Miniature internal boring tool

Abstract

A micro internal boring tool includes two to four shank flat surfaces and two to four integrally formed teeth. The outermost point of the cutting edge of the tooth defines an outer cutting diameter (OD) satisfying the condition: 2 mmlt; oDlt; 9 mm.

Description

Technical Field

[0001] The subject matter of this application relates to a miniature internal boring tool (hereinafter also referred to as a "tool" for the sake of brevity). Background Technology

[0002] An internal boring tool enters the cavity (typically a cylindrical hole) of a rotating workpiece and forms grooves or threads.

[0003] The term "micro" refers to the boring tool with an external cutting diameter of less than 9 mm that this application relates to.

[0004] It will be understood that such small external cutting diameters for tools designed to operate within tiny holes present some design challenges that do not exist with other tools. For example, balancing tool rigidity with chip evacuation requirements is a critical consideration.

[0005] Therefore, the applicant has successfully sold a commercially available knife under the name "Piccocut" for many years (one example of which is named Picco R 050.20.3-10; https: / / www.iscar.com / eCatalo). G / Family.aspx f N um=3177&mapp=T G &app=0& G FSTYP=M&fr=1), hereinafter referred to as "Example Cutting Tool of the Prior Art", is described in detail below and in the accompanying drawings.

[0006] This application aims to improve upon existing example cutting tools that have some common features mentioned below.

[0007] Existing example cutting tools and the cutting tools according to the present invention operate primarily by moving the foremost cutting edge and the nose cutting edge of the teeth in a forward direction into the inner surface of a hole in a rotating workpiece. Such tools can also be used to enlarge existing holes, or to create threads using a tooth geometry typically slightly different from that shown in the figures. Due to the geometry of such tools, they are typically not used for machining in a backward direction.

[0008] In particular, unlike many other tool types, prior art example tools and the tools of this invention have a shank portion with a flat surface for high-precision positioning of their cutting edges. This positioning facilitates a so-called "plug-and-play" clamping of the tool in a corresponding prior art tool holder without requiring manual positioning of the cutting edges. Specifically, the shank portion and the flat surface are designed so that the tools of this application are compatible with prior art tools (e.g., "Passcut," https: / / www.iscar.com / eCatalo).G / Family.aspx f N um=514&mapp=T G &app=0& G FSTYP=M&fr=1) is used in the same retainer.

[0009] Generally, for ease of reference, the distinguished features of prior art cutting tools with letters are suffixed with the number "2" (or "3" if additional elements are present). For example, the neck length of this invention is represented as "L". N Therefore, the equivalent neck length of existing cutting tools will be expressed as "L". N2 Furthermore, for ease of viewing, the equivalent features of existing cutting tools that only have numbers will be offset by "100". For example, the cutting tool of the present invention is represented as "10", while the equivalent existing cutting tool is represented as "110". Summary of the Invention

[0010] Existing cutting tools have been popular in the market for many years, and this invention aims to improve upon them.

[0011] According to a first aspect of the subject matter of this application, a miniature internal boring tool is provided, comprising a shank portion and a cutting portion; the shank portion includes two to four shank flat surfaces; the cutting portion includes two to four integrally formed outwardly extending teeth; each tooth includes a cutting edge; and the outermost point of the cutting edge in the external direction defines an outer cutting diameter O satisfying the following condition. D 2mm <O D <9mm.

[0012] The above description outlines the basic concept of the present invention: a micro-tool with a defined, minute external cutting diameter. As shown by the flat shank surface used for positioning a single-tooth cutting edge with high precision for boring, this tool is configured for internal boring, whereas tools configured for rotary cutting actions do not require such positioning. Furthermore, compared to the prior art tools described above, this tool now has a significant advantage because it now has more than one tooth, thereby significantly extending the overall tool life.

[0013] While increasing the number of teeth on a cutting tool is a known benefit, to the applicant's knowledge, this has never been used in micro internal boring tools, and for good reason. The reason is that within a tiny hole, the space for chip removal is extremely limited, and reducing the material in the cutting section would decrease structural strength (thus increasing tool vibration and degrading its performance). Therefore, a careful balance needs to be maintained between material and chip removal space.

[0014] It will be understood that when referring to "two to four teeth" in the specification and claims, this language is intended to exclude one tooth, and also excludes five or more teeth. The same applies to other elements defined with similar language.

