JP7185127B2 - Drill - Google Patents

Description

TECHNICAL FIELD The present invention relates to a drill in which a pair of thinning surfaces sandwiching a rotating shaft form a chisel edge, and the thrust received by the tip surface of the drill body from a work material during cutting is reduced.

Forming the chisel edge from a pair of thinning surfaces sandwiching the rotation axis increases the crossover amount, which is the distance between the flank side portions on the forward side in the rotation direction, of the pair of thinning surfaces. It is meaningful to reduce the contact area of (tip surface) with the work material. As a result, there is an advantage that the thrust that the drill tip receives from the work material during cutting can be reduced (see Patent Documents 1 to 6).

On the other hand, if the amount of misalignment between a pair of thinning surfaces is large (Patent Documents 2, 3, 6, and 7), the flank surface (second surface) formed on the rear side in the rotational direction of the cutting edge is closer to the thinning surface. Since the width in the rotational direction of the portion is also reduced, there is a disadvantage that the strength against the torque, which is the resistance that the cutting edge receives from the work material, tends to decrease.

If the difference between the thinning surfaces is increased, the width in the rotational direction of the drill body in the area sandwiched between the cutting edge and the thinning surface in the second surface will be narrowed. Torque acts on the flank in the direction of rotation, and the degree of shear stress due to torque is proportional to the radial distance from the rotation axis (center). Since chipping is likely to occur in the blade, there is a limit to setting a large crossover amount.

Japanese Patent Application Laid-Open No. 6-91415 (claim 1, paragraphs 0009 to 0012, FIG. 1) Japanese Patent Application Laid-Open No. 2008-213121 (claim 1, paragraphs 0014 to 0019, FIG. 3) Japanese Patent Application Laid-Open No. 2008-296313 (claim 1, paragraphs 0023 to 0031, FIGS. 3 and 6) JP 2015-139845 A (claim 1, paragraphs 0020 to 0028, FIGS. 2 to 4) JP 2015-155137 A (claim 1, paragraphs 0010 to 0032, FIGS. 2 and 3) WO 2016/158463 (Claim 1, paragraphs 0022-0029, 0027-0040, FIGS. 3-5) Japanese Patent Application Laid-Open No. 2006-212724 (claim 1, paragraph 0006, FIG. 1)

Even in Patent Documents 2, 3, 6, and 7, which secure a misalignment amount between a pair of thinning surfaces, the cutting edge is formed from the radial outer peripheral side to the chisel edge (Patent Document 2 paragraph 0015, Patent Document 3 Paragraph 0024, Paragraphs 0027 and 0028 of Patent Document 6, 0007 of Patent Document 7), the thinning surface sandwiching the second surface on the rear side in the rotational direction of the cutting edge is formed only approximately to the end of the chisel edge ( FIG. 3 of Patent Document 2, FIG. 3 of Patent Document 3, and FIG. 1 of Patent Document 6).

In this way, in any patent document, there is a limit to deeply inserting the thinning surface into the second surface (flank) side on the rear side in the rotational direction of the cutting edge, for example, the radial center (rotational axis) of the second surface There is no example of forming a belt-like partial section except for the thinning surface on the side. At first glance, in Patent Document 6, the second surface seems to be formed in a strip shape, but since there is no cutting edge between the chisel edge and the portion of the thinning near the rotation axis O in the rotation direction, the work material Since it does not participate in the cutting of the workpiece, it does not receive torque from the work material.

From the above background, the present invention increases the resistance to the torque received from the work material in the section near the center in the radial direction of the cutting edge, and makes it possible to make the thinning surface face the radially outer peripheral side and deeply enter the second surface side. We propose a drill of the form to make

A drill according to the first aspect of the invention is characterized by a pair of cutting edges formed on a tip surface of an axial tip of a drill body facing forward in a rotational direction;
A chip discharge groove formed between the cutting edge and a flank located on the rear side in the rotation direction of each cutting edge in the rotation direction,
A pair of thinning surfaces formed between the rear side of each flank in the rotational direction and the chip discharge groove,
A drill in which a chisel edge passing through the rotation axis of the drill body and in contact with the thinning surfaces is formed between the pair of thinning surfaces,
The cutting edge is divided into an inner edge that continues from the end of the chisel edge to the radially outer peripheral side of the tip surface, and an outer edge that continues from the inner edge to the radially outer peripheral side,
Of the flanks, the width in the rotational direction of at least the section of the inner edge of the second surface formed continuously on the rear side in the rotational direction of the cutting edge is formed in a shape that gradually expands radially toward the outer peripheral side. is,
The total length of the chisel edge is the boundary line between the pair of thinning surfaces, and when the tip end surface of the drill body is viewed in the direction of the rotation axis, the total length of the extension line of the chisel edge does not overlap the inner cutting edge. , passing through the range of the second surface .

The "tip face of the drill body" refers to the end face of the tip (tip face 30) of the drill body shown in FIG. "When the tip end face 30 of the drill body is viewed in the axial direction (direction of the rotation axis O)" means that "the tip face 30 is on the opposite side of the tip end side of the drill body in the axial direction in the direction of the rotation axis O. When viewed toward the part 2 side". "Drill body" refers to the body (whole) of the drill 1 . Since the cutting edge 4 is a pair, the number (number of sheets) of the cutting edge 4 is two (sheets). The pair of cutting edges 4, 4 are formed at point-symmetrical positions with respect to the rotation axis O (with respect to the rotation axis O), and since there are two, at least a part of the cutting edge 4 (the inner edge 41) has a straight ridgeline. If so, the edges are parallel to each other.

The "flank located on the rear side in the rotation direction of each cutting edge" in claim 1 refers to the second surface 61 formed continuously on the rear side in the rotation direction of the cutting edge 4, and the rotation of the second surface 61 In some cases, it refers to the third surface 62 when the third surface 62 is continuously formed on the direction rear side, and in other cases it refers to the entire flank surface 6 that combines the second surface 61 and the third surface 62 . As the flank 6, the fourth and subsequent surfaces may be formed. The “chip discharge groove 7 formed between the rear side of the flank 6 in the rotational direction and the cutting edge 4” is the rear side of the flank 6 in the rotational direction and the cutting edge 4 located on the rear side in the rotational direction. It means that the chip discharge groove 7 is formed between.

