Step drill and method for drilling a hole in a workpiece by using a step drill - Patent Application 20070122997

Abstract

A step drill and a method for drilling a hole in a workpiece by using the step drill, the step drill having a hole-cutting portion (3) and at least two flutes (5, 5') extending on the hole-cutting portion, the hole-cutting portion (3) having step sections, each step section and the at least two flutes (5, 5') forming at least two cutting edges (An, An') distributed in the circumferential direction of the step section, the at least two cutting edges on at least one of the step sections having at least a first cutting edge (An) and a second cutting edge (An'), each of the first cutting edge (An) and the second cutting edge (An') being arranged in at least two segments. The drill bit is constructed with a first cutting edge (An) and a second cutting edge (An'), each of which therefore comprises at least two cutting edge segments, and the first cutting edge (An) and the second cutting edge (An') are at least partially different from each other in the structure of their cutting edge segments, or one of the first cutting edge (An) and the second cutting edge (An') is formed in one segment, while the other cutting edge is formed in at least two segments, and a method for drilling a hole in a workpiece by using a stepped drill comprises cutting a first material portion on the workpiece using the first cutting edge (An) and cutting a second material portion on the workpiece using the second cutting edge (An'). By changing the cutting length and the angle value of the cutting angle of the cutting edges of the drill bit, the cutting force is reduced and the cutting sharpness is improved.

Description

[Technical Field]

[0001] The present invention relates to a step drill and a method for drilling a hole in a workpiece by using a step drill. [Background technology]

[0002] A stepped drill is a type of pagoda-shaped drill bit consisting of a drill point, an adjacent reaming section with a stepped profile, and a shank. Its shape gives it the name "step drill." The stepped profile is formed by multiple step sections that increase in size in the feed direction, each step section including a frusto-conical section and an adjacent cylindrical section. A stepped drill has at least one flute, chip flute, or cutting flute on its drill point and reaming section, which intersects with the surface of the frusto-conical section to form a reaming major cutting edge. Therefore, multiple flutes on the same frusto-conical surface form multiple reaming major cutting edges.

[0003] The step drill has the following machining process: start the step drill, drill an initial small hole with the drill tip, and then ream it in stages to obtain the required hole diameter. By using one step drill, holes with multiple diameters can be drilled (or reamed) once the workpiece is chucked.

[0004] An ideal choice for drilling holes in sheet metal, the step drill is suitable for cutting non-ferrous metals with a thickness of 1.5mm, plastic or wood with a maximum thickness of 4.0mm, and steel plate with a thickness of 4.0mm.

[0005] 1, a prior art step drill 100 generally has two symmetrical oblique flutes, or more specifically, helical flutes 105, 105' (as shown in FIG. 1) or straight flutes (not shown), and each reaming main cutting edge A'n on each step section T'n of the step drill 100 is one single segment, i.e., one single straight segment (when the flutes are straight flutes) or one single curved segment (when the flutes are oblique flutes, or more specifically, helical flutes 105, 105'). FIG. 1 shows a one-segment curved section for oblique flutes, or more specifically, helical flutes 105, 105'.

[0006] 1 and 2, the main cutting edges on the first helical flute 105 are A'1, A'2...A'i...A'n, respectively. Typical cutting angles of the cutting edges on the first helical flute 105 are rake angle γn, clearance angle αn, edge inclination angle (helical angle) β, and depth of cut and auxiliary angle λ, and these cutting angles are distributed according to determined design rules and requirements.

[0007] The main cutting edges on the second helical flute 105' (which are distributed symmetrically at 180° around the first helical flute 105 on the circumference) are designated A'1', A'2'...A'i'...A'n', respectively, and are identical in structure to the corresponding main cutting edges on the first helical flute 105, i.e., A'1'=A'1, A'2'=A'2, ..., A'i'=A'i, A'n'=A'n. Also, the typical cutting angles of the cutting edges on the second helical flute 105' are the rake angle γn', clearance angle αn', cutting inclination angle (helical angle) β', and depth of cut and auxiliary angle λ', which are distributed according to the same design rules and requirements as for the first helical flute 105, i.e., γn'=γn, αn'=αn, β'=β, λ'=λ.

[0008] That is, the main cutting edges on each step section T'n, which are symmetrical by 180° in the circumferential direction, are the same, and as a result, their cutting functions are also the same. With this in mind, referring to the shaded area shown in Figure 10, this shaded area indicates the cutting area of each main cutting edge on the same step section T'n, and this cutting area has a cutting depth of f / 2 and a cutting length A'n corresponding to the total length A'n of the main cutting edges. The cutting area cut by each main cutting edge is exactly the same, and all main cutting edges cut over the entire cutting length A'n.

[0009] However, in practice, it has been found that the conventional step drill with the above design has several problems, such as large cutting force, poor cutting sharpness, difficult chip breaking, high cutting heat and low machining efficiency. Summary of the Invention

[0010] Therefore, the present invention is intended to provide a step drill and a method for drilling a workpiece by using a step drill, which can solve at least one of the above technical problems existing in the prior art.

[0011] According to one aspect of the present invention, the operation is carried out according to a stepped drill, the stepped drill having a hole-making portion and at least two flutes extending on the hole-making portion, the hole-making portion comprising one or more step sections, each step section and the at least two flutes forming at least two cutting edges distributed in the circumferential direction of the step section; the at least two cutting edges on at least one of the step sections include at least a first cutting edge and a second cutting edge; the first cutting edge and the second cutting edge are each constructed in at least two segments, thus each including at least two cutting edge segments, and the first cutting edge and the second cutting edge differ from each other at least in part in the structure of their cutting edge segments; or One of the first cutting edge and the second cutting edge is formed in one segment, while the other cutting edge is formed in at least two segments, and thus includes at least two cutting edge segments.

[0012] In the present invention, the term "structure" should be understood broadly and may include geometric structures or parameters such as the geometric shape (e.g., straight or curved blade, cutting depth / auxiliary angle λ, etc.), size or number of each cutting edge segment / cutting edge segments.