[0015] The invention has been tested and found to have sufficient structural strength and acceptable chip removal.

[0016] In the most preferred embodiment, the blade has three teeth. Although four teeth are even more desirable, it is considered sufficient to meet the condition of 2mm. <O D Smaller external cutting diameter O <6mm D Unacceptable performance or chip removal will not be achieved.

[0017] According to a second aspect of the subject matter of this application, a miniature internal boring tool is provided, comprising: a shank portion; a cutting portion extending from the shank portion; and a central axis extending through the center of the shank portion and the cutting portion; the central axis defining: a cutting direction; a forward direction from the shank portion toward the cutting portion; a rearward direction opposite to the forward direction; an outward direction perpendicular to the central axis and extending outward from the central axis; and an inward direction opposite to the outward direction; the shank portion includes: a rear end; and a peripheral shank surface extending from the rear end to the cutting portion; the peripheral shank surface includes: two to four shank flat surfaces; and two to four shank curved surfaces; the shank flat surfaces and shank curved surfaces alternate around the central axis; the cutting portion includes: a neck portion extending from the shank portion to the cutting portion; a slit portion extending forward from the neck portion; a front end; and an imaginary plane perpendicular to the central axis and located at the front end; The cutting portion includes: two to four integrally formed and angledly spaced teeth that extend further outward than the neck portion; and multiple cuts; each tooth includes: a front cutting surface; a rear cutting surface; a cutting edge extending along the intersection of the front and rear cutting surfaces; and the rear cutting surface includes: a foremost rear cutting sub-surface; and a rearmost rear cutting sub-surface; the cutting edge includes: a foremost cutting sub-edge extending along the intersection of the front and rear cutting sub-surfaces; a rearmost cutting sub-edge extending along the intersection of the front and rear cutting sub-surfaces; and a nose cutting sub-edge connecting the foremost and rearmost cutting sub-edges; a transition corner is formed between the front cutting surface of at least one tooth and the rear cutting surface of an adjacent tooth of said at least one tooth, said adjacent tooth being positioned further outward than the front cutting surface along the cutting direction; wherein: the outermost point of the cutting edge in the outward direction defines an outer cutting diameter (O) that satisfies the condition. D ): 2mm <O D <9mm.

[0018] It will be understood that the outward direction can also be called the outward radial direction, and the inward direction can also be called the inward radial direction. For the sake of brevity, they will be referred to as the "outward direction" and the "inward direction" in this article.

[0019] This aspect is largely similar to the aforementioned aspects, but a more detailed description of the cutting tool is given. A significant addition is the addition of a central axis extending through the center of the shank and the cutting portion, a distinguishing feature from prior art tools, as shown in the figure. Prior art tools benefit from a simplified manufacturing process due to this eccentricity (eliminating the need to grind the curved surface, indicated as "127," of the neck portion extending flush with the shank). Figure 10 However, the present invention abandons this advantage in order to achieve other advantages for its additional teeth.

[0020] According to a third aspect of the subject matter of this application, a miniature internal boring tool is provided, comprising: a shank portion and a cutting portion; the shank portion includes a flat shank surface; the cutting portion includes an integrally formed outwardly extending tooth, the tooth including: a front cutting surface; a rear cutting surface; and a cutting edge extending along the intersection of the front cutting surface and the rear cutting surface; in a view perpendicular to the front cutting surface, the foremost cutting sub-edge of the tooth forms an outward angle of attack A with an imaginary plane PI. E It meets the condition: 4° E <16°; and the outermost point of the cutting edge along the outer direction defines the outer cutting diameter (O) that satisfies the condition. D ): 2mm <O D <9mm; The difference in this respect lies in the discovery of a particularly advantageous cutting edge structure during development, which will be elaborated upon below. Therefore, unlike the aforementioned aspects, this aspect is not limited to multiple teeth. It will be understood that this aspect may also include any or all of the features described above in conjunction with the foregoing aspects, as well as the features generally described below.

[0021] It will also be understood that the foregoing is a summary, and any of the foregoing aspects may include any of the features described below. Specifically, the following features may apply to any of aspects 1 through 3 above: A. The cutting tool may include a central axis extending through the center of the shank portion and the cutting portion. This structure is disadvantageous for prior art single-tooth embodiments, but is compensated for by the benefits of multiple teeth according to the invention.