"A pair of thinning surfaces" means that two thinning surfaces 8, 8 form a pair. The pair of thinning surfaces 8, 8 are formed at point-symmetrical positions with the rotation axis O interposed therebetween (with respect to the rotation axis O). "The chisel edge 5 passing through the rotation axis O and in contact with the thinning surfaces 8, 8" means that the entire length of the chisel edge 5 passing through the rotation axis O is in contact with (facing) both of the pair of thinning surfaces 8, 8. say .

As shown in FIGS. 1 and 2, the entire length of the chisel edge 5 is in contact with the thinning surface 8, so that the entire length of the chisel edge 5 becomes the boundary line between the pair of thinning surfaces 8, 8 (claim 1 ). This means that the boundary line 84 between the thinning surface 8 and the second surface 61 on the forward side in the rotational direction intersects the end (point P) of the chisel edge 5, so FIG . 7, the boundary lines 84, 84 of both thinning surfaces 8, 8 may be in an arrangement state in which the chisel edge 5 or the rotation axis O is interposed.

“Missing each other” means that each boundary line 84 is positioned beyond the rotation axis O when the thinning surface 8 including each boundary line 84 is viewed from the radially outer peripheral side, and each boundary line 84 is located on the rotation axis O The extension line on the side of the thinning surface 8 on the opposite side intersects the boundary line 85 (the boundary line 85 between the thinning surface 8 and the flank surface 6) continuous with the boundary line 84 of the thinning surface 8 Say things. In this case, since the area of the thinning surface 8 that occupies the area of the tip end face 30 when viewed in the axial direction is increased, it can be said that the chip accommodation capacity of the thinning face 8 is improved.

In claim 1, "the cutting edge 4 is an inner cutting edge 41 that continues from the end (point P) of the chisel edge 5 to the radially outer peripheral side of the tip surface 30" is a straight line that forms a convex ridge toward the tip surface 30 side. It means that the cutting edge 4 starts from one end (point P) of the chisel edge 5 and is continuously formed radially outward. A section of the cutting edge 4 near the end P of the chisel edge 5 is an inner cutting edge 41 . When the tip surface 30 is viewed in the axial direction, the chisel edge 5 is straight, so the cutting edges 4 are formed radially outward from both ends (P, P) of the straight line (chisel edge 5). become.

The cutting edge 4 is in contact with the end P of the chisel edge 5 as shown in FIG. and an outer cutting edge 42 which is in contact with the radially outer edge (point Q) of the inner cutting edge 41 and continues to the radially outer circumferential side. Since the point Q is the boundary (intersection point) between the inner cutting edge 41 and the outer cutting edge 42, the (convex) ridgeline connecting the points P and Q is the inner cutting edge 41 (ridgeline PQ or QP). In addition to this, when the chisel edge 5 is the boundary line between the pair of thinning surfaces 8, 8 as described above (claim 1 ), the thinning surface 8 has a chisel edge when the tip end surface 30 is viewed in the axial direction. 5 and passing through the ridge line QP and the chisel edge 5 (straight line PP), or as a plane or curved surface containing the ridge line QP and the chisel edge 5 (straight line PP), the rotational direction rear side of the ridge line QP (chip discharge groove 6 side) formed to.

As will be described later, in FIGS. 1 and 2 showing an example in which the thinning surface 8 is divided into two stages (claim 5 ), the boundary line between the first thinning surface 81 and the second thinning surface 82 The point where 86 intersects the cutting edge 4 is depicted as the intersection Q as the boundary between the inner cutting edge 41 and the outer cutting edge 42, but the intersection Q is not related to the intersection of the boundary line 86 and the cutting edge 4. .

In claim 1, "the section of at least the inner edge 41 of the second surface 61 formed continuously on the rear side in the rotational direction of the cutting edge 4 in the flank 6" means that the entire second surface 61 is radially 2, refers to a region located on the rear side in the rotational direction of the inner cutting edge 41 when divided into a section of the inner cutting edge 41 and a section of the outer cutting edge 42 according to the division of the cutting edge 4 in the radial direction. The "section of the inner cutting edge 41 of the second surface 61" and the "section of the outer cutting edge 42 of the second surface 61" respectively correspond to the "inner peripheral side second surface 61a" and the "outer peripheral side second surface 61b" described later. (Claim 3 ).

The rotation direction of the region (inner peripheral side second surface 61a) on the rear side in the rotational direction of the section of the inner cutting edge 41 in this second surface 61 (the section near the radial center (rotational axis O) of the second surface 61) is formed in a shape whose width gradually expands toward the outer peripheral side in the radial direction (claim 1). This means that the drill body is radially directed from the end (point P) of the chisel edge 5 to the boundary (point of intersection Q) between the inner cutting edge 41 and the outer cutting edge 42 and the rearward position in the rotational direction. is formed in a shape in which the width in the direction of rotation of is gradually expanded. "Toward the boundary (intersection point Q) between the inner cutting edge 41 and the outer cutting edge 42 and the position on the rear side in the rotational direction" means "toward the intersection Q from the end P of the chisel edge 5 and to the rearward of the intersection Q in the rotational direction." It means "toward two directions toward the position of the side". The ridgeline of the section from the end P of the chisel edge 5 to the intersection point Q is the inner cutting edge 41, and the ridgeline of the section from the intersection point Q to the radially outer edge (edge) of the cutting edge 4 is the outer cutting edge 42.

A section of the inner cutting edge 41 on the second surface 61 has a width in the direction of rotation in two directions, ie, the direction from the end P of the chisel edge 5 to the intersection Q and the direction toward the position on the rear side of the intersection Q in the rotation direction. By being formed into a gradually expanding shape, the chisel edge 5 is formed into a shape whose width gradually expands from the end P of the chisel edge 5 toward the outer peripheral side in the radial direction. Specifically, the section of the inner cutting edge 41 in the second surface 61 (the inner peripheral second surface 61a) has a triangular shape with the end P of the chisel edge 5 as the apex, or a sector centered at the end P of the chisel edge 5. It becomes a shape or the like that approximates the shape or the like.