[0013] The technical effects that this drill can bring include, but are not limited to, changing the initial one-section linear cutting edge to a multi-segment cutting edge with at least two sections, and the overall length of the cutting edge is greater than the overall length of the initial cutting edge, thereby decomposing the cutting force borne (loaded) per unit cutting edge length and dispersing the cutting heat. The multi-segment cutting edge and the multi-segment cutting edge or one-segment cutting edge can be combined with each other to create a compound cutting effect, thus cutting material in multiple segments, thereby serving to decompose the cutting. The cutting area borne by each cutting edge is small, and as a result, only reduced cutting force is required during cutting.

[0014] Advantageously, the first cutting edge is only partially involved in cutting on its first extension segment, the radial distance of the first extension segment from the longitudinal axis of the step drill being greater than the radial distance of a segment of the second cutting edge from the longitudinal axis of the step drill, which is in the same axial position as the first extension segment; The second cutting edge is only partially involved in cutting on its second extension segment, and the radial distance of the second extension segment from the longitudinal axis of the stepped drill is greater than the radial distance of a segment of the first cutting edge that is at the same axial position as the second extension segment from the longitudinal axis of the stepped drill.

[0015] Advantageously, the first extension segment includes at least one first cutting edge cutting area, and the second extension segment includes at least one second cutting edge cutting area, and under a hypothetical condition in which the first cutting edge and the second cutting edge are joined by rotating around the longitudinal axis of the stepped drill, the first cutting edge cutting area and the second cutting edge cutting area are adjacent to each other in the axial or radial direction of the stepped drill.

[0016] Advantageously, the first extension segment includes at least two first cutting edge cutting areas spaced apart from each other, and the second extension segment includes at least one second cutting edge cutting area, and under a hypothetical condition in which the first cutting edges and the second cutting edges are joined by rotating around the longitudinal axis of the stepped drill, the one second cutting edge cutting area is located between the two first cutting edge cutting areas in the axial or radial direction of the stepped drill.

[0017] Advantageously, the at least two-segment first cutting edge and / or second cutting edge comprises first cutting edge segments and second cutting edge segments arranged consecutively with respect to the feed direction, and the first cutting edge segments and second cutting edge segments of the at least two-segment first cutting edge differ from each other in infeed / auxiliary angles with respect to the feed direction, and / or the first cutting edge segments and second cutting edge segments of the at least two-segment second cutting edge differ from each other in infeed / auxiliary angles with respect to the feed direction.

[0018] Advantageously, in a virtual state in which the first cutting edge and the second cutting edge are united by rotating around the longitudinal axis of the stepped drill, the first cutting edge segment and / or the second cutting edge segment of the at least two-segment first cutting edge intersects with the first cutting edge segment and / or the second cutting edge segment of the at least two-segment second cutting edge, or the one-segment cutting edge of one of the first and second cutting edges is connected with the first cutting edge segment and / or the second cutting edge segment of the other at least two-segment cutting edge.

[0019] Advantageously, the first cutting edge segments of the at least two-segment first cutting edge and the first cutting edge segments of the at least two-segment second cutting edge differ from each other in cutting / supplementary angles relative to the feed direction, and the second cutting edge segments of the at least two-segment first cutting edge and the second cutting edge segments of the at least two-segment second cutting edge differ from each other in cutting / supplementary angles relative to the feed direction, or The one-segment cutting edge of one of the first and second cutting edges and the first and / or second cutting edge segments of the other at least two-segment cutting edge have different cutting depth / auxiliary angles relative to the feed direction.

[0020] Advantageously, the length of the first cutting edge segment of the at least two-segment first cutting edge is smaller than the length of the at least two-segment second cutting edge, and the radial distance from the first cutting edge segment of the at least two-segment first cutting edge to the longitudinal axis of the stepped drill is greater than the radial distance from the first cutting edge segment of the at least two-segment second cutting edge to the longitudinal axis of the stepped drill at the same axial position.

[0021] Advantageously, at least one of the cutting edge segments of the at least two-segment first cutting edge or the second cutting edge may be formed by locally reducing material on an initial one-segment cutting edge.

[0022] Advantageously, each cutting edge segment of the at least two-segment first cutting edge and / or second cutting edge is constructed as a straight section or a curved section.

[0023] Advantageously, at least one of the horizontal blade segments adjacent to the first cutting edge is offset a distance in the radial direction from at least one of the horizontal blade segments adjacent to the second cutting edge.

[0024] Advantageously, the cutting edges formed by the same groove on different step sections are at least partially different in construction or identical.

[0025] Advantageously, the grooves are configured as straight grooves or helical grooves.

[0026] According to another aspect of the invention, operations are performed according to a method for drilling a hole in a workpiece by using a stepped drill, the stepped drill having a hole-drilling portion and at least two flutes extending on the hole-drilling portion, the hole-drilling portion comprising one or more step sections, each step section and the at least two flutes defining at least two cutting edges distributed in a circumferential direction of the step section, the at least two cutting edges on at least one of the step sections comprising at least a first cutting edge and a second cutting edge; The method comprises: cutting a first material portion on the workpiece using a first cutting edge, wherein the first material portion extends over only a portion of the length of the first cutting edge; The method includes at least the step of cutting a second material portion on the workpiece using the second cutting edge, wherein the second material portion extends over only a portion of the length of the second cutting edge.

[0027] Advantageously, the first material portion comprises at least one first sub-material portion and the second material portion comprises at least one second sub-material portion adjacent to the first sub-material portion.

[0028] Advantageously, the first material portion comprises at least two first sub-material portions spaced apart from one another, and the second material portion comprises at least one second sub-material portion located between the two first sub-material portions.

[0029] Advantageously, the step drill is a step drill according to the invention.

[0030] Those skilled in the art will appreciate the advantages of the corresponding embodiments, as well as various additional embodiments, by reading the following detailed description of the corresponding embodiments with reference to the drawings included below.