[0022] ​B. The peripheral shank surface may preferably include two to four shank flat surfaces. It will be understood that cylindrical peripheral shank surfaces are used in many other tools because they offer the highest accuracy, especially in terms of runout. However, since it is not impossible to determine a method for positioning the cutting edge as needed, it must be pointed out that this feature is not essential. Nevertheless, for internal boring purposes, precise positioning of the cutting edge to be used (hereinafter also referred to as the "working cutting edge") is required, and therefore, a shank flat surface is certainly highly preferred. Preferably, there is one shank flat surface per tooth, but depending on the tool holder (not shown) designed to hold the tool, this number can vary and is not inconceivable.

[0023] C. Preferably, the flat surface of the shank extends to the rear end. It should be understood that the flat surface of the shank is not the well-known so-called Weldon plane. This invention relates to micro-tools measured in millimeters, and is therefore designed to hold screws that are tiny, yet still relatively large compared to these micro-tools. For example, the length L of the flat surface of the shank of this invention... F The handle length L can be S At least 30% (L) F ≥0.3L S Preferably at least 50% (L) F ≥0.5L S ), and most preferably at least 80% (L F ≥0.8L S This is clearly different from the relatively small Weldon plane, at least relative to the shank formed on it. For similar reasons, the shank plane is very large relative to the Weldon plane. In other words, the width WF of the flat surface of the shank can be greater than the width of the adjacent curved surface of the shank.

[0024] D. Preferably, one of the flat surfaces of each shank and one of the axially aligned teeth on each cutting edge surface form a pair, and the pairs extend at right angles to each other.

[0025] E. Preferably, the curved surface of the handle alternates with the flat surface of the handle.

[0026] F. Preferably, the curved surface of the handle is a cylindrical surface.

[0027] G. Multiple cuts can be two to four, but are not required to be, as will be understood in the prior art, where a single tooth is associated with two cuts. However, preferably, the number of cuts corresponds exactly to the total number of teeth in the tool. To clarify, in prior art tools, a single tooth has two independently formed cuts, which is less desirable than a single cut per tooth. Although helical cuts are feasible and were initially tested, better machining results were found with non-helical, or in other words, planar cuts.

[0028] H. Although there were concerns about adequate chip removal, it was found that even with relatively short kerfs (compared to prior art tools), sufficient chip removal was provided, even if a longer kerf was initially thought to be required. For example, the kerf length L of the present invention... G It can be smaller than the neck length L N 35% (L) G <0.35L N Preferably less than 25% (L) G <0.25L N ), and most preferably less than 22% (L) G <0.22L N This is clearly different from existing cutting tools, which have a cutting length L. G2 Its neck length L N2 Approximately 58%. Although the minimum incision length L has not yet been tested. G However, it was found that manufacturing 0.12L met the requirements. N <L G <0.22L N Length of cut L G The cut is advantageous. In other words, it was found that manufacturing with a 1mm cut meets the condition. <L G <2.2mm, more preferably 1.3mm <L G Cut length L <1.9mm G The incision is advantageous.

[0029] I. Preferably, two to four flat shank surfaces and two to four teeth are exactly three flat shank surfaces and exactly three teeth. As mentioned above, this is more advantageous than two teeth, but less advantageous than four teeth. However, considering the machining applications and the limitations of available space, this is considered the optimal number of teeth, at least for meeting the condition of 2mm. <O D <6mm external cutting diameter (O D That is true for this.

[0030] J. The shank portion may have one or more coolant slots. Preferably, each cutting edge has one coolant slot. Preferably, the coolant slots are axially aligned with the corresponding cutting edge. Preferably, the coolant slots extend through the shank portion into the neck portion.

[0031] K. The outermost point of the cutting edge along the external direction defines the outer cutting diameter (O). D Preferably, the outermost point is located on the nose cutting sub-edge of the cutting edge.

[0032] L. In a view perpendicular to the front surface of one of the teeth, the foremost cutting edge of that tooth can extend in the forward direction and preferably forms an external angle of attack A with the imaginary plane PI. E It meets the condition: 4° E <16°. This angle is designed to improve the structural strength of micro internal boring tools during typical machining operations in the forward direction as described above, relative to existing technology tools. For a relatively small outward angle of attack A... E The test was successful. The preferred angle of attack, A. E At 6° E Within the range of <12°, and more preferably within 6°. E Within the range of <10°.