Of the two lines directed in two directions from the center of the triangular vertex or fan shape, the line on the front side in the rotation direction is the cutting edge 4 (inner edge 41 (ridgeline PQ)), and the rear side in the rotation direction. is a boundary line 84 between the second surface 61 (the inner peripheral second surface 61a) and the thinning surface 8 on the rear side in the rotation direction. The lines in these two directions are not necessarily straight lines, and may be curved lines. Since the boundary line 84 on the rear side in the rotation direction of the inner cutting edge 41 (ridge line PQ) faces the direction along the chisel edge 5 (straight line PP) passing through the rotation axis O, it faces the direction along the radial direction. Since the inner cutting edge 41 is formed radially outward from the end P of the chisel edge 5 (Claim 1), when the tip end surface 30 is viewed in the axial direction, the extension of the chisel edge 5 corresponds to the rotation of the inner cutting edge 41. The chisel edge 5 can be formed so as to pass through the range of the second surface 61 that continues to the direction rearward side (claim 1 ).

"The extension of the chisel edge 5 (straight line PP) passes within the range of the second surface 61 on the rear side in the rotational direction of the inner cutting edge 41" means that when the tip surface 30 is viewed in the axial direction, as shown in FIG. Secondly, the extension line of the chisel edge 5 passes through the range from the state where the extension line overlaps with the inner cutting edge 41 (ridgeline PQ) to the state where it overlaps with the boundary line 84 between the rear side of the rotation direction of the second surface 61 and the thinning surface 8. To tell. In FIG. 2, the extension of the chisel edge 5 is indicated by a dashed line.

"The extension line of the chisel edge 5 (straight line PP) overlaps the inner cutting edge 41" means that the inner cutting edge 41 (ridge line PQ) is a straight line continuous with the chisel edge 5 when the tip surface 30 is viewed in the axial direction (the straight line is to draw) or to have a gentle curve that is close to a continuous straight line (to draw a curve). The fact that the extension line of the chisel edge 5 draws a curve close to a straight line means that at least the chisel edge 5 and the inner blade 41 do not form a discontinuous line across the intersection P of the chisel edge 5 and the inner blade 41, or In other words, the tangent of the near inner cutting edge 41 does not form a distinct angle with the chisel edge 5 .

In this case (in claim 1 ), as shown in FIGS. 6 and 7, the extension of the chisel edge 5 (straight line PP) passes through the front side of the inner cutting edge 41 (ridgeline PQ) in the rotational direction, and the inner cutting edge 41 and the chisel edge are aligned. form an obtuse angle, as shown in FIGS. It becomes easy to bring the portion to the rear side in the rotational direction of the second surface 61 including the intersection point Q. 6 and 7, the inner cutting edge 41 (boundary line 83) of each cutting edge 4 can be easily moved to the rear side in the rotational direction of the second surface 61. Since the boundary line 83 between 41 and the thinning surface 8 can retreat rearward in the rotational direction, the volume inside the thinning surface 8 increases. As a result, the capacity of the thinning surface 8 to accommodate chips is increased, and the effect of suppressing clogging of chips and the discharging performance are improved .

As can be seen from a comparison of FIGS. 6 and 7 with FIG. 1, there is a gap between a pair of thinning surfaces 8, 8 sandwiching the chisel edge 5 and the second surfaces 61, 61 which are in contact with each other on the forward side in the rotational direction. It is to bring the boundary lines 84, 84 closer to each other (reduce the distance between straight lines passing through the boundary lines 84, 84) and to reduce the angle formed by the chisel edge 5 (straight line PP) and the boundary line 84. The increase in the volume of the thinning surface 8 also reduces the area of the tip surface 30 when viewed in the axial direction. The effect of reducing the thrust and torque received from the work material is also improved.

In claim 1, the section of the inner cutting edge 41 in the second surface 61 (the area sandwiched between the ridge line PQ (boundary line 83) and the boundary line 84 (inner peripheral second surface 61a)) extends radially from the point P By forming a shape in which the width gradually expands in the rotational direction toward the outer peripheral side, torque (torsion moment) from the work material acting from the inner cutting edge 41 particularly on the section of the inner cutting edge 41 in the second surface 61 The resistance (shear stress) of the section of the inner cutting edge 41 can be made uniform. As a result, any part in the section (inner peripheral side second surface 61a) of the inner cutting edge 41 is less likely to become a weak point against torque, and the inner cutting edge 41 is less likely to be chipped. As described above, the "section of the inner cutting edge 41 in the second surface 61" includes the inner cutting edge 41 (ridgeline PQ), the inner peripheral second surface 61a on the rear side in the rotational direction, and the thinning surface 8 on the rear side in the rotational direction. It refers to a triangular area sandwiched between and a boundary line 84 between .

Specifically, as described above, in the section of the inner cutting edge 41, the torque acts on the inner peripheral second surface 61a of the second surface 61 from the inner cutting edge 41 toward the rear in the rotational direction, and the torque is applied to the inner circumferential side second surface 61a of the second surface 61 in the section of the inner cutting edge 41. is proportional to the radial distance r from the center (rotational axis O) (τ = (T / Ip) r ( Ip is the polar moment of inertia)). This means that the greater the radial distance r from the rotation axis O, the greater the shear stress acting on that portion (second surface 61), and the shear stress is proportional to the radial distance r from the center. It means that it increases linearly from the cutting edge 4 to draw a triangle.

Therefore, the width in the rotational direction of the second surface 61 (the section of the inner cutting edge 41 (inner peripheral second surface 61a)) that bears the torque T is the radius If it is formed in a shape that gradually expands toward the outer peripheral side of the direction (claim 1), the resistance to the torque (shear stress) of the second surface 61 (inner peripheral side second surface 61a) is uniform in each part in the radial direction. becomes easier. Since the resistance to torque is uniform at each radial portion, any portion of the inner blade 41 in the radial direction is relatively unlikely to become a weak point, and damage (chipping) of each radial portion of the inner blade 41 is prevented. Improves safety.