[0031] Embodiments of the present invention will now be described with reference to the accompanying drawings. These drawings do not necessarily depict embodiments to scale; rather, the drawings used for illustration are implemented in a schematic manner and / or in slightly modified form. For additional aspects of the teachings that can be directly identified from the drawings, reference may be made to the relevant prior art. It should be noted here that various modifications and variations in the form and details of the embodiments may be made without departing from the general concept of the present invention. The features of the present invention disclosed in this specification and in the drawings may be essential to the modified solution of the present invention, either individually or in any combination. In addition, all combinations consisting of at least two of the features disclosed in this specification and / or in the drawings are within the scope of the present invention. The general concept of the present invention is not limited to the exact form or details of the preferred embodiments described and shown below.

[0032] The drawings include the following figures: [Brief explanation of the drawings]

[0033] [Figure 1] FIG. 1 is a schematic side view of a prior art step drill. [Figure 2] FIG. 2 is an enlarged schematic partial cross-sectional view of the stepped drill shown in FIG. 1 taken along the cross-sectional line NN. [Figure 3] FIG. 3 is a schematic side view of a step drill having a compound cutting edge according to the present invention. [Figure 4] FIG. 4 is a schematic enlarged partial cross-sectional view of the step drill having the composite cutting edge shown in FIG. 3 taken along the section line Ni-Ni. [Figure 5] FIG. 5 is a schematic enlarged view of a portion I of the step drill having a compound cutting edge shown in FIG. [Figure 6]FIG. 6 is a schematic enlarged view of part II of the step drill having the compound cutting edge shown in FIG. 3, in which the first cutting edge of FIG. 5 is merged with the second cutting edge after being rotated 180° around the longitudinal axis of the step drill. [Figure 7] FIG. 7 is a schematic diagram showing the second cutting edge of part II of a step drill having a compound cutting edge as shown in FIG. 3 after being rotated 180° around the longitudinal axis of the step drill and merging with the first cutting edge of part I. [Figure 8] FIG. 8 is a schematic view of the first cutting edge of FIG. 7, with the two first extension segments indicated by hatching. [Figure 9] FIG. 9 is a schematic view of the second cutting edge of FIG. 7, with one second extension segment indicated by hatching. [Figure 10] FIG. 10 is a schematic diagram showing the cutting of two cutting edges or teeth of a prior art step drill, where the cutting area of each cutting edge is indicated by hatching. [Figure 11] FIG. 11 is a schematic diagram showing one embodiment of compound cutting with one-segment cutting edges and multi-segment cutting edges on a step section, where one cutting area of each cutting edge is indicated by hatching. [Figure 12] FIG. 12 is a schematic diagram showing another embodiment of compound cutting with one-segment cutting edges and multi-segment cutting edges on a step section, where one and two cutting areas of each cutting edge are indicated by hatching. [Figure 13] FIG. 13 shows a schematic diagram of another embodiment of a combination of cutting edges on the n-th step section Tn of a step drill. [Figure 14] FIG. 14 shows a schematic diagram of another embodiment of a combination of cutting edges on the n-th step section Tn of a step drill. [Figure 15] FIG. 15 shows a schematic diagram of another embodiment of a combination of cutting edges on the n-th step section Tn of a step drill. [Figure 16]FIG. 16 shows a schematic diagram of another embodiment of a combination of cutting edges on the n-th step section Tn of a step drill. [Figure 17] FIG. 17 shows a schematic diagram of another embodiment of a combination of cutting edges on the n-th step section Tn of a step drill. [Figure 18] FIG. 18 shows a schematic diagram of another embodiment of a combination of cutting edges on the n-th step section Tn of a step drill. [Figure 19] FIG. 19 shows a schematic diagram of another embodiment of a combination of cutting edges on the n-th step section Tn of a step drill. DETAILED DESCRIPTION OF THE INVENTION

[0034] An exemplary embodiment of a step drill 1 with a composite cutting edge according to the present invention is described below. In this description, for purposes of explanation only, various systems, structures, and devices are schematically illustrated in the drawings, but not all features of actual systems, structures, and devices are described. For example, well-known functions or structures are not described in detail to avoid unnecessary detail that obscures the present invention. Of course, it should be understood that in any actual application, many specific implementation decisions must be made to achieve the specific goals of a developer or user and must comply with system-related and industry-related constraints. These specific goals may vary depending on the actual application. In addition, it should be understood that making such specific implementation decisions can be complex and time-consuming, but this is a routine task for those skilled in the art who would benefit from the present invention.

[0035] The terms and phrases used herein should be understood and interpreted to have a meaning consistent with the understanding of those terms and phrases by those skilled in the relevant art. Consistent use of a term or phrase herein is not intended to imply a particular definition of the term or phrase, i.e., a definition that is different from the ordinary and customary meaning as understood by those of ordinary skill in the art. For any term or phrase intended to have a special meaning, i.e., a meaning that is different from that understood by those of ordinary skill in the art, this special definition will be expressly set forth herein by definition, directly and unambiguously giving the term or phrase a special definition.

[0036] Unless the context otherwise requires, throughout the following description, the word "comprising" and its variations such as "including" are to be interpreted in their open and inclusive sense, i.e., "including but not limited to."

[0037] Throughout this description, references to terms such as "one embodiment," "one embodiment," "some embodiments," "example," "particular examples," or "some examples" are intended to mean that the particular feature, structure, material, or characteristic described with reference to the embodiment(s) or example(s) is included in at least one embodiment or example of the invention. Thus, the appearances of the phrase "in one embodiment" or "in one embodiment" in various places throughout this specification do not necessarily refer to a single embodiment. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

[0038] Additionally, terms such as "first," "second," and similar terms are used for descriptive purposes only and may not be construed as indicating or implying relative importance or as implying the number of technical features. Thus, a feature defined as "first," "second," etc. may explicitly or implicitly include one or more of the features. In the present description, "plurality" means two or more, unless otherwise specified.

[0039] With reference to schematic figures 3 to 12, an exemplary embodiment of a step drill 1 with compound cutting edges (hereinafter referred to as step drill 1) according to the present invention will be described below.

