line parallel to the axis O to the rear end side, For example, the tip end of the drill body 1 extends toward the tip side of the drill body 1 at a twist angle substantially equal to the twist angle θ of the chip discharge groove 4 and reaches the tip flank 6, and is again parallel to the axis O before reaching the tip relief surface 6. When the tip end of the drill body 1 is directed to the left side, it extends to the side and intersects the outer peripheral side ridge line portion M of the wall surface facing the drill rotation direction T of the chip discharge groove 4 at the intersection N. In the side view, as shown in FIGS. 5 and 6, an inverted Z-shape is formed.

  In the third embodiment, as in the first embodiment, the portion reaching the intersection N is set as the rear end of the margin portion 9, and the margin portion 9 is crushed at the intersection N so that the width in the circumferential direction is reduced. However, in the fourth embodiment, the intersection ridge line L extends from the intersection with the front end flank 6 in a straight line parallel to the axis O toward the rear end rather than the intersection N in the fourth embodiment. Is located on the rear end side of the axis O direction and is the rear end portion of the margin portion 9, and thus the cross ridge line L extends from the intersection with the front end flank 6 to the rear end side, and the drill rotation direction from this portion The margin portion 9 is crushed at the bending point P with the portion extending toward the tip side of the drill body 1 toward the T side so that the circumferential width becomes zero.

  Further, in the fifth embodiment shown in FIG. 7, the intersection ridge line L extends from the intersection with the tip flank 6 to the rear end side in parallel to the axis O, and then drills along a plane perpendicular to the axis O. It extends to the rotation direction T side, and then extends again toward the rear end side in parallel with the axis O, and intersects the outer peripheral side ridge line portion M of the chip discharge groove 4 facing the drill rotation direction T at the intersection N. As in the third embodiment, the portion reaching the intersection N is set as the rear end portion of the margin portion 9, and the width in the circumferential direction is gradually reduced to zero toward the rear end side. .

  Further, in the sixth embodiment shown in FIG. 8, after the intersecting ridge line L extends from the intersection with the front end flank 6 to the rear end side in parallel to the axis O, for example, substantially equal to the twist angle θ of the chip discharge groove 4. The drill of the chip discharge groove 4 extends to the rear end side of the drill body 1 as it goes to the rear side of the drill rotation direction T at a twist angle, and is further bent to extend to the rear end side in parallel with the axis O. It intersects with the outer peripheral side ridge line portion M of the wall surface facing the rotation direction T at the intersection N. Therefore, the width reaching the intersection N is gradually decreased toward the rear end side, and the circumferential width gradually decreases to 0. This is the rear end portion of the margin portion 9.

  On the other hand, in the first to sixth embodiments, there is one margin portion 9 on one second picking surface 8, whereas in the seventh embodiment shown in FIG. This is a so-called double margin type in which margin portions 9 are formed on both sides of the drill rotation direction T side and the rear side thereof.

  Among these, the first margin portion 9A formed on the drilling direction T side of the second picking surface 8 is substantially the same as the twist angle θ of the chip discharge groove 4 from the intersection of the intersecting ridge line L with the tip flank 6, for example. It extends so as to twist toward the rear end side of the drill body 1 toward the rear side in the drill rotation direction T at an equal twist angle, and then bends so as to extend toward the rear end side in parallel with the axis O. It intersects with the outer peripheral side ridge line portion M of the wall surface facing the drill rotation direction T of the chip discharge groove 4 adjacent to the chamfering surface 8 on the drill rotation direction T side at the intersection N.

  Further, the second margin portion 9B on the rear side (heel side) of the drilling direction T of the second picking surface 8 is, for example, a twist angle θ of the chip discharging groove 4 from the intersection of the intersecting ridge line L with the tip flank 6. Extending to the rear end side of the drill body 1 toward the rear side in the drill rotation direction T at a twist angle substantially equal to that of the drill body, and then bending to extend to the front end side in parallel to the axis O. It intersects with the outer peripheral side ridge line part of the wall surface facing the drill rotation direction T rear side of the chip discharge groove 4 adjacent to the drill rotation direction T rear side of the cutting surface 8.

  Further, in the seventh embodiment, the rear end portion of the first margin portion 9A is located on the rear end side in the axis O direction with respect to the second margin portion 9B, and the first and second margin portions 9A, 9A, The width in the circumferential direction of the margin portion 9 combined with 9B gradually decreases to 0 toward the rear end side at the rear end portion of the first margin portion 9A so that the margin portion 9 is crushed. Note that a portion where the intersecting ridge line L of the first and second margin portions 9A and 9B extends in parallel to the axis O extends along one straight line.

  Also in the twist drills of the second to seventh embodiments configured in this way, the rear end portion of the margin portion 9 is gradually reduced in the circumferential width toward the rear end side as described above. Therefore, as in the first embodiment, until the machining hole penetrates the workpiece, the tip of the blade 3 is guided straight along the axis O while the machining hole is It is possible to prevent the work material from being drawn toward the rear end side of the drill body 1 after passing through and the margin portion 9 comes out of the through hole.

  Further, when the blade portion 3 is further pulled out from the through hole, even if the intersecting ridge line L has a portion extending along a plane perpendicular to the axis O as in the fifth embodiment, for example, Further, the margin portion 9 comes into contact with the through-hole from the position where the circumferential width becomes 0, and the circumferential contact width gradually becomes longer and is pulled out. There is no such thing as getting stuck on the periphery. Therefore, it is possible to prevent the work material from being lifted when the drill body 1 is pulled out from the drilling machine, or from being pulled toward the operator in the case of drilling work with a hand-held electric drill, Smooth and stable through-hole drilling can be performed.

  In these first to seventh embodiments, the pair of chip discharge grooves 4 are formed in the blade portion 3 on the tip end side of the drill body 1 in a 180-degree rotational symmetry with respect to the axis O, and the wall surface faces the drill rotation direction T. Although the case where the present invention is applied to the two-blade twist drill in which the cutting edge 5 is formed on the tip side ridge line portion of the cutting edge 5 is described, the number of the chip discharge grooves 4 and the cutting edges 5 may be three or more. The widths of the chip discharge grooves 4 and the land portions 7 are not necessarily the same.

DESCRIPTION OF SYMBOLS 1 Drill main body 3 Cutting edge part 4 Chip discharge groove 5 Cutting edge 6 Tip flank 7 Land part 8 Fitting surface 9 Margin part 10 Boundary part O Drill body 1 axis T Drill rotation direction L The outer peripheral surface and boundary part of a margin part Crossing ridgeline M with the outer peripheral side ridgeline part of the wall surface facing the drill rotation direction T of the chip discharge groove 4 N

Claims (1)

  A chip discharge groove that is helically twisted around the axis is formed on the outer periphery of the tip of the drill body that is rotated in the drill rotation direction around the axis, and the tip ridge of the wall surface facing the drill rotation direction of the chip discharge groove A cutting edge is formed, and a margin part is formed on the second face of the drill body extending from the outer peripheral side ridge line part of the wall surface to the rear side in the drill rotation direction. The twist drill is characterized in that the width in the circumferential direction gradually decreases toward the rear end side in the axial direction so that the width becomes 0 in a range where the chip discharge groove is formed.

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