Drill and drill head with secondary clearance surface

Abstract

drill (10) configured for drilling ductile materials, a central axis (A C ) has a front-back direction that defines a front-back direction and has a drill body (12) and a removable drill head (14): wherein the drill head (14) has: several cutting sections (16); wherein each cutting section (16) has: a chip surface (18); an open space (20); a cutting edge (22) which is formed on an intersection line between the rake and clearance surfaces (18, 20) and extends rearward to a cutting edge end (24) and has a cutting circle diameter (D) C ) of the drill (10) defined; and a secondary free area (26) extending from the free area (20) to the rear and also extending from the rake surface (18); where: each secondary clearance surface (26) extending from the end of the cutting edge (24) lies outside the cutting circle diameter (D)C extends; Each secondary free area (26) has a secondary free area end (28) adjacent to the free area (20) and is located outside the cutting circle diameter (D). C ) is located; the secondary open space end (28) is located at an intersection line between a flank surface (42) and the secondary open space (26); the flank surface (42) extends inwards from a point outside the cutting circle diameter (D) C ) to a point within the cutting circle diameter (D C ) extends to provide a relief function; and an outer diameter clearance surface (44) extends along a circumference from the flank surface (42) in a direction away from the cutting edge end (24) and lies completely within the cutting circle diameter (D) C ) is located.

Description

Field of the invention

[0001] The subject matter of the present application is secondary clearance surfaces, in particular secondary clearance surfaces of drills and drill heads configured for drilling ductile materials such as low-carbon steel and alloy steel. Background of the invention

[0002] One measure of drilling quality is the finish applied to the workpiece. Performing high-quality finishing on ductile materials, such as low-carbon or alloy steel, can be particularly challenging, and improved finish is often a desired outcome.

[0003] US 8,419,322 B2 discloses a tool for use in a preformed round hole. More specifically, it discloses a cutting insert with a secondary cutting edge flank adjacent to a secondary cutting edge in the opposite direction of rotation and having a support element arranged at a distance from the primary cutting edge in the opposite direction of feed. The support element has a radius of revolution that is larger than a hole circle radius of the cutting insert during a drilling operation. The support element is intended to be capable of fulfilling both a supporting function and a smoothing function.

[0004] EP 1 475 173 A1 discloses a drill with a drill head having two opposing surfaces and two longitudinal sides running parallel to a rotational axis of the drill. A rear surface and two front surfaces define two front cutting edges connected by two inclined intermediate edges arranged on the sides of a transverse central edge. The sides have a maximum extension diameter that is larger than a further diameter of a cutting circle defined by an extension of the front edges.

[0005] JP 2003-136317 A discloses a drill with a polishing edge having an outer diameter larger than the outer diameter of a cutting edge.

[0006] US 2007 / 227766 A1 discloses a drill with a chip ejection groove formed on a distal cutting portion of a body. The chip ejection groove is formed in a single-stripe shape.

[0007] It is an object of the present application to provide a new and improved drill or drill head. Summary of the invention

[0008] The subject matter of the present application is suitable for drills and drill heads configured to create and / or deepen preformed holes. Notably, drills according to the present application are configured only for axial machining (e.g., drilling) and not for machining in a non-axial direction (e.g., shoulder milling, ramping). More specifically, drills according to the present application are configured only for drilling holes with a diameter corresponding to a cutting diameter of the tool. Nevertheless, the term "drill" includes drills configured to rotate and static drills configured to be static while a workpiece rotates.

[0009] According to a first aspect of the subject matter of the present application, a drill or drill head is provided having a central axis A C defining a front-to-back direction, and comprising: a plurality of cutting sections; each cutting section comprising: a rake face; a flank face; a cutting edge formed at an intersection line between the rake and flank faces and extending rearward to a cutting edge end, and thereby defining a cutting circle diameter of the drill; and a secondary flank extending rearwardly from the flank and also extending from the rake face; each secondary flank having a secondary flank end adjacent to a flank and being located outside the cutting circle diameter.

[0010] The secondary flank and in particular the secondary flank end demonstrably fulfills a polishing function, and test results obtained so far have surprisingly shown that the longevity of a drill or drill head with such a secondary flank end has obviously increased compared to comparable tools.