[0033] M. External cutting diameter (O) D (Meets the following condition: 2mm) <O D <9mm, this is how "micro" is defined for the purposes of this application. It will be understood that for smaller outer cutting diameters (O... D Certain features are more advantageous, where balancing the conflicting considerations between structural strength and chip removal space becomes more critical. Preferably, the outer cutting diameter (O) D (Meets the following condition: 2mm) <O D <6mm, and more preferably: 2.5mm <O D <4mm.

[0034] N. The front surface of the cutting edge may include: a front sub-surface of the front cutting edge extending between the foremost cutting sub-edge, the rearmost cutting sub-edge, and the nose cutting sub-edge; a concave front sub-surface of the cutting edge extending from the front sub-surface of the front cutting edge and extending further inward than the front sub-surface of the front cutting edge; and a rear sub-surface of the cutting edge extending from the concave front sub-surface of the front cutting edge and extending further inward than the concave front sub-surface of the front cutting edge.

[0035] O. In the view along the central axis in the rearward direction (e.g., corresponding to...) Figure 11 (View), the front sub-surface of the flank cutting edge preferably extends along a substantially straight path to the transition corner of its adjacent tooth. It will be understood that this allows for more chip removal space compared to if the front sub-surface of the flank cutting edge had a convex shape or bulge (as is typical for rotary cutting tools, for momentum purposes only).

[0036] P. A transition corner can be formed between the rake surface of one tooth and the flank surface of another tooth, the latter positioned further away from the rake surface along the cutting direction. In a rearward view along the central axis, the transition corner can be a sharp corner. In other words, the transition corner has no convex shape. Or, a sharp corner is discontinuous. ​​​

[0037] Q: The cutting tool may include exactly three flat shank surfaces and exactly three teeth, wherein, in a rearward view along the central axis, at the front end coinciding with an imaginary plane, it is defined by two adjacent cutting edges and by an outer cutting diameter O. D The void region A enclosed by the defined circular segment SC V Condition met: 0.1O D V <0.25O D Preferably 0.12O D V <0.22O D And most preferably 0.14O D V <0.20O D .

[0038] R. The neck portion may have a basic cylindrical cross-section (except where it transitions from the handle portion). The neck portion may have a neck length L. N .

[0039] S. The cutting tool can be rotationally symmetrical. The cutting tool can be 120° rotationally symmetrical.

[0040] T. The chip discharge angle θ, which can be measured between the front and rear cutting edge surfaces, is preferably an obtuse angle to provide chip discharge space. In embodiments with three teeth, it more preferably satisfies the condition 95°≤θ≤125°, and most preferably satisfies the condition 110°≤θ≤120°, taking into account that the chip discharge space needs to be maximized while still being limited by the area occupied by multiple teeth. Attached Figure Description

[0041] To better understand the subject matter of this application and to show how it can be implemented in a compatible manner in practice, reference is now made to the accompanying drawings, in which: Figure 1 This is a perspective view of the cutting tool according to the present invention; Figure 2 yes Figure 1 The tool in the middle along the central axis A C The backend view; Figure 3 yes Figure 1 The side view of the cutting tool is a view perpendicular to the front surface of the cutting edge of the left tooth; Figure 4 Is with Figure 3 A similar side view of the tool, except that the tool is rotated 90 degrees, making Figure 3 The cutting edge of the left tooth is now centered. Figure 5 Is with Figure 3 Same view;​​​ Figure 6 Is with Figure 4 Same view; Figure 7 This is a side view of a cutting tool in the prior art, presented in the context of... Figure 3 A similar view, specifically, a view perpendicular to the front surface of the cutting edge of the left tooth; Figure 8 yes Figure 7 A side view of an existing technology cutting tool, presented in contrast to Figure 4 A similar view, specifically, shows the tool rotated 90 degrees, making... Figure 7 The cutting edge of the left tooth is now centered. Figure 9 yes Figure 1 The cutting tool in the middle is along the central axis A C The front view (also known as a "view along the central axis in the rearward direction") shows the workpiece's internal hole, within which the cutting portion of the tool is received, indicated by dashed lines; and the shaded portion indicates hole area A. B The area of ​​the hole is perpendicular to the central axis A. C And located at the imaginary plane at the front end, between the cutting part and the internal hole; Figure 10 yes Figure 7 The existing technology tool in the middle is along the central axis A C2 The front view has the ability to combine Figure 9 The description includes similar dashed and shaded areas; and Figure 11 Is with Figure 9 The same view, except that the dashed line in this figure indicates the cutting diameter, and the shaded area schematically indicates the area along the central axis A. C And the gap region A at the imaginary plane at the front end V The gap region A V Located between the cutting sections, and formed by the outer cutting diameter O D Enclosed by a defined circular segment SC. Detailed Implementation