The resistance to the torque (shear stress) of the section of the inner cutting edge 41 in the second surface 61 (the inner peripheral second surface 61a) is equalized at each part in the radial direction, and the safety against breakage is increased. It becomes possible to adjust or suppress the size of the width (depth) in the rotational direction of the section of the inner cutting edge 41 in the surface 61 . As a result, the thinning surface 8 formed between the rear side of the second surface 61 in the rotation direction and the chip discharge groove 7 is formed on the rear side in the rotation direction of the section of the inner cutting edge 41 in the second surface 61 as described above. , can be formed so as to extend to the outer peripheral side in the radial direction (claim 2 ).

In other words, in the radial direction of the tip end face 30, as shown in FIG. Via the chisel edge 5 from the boundary (intersection point Q) between the inner cutting edge 41 and the outer cutting edge 42 of the pair of cutting edges 4, 4, the boundary between the inner cutting edge 41 and the outer cutting edge 42 of the other cutting edge 4 (intersecting point Q) It is possible to form even a position on the rear side in the rotational direction of the (claim 2 ). This makes it easier to move the boundary line 85 between the thinning surface 8 and the flank 6 (the second surface 61 and the third surface 62) with which the thinning surface 8 and the flank 6 (the edge thereof) contact the radially outer side. As a result, a large volume can be secured on the thinning surface 8, which leads to the advantage of being able to increase the ability to accommodate chips within the thinning surface 8 and suppress clogging of chips. A boundary line 85 between the thinning surface 8 and the flank surface 6 is oriented along a radial direction that intersects the boundary line 84 as shown in FIG.

Since the thinning surface 8 passes through the ridge line QP and the chisel edge 5 (straight line PP) as described above, in claim 2 , when viewed from the side of the starting position of the thinning surface 8, the portion beyond the chisel edge 5 sandwiches the chisel edge 5. The second surface 61 (the second surface 61b on the outer peripheral side) is located on the outer side.

Since the thinning surfaces 8, 8 are paired with the chisel edge 5 (straight line PP) interposed therebetween, the portions of the paired thinning surfaces 8, 8 beyond the chisel edge 5 are radially aligned with each other with the chisel edge 5 (rotational axis O) interposed therebetween. Since the thinning surfaces 8, 8 are in a crossed state, it is possible to secure a large crossing amount between the pair of thinning surfaces 8, 8. - 特許庁As a result, it is possible to reduce the area of the tip end surface 30 that contacts the work material when cutting the work material, so that the thrust and torque, which are the resistance that the tip end surface 30 receives from the work material, can be reduced. Become. "Amount of misalignment between the thinning surfaces 8, 8" is a portion (the boundary line 84 is curved to the boundary line 85) in the direction of the chisel edge 5 and enters the second surface 61 (outer peripheral side second surface 61b) of each thinning surface 8. It refers to the distance between the transitioning parts).

In claim 1 , the boundary line 83 between the inner cutting edge 41 and the thinning surface 8 with which it contacts can be easily shifted to the rear side in the rotation direction of the second surface 61, and in claim 2 , the thinning surface 8 and the front side in the rotation direction are in contact. Although the boundary line 84 between the second surface 61 and the second surface 61 can be easily brought to the radially outer side, the volume on the thinning surface 8 is increased and the area of the tip surface 30 is decreased. Advantages of increased and reduced drag from the work material are obtained.

In claim 1, the width in the direction of rotation of the section (inner peripheral side second surface 61a) of the inner cutting edge 41 in the second surface 61 is formed in a shape that gradually expands from the rotation axis O side toward the radial direction outer peripheral side. Thus (claim 1), when the entire second surface 61 is viewed in the radial direction as described above, the inner peripheral second surface 61a that is the section of the inner cutting edge 41 and the outer peripheral side 2 It can be divided radially into the second surface 61b (Claim 3 ). More specifically, the second surface 61 extends in the radial direction of the tip surface 30 from the end P of the chisel edge 5 toward the radially outer side to the boundary Q between the inner cutting edge 41 and the outer cutting edge 42 . It is divided into a second surface 61a and an outer second surface 61b that is continuous with the radially outer circumference of the inner second surface 61a (claim 3 ).

As described above, the inner second surface 61a is formed in a triangular shape with the end P of the chisel edge 5 as the vertex. On the inner cutting edge 41 (boundary line 83), it extends up to the boundary Q between the inner cutting edge 41 and the outer cutting edge 42. On the boundary line 84 between the inner peripheral second surface 61a and the thinning surface 8 on the rear side in the rotational direction, the boundary Q to the intersection of the boundary line 84 and a line directed toward the rear side in the rotational direction.

The inner peripheral second surface 61a extends from the inner cutting edge 41 (boundary line 83) toward the rear side in the rotational direction to the boundary line 84 located on the rearward side in the rotational direction from the boundary (intersection point Q) between the inner cutting edge 41 and the outer cutting edge 42. It is an area on the boundary line 84 up to the part where the boundary line 84 curves and transitions to the boundary line 85 . The second surface 61b on the outer peripheral side indicates a region that continues from the second surface 61a on the inner peripheral side to the outer peripheral side in the radial direction. When the second surface 61 is divided into the inner peripheral second surface 61a and the outer peripheral second surface 61b, the boundary line 84 curves and shifts to the boundary line 85, so that the inner cutting edge 41 and the outer cutting edge 42 are separated. The thinning surface 8 formed from the boundary (intersection point Q) or its vicinity has a curved surface that continues to the rear side in the rotation direction of the inner peripheral second surface 61a and the chip discharge groove 7 side of the outer peripheral second surface 61b. Item 3 ).

Specifically, as the boundary line 84 curves and transitions to the boundary line 85, for example, the third surface 62 is continuously formed on the rear side in the rotation direction of the second surface 61b on the outer peripheral side. A thinning surface 8 is formed continuously from the chip discharge groove 7 side of the surface 61b to the chip discharge groove 7 side of the third surface 62 (
Claim 4 ).