[0011] It is understood that, prior to this disclosure, a drill or drill bit with the above geometry would, as expected, be destroyed under compression in a hole being drilled. Theories have been put forward, and tests have surprisingly confirmed, that at least when drilling low-carbon and alloy steel (as was believed to be due to their ductility), such a geometry is not adversely affected.

[0012] According to a further aspect of the subject matter of the present application, a drill or drill bit is provided having a cutting portion; wherein the cutting portion has a secondary flank; wherein the secondary flank has a secondary flank end adjacent to a flank and is located outside a cutting circle diameter.

[0013] It is understood that the foregoing is a summary, and that each of the aforementioned aspects may further include any of the features described below. In particular, the following features, alone or in combination, may be suitable for each of the aforementioned aspects: A. A drill or drill bit may have a central axis A C that defines a front-back direction. A drill or drill bit can be rotationally symmetrical about the central axis A C Cutting edge ends of a drill or drill bit can be circumferentially aligned around the central axis AC be equally spaced. Secondary clearance surfaces of a drill or drill bit can be arranged along the circumference around the central axis A C be equally spaced. B. A drill or drill bit may have multiple cutting sections. C. A cutting section may have a rake face, a flank face and a cutting edge formed at an intersection line between the rake and flank faces. D. A cutting edge may extend rearward to a cutting edge end that defines a cutting diameter of the drill bit or drill head. A cutting edge may be configured for drilling ductile materials, such as low-carbon steel and alloy steel. A cutting edge may have a rake angle θ of 20 to 30 degrees (20° ≤ θ ≤ 30°) at a cutting edge end. E. A cutting section may have a secondary flank extending rearwardly from a clearance face and also extending from a rake face. F. A secondary flank may have a secondary flank end adjacent to a flank and located outside the cutting diameter. In other words, a secondary flank end is located further from the centerline A C away than a cutting edge end. In other words, a secondary flank end forms a point furthest from the center axis A C . G. A secondary flank may extend from a cutting edge end outside a cutting circle diameter. A secondary flank may extend from the cutting edge end outside the cutting circle diameter and continuously increase the distance from the cutting circle diameter to a secondary flank end. The continuous increase in distance may occur at a decreasing degree (i.e., with a convexly curved shape in its plan view). H. A cutting section may have a minor flank edge extending along an intersection line between a minor flank and a rake face. A minor flank may have an end extending outside a cutting circle diameter at any axial location along the minor flank edge. A minor flank may extend outside the cutting circle diameter from the minor flank edge at any axial location along the minor flank edge. A minor flank may continuously increase the distance from the cutting circle diameter to an end at any axial location along the minor flank edge. The continuous increase in distance may be in a decreasing degree (i.e., having a convexly curved shape in its plan view). I. A secondary flank end may extend outside a cutting circle diameter by a projection distance D P of at least one micrometer (D P≥ 0.001 mm). For drills with a cutting diameter D C from eight to nineteen millimeters (8 mm ≤ D C ≤ 19 mm) a preferred tested projection distance D P outside the cutting circle diameter D C two to eight micrometers (0.002 mm ≤ D P ≤ 0.008 mm). For drills with a cutting diameter D C from twenty to twenty-five millimeters (20 mm ≤ D C ≤ 25 mm) was a preferred tested projection distance D P three to ten micrometers (0.003 mm ≤ D P ≤ 0.010 mm) outside the cutting circle diameter D C . For drills with a cutting diameter D C less than eight millimeters, a preferred projection distance D P one to six micrometers (0.001 mm ≤ D P ≤ 0.006 mm). For drills with a cutting diameter D Cgreater than twenty-five millimeters, a preferred projection distance D P four to twelve micrometers (0.004 mm ≤ D P ≤ 0.012 mm). A preferred range of projection distances D P would be one to twelve micrometers (0.001 mm ≤ D P ≤ 0.012 mm). A most preferred tested range of projection distances D P is two to ten micrometers (0.002 ≤ D P ≤ 0.010 mm). Notwithstanding this, it should also be noted that it has been determined that a flank end extending outside a cutting diameter by a projection distance D P of at least two micrometers (D P ≥ 0.002 mm) exhibits better performance than at least one micrometer (D P ≥ 0.001 mm). A secondary flank can have an end at any axial location that extends outside the cutting diameter by a projection distance D Pwhich corresponds to the values ​​mentioned above in connection with the end of the secondary open space. J. An entire secondary flank may be located outside the cutting circle diameter. K. A secondary clearance surface may extend over an axial distance of not more than 0.1 mm from a clearance surface, preferably not more than 0.01 mm from the clearance surface. L. A secondary flank may include a secondary flank portion. The secondary flank portion may be the only portion of the secondary flank that has an end located outside the cutting diameter. The secondary flank portion may extend an axial distance of no more than 0.1 mm from a flank, preferably no more than 0.01 mm from the flank. M. Each cutting section or secondary flank of a drill or drill bit (i.e., all cutting sections or all secondary flanks) may have one or more of the features listed above. N. A secondary open space width W M , measured from the cutting edge end 24 to the flank surface 42, can be between 5% and 10% of the cutting circle diameter D C (0.05 D C ≤ W M ≤ 0.10 D C ). A range of 6% ± 1% has been successfully tested. Brief description of the drawings