[0042] refer to Figures 1 to 4 This shows a miniature internal boring tool 10 including a shank portion 12 and a cutting portion 14.

[0043] Central axis A C It extends through the center of the shank portion 12 and the cutting portion 14.

[0044] Central axis A C The cutting direction D is defined. C Forward direction D F 、and forward direction DF Opposite backward direction D R Perpendicular to the central axis A C and from the central axis A C Outward extension direction D O ( Figure 2 To best display Figure 3 and Figure 4 The extra arrow in the image is to illustrate the outward direction D. O It is not a single direction, but originates from the central axis A. C (all outward directions), and related to outward direction D O Opposite inward direction D I ( Figure 2 To best display Figure 3 and Figure 4 The extra arrow in the middle is to illustrate the inward direction D. I Not in a single direction, but pointing towards the central axis A. C (All inward directions).

[0045] The shank portion 12 includes a rear end 16 and a peripheral shank surface 18 extending from the rear end 16 to the cutting portion 14.

[0046] The peripheral handle surface 18 includes three flat handle surfaces 20 (labeled 20a, 20b, and 20c, respectively). For simplicity, the components below may be referred to by general designations, for example, "20" to refer to the flat handle surface, instead of their individual designations 20a, 20b, and 20c. The peripheral handle surface 18 also includes three (preferably cylindrical) curved handle surfaces 22 (labeled 22a, 22b, and 22c, respectively).

[0047] Although there appear to be six shank flat surfaces 20, it will be understood that the coolant grooves 24 formed in the shank portion 12 (labeled 24a, 24b, 24c respectively) are optional, and therefore the designated shank flat surfaces (20a, 20b, 20c) indicated above are pairs of shank flat sub-surfaces, which are considered as a single shank flat surface. In particular, they may be functionally identical (e.g., screws from the tool holder, not shown, are intended to simultaneously contact two shank flat sub-surfaces of a single pair, e.g., the pair of shank flat sub-surfaces both labeled "20a").

[0048] The cutting portion 14 includes a neck portion 26, a cut portion 28, a front end 29, and an imaginary plane P perpendicular to the central axis AC and located at the front end 29. I .

[0049] The neck portion 26 has a basic cylindrical cross-section (see, for example, see...). Figure 2 ), and neck length L N ( Figure 6 In this example, the diameter is 8.4 mm. However, it should be noted that the overall structure, geometry, and dimensional proportions of this embodiment are not limited to the specific dimensions mentioned in the discussion of the figures, but are equally applicable to cutting tools with dimensions within the range mentioned above.

[0050] The cross-section of the neck portion has a diameter ø, which is 2.1 mm in this example.

[0051] The cut portion 28 includes three integrally formed teeth 30 (marked as 30a, 30b, and 30c respectively) and three planar cuts 32 (marked as 32a, 32b, and 32c respectively).

[0052] In this example, the cutter 10 has three teeth 30, and therefore around the central axis A. C It is rotationally symmetric at 120° (because 360° divided by the number of teeth equals 120). Since tooth 30 is identical to other elements, the above and following description may refer to a single sub-element, and it should be understood that it applies to all other identical elements. It should also be understood that the cutting tool according to the invention can have slight, non-exact differences, such as slightly different kerf lengths, without any change in efficiency. Furthermore, it should be understood that the invention does not require all elements to be identical, and this is merely a preferred configuration.

[0053] Each tooth 30 includes a front cutting surface 34, a back cutting surface 36, and a cutting edge 38.

[0054] Also refer to Figure 11 The front surface 34 may include: a front sub-surface 34a, a rear sub-surface 34b, and a concave front sub-surface 34c.

[0055] The back surface 36 includes the foremost back sub-surface 36a and the last back sub-surface 36b.

[0056] In this exemplary embodiment, the chip discharge angle θ is 117°.