[0040] Referring to FIG. 3 , a step drill 1 may include a drill tip 2 for drilling holes, an adjacent reaming portion 3 for reaming, and a shank portion 4. The drill tip 2 and the reaming portion 3 may together form the working portion of the step drill 1 for drilling holes and reaming. The reaming portion 3 may include multiple step sections Tn (n=1, 2, 3, ..., i, ...) successively adjacent to one another, each step section Tn including a frusto-conical section and an adjacent cylindrical section. The step sections Tn may operate in groups to perform a stepped reaming function. Each step section Tn has a diameter that gradually increases from the drill tip 2 with respect to the feed direction F. In FIG. 3 , the diameter dn of the nth step section Tn (specifically, its cylindrical section) rearward in the feed direction f and the diameter di of the ith step section Ti (specifically, its cylindrical section) forward in the feed direction f are exemplarily given, from which it can be seen that dn>di.

[0041] Here, the cutting portion may be provided with two flutes 5, 5' configured as chip flutes: a first flute 5 having a substantial portion facing outward from the plane of the drawing page, and a second flute 5' having a substantial portion facing inward from the plane of the drawing page. The first flute 5 and the second flute 5' may extend spirally from one end of the cutting portion to the other and may be radially or rotationally symmetrical with each other in the circumferential direction about the longitudinal axis 6 of the step drill 1. On each step section Tn, the first flute 5 may intersect with the truncated cone section of the step section Tn to form a first cutting edge An (illustrated by a thick solid line in FIGS. 5 to 9), and the second flute 5' may intersect with the truncated cone section of the step section Tn to form a second cutting edge An' (illustrated by a thick dotted line in FIGS. 5 to 9) circumferentially spaced apart from the first cutting edge An. Therefore, two cutting edges An and An' may be formed on each step section Tn, and each of the two cutting edges An and An' may have a cutting depth of f / 2.

[0042] In other embodiments, three or more grooves 5, 5' may be provided on the machining portion, and these grooves 5, 5' may be evenly distributed in the circumferential direction and rotationally symmetrical around the longitudinal axis 6, so that three or more cutting edges An, An' may be formed on each step section Tn.

[0043] In another embodiment, each flute 5, 5' may be configured as a straight flute, i.e. extending in a straight line from one end of the working part to the other, thus forming a cutting edge in the form of a straight section.

[0044] Unlike the prior art, each cutting edge An, An' on at least one step section Tn of the step drill 1 of the present invention may have a multi-segment structure, more precisely, a broken-line structure, i.e., each cutting edge An, An' may include at least two cutting edge segments An1, An2, An1', An2' that are consecutively adjacent to each other, and these cutting edge segments may together form the entire cutting edge An, An'.

[0045] In the case of a straight groove, each cutting edge segment An1, An2, An1', An2' can be configured as a straight section. In the case of a curved groove 5, each cutting edge segment An1, An2, An1', An2' can be formed as a curved section. However, in the present invention, since the small cutting edges An and An' are essentially designed to be composed of multiple smaller cutting edge segments An1, An2, An1', An2', they can also be realized as straight sections by using a machining process according to specific functional requirements. In the present invention, regardless of whether the groove is straight or curved, each cutting edge segment An1, An2, An1', An2' can be remachined into a straight section or an arc-shaped curved section with a different radius of curvature according to specific requirements. That is, each cutting edge can be composed of only straight cutting edge segments, only curved cutting edge segments, or a combination of straight and curved cutting edge segments. Straight or curved cutting edge segments An1, An2, An1', An2' are all within the scope of protection of the present invention, and the concept of the present invention can also be applied to straight or curved cutting edges or cutting edges of any other shape. For ease of understanding, only simplified straight cutting edge segments An1, An2, An1', An2' will be described below.

[0046] As described above, adjacent cutting edge segments An1, An2, An1', An2' of each cutting edge An, An' may be angled relative to one another to form a section of a multi-segment line (i.e., multi-straight or multi-curved line), or the adjacent cutting edge segments may form an abrupt change or transition point at their adjacent locations, or the adjacent cutting edge segments may have different inclinations relative to one another.

[0047] In this embodiment, cutting edge segments of a straight section are taken as an example, that is, each cutting edge An, An' on each step section may include multiple straight cutting edge segments An1, An2, An1', An2', and these straight cutting edge segments may jointly form the cutting edge An, An' in the form of a multi-segment line. In this embodiment, the number of cutting edge segments An1, An2, An1', An2' of each cutting edge An, An' on each step section Tn may be two, that is, a front first cutting edge segment An1, An1' and a rear second cutting edge segment An2, An2' in the feed direction F.

[0048] 3, for the ith step section Ti, the first cutting edge Ai thereon may include a first cutting edge segment Ai1 followed by a second cutting edge segment Ai2, which may be of different lengths and may be at an angle relative to each other. The blade inclination angle (helical angle) βi can be seen in FIG.

[0049] 4 shows a partial enlarged view of the first cutting edge on the step section at a point on the cutting edge (specifically, the cutting edge of the first cutting edge segment) taken along the section line Ni-Ni in FIG. 3, where γni is the normal rake angle and αni is the normal relief angle. The cutting angle and cutting force borne at each point on the cutting edge are also different, which can be used to analyze the cutting principle of the cutting tool.

[0050] The structures of the first cutting edge An and the second cutting edge An' on the n-th step section Tn and their combined cutting method will be exemplarily described below with reference to FIGS.

[0051] 5, the first cutting edge An on the nth step section Tn is indicated by a thick solid line and may include a first cutting edge segment An1 in the forward direction of feed F and a second cutting edge segment An2 in the rearward direction of feed F. The lengths of the first cutting edge segment An1 and the second cutting edge segment An2 may be different from each other, specifically, the former may be smaller than the latter, and may form an angle, here an obtuse angle, with each other so that they may collectively form a two-segment multi-section wire blade.

[0052] The second cutting edge segment An2 may be formed by reducing material, such as by cutting away material, at an upper portion of the initial one-segment cutting edge A'n, while the first cutting edge segment An1 may then be formed by the cutting edge portion remaining after cutting away part of the material, such that the cutting edge angle λn1 of the first cutting edge An at the first cutting edge segment An1 remains unchanged compared to the cutting edge angle λn0 of the one-segment cutting edge A'n, while the supplementary angle λn2 of the first cutting edge An at the second cutting edge segment An2 is reduced compared to λn0 or λn1, i.e., λn2<λn1=λn0.