In this case, the portion of the thinning surface 8 near the flank 6 (the boundary line 85 between the thinning surface 8 and the flank 6 (the flank 6 with which the thinning surface 8 is in contact with the radially outer peripheral side)) is the second surface on the outer peripheral side. By continuing from the chip discharge groove 7 side of 61b to the chip discharge groove 7 side of the third surface 62, the boundary line 85 between the thinning surface 8 and the flank surface 6 extends from the chisel edge 5 to the outer peripheral second surface 61b side. After entering the outer peripheral side in the radial direction, it goes to the rear side in the rotational direction and faces in two directions. As a result, when the tip end surface 30 is viewed in the axial direction, the portion of the thinning surface 8 near the second surface 61b on the outer peripheral side is deeply recessed toward the second surface 61b on the outer peripheral side, and the space above the thinning surface 8 is formed. Since the capacity is increased, the chip accommodation capacity on the thinning surface 8 is increased, and chip clogging on the thinning surface 8 is less likely to occur.

Further, when the tip end face 30 is viewed in the axial direction, the thinning surface 8 extends from the flank surface 6 on the front side in the rotational direction to the chip discharge groove 7 side on the rearward side in the rotational direction. If it is divided into a second thinning surface 82 deeper than the first thinning surface 81 (claim 5 ), a convex ridge toward the tip surface 30 is formed between the first thinning surface 81 and the second thinning surface 82. Since the boundary line 86 is formed, it is possible to expect the cutting effect of chips at the boundary line 86 . The “flank 6” referred to here mainly refers to the second surface 61 .

"From the side of the flank 6 (second surface 61) on the forward side in the rotational direction to the side of the chip discharge groove 7 on the rearward side in the rotational direction" means "when viewed from the thinning surface 8, it is located on the forward side in the rotational direction. from the side of the second surface 61 toward the side of the chip discharge groove 7 located on the rear side in the rotational direction. The "second-stage thinning surface 82 deeper than the first-stage thinning surface 81" means that the first-stage thinning surface 81 (surface) is two-stage when viewed from the tip surface 30 in the axial direction toward the shank portion 2 side. It means that the second thinning surface 82 (surface) is located in front (closer to the tip surface 30) than the second thinning surface 82 (surface), and the second stage thinning surface 82 (surface) is located closer to the shank portion 2 than the first stage thinning surface 81 (surface).

When the tip surface 30 is viewed from the second surface 61 on the forward side in the rotational direction toward the chip discharge groove 7 side on the rearward side in the rotational direction, the first-stage thinning surface 81 is closer to the second surface 61 on the forward side in the rotational direction. , and the second-stage thinning surface 82 is positioned closer to the chip discharging groove 7 , so that an angle is formed between the first-stage thinning surface 81 and the second-stage thinning surface 82 .

As described above, the boundary line 86 between the first-stage thinning surface 81 and the second-stage thinning surface 82 forms a convex ridgeline toward the tip surface 30 side, and protrudes (ridge-like) toward the tip surface 30 side. protrude continuously. Therefore, when the chips come into contact with the boundary line 86 while being rounded into a conical shape along the first-stage thinning surface 81 and the second-stage thinning surface 82, the boundary line 86 moves against the chip in the axial direction (longitudinal direction) of the conical shape. It is in a state of applying a shearing force (cutting force) in a direction that intersects the vertical direction). By applying a shearing force in a direction intersecting the axial direction to the chips whose boundary line 86 between the first-stage thinning surface 81 and the second-stage thinning surface 82 is rounded into a conical shape, the chips are axially rolled up into a conical shape. Since the chips that are about to grow can be divided in the axial direction, the chips are prevented or suppressed from growing in the axial direction.

Here, when viewed from the chip discharge groove 7 side as described above, the thinning surface 8 is formed toward the rear side of the ridge line QP, the chisel edge 5 (straight line PP), and the ridge line PQ continuing to the straight line PP in the rotational direction. Therefore, a boundary line 86 between the first-stage thinning surface 81 and the second-stage thinning surface 82 forms a convex curved line toward the second surface on the forward side in the rotational direction when viewed from the chip discharging groove 7 side. It is formed.

From this shape, when the chip is rounded into a conical shape, for example along the second thinning surface 82, a curve such that the boundary line 86 cuts the cone into a truncated cone and a cone in a plane that intersects the axis (center) of the cone. Therefore, it becomes easy to act to separate the chips that tend to be rounded into a conical shape in the axial direction. The line of intersection between the cone and the plane (cut plane) that intersects the axis (center) of the cone and cuts the cone is circular or elliptical. This is because, if the boundary line 86 between them has a curved shape convex toward the second surface 61, this boundary line 86 draws a curve close to the line of intersection between the cone and a plane that intersects the axis of the cone.

The cutting edge is divided into an inner edge that continues from the end of the chisel edge to the radial direction outer peripheral side of the tip surface of the drill body, and an outer edge that continues from the inner edge to the outer peripheral side. At least the section of the inner cutting edge of the second surface formed continuously on the side is directed from the end of the chisel edge to the boundary between the inner cutting edge and the outer cutting edge and the rearward position in the rotational direction of the drill body. Since it is formed in a shape in which the width gradually increases, it is possible to easily equalize the resistance force against the torque of the second surface at each portion in the radial direction. As a result, any portion of the inner cutting edge in the radial direction is relatively unlikely to become a weak point, and safety against breakage (chipping) of each portion in the radial direction of the inner cutting edge is improved.