[0014] For a better understanding of the subject matter of the present application and to show how the same may be carried out in practice, reference is now made to the accompanying drawings, in which: Fig. 1A is a side view of a drill according to an embodiment of the subject matter of the present application; Fig. 1B is a front view or top view of a drill in Fig. 1A; Fig. 2A is a perspective side view of a drill head of the drill in Fig. 1A and Fig. 1B; Fig. 2B is a first side view of the drill head in Fig. 2A; Fig. 2C is a second side view of the drill head in Fig. 2A, rotated by 90° relative to the Fig. Illustration shown in Figure 2B; Fig. 3 is an enlarged view of the circled section of the drill head in Fig. 2C; Fig. 4 is a front view or plan view of the Fig. 2A shown drill head; Fig. 5A is a schematic view of a known embodiment that could occur in a region of a known tool similar to that shown in Fig. 4 corresponds to the circled area; Fig. Figure 5B is a schematic view of another embodiment that could occur in a region of a known tool similar to that shown in Fig. 4 circled area; and Fig. 5C is a schematic view of the Fig. 4 circled area. Detailed description

[0015] Reference is made to Fig. 1A and Fig. 1B, illustrating a drill 10 according to the subject matter of the present application.

[0016] The drill 10 may include a drill body 12 and a drill head 14 configured to be mounted to a drill body 12.

[0017] The drill 10 is intended for metal cutting or machining operations, and the drill head 14 is typically made of extremely hard and wear-resistant material, such as cemented carbide, either by compression molding and subsequent sintering of carbide powders in a binder or by powder transfer molding.

[0018] A central axis A C , by which the drill 10 is configured in a direction of rotation D R rotates, extends through the center of the drill body 12 and drill head 14 and can have a front-back direction D FR define.

[0019] With reference to Fig. 2A to 2C, the drill head 14 has a plurality of cutting sections 16 which are located behind a transverse cutting edge 17 of the drill head 14.

[0020] Each cutting section 16 has a chip surface 18, a flank surface 20 and a cutting edge 22 formed on an intersection line between the chip and flank surfaces 18, 20.

[0021] Also with reference to Fig. 4, the cutting edge 22 can extend from the cross cutting edge 17 backwards to a cutting edge end 24, which has a cutting circle diameter D C It is clear from the drawings that the use of the words “rear” or “backward” in the front-to-back direction D FR are not to be understood as strictly parallel to the central axis.

[0022] The rake face 18 is configured so that chips (not shown) from a workpiece (not shown) flow over it.

[0023] In Fig. 2B, a rake angle θ at the cutting edge end 24 is shown schematically.

[0024] The flank surface 20 can form an acute internal angle β with the rake surface 18, shown schematically, in order to relieve the load during drilling.

[0025] In this non-limiting example, the cutting edge 22 may have two cutting edge portions. For example, the cutting edge 22 may have: a minor cutting edge portion 22A extending rearwardly from the chisel edge 17, and a major cutting edge portion 22B extending from the minor cutting edge portion 22A to the cutting edge end 24. The minor cutting edge portion 22A also extends radially, as shown, while the major cutting edge portion 22B may form an obtuse internal angle α therewith. In any case, the minor cutting edge portions 22A are preferably one-third to one-quarter the length of the major cutting edges 22B.