[0057] In this example, such as Figure 2 As can be seen from the best viewpoint, the foremost side cutting edge rear surface 36a has two facets, namely the first rear facet 36a1 connected to the cutting edge 38 and the second rear facet 36a2 extending from the first rear facet 36a1.

[0058] In addition, Figure 11In the diagram, the acute-angle transition corner is marked "40" and is shown as being located at the intersection of one of the front cutting surfaces 34 and one of the rear cutting surfaces 36, with the rear cutting surface 36 positioned further away from the front cutting surface 34 along the cutting direction DC. More precisely, the transition corner 40 is located at the intersection of the rear cutting surface 34b and the second rear cutting facet 36a2.

[0059] Back Figure 3 and Figure 4 The cutting edge 38 includes the foremost cutting sub-edge 38a, the rearmost cutting sub-edge 38b, and the nose cutting sub-edge 38c.

[0060] In this example, and in the preferred embodiment, the nose cutting edges 38c of all teeth 30 constitute the outermost and foremost points of the tool 10. Therefore, for example, the imaginary plane PI is defined by the nose cutting edges 38c because they encompass the foremost point of the tool 10. Another example is that the nose cutting edges 38c define the outer cutting diameter O. D ( Figure 2 ), because they include the outermost point of tool 10. In this example, the outer cutting diameter (O) D The diameter is 2.7mm.

[0061] Special attention Figure 5 and Figure 6 The foremost cutting edge 38a forms an external angle of attack A with the imaginary plane PI. E In this example, it is 8°.

[0062] The last cutting edge 38b of the tooth is perpendicular to the forward direction D. F Forming an outer angle of attack A R In this example, it is 20°.

[0063] The cutting part 14 has a cutting length L C In this example, it is 10mm.

[0064] Each cut 32 has a cut length L G This is defined as extending from the rearmost side cut edge 32a to the foremost point of the tooth 30 associated with the cut 32 (in this example, this foremost point coincides with the imaginary plane PI, or alternatively, with the nose cutting edge 38c defining the imaginary plane PI). In this example, the cut length L G It is 1.6mm.

[0065] The final side cutting edge 38b has a back edge length L R In this example, it is 0.6mm.

[0066] The flat surface 20 of the handle extends to the rear end 16 and has a flat surface length L. FIn this example, it is 17.5mm.

[0067] The flat surface 20 of the handle may have a flat surface width WF, which is 2.6 mm in this example.

[0068] The handle portion 12 includes a cylindrical handle sub-portion 42 between the handle flat surface 20 and the neck portion 26, and has a total handle length L. S In this example, it is 21mm.

[0069] like Figure 2 As shown, the coolant inlet 24 is axially aligned with the corresponding cutting edge 38. The coolant inlet 24 extends from the shank portion 12 into the neck portion.

[0070] Each shank flat surface 20 is axially aligned with one of the front cutting surfaces 34 of each tooth, forming a pair.

[0071] like Figure 2 As shown, for illustrative purposes only, the shank flat surface labeled 20a is paired with one of the front cutting surfaces, which is labeled "34d" for illustrative purposes, thus forming a pair. As shown, the shank flat surface 20a and the front cutting surface 34d (specifically, the front sub-edge surface of the front cutting surface 34d (arbitrarily labeled "34e")) extend at right angles.

[0072] like Figure 11 As shown, the front surface 34b of the rear blade extends along a basically straight path to the transition corner 40.

[0073] Now for reference Figures 5 to 8 It will have some significant differences in Figure 7 and Figure 8 The prior art cutting tool 110 is compared with the example cutting tool 10 of the present invention.

[0074] In the existing cutting tool 110, axis A C2 It does not extend through the center of both the shank portion 112 and the cutting portion 114.

[0075] There is a single flat surface 120 on the handle and a single curved surface 122 on the cylindrical handle.

[0076] The curved surface 122 of the handle extends flush with the curved surface 127 of the neck portion 126, the significance of which has been explained above.

[0077] The cutting part 114 has a cutting length L C2 In this example, it is 10.3 mm.

[0078] The neck portion 126 has a neck length L N2In this example, it is 6.5 mm. This will be understood to be the equivalent length of the cylindrical cross-sectional portion of the cut portion 114. Alternatively, if the partial cut 132 is included, the neck portion 126 can be considered to have an alternative neck length L. N3 In this example, it is 8.1 mm. In any case, it will be understood that the cutter 10 does not have an upward inclination, arbitrarily marked 132d, and a corresponding cut portion that removes more material from the cylindrical cross-sectional portion of the neck portion 126.