An end view showing an example of manufacturing a drill when the tip face of the drill body is viewed in the axial direction when the extension line of the chisel edge passes through the range of the second surface of the flank face of the tip face of the drill body. be. FIG. 2 is an enlarged view of the chisel edge portion of FIG. 1; FIG. 2 is a side view of the tip surface of the drill shown in FIG. 1 as seen from slightly obliquely above in the direction of line xx. FIG. 2 is a side view of the cutting edge of the drill shown in FIG. 1 when viewed in the direction of line xx perpendicular to the axis of rotation; Fig. 2 is a side view showing the entire drill body shown in Fig. 1; (a) is an end view showing a reference manufacturing example of a drill when the tip surface of the drill body is viewed in the axial direction when the inner cutting edge and the chisel edge form an obtuse angle, and (b) is an enlarged view of (a). be. (a) is an end view showing another reference manufacturing example of a drill when the tip surface of the drill body is viewed in the axial direction when the inner cutting edge and the chisel edge form an obtuse angle; (b) is an enlarged view of (a). It is a diagram. FIG. 10 is an end view showing a reference manufacturing example of a drill when the boundary line between the thinning surface and the second surface with which the front side in the rotational direction is in contact intersects with a point other than the end (point P) of the chisel edge.

1 and 5 show a pair of cutting edges 4, 4 formed on a tip surface 30 at the axial tip of the drill body facing forward in the rotational direction, and a flank located on the rearward side in the rotational direction of each cutting edge 4. A chip discharge groove 7 formed between the rear side in the rotational direction of 6 and the cutting edge 4, and a pair of thinning surfaces 8 formed between the rear side in the rotational direction of each flank 6 and the chip discharge groove 7, 8, and a chisel edge 5 passing through the rotation axis O of the drill body between a pair of thinning surfaces 8, 8 and at least partially in contact with the thinning surfaces 8, 8 is formed.

As shown in FIG. 5, the drill body (drill 1) has a shank portion 2 located on the rear side in the direction of the axis (rotational axis O) of the drill body and a blade portion 3 formed on the tip side in the axial direction. A pair of (two) cutting edges 4 , 4 are formed on a tip surface 30 at the tip of the blade portion 3 in the axial direction. Hereinafter, the drill body refers to the body of the drill 1 . Although the drawing shows an example of a solid type drill 1 in which the blade portion 3 is integrated with the drill body, the blade portion 3 is detachably fixed to and held by the drill body. In some cases.

The “tip face 30 ” refers to the region (part) excluding the chip discharge groove 7 and the thinning face 8 when the tip face 30 of the drill body is viewed in the direction of the rotation axis O, and indicates the region of the flank face 6 . In the drawing, as shown in FIG. 1, a second surface 61 as a flank 6 is formed continuously on the rear side of the cutting edge 4 in the rotational direction, and a third surface 61 as the flank 6 is formed on the rear side in the rotational direction of the second surface 61. Although the numbered surface 62 is formed continuously, in this case, the flank surface 6 is a region where the second surface 61 and the third surface 62 are combined.

As shown in FIGS. 1 and 2, the cutting edge 4 is formed from the end (point P) of the chisel edge 5 (straight line PP) to the radially outer peripheral side of the tip end face 30. In the radial direction of the tip end face 30, the chisel edge 5 It is divided into an inner cutting edge 41 (ridgeline PQ) on the inner peripheral side that contacts the end (point P) of the inner cutting edge 41 and an outer cutting edge 42 that continues from the inner cutting edge 41 to the outer peripheral side in the radial direction. A boundary between the inner cutting edge 41 and the outer cutting edge 42 is an intersection point Q, and the outer cutting edge 42 is formed continuously from the intersection point Q to an end portion (edge) on the radially outer peripheral side. In the drawing, the inner cutting edge 41 (ridgeline PQ) is formed in a straight line and the outer cutting edge 42 (ridgeline Q~) is formed in a curved shape, but the shape of the inner cutting edge 41 and the outer cutting edge 42 is not limited to this.

The outer cutting edge 42 (ridge line Q~) may be formed so as to draw a continuous curve from the inner cutting edge 41 (ridge line PQ). The second surface 61 side of the intersecting point Q is made obtuse, or the intersecting point Q is curved so that the inner cutting edge 41 comes into contact with the work material first when the drill body rotates around the rotation axis O. Then, the outer cutting edge 42 comes into contact with the work material after the inner cutting edge 41 .

Among the flanks 6, the width in the rotational direction of at least the section of the inner cutting edge 41 (inner peripheral side second surface 61a described later) of the second surface 61 formed continuously on the rear side of the cutting edge 4 in the rotational direction is the radius It is formed in a shape that gradually expands toward the direction outer peripheral side. In other words, in the radial direction of the tip surface 30, as shown in FIG. ), the width of the drill body in the rotational direction gradually increases. Here, "from the end (point) P to the boundary Q and the position on the rear side in the rotational direction" means "from the radial center (rotational axis O) side to the radial outer peripheral side, the direction of the point Q and the It means "toward two directions along the boundary line 84".

Since the cutting edge 4 is divided in the radial direction into an inner cutting edge 41 on the inner peripheral side and an outer cutting edge 42 on the outer peripheral side, according to this division, the second surface 61 is defined as "the inner cutting edge 41 of the second surface 61 It is divided into an "inner peripheral side second surface 61a" corresponding to the "section" and an "outer peripheral side second surface 61b" on the outer peripheral side. The ridgeline on the forward side in the rotational direction of the inner peripheral second surface 61a is the inner cutting edge 41, and the ridgeline on the forward side in the rotational direction of the outer peripheral second surface 61b is the outer cutting edge .

Since the inner peripheral second surface 61a is formed in a shape in which the width in the direction of rotation of the drill body gradually increases toward the outer peripheral side in the radial direction, the inner cutting edge 41 that defines the inner peripheral second surface 61a and the inner periphery The area sandwiched between the side second surface 61a and the boundary line 84 between the thinning surface 8 on the rear side in the rotational direction is formed in a triangular shape or a sector shape similar thereto. Since the inner circumference side second surface 61a is formed in a triangular shape or the like, the entire length (ridgeline PQ) of the inner cutting edge 41 has a uniform resistance against the torque acting on the inner circumference side second surface 61a from the work material. Since it has a force, it is more secure against damage due to torque than when the inner peripheral side second surface 61a has a shape other than a triangular shape or the like.