[0026] The drill head 14 has a plurality of secondary flanks 26. The secondary flanks 26 are identical (as are the cutting sections 16), and therefore, reference is made below only to one of the secondary flanks 26.

[0027] Regarding rotational symmetry with special reference to Fig. 4, it should be noted that each cutting edge end 24 and / or each secondary flank 26 of the drill head is uniformly circumferentially spaced about the central axis A C are spaced apart (S A = S B ), to reduce an imbalance of forces when the secondary clearance surfaces 26 contact an inner surface of a hole (not shown).

[0028] With reference also to Fig. 4 and Fig. 5C, the secondary flank 26, at least in the vicinity of the flank 20, has a secondary flank end 28 which is located outside the cutting circle diameter D C and which is the furthest point of the secondary free area 26 from the central axis A C forms.

[0029] If we Fig. 5A and Fig. 5B, known designs are shown therein which serve to understand the subject matter of the present application. Each known drill 10A, 10B has a cutting diameter D CA , D CB , a cutting edge end 24A, 24B, a secondary flank 26A, 26B and a secondary flank end 28A, 28B. The known drill 10A in Fig. 5A is designed so that its secondary flank 26A extends along the cutting diameter D CA and consequently its secondary flank end 28a also corresponds to the cutting circle diameter D CA The well-known drill 10B in Fig. 5B is designed so that its secondary flank 26B is within the cutting diameter D CB and consequently its secondary flank end 28B is located within the cutting circle diameter D CB .

[0030] With reference only to Fig. 5C, the secondary flank surface 26 can extend from a cutting edge end 24 outside the cutting circle diameter D C More precisely, at a point (schematically shown with the reference number “30”) adjacent to the cutting end 24, the secondary flank is already outside the cutting circle diameter D C .

[0031] The secondary free area 26, in particular the secondary free area end 28, can extend over a projection distance D P of at least one micrometer (0.001 mm ≤ D P ) outside the cutting circle diameter D C extend.

[0032] Extensive tests have shown that a larger projection distance range D P , at least for certain cutting diameters D C is preferred. More specifically, recent tests have shown that for drills with a cutting diameter D C from 8 eight to nineteen millimeters (8 mm ≤ DC ≤ 19 mm) a better behavior at a projection distance D P from two to eight micrometers (0.002 mm ≤ D P ≤ 0.008 mm) outside the cutting circle diameter D C It was also found that drills with a cutting diameter D C from twenty to twenty-five millimeters (20 nm ≤ D C ≤ 25 mm) a better behavior at a projection distance D P from three to ten micrometers (0.003 mm ≤ D P ≤ 0.010 mm) outside the cutting circle diameter D C It is understood that drills can also be manufactured with diameters smaller than eight millimeters and larger than twenty-five millimeters. Although tests with other diameters have not yet been conducted, it is assumed, based on extrapolations from the above test results, that drills with a cutting diameter D Cless than eight millimeters a preferred projection distance D P from one to six micrometers (0.001 mm ≤ D P ≤ 0.006 mm). Similarly, according to projections, drills with a cutting diameter D C greater than twenty-five millimeters a preferred projection distance D P from four to twelve micrometers (0.004 mm ≤ D P ≤ 0.012 mm). Accordingly, a preferred range of projection distances D P from one to twelve micrometers (0.001 mm ≤ D P ≤ 0.012 mm). However, it should be noted that a maximum upper limit of the projection distance D P , where this concept no longer works, has not yet been found. Regardless of this, it should also be noted that it has been established that a free-field end extending over a projection distance D P of at least two micrometers (D P≥ 0.002 mm) outside a cutting circle diameter, has a better behavior than at least one micrometer (D P ≥ 0.001 mm). In any case, the successfully tested area and thus the most preferred tested area is a projection distance D P from two to ten micrometers (0.002 ≤ D P ≤ 0.010 mm), with even more preferred diameter-specific ranges being those described above.

[0033] The secondary flank 26 may have a convex curved shape (ie it extends continuously outside the cutting circle diameter D C in decreasing degree).