[0079] The neck portion 126 has a diameter ø2 at its basically cylindrical part, which in this example is 2.3-2.4 mm depending on the measurement direction.

[0080] Regardless of the direction, it should be understood that the design results in a smaller diameter ø due to the inclusion of multiple teeth in the tool 10, which is an issue for stability, but has been found to provide suitable performance.

[0081] More notably, for a comparative kerf length L of 3.8 mm... G2 The incision 132 is significantly longer. Alternatively, there is an alternative, even larger incision length L of 2.2 mm. G3 .

[0082] Similarly, the last side cutting sub-edge 138b has a back edge length LR2 of 0.96 mm, which is also significantly longer.

[0083] The significance of the above numerical comparisons is that, even for significantly smaller cuts and longer neck sections with cylindrical cross-sections, it is surprisingly found that the tool according to the invention still has sufficient chip removal space and sufficient rigidity.

[0084] Finally, it should be noted that the outer angle of attack A E2 It is 20°.

[0085] Despite the differences shown above, it should be noted that tool 10 successfully provides material removal performance similar to that of prior art tool 110.

[0086] To illustrate the importance of chip removal, please now pay attention. Figure 9 and Figure 10 They schematically show the cutting portions of the tool 10 and the prior art tool 110 in a hole B of an exemplary workpiece, which has an exemplary hole diameter ø3 of 2.8 mm.

[0087] The following section will discuss some comparative dimensions.

[0088] Regarding the cutting tool 10, the foremost cutting edge dimension M is measured from the starting point of the nose cutting sub-edge 38c of the working cutting edge 38 that contacts hole B to the concave cutting edge rake surface 34c. F In this example, it is 0.5 mm. The transition dimension M is measured from the nose cutting edge 38c to the transition corner 40. T In this example, it is 1.2mm. This is schematically shown as hole area A. B The chip removal space is from one cutting edge 38 to another cutting edge 38 along the cutting direction, and in this example, it is approximately 17% of the area of ​​the imaginary plane PI within the hole B.

[0089] In comparison, the prior art tool 110 has the following relevant comparative dimensions: the size of the foremost cutting edge M F2 It is 1.15mm. Basic comparison transition size M T2 (Even without an additional cutting edge) 1.3mm. Schematic shown as hole area A. B2 The chip removal space is approximately 49% of the area of ​​the imaginary plane PI within hole B.

[0090] Therefore, even with the significantly reduced chip removal space and the seemingly smaller cutting edge or rake surface, tool 10 still provides material removal performance similar to that of prior art tool 110 and surprisingly successful (considering the smaller chip removal space) while maintaining sufficient rigidity.

[0091] It will be understood that, given the outer diameter O of the tool D The very small difference between it and hole B is not a simple matter.

[0092] The dimensions described above will now be discussed similarly, without reference to the workpiece or hole B.

[0093] refer to Figure 11 The dashed line represents the outer cutting diameter O. D The dashed line schematically indicates the gap area A. V The gap region is perpendicular to the central axis A. C And located at the imaginary plane at the front end, between the cutting parts, and by the outer cutting diameter O D Enclosed by a defined circular segment SC.

[0094] Regarding the cutting tool 10, the foremost cutting edge dimension M is measured from the starting point of the nose cutting sub-edge 38c of the working cutting edge 38 that contacts hole B to the concave cutting edge rake surface 34c. F The transition dimension M is 0.5 mm, measured from the nose cutting edge 38c to the transition corner 40. T It is 1.2mm. This is schematically shown as hole area A. BThe chip removal space is from one cutting edge 38 to another cutting edge 38 along the cutting direction, and is approximately 17% of the area of ​​the imaginary plane PI within the hole B.

[0095] The above description includes exemplary embodiments, but does not exclude non-exemplary embodiments within the scope of the claims of this application.