[0053] Also, as can be seen from FIG. 5, the length An1 of the first cutting edge segment An1 of the first cutting edge An and the length An2 of the second cutting edge segment An2 are both smaller than the length A'n of the first cutting edge A'n of the initial one-segment type, but the sum of the two is clearly larger than the length A'n of the first cutting edge A'n of the initial one-segment type, i.e., An1 <An2<A’nであり、An1+An2> It is A'n.

[0054] 6, a combined comparison is made between a first cutting edge An, shown by a thick solid line, and a second cutting edge An', shown by a thick dotted line, after being rotated 180° around the longitudinal axis 6 of the step drill as shown in FIG. 5. The second cutting edge An' may include a first cutting edge segment An1' leading in the feed direction F and a second cutting edge segment An2' trailing in the feed direction F. The lengths of the first cutting edge segment An1' and the second cutting edge segment An2' of the second cutting edge An' may be different from each other, specifically, the former may be smaller than the latter, and they may form an angle, here an obtuse angle, with each other so that they collectively form a two-segment multi-segment wire cutting edge An'. The length An1' of the first cutting edge segment An1' of the second cutting edge An' and the length An2' of the second cutting edge segment An2' are both smaller than the length A'n of the first cutting edge A'n of the initial one-segment type, but the sum of the two is clearly greater than the length A'n of the first cutting edge A'n of the initial one-segment type, i.e., An1' <An2’<A’nであり、An1’+An2’> It is A'n.

[0055] Referring to FIG. 7, a combined comparison is made between the second cutting edge An′, illustrated by the thick solid line, and the first cutting edge An, illustrated by the thick dotted line, after being rotated 180° about the longitudinal axis 6 of the stepped drill as shown in FIG. 5.

[0056] Referring to Figures 6 and 7, a combined comparison between the two cutting edges An and An' can better illustrate the different structures of the two cutting edges and how they can be used in combination to form a "compound edge" for compound cutting.

[0057] Referring to Fig. 7, the first horizontal blade section in the forward direction in the feed direction F adjacent to the first cutting edge segment An1 of the first cutting edge An may be parallel to the first horizontal blade section in the forward direction in the feed direction F adjacent to the first cutting edge segment An1' of the second cutting edge An'. The former may be separated from the longitudinal axis 6 by a distance δ more than the latter. The first cutting edge segment An1 of the first cutting edge An may be parallel to the first cutting edge segment An1' of the second cutting edge An'. At the same axial position, the former may be separated from the longitudinal axis 6 by a distance δ more than the latter. The length An1 of the first cutting edge segment An1 of the first cutting edge An may be smaller than that of the first cutting edge segment An1' of the second cutting edge An', that is, An1 < An1'. Therefore, the first cutting edge segment An1' of the second cutting edge An' may intersect the second cutting edge segment An2 of the first cutting edge An.

[0058] The cutting angle λn1 of the first cutting edge segment An1 of the first cutting edge An is equal to the cutting angle λn1' of the first cutting edge segment An1' of the second cutting edge An' and is also equal to the cutting angle λn0 of the initial one-segment type first cutting edge A'n, that is, λn1 = λn1' = λn0.

[0059] Also, the second horizontal blade section in the forward direction in the feed direction F adjacent to the second cutting edge segment An2 of the first cutting edge An may be parallel to the second horizontal blade section in the rearward direction in the feed direction F adjacent to the second cutting edge segment An2' of the second cutting edge An'. The former may be separated from the longitudinal axis 6 by a distance δ more than the latter. The second cutting edge segment An1' of the second cutting edge An' may intersect the second cutting edge segment An2 of the first cutting edge An.

[0060] The cutting edge angle λn2 of the second cutting edge segment An2 of the first cutting edge An is greater than the cutting edge angle λn2' of the second cutting edge segment An2' of the second cutting edge An', and both of these cutting edges are smaller than the cutting edge angle λn1 of the first cutting edge segment An1 of the first cutting edge An, or the cutting edge angle λn1' of the first cutting edge segment An1' of the second cutting edge An', or the cutting edge angle λn0 of the initial one-segment first cutting edge A'n, i.e., λn2'<λn2<λn1=λn1'=λn0.

[0061] Thus, referring to FIG. 8 , the first cutting edge An′ may extend axially outward partially beyond the second cutting edge An′ (compared at the same axial position) due to its first extension sections S1, S2, which may be two planar sections S1, S2 separated from each other. The two first extension sections S1, S2 of the first cutting edge An are indicated by hatching, and they form two spaced-apart first cutting edge cutting areas S1, S2. The feed rate during drilling is f=mm / rpm (mm / revolution). The cutting depth of the first extension sections S1, S2 is a maximum of f / 2. The cutting areas S1, S2 of the first cutting edge may extend only over a portion of the length of the first cutting edge An. The cutting areas S1, S2 of the first cutting edge may correspond to the cross-sectional area of the material or chips cut by the first cutting edge An in each rotation.

[0062] Here, the cutting of the first cutting edge An is based on the cutting of the second cutting edge An', and the two first cutting edge cutting areas S1 and S2 of the first cutting edge An form two cutting areas S1 and S2 with different shapes, so that the total area S cut by the first cutting edge An can be: S = S1 + S2. The two cutting areas S1 and S2 can be separated from each other so as to create a strict chip-shunting effect when the first cutting edge An cuts. In addition, the residual burr (not shown) left after the cutting process by the second cutting edge An' can also be cut off by the first cutting edge An, in which case the total area S cut by the first cutting edge An can be: S = S1 + S2 + residual burr area.

[0063] Referring to FIG. 9 , the second cutting edge An′ can extend axially outward partially beyond the first cutting edge An′ (compared at the same axial position) by its second extension section S3, which can be a single planar triangular section S3 here. The second extension section S3 of the second cutting edge An′ is indicated by hatching and forms a second cutting edge cutting area S3. The feed rate during drilling is f=mm / rpm (mm / revolution). The cutting depth of the second extension section S3 is a maximum of f / 2. The second cutting edge cutting area S3 can extend over only a portion of the length of the second cutting edge An′. The second cutting edge cutting area S3 can correspond to the cross-sectional area of the material or chips cut by the second cutting edge An′ in each rotation.