[0034] The secondary open space end 28 can be located in a secondary open space section 32 of the secondary open space 26.

[0035] With reference now to Fig. 3, the secondary flank section 32 extends between an upper boundary 33 at an intersection line between the flank 20 and the secondary flank 26 to an imaginary lower boundary 34 (which is located at an axial distance D A from 0.01 mm to 0.1 mm from the flank 20 or, more precisely, from the upper limit 33). It is understood that due to the receding geometry of the secondary flank 26, as perhaps best described in Fig. 2C and Fig. 3, the engagement between the drill head 14 and a hole to be drilled (not shown) is configured to extend to the imaginary lower boundary 34. In other words, the secondary flank portion 32 may be the only portion of the secondary flank 26 configured to contact a hole (not shown), but it should be understood that, due to tolerances, additional portions of the secondary flank 26 may also contact the hole.

[0036] Accordingly, it is understood that, although the example shown has a preferred geometry, the entire secondary flank 26 could be formed entirely by a surface shown as the secondary flank portion 32. In this case, the cutting portion 16 could extend radially inward at axial locations lower than the secondary flank portion 32 (not shown).

[0037] In any case, the secondary flank 26 has a secondary flank edge 36 which extends along an intersection line between the secondary flank 26 and the rake face 18. The secondary flank 26, as in Fig. 2C and Fig. 3, can be designed with a receding geometry.

[0038] In each cross-section taken at the axial locations which are not adjacent to the flank 20 (ie which are axially spaced from the flank 20; random axial locations are used at the locations designated 38 and 40 merely for exemplary purposes), the secondary flank 26 has a shape similar to the shape of the secondary flank portion 32 and as shown in the Fig. 3 and Fig. 5C shown.

[0039] The secondary flank 26 extends from the secondary flank edge 36 to the secondary flank end 28. The secondary flank end 28 can be located at an intersection line between the flank surface 42 and the secondary flank 26.

[0040] A secondary open space width W M , measured from the cutting edge end 24 to the flank surface 42, can be between 5% and 10% of the cutting circle diameter D C (0.05 D C ≤ W M ≤ 0.10 D C ).

[0041] The flank surface 42 may extend inwardly towards the drill head 14. In any case, as shown in Fig. 5C, the flank surface 42 from a location outside the cutting circle diameter D C up to a point within the cutting circle diameter D C . In other words, the flank surface 42 is configured to fulfill a relief function (ie, it can be considered as a relief surface).

[0042] An outside diameter flank surface 44 may extend circumferentially from the flank surface 42 in a direction away from the cutting edge end 24. The outside diameter flank surface 44 may be located entirely within the cutting diameter D C condition.

[0043] The above description contains an embodiment and details and does not exclude embodiments and details not listed from the claimed scope of the present application.