For this reason, as shown in FIGS. 3 and 4, the section of the inner blade 41 is not honed (formed) to prevent breakage (chipping), and the inner blade 41 is given a delicate cutting ability. ing. On the other hand, for the purpose of preventing chipping due to no honing (formation) in the inner cutting edge 41, the rake angle in the axial direction of the inner cutting edge 41 is made negative, and the thickness of the cutting portion 3 in the section of the inner cutting edge 41 is increased. The term "negative rake angle in the axial direction" means that the tangential plane of the portion of the thinning surface 8 that becomes the rake surface that continues forward in the rotation direction of the inner cutting edge 41 and the inner peripheral second surface 61a It means that the angle formed to the side is larger than 90° when viewed in the direction of the inner blade 41.

On the other hand, since the outer cutting edge 42 does not require as fine a cutting ability as the inner cutting edge 41, the outer cutting edge 42 is formed with honing 42a as shown in FIGS. is doing. Along with this, the rake angle in the axial direction of the outer cutting edge 42 is made positive. The term "positive rake angle in the axial direction" means that the angle formed between the tangential plane of the rake face portion continuing forward in the rotation direction of the outer cutting edge 42 and the second surface 61b on the outer peripheral side toward the cutting portion 3 side is Less than 90° when viewed in the direction of 42.

As shown in FIG. 1, a margin 9 continues from the radial outer edge of each cutting edge 4 toward the axial rear side (shank portion 2 side) of the drill body. A third surface 62 is formed in a section of the land 10 which is a portion on the rear side of the margin 9 in the rotational direction. In the drawing, the second surface 61 is formed from the margin 9 to the land 10 in the circumferential direction of the drill body.

When the thinning surface 8 is viewed from the chip discharge groove 7 side, as shown in FIG. It is formed so as to form the side surfaces of the second surface 61 (the second surface 61b on the outer peripheral side) and the third surface 62 facing the chip discharge groove 7 side. The boundary line between the thinning surface 8 and the ridgeline on the forward side in the rotational direction of the outer peripheral side second surface 61b is the outer cutting edge 42, and the boundary line 83 with the ridgeline on the forward side in the rotational direction of the inner peripheral side second surface 61a is the inner side. It is the blade 41 .

The thinning surface 8 formed from the boundary Q between the inner cutting edge 41 and the outer cutting edge 42 toward the second surface 61 is the chip discharge groove 7 on the rear side in the rotation direction of the inner peripheral second surface 61a and the outer peripheral second surface 61b. It has a continuous curved surface on the side. When the third surface 62 is formed continuously behind the second surface 61 in the rotation direction, the thinning surface 8 extends from the second surface 61b on the outer peripheral side toward the chip discharge groove 7 to the third surface 62 toward the chip discharge groove 7. is formed continuously.

1 and 2 also show that the entire length of the chisel edge 5 is the boundary line between the pair of thinning surfaces 8, 8, and the boundary lines 84, 84 of both thinning surfaces 8, 8 intersect the chisel edge 5 or the rotation axis O. 1 shows an example of fabrication of a drill 1 in the state shown. In this example, when each thinning surface 8 is viewed from the radially outer peripheral side, each boundary line 84 of each thinning surface 8 crosses the rotation axis O shown in FIG. A boundary line 85 (between the thinning surface 8 and the flank 6 border line 85). 1 and 2, the thinning surface 8 occupies the area of the entire tip surface 30 when the tip surface 30 is viewed in the axial direction in comparison with the example shown in FIGS. 6 and 7 described later. There is an advantage that the area is enlarged and the chip accommodation capacity of the thinning surface 8 is increased.

In the drawing, when the tip surface 30 of the drill body is viewed in the direction of the rotation axis O, the first thinning surface 8 is thinned from the side of the flank surface 6 on the front side in the rotation direction to the side of the chip discharge groove 7 on the rear side in the rotation direction. It is divided into a surface 81 and a second-stage thinning surface 82 deeper than the first-stage thinning surface 81, and between the first-stage thinning surface 81 and the second-stage thinning surface 82, a ridge line ( border 86). The boundary line 86 is a convex ridge toward the tip end surface 30, so that when the chips grow along the first-stage thinning surface 81 and the second-stage thinning surface 82 in a conical shape, the chips are axially moved. It works to divide.

In the drawings, when the tip end face 30 is viewed in the axial direction, the direction of the chisel edge 5 is oriented so that the extension line of the chisel edge 5 (straight line PP) passes within the range of the second surface 61 (inner peripheral second surface 61a). By adjusting, the inner edge 41 (boundary line 83) of each cutting edge 4 is moved to the rear side in the rotation direction of the second surface 61, and the volume in the thinning surface 8 is increased from the examples shown in FIGS. .

Chips growing along the first-stage thinning surface 81 and the second-stage thinning surface 82 continue to contact at least one of the first-stage thinning surface 81 and the second-stage thinning surface 82, and are twisted and twisted. Attempts to grow while curling into a cone shape. In this relationship, when the first-stage thinning surface 81 and the second-stage thinning surface 82 try to round the chips, both the first-stage thinning surface 81 and the second-stage thinning surface 82 have the tip end surface 30 in the axial direction. It is appropriate that the curved surface is concave toward the tip surface 30 side when viewed from above. Forming both thinning surfaces 81 and 82 with concave surfaces also increases the volume within the thinning surface 8 .

6 and 7, as shown in each (b), the chisel edge 5 (straight line PP), the extension line indicated by the dashed line passes the rotation direction front side of the inner blade 41 (boundary line 83 (ridgeline PQ)), the inner side A production example (reference example) in which the blade 41 and the chisel edge form an obtuse angle is shown. In this case, the chisel edge 5 faces forward in the rotational direction with respect to the inner blade 41 and does not pass through the range of the inner peripheral side second surface 61a. 41, 41) is ensured, and as a result, the width in the rotational direction of the inner peripheral side second surface 61a becomes large.