[0064] Here, the cutting of the second cutting edge An' is based on the cutting of the first cutting edge An, and the second cutting edge cutting area S3 of the second cutting edge An forms a single cutting area S3, so that the total area S' cut by the first cutting edge An can be: S'=S3. The second cutting edge An' cannot produce a chip shunting effect when cutting, where S>S'.

[0065] The size and number of the cutting regions or cutting areas S1, S2, S3 of the first cutting edge An and the second cutting edge An' are not limited to this embodiment and can be changed according to changes in the respective structures of the two cutting edges An, An' or tool parameters. Generally speaking, the first cutting edge An may have at least one cutting region or cutting area, and the second cutting edge An' may have at least one cutting region or cutting area, which may be involved in cutting material at different portions on the workpiece, such as a plate, and thus may be combined with each other to complete the cutting of material from the workpiece. Therefore, in the present invention, this is called a "composite blade."

[0066] 10, the existing step drill 101 has two cutting edges A'n and A'n', each of which is a one-segment type, and cutting is performed over the entire cutting edge length A'n and A'n', and the cutting area S4 of each cutting edge per rotation is the same. Therefore, the chip separation effect cannot be constantly achieved, and the cutting force is large.

[0067] In summary, in this embodiment, each cutting edge An, An' can be divided into two cutting edge segments An1, An2 and An1', An2', respectively. That is, the initial two single-line cutting edges become two groups of double-line cutting edges. The main angle or auxiliary angle λ of the cutting edges can vary significantly. At the same time, the helix angle βi (i.e., the blade inclination angle) of each segment can also vary to a certain extent. In addition, the total length of the cutting edges divided into multiple cutting edge segments An1, An2 or An1', An2' is greater than the length of the initial cutting edges An, An'. This breaks down the cutting force borne (loaded) per unit cutting edge length, has a very good effect on chip separation, and therefore disperses cutting heat.

[0068] The structure of the cutting edges on the nth step section Tn of the step drill 1 in this embodiment has been described above. In this embodiment, both the first cutting edges An and the second cutting edges An' may be provided with a multi-segment structure. Furthermore, for step sections other than the nth step section Tn, for example, adjacent thereto, the tooth profile or structure of the first cutting edges may be the same as that of the first cutting edges An on the nth step section Tn, and the tooth profile or structure of the second cutting edges may be the same as that of the second cutting edges An' on the nth step section Tn.

[0069] In other embodiments, referring to Figures 11 and 12, for the nth step section Tn, only one of the two cutting edges can be arranged in a multi-segment structure, while the other cutting edge A'n can still be arranged in a one-segment structure, and these cutting edges can still be combined to cut in various possible specific structures, and each extension section S1, S2, S3 or cutting edge cutting area S1, S2, S3 can also be formed as a combination of two multi-segment cutting edges.

[0070] 11, the horizontal cutting sections adjacent to the two cutting edges on the same side may have the same radial dimension, so that they coincide with each other after rotation. The two cutting edges are adjacent to each other in the radial or axial direction of the step drill (in a virtual state where the two cutting edges are united by rotation), forming triangular extension sections S1, S2 or cutting edge cutting areas S1, S2, respectively, which can cut in combination with each other.

[0071] In Fig. 12, the radial dimensions of horizontal cutting sections adjacent to two cutting edges on the same side may differ by a distance δ. One of these cutting edges forms two extension sections S1, S2 or cutting edge cutting areas S1, S2 spaced apart from each other in the radial or axial direction of the step drill, while the other cutting edge forms one extension section S3 or cutting edge cutting area S3 located between the two extension sections S1, S2. This can produce a strict chip separation effect during cutting.

[0072] 13-19 each show schematic diagrams of other embodiments of cutting edge combinations on the n-th step section Tn of the step drill 1. In various embodiments, some cutting edge segments are formed as straight sections and other cutting edge segments are formed as curved sections, and these straight or curved sections on different cutting edges perform compound cutting. The straight and curved sections can be obtained by suitable machining methods.

[0073] In FIG. 13 , the radial dimensions of the horizontal blade sections adjacent to the two cutting edges An and An′ on the same side can differ by a distance δ. The two cutting edge segments An1 and An2 of the first cutting edge An are straight sections, while the first cutting edge segment An1′ of the second cutting edge An′ is a concave curved section with a diameter R, and the second cutting edge segment An2′ of the second cutting edge An′ is also straight. The second cutting edge An′ has two extension sections S1 and S2 or cutting edge cutting areas S1 and S2 spaced apart from each other in the radial or axial direction of the step drill, while the first cutting edge An has one extension section S3 or cutting edge cutting area S3 located between the two extension sections S1 and S2. This can produce a strict chip separation effect during cutting.

[0074] 14, the horizontal blade sections adjacent to the same side of two cutting edges An and A'n may have the same radial dimension, so that they coincide with each other after rotation. The first cutting edge segment An1 of the first cutting edge An is a concave curved section having a diameter R, and the second cutting edge segment An2 of the first cutting edge An is a straight section, while the second cutting edge segment A'n is a one-segment straight section. Each cutting edge has adjacent extension sections S1 and S2 or cutting edge cutting areas S1 and S2.

[0075] In FIG. 15 , the radial dimensions of the horizontal blade sections adjacent to the two cutting edges An and An′ on the same side can differ by a distance δ. The first cutting edge segment An1 of the first cutting edge An is a concave curved section with a radius of curvature R, while the first cutting edge segment An1′ of the second cutting edge An′ is a concave curved section with a radius of curvature R′, where R and R′ can be the same or different. The second cutting edge segment An2 or An2′ of the first cutting edge An or the second cutting edge An′ is a straight section. The second cutting edge An′ has two extension sections S1 and S2 or cutting edge cutting areas S1 and S2 spaced apart from each other in the radial or axial direction of the step drill, while the first cutting edge An has one extension section S3 or cutting edge cutting area S3 located between the two extension sections S1 and S2. This can create a strict chip separation effect during cutting.