Claims

[1] Drill (10) configured for drilling ductile materials, having a central axis (A C ) defining a front-to-back direction, and having a drill body (12) and a removable drill head (14): wherein the drill head (14) comprises: several cutting sections (16); wherein each cutting section (16) comprises: a chip surface (18); an open space (20); a cutting edge (22) formed at an intersection line between the chip and flank surfaces (18, 20) and extending rearwardly to a cutting edge end (24) and thereby having a cutting circle diameter (D C ) of the drill (10); and a secondary clearance surface (26) extending rearwardly from the clearance surface (20) and also extending from the rake surface (18); where: each secondary flank (26) starting from the cutting edge end (24) is outside the cutting circle diameter (DC ) extends; each secondary flank (26) has a secondary flank end (28) adjacent to the flank (20) and is located outside the cutting circle diameter (D C ) is located; the secondary flank end (28) is located at an intersection line between a flank surface (42) and the secondary flank (26); the flank surface (42) extends inwards from a point outside the cutting circle diameter (D C ) to a point within the cutting circle diameter (D C ) to provide a relief function; and an outer diameter clearance surface (44) extends along a circumference of the flank surface (42) in a direction away from the cutting edge end (24) and is located entirely within the cutting circle diameter (D C ) is located. [2] Drill (10) according to claim 1, wherein each cutting portion (16) further comprises a secondary flank edge (36) extending along an intersection line between each secondary flank edge (26) and the rake face (18), and each secondary flank edge (26) extending from the secondary flank edge (36) extends outside the cutting circle diameter (D C ) extends. [3] Drill (10) according to claim 1 or 2, wherein the distance from the cutting circle diameter (D C ) is continuously increased up to the end of the secondary open space (28). [4] Drill (10) according to claim 3, wherein the continuous increase in distance occurs in a decreasing degree. [5] Drill (10) according to one of claims 1 to 4, wherein each secondary flank (26) at each axial location is outside the cutting circle diameter (D C ) by a lead distance (D P) extends within the same area as the secondary free area end (28). [6] Drill (10) according to claim 5, wherein each secondary flank end (28) is outside the cutting circle diameter (D C ) by a lead distance (D P ), where the condition 0.001 mm ≤ D P ≤ 0.012 mm is met. [7] Drill (10) according to claim 5 or 6, wherein each secondary flank end (28) is outside the cutting circle diameter (D C ) by a lead distance (D P ) of at least two micrometers, where the condition D P ≥ 0.002 mm is met. [8] Drill (10) according to claim 7, wherein each secondary flank end (28) is outside the cutting circle diameter (D C ) by a lead distance (D P ) from two to ten micrometers, where the condition 0.002 ≤ D P ≤ 0.010 mm is met. [9] Drill (10) according to one of claims 1 to 4, wherein: (a) the cutting circle diameter (D C ) is smaller than eight millimeters (D C < 8 mm) and each secondary flank end (28) is outside the cutting circle diameter (D C ) by a lead distance (D P ) from one to six micrometers (0.001 mm ≤ D P ≤ 0.006 mm); or (b) the cutting circle diameter (D C ) eight to nineteen millimeters (8 mm ≤ D C ≤ 19 mm) and each secondary flank end (28) is outside the cutting circle diameter (D C ) by a lead distance (D P ) from two to eight micrometers (0.002 mm ≤ D P ≤ 0.008 mm); or (c) the cutting circle diameter (D C ) from twenty to twenty-five millimeters (20 mm ≤ D P ≤ 25 mm) and each secondary flank end (28) is outside the cutting circle diameter (D C) by a lead distance (D P ) from three to ten micrometers (0.003 mm ≤ D P ≤ 0.010 mm); or (d) the cutting circle diameter (D C ) is greater than twenty-five millimeters (D C > 25 mm) and outside the cutting circle diameter (D C ) by a lead distance (D P ) from four to twelve micrometers (0.002 mm ≤ D P ≤ 0.008 mm). [10] Drill (10) according to one of claims 1 to 9, wherein each secondary flank (26) extends over an axial distance which is not more than 0.1 mm from the flank (20), preferably not more than 0.01 mm from the flank (20). [11] Drill (10) according to one of claims 1 to 10, wherein each secondary flank (26) has a secondary flank portion (32) which is the only portion of the secondary flank (26) having an end extending outside the cutting circle diameter (D C), wherein the secondary flank section (32) extends over an axial distance which is not more than 0.1 mm from the flank (20), preferably not more than 0.01 mm from the flank (20). [12] Drill (10) according to one of claims 1 to 11, wherein each cutting edge end (24) is circumferentially bent about the central axis (A C ) is evenly spaced. [13] Drill (10) according to one of claims 1 to 12, wherein the cutting edge (22) at the cutting edge end (24) has a rake angle (θ) of twenty to thirty degrees, the condition 20° ≤ θ ≤ 30° being met. [14] Drill (10) according to one of claims 1 to 13, wherein a secondary flank width (W M ), measured from the cutting edge end (24) to the flank surface (42), between 5% and 10% of the cutting circle diameter (D C ), where the condition 0.05D C ≤ W M ≤ 0.10D C is fulfilled. [15] Drill (10) according to one of claims 1 to 14, wherein each of the cutting edges (22) has a secondary cutting edge portion (22A) and a main cutting edge portion (22B) extending from the secondary cutting edge portion (22A), wherein the secondary cutting edge portions (22A) are preferably one-third to one-quarter the length of the main cutting edges (22B). [16] Drill (10) according to one of claims 1 to 15, wherein the secondary flank (26) is formed with a receding geometry.

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