On the other hand, in the example shown in FIG. 1, as can be seen from the comparison between FIG. 2, which is an enlarged view of FIG. 1, and each of FIGS. 61 (inner peripheral side second surface 61a), the distance between the pair of inner blades 41, 41 sandwiching the chisel edge 5 (between the extension lines of the inner blades 41, 41) is increased in FIGS. 2, and the inner cutting edge 41 is retracted rearward in the rotational direction. As a result, the width in the direction of rotation of the inner peripheral side second surface 61a is relatively smaller than in the examples shown in FIGS. The storage capacity of is increased, and the effect of suppressing chip clogging is improved.

7 shows an example in which the distance between the inner blades 41, 41 (boundary lines 83, 83) is smaller than the example shown in FIG. 6, and FIG. 1 shows an example in which the distance is smaller than the example shown in FIG. ``The distance between the inner blades 41, 41 is relatively large. It is also because the angle formed by is relatively large. In the examples shown in FIGS. 6 and 7, as a result of "the distance between the inner blades 41, 41 being relatively large" in comparison with the example shown in FIG. becomes relatively large, and the width of the inner peripheral second surface 61a in the rotational direction becomes relatively large.

In conclusion, if the extension of the chisel edge 5 (straight line PP) passes through the range of the second surface 61 as shown in FIGS. The width in the rotational direction of the inner peripheral side second surface 61a is relatively smaller than when passing through the front side in the rotational direction of the inner cutting edge 41 (ridge line PQ), which is the boundary line 83, and the volume within the thinning surface 8 is increased. leads to

FIG. 8 shows the case where the drill 1 is manufactured so that the boundary line 84 between the thinning surface 8 and the second surface 61 with which the front side in the rotational direction is in contact intersects with a point other than the end (point P) of the chisel edge 5 (reference example ) of the chisel edge 5 and its ends P, P and the boundary line 84. FIG. The thinning surface 8 of this example has an intermediate shape between the manufacturing example shown in FIG. 1 and the manufacturing examples shown in FIGS.

1……drill (drill body),
2 ...... shank part,
3 ... blade portion, 30 ... tip surface,
4 …… cutting edge,
41... inner blade, 42... outer blade, 42a... honing,
5 …… chisel edge,
6... flank, 61... second surface, 61a... second surface on inner peripheral side, 61b... second surface on outer peripheral side, 62... third surface,
7 ... chip discharge groove,
8 …… Thinning surface,
81 …… 1st stage thinning surface, 82 …… 2nd stage thinning surface,
83 Boundary line between the inner blade 41 and the thinning surface 8 with which it contacts (the inner blade 81 and the thinning surface 8 on the front side in the rotational direction),
84 Boundary line between the thinning surface 8 and the second surface 61 (the second surface 61 and the thinning surface 8 on the rear side in the rotation direction) with which the front side in the rotation direction is in contact,
85 Boundary line between the thinning surface 8 and the flank 6 with which the radially outer peripheral side is in contact (the flank 6 and the thinning surface 8 on the rear side in the rotational direction);
86: Boundary line between the first stage thinning surface 81 and the second stage thinning surface 82,
87...... Boundary line between the thinning surface 8 and the chip discharge groove 7,
9......margin, 10...land,
O……Rotating axis,
P ... the end of the chisel edge 5 (the intersection of the chisel edge 5 and the inner cutting edge 41),
Q Boundary (point of intersection) between the inner cutting edge 41 and the outer cutting edge 42 .

Claims (5)

a pair of cutting edges formed on the tip surface of the axial tip of the drill body facing forward in the rotational direction;
A chip discharge groove formed between the cutting edge and a flank located on the rear side in the rotation direction of each cutting edge in the rotation direction,
A pair of thinning surfaces formed between the rear side of each flank in the rotational direction and the chip discharge groove,
Passing on the rotation axis of the drill body between the pair of thinning surfaces,A drill having a chisel edge in contact with the thinning surface,
The cutting edge is divided into an inner edge that continues from the end of the chisel edge to the radially outer peripheral side of the tip surface, and an outer edge that continues from the inner edge to the radially outer peripheral side,
Of the flanks, the width in the rotational direction of at least the section of the inner edge of the second surface formed continuously on the rear side in the rotational direction of the cutting edge is formed in a shape that gradually expands radially toward the outer peripheral side. is,
The total length of the chisel edge is the boundary line between the pair of thinning surfaces, and when the tip end surface of the drill body is viewed in the direction of the rotation axis, the total length of the extended line of the chisel edge does not overlap the inner cutting edge. , passing through the second range A drill characterized by: The thinning surface is attached to one side of the tip surface in the radial direction across the chisel edge, and passes through the chisel edge from the boundary between the inner edge and the outer edge of one of the pair of cutting edges. 2. The drill according to claim 1 , wherein, of the pair of cutting edges, it is formed up to a position on the rear side in the rotational direction of the boundary between the inner cutting edge and the outer cutting edge of the other cutting edge. . In the radial direction of the tip surface, the second surface is the inner second surface of the section including the end of the chisel edge to the boundary between the inner cutting edge and the outer cutting edge, and the inner second surface of the inner peripheral second surface. It is divided into the second surface on the outer peripheral side that is continuous with the outer peripheral side in the radial direction,
The thinning surface formed from the boundary between the inner cutting edge and the outer cutting edge, or the vicinity thereof, is a curved surface that continues to the rear side of the second surface on the inner peripheral side in the rotation direction and the second surface on the outer peripheral side to the chip discharge groove side. 3. A drill according to claim 2 , comprising: A third surface is formed continuously on the rear side of the second surface on the outer peripheral side in the rotational direction, and the thinning surface extends from the chip discharge groove side of the second surface on the outer peripheral side to the chip discharge groove side of the third surface. 4. A drill according to claim 3 , characterized in that it is formed continuously. When the tip surface of the drill body is viewed in the direction of the rotating shaft, the thinning surface is a first-stage thinning surface extending from the flank surface on the front side in the rotation direction to the chip discharge groove side on the rear side in the rotation direction. 5. A drill according to any one of claims 1 to 4 , characterized in that it is divided into a second-stage thinning surface deeper than the first-stage thinning surface.

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