[0076] In FIG. 16, the horizontal blade sections adjacent to the two cutting edges An and A'n on the same side may have the same radial dimensions, so that they coincide with each other after rotation. The first cutting edge segment An1 of the first cutting edge An is a concave curved section with a radius of curvature R, while the first cutting edge segment An1' of the second cutting edge An' is a concave curved section with a radius of curvature R', where R and R' can be the same or different. The second cutting edge segments An2 and An2' of the first cutting edge An or the second cutting edge An' are straight sections. The second cutting edge An' has two extension sections S1 and S2 or cutting edge cutting areas S1 and S2 spaced apart from each other in the radial or axial direction of the step drill, while the first cutting edge An has one extension section S3 or cutting edge cutting area S3 located between the two extension sections S1 and S2. This can create a strict chip separation effect during cutting.

[0077] In FIG. 17, the horizontal blade sections on the same side adjacent to the two cutting edges An and A’n may have the same radial dimension, and as a result, they will coincide with each other after rotation. The first cutting edge segment An1 of the first cutting edge An is a concave curve section having a radius of curvature R2, while the first cutting edge segment An1’ of the second cutting edge An’ is a concave curve section having a radius of curvature R’, where R2 < R’. The second cutting edge segment An2 of the first cutting edge An is a convex curve section having a radius of curvature R1, where (although not essential) R1 = R2, and the second cutting edge segment An2’ of the second cutting edge An’ is a straight line section. Each cutting edge has extension sections S1, S2 adjacent to each other or cutting edge cutting areas S1, S2.

[0078] In FIG. 18, the horizontal blade sections on the same side adjacent to the two cutting edges An and A’n may have the same radial dimension, and as a result, they will coincide with each other after rotation. The first cutting edge segment An1 of the first cutting edge An is a concave curve section having a curvature diameter R2, while the second cutting edge segment An2 of the first cutting edge An is a convex curve section having a radius of curvature R1, where (although not essential) R1 = R2, and the second cutting edge segment A’n is a one-segment type and is a straight line section. Each cutting edge has extension sections S1, S2 adjacent to each other or cutting edge cutting areas S1, S2.

[0079] In FIG. 19, the horizontal blade sections on the same side adjacent to the two cutting edges An and A’n may have the same radial dimension, and as a result, they will coincide with each other after rotation. The first cutting edge segment An1 of the first cutting edge An is a straight line section, while the second cutting edge segment An2 of the first cutting edge An is a convex curve section having a radius of curvature R. The first cutting edge segment An1’ of the second cutting edge An’ is a concave curve section having a radius of curvature R’, while the second cutting edge segment An2’ of the second cutting edge An’ is a straight line section. Each cutting edge has extension sections S1, S2 adjacent to each other or cutting edge cutting areas S1, S,

[0080] In other embodiments, for a step section Tn other than, for example, an adjacent step section Tn, the tooth profile or structure of its first cutting edge may be different from that of the first cutting edge An on the nth step section Tn, and / or the tooth profile or structure of its second cutting edge may be different from that of the second cutting edge An′ on the nth step section Tn. For example, these differences may be reflected in the number, length, area, or arrangement of each cutting edge segment An1, An2, An1′, An2′, the magnitude of the cutting depth / auxiliary angle λ, etc.

[0081] In other embodiments, the cutting edges on only some of the step sections Tn of the step drill 1 may be designed as the multi-segment composite cutting edges described above, while the cutting edges on the other step sections Tn may also be arranged in an initial one-segment configuration.

[0082] Referring to the above description of these embodiments, the step drill 1 having a composite cutting edge according to the present invention is characterized by: (1) The initial one-section linear (straight or curved) cutting edge is changed to a multi-segment (straight or curved) cutting edge of at least two sections, and the total length of the cutting edge is greater than the total length of the initial cutting edge, so that the cutting force borne (loaded) per unit cutting edge length is resolved, and in this case, the cutting heat is dispersed. (2) In particular, the main angle or auxiliary angle λn has a significant change so as to change the direction of the cutting force and have the effect of chip diversion. Also, the cutting edge inclination angle (helix angle) βn of each cutting edge segment An1, An2, An1', An2' can also have a certain degree of change so as to change the direction of chip evacuation. (3) At least two straight or curved main cutting edges on the same step section Tn have different structures or tooth shapes, for example, different lengths and / or inclination angles, and even different numbers of sections in a multi-section cutting edge.

[0083] The distinctive feature of the step drill 1 with compound cutting edges is that it changes the initial cutting length of each cutting edge and the angle value of each cutting angle, thus changing the initial state during the cutting process, and accordingly has the following advantageous effects: 1. The cutting force is reduced, power is saved, and the machining range can be increased by using the same cutting tool. 2. The cutting sharpness is improved, the processing efficiency is improved, and the useful value of the cutting tool is also improved. 3. It is easy to break off the chips, so as to promote timely removal of chips and dissipation of cutting chip heat in time, and free up space for larger cooling space. 4. The service life of cutting tools is extended, which is advantageous for long-term processing. 5. Compared to conventional stepped drills, the thickness of the plate that can be drilled in one go is increased.

[0084] In addition, compared to the large cutting area of a conventional single-segment cutting edge, according to the present invention, multi-segment cutting edges and multi-segment cutting edges or single-segment cutting edges can be combined with each other to produce a compound cutting action. In the prior art, material is completely cut all at once along the length of the cutting edge, but in the present invention, material is cut in multiple sections, thus producing a decomposed cutting effect. The cutting area borne by each cutting edge is small, so that only reduced cutting force is required during cutting. Also, the chip separation effect can be more easily produced. In addition, by controlling the cutting angle of each section, burrs and the like can be better controlled.

[0085] The present invention may include any feature or combination of features, or the general concept thereof, implicitly or explicitly disclosed herein, and is not limited to any defined scope as recited above. Any of the elements, features, and / or structural arrangements described herein may be combined in any suitable manner.

[0086] It will be apparent to those skilled in the art having the benefit of the teachings herein that the particular embodiments disclosed above are illustrative only, and that the invention may be modified and practiced in different but equivalent manners. It is therefore evident that changes and modifications may be made to the particular embodiments disclosed above and all such variations are considered to be within the scope and spirit of the invention.