Claims

1. A miniature internal boring tool, comprising: Handle portion; The cutting portion extending from the shank portion; as well as The central axis extends through the center of the shank portion and the cutting portion; The central axis defines: Cutting direction; Forward direction from the shank portion toward the cutting portion; A backward direction opposite to the forward direction; An outward direction that is perpendicular to and extends outward from the central axis; as well as An inward direction, opposite to the outward direction; The handle portion includes: Backend; and The peripheral shank surface extends from the rear end to the cutting portion; The peripheral handle surface includes: Two to four flat surfaces on the handle; and Two to four curved surfaces on the handle; The flat surface of the handle and the curved surface of the handle alternate around the central axis; The cutting portion includes: The neck portion extends from the shank portion to the cutting portion; The incision extends forward from the neck portion; Front-end; and An imaginary plane perpendicular to the central axis and located at the front end; The cut portion includes: Two to four integrally formed, angledly spaced teeth that extend further outward than the neck portion; and Multiple incisions; Each tooth includes: The front surface of the cutting edge; Back surface; A cutting edge extending along the intersection of the front and rear surfaces; and The back surface of the cutting edge includes: The frontmost side edge and the rear surface; and Finally, the side blade is on the back surface; The cutting edge includes: The foremost cutting sub-edge extends along the intersection of the front surface of the cutting edge and the foremost rear sub-edge surface; The last side cutting sub-edge extending along the intersection of the front surface and the last side rear surface; and A nose-shaped cutting edge that connects the foremost cutting edge and the last cutting edge; The transition corner is formed between the front surface of at least one of the teeth and the rear surface of an adjacent tooth of the at least one of the teeth, the adjacent tooth being positioned further away from the front surface along the cutting direction; in: The outermost point of the cutting edge along the outer direction defines the outer cutting diameter (O) that satisfies the condition. D ): 2mm <O D <9mm.

2. The miniature internal boring tool according to claim 1, wherein, In a view perpendicular to the front surface of one of the teeth, the foremost cutting edge of the tooth can extend in the forward direction and form an outward angle of attack A with the imaginary plane PI. E It meets the condition: 4° E <16°.​ 3. The miniature internal boring tool according to claim 2, satisfying the condition: 6° E <12°.​ 4. The miniature internal boring tool according to claim 3, satisfying the condition: 6° E <10°.​ 5. The miniature internal boring tool according to any one of claims 1 to 4, further satisfying the condition: 2mm <O D <6mm.

6. The miniature internal boring tool according to claim 5 further satisfies the condition: 2.5mm <O D <4mm.

7. The miniature internal boring tool according to any one of claims 1 to 6, comprising exactly three flat shank surfaces and exactly three teeth, wherein the outer cutting diameter (O) D (Meets the following condition: 2mm) <O D <6mm.

8. The miniature internal boring tool according to any one of claims 1 to 7, wherein, The total number of cuts corresponds exactly to the total number of teeth.

9. The miniature internal boring tool according to any one of claims 1 to 8, wherein, One of the plurality of incisions has a length L parallel to the central axis. G The neck has a neck length L parallel to the central axis. N The cut length L G Condition L is satisfied G <0.35L N .

10. The miniature internal boring tool according to claim 9, wherein, The cut length L G Condition L is satisfied G <0.25L N .

11. The miniature internal boring tool according to claim 10, wherein, The cut length L G Condition L is satisfied G <0.22L N .

12. The miniature internal boring tool according to any one of claims 1 to 11, wherein, One of the tooth's cutting edge surfaces includes: The front surface of the front cutting edge extends between the foremost cutting edge, the last cutting edge, and the nose cutting edge; A concave front edge surface, which extends from the front edge surface and extends further in the inward direction than the front edge surface; and The rear cutting edge front surface extends from the concave cutting edge front surface and extends further in the inward direction than the concave cutting edge front surface; In a rearward view along the central axis, the front sub-surface of the rear cutting edge extends along a generally straight path to the transition corner of the tooth adjacent to it along the cutting direction.

13. The miniature internal boring tool according to claim 12, wherein, In a view along the central axis in the rearward direction, the transition corner is a sharp corner.

14. The miniature internal boring tool according to any one of claims 1 to 13, wherein, In a view along the central axis in the rearward direction, the transition corner is a sharp corner.

15. The miniature internal boring tool according to any one of claims 1 to 14, comprising exactly three flat shank surfaces and exactly three teeth, wherein, In the rearward view along the central axis, at the front end coinciding with the imaginary plane, the outer cutting diameter O is defined between two adjacent cutting edges. D The void region A enclosed