Claims

1. A step drill, the step drill having a hole-drilling portion and at least two flutes extending on the hole-drilling portion, the hole-drilling portion comprising one or more step sections, each step section and the at least two flutes forming at least two cutting edges distributed in a circumferential direction of the step section; the at least two cutting edges on at least one of the step sections include at least a first cutting edge and a second cutting edge; the first cutting edge and the second cutting edge are each constructed in an at least two-segment manner, thus each comprising at least two cutting edge segments, and the first cutting edge and the second cutting edge differ from each other at least partially in the structure of their cutting edge segments; or One of the first cutting edge and the second cutting edge is formed in one segment, while the other cutting edge is formed in at least two segments, and thus includes at least two cutting edge segments. A stepped drill characterized by:

2. the first cutting edge is only partially involved in cutting on its first extension segment, and the radial distance of the first extension segment from the longitudinal axis of the step drill is greater than the radial distance of a segment of the second cutting edge at the same axial position as the first extension segment from the longitudinal axis of the step drill; The second cutting edge is only partially involved in cutting on its second extension segment, and the radial distance of the second extension segment from the longitudinal axis of the step drill is greater than the radial distance of a segment of the first cutting edge at the same axial position as the second extension segment from the longitudinal axis of the step drill.

2. The step drill according to claim 1 .

3. 3. The stepped drill according to claim 2, wherein the first extension segment includes at least one first cutting edge cutting area, the second extension segment includes at least one second cutting edge cutting area, and the first cutting edge cutting area and the second cutting edge cutting area are adjacent to each other in the axial or radial direction of the stepped drill under a virtual state in which the first cutting edge and the second cutting edge are joined by rotating about the longitudinal axis of the stepped drill.

4. 3. The stepped drill according to claim 2, wherein the first extension segment includes at least two first cutting edge cutting areas spaced apart from each other, the second extension segment includes at least one second cutting edge cutting area, and the one second cutting edge cutting area is located between the two first cutting edge cutting areas in the axial or radial direction of the stepped drill under a virtual state in which the first cutting edges and the second cutting edges are joined by rotating around the longitudinal axis of the stepped drill.

5. 2. The step drill according to claim 1, wherein the at least two-segment first cutting edge and / or the second cutting edge comprises first cutting edge segments and second cutting edge segments arranged consecutively with respect to the feed direction, and the first cutting edge segments and the second cutting edge segments of the at least two-segment first cutting edge have different lead angles / supplement angles with respect to the feed direction, and / or the first cutting edge segments and the second cutting edge segments of the at least two-segment second cutting edge have different lead angles / supplement angles with respect to the feed direction.

6. In a virtual state in which the first cutting edge and the second cutting edge are united by rotating around the longitudinal axis of the step drill, The first cutting edge segment and / or the second cutting edge segment of the at least two-segment first cutting edge intersects with the first cutting edge segment and / or the second cutting edge segment of the at least two-segment second cutting edge, or The one-segment cutting edge of one of the first cutting edge and the second cutting edge is connected to the first cutting edge segment and / or the second cutting edge segment of the other at least two-segment cutting edge.

6. The step drill according to claim 5.

7. The first cutting edge segment of the at least two-segment first cutting edge and the first cutting edge segment of the at least two-segment second cutting edge have different cutting edge angles / supplementary angles relative to the feed direction, the second cutting edge segment of the at least two-segment first cutting edge and the second cutting edge segment of the at least two-segment second cutting edge have different cutting edge angles / supplementary angles relative to the feed direction, or the one-segment cutting edge of one of the first and second cutting edges and the first and / or second cutting edge segment of the other at least two-segment cutting edge have different cutting edge angles / supplementary angles relative to the feed direction.

6. The step drill according to claim 5.

8. a length of the first cutting edge segment of the at least two-segment first cutting edge is shorter than a length of the at least two-segment second cutting edge; A radial distance from the first cutting edge segment of the at least two-segmented first cutting edge to the longitudinal axis of the step drill is greater than a radial distance from the first cutting edge segment of the at least two-segmented second cutting edge to the longitudinal axis of the step drill at the same axial position.

8. The step drill according to claim 7, wherein the step drill is

9. 2. The step drill of claim 1, wherein at least one of the cutting edge segments of the at least two-segment first or second cutting edges can be formed by locally reducing material on an initial one-segment cutting edge.

10. The step drill according to claim 1 , characterized in that each cutting edge segment of the at least two-segment first cutting edge and / or second cutting edge is constructed as a straight section or a curved section.

11. 2. The step drill of claim 1, wherein at least one of the horizontal cutting segments adjacent the first cutting edge is radially offset a distance from at least one of the horizontal cutting segments adjacent the second cutting edge.

12. 2. The step drill according to claim 1, characterized in that the cutting edges formed by the same flutes on different step sections are at least partially different in structure or identical.

13. The step drill according to claim 1 , wherein the flutes are configured as straight flutes or helical flutes.

14. A method for drilling a hole in a workpiece by using a step drill, the step drill having a hole-drilling portion and at least two flutes extending on the hole-drilling portion, the hole-drilling portion comprising one or more step sections, each step section and the at least two flutes forming at least two cutting edges distributed in a circumferential direction of the step section, the at least two cutting edges on at least one of the step sections comprising at least a first cutting edge and a second cutting edge; The method comprises: cutting a first portion of material on a workpiece using the first cutting edge, wherein the first portion of material extends over only a portion of the length of the first cutting edge; using the second cutting edge to cut a second portion of material on the workpiece, wherein the second portion of material extends over only a portion of the length of the second cutting edge. A method characterized by:

15. 15. The method of claim 14, wherein the first material portion includes at least one first sub-material portion, and the second material portion includes at least one second sub-material portion adjacent to the first sub-material portion.

16. 15. The method of claim 14, wherein the first material portion includes at least two first sub-material portions spaced apart from one another, and the second material portion includes at least one second sub-material portion located between the two first sub-material portions.

17. The method according to claim 14, characterized in that the stepped drill is a stepped drill according to any one of claims 1 to 13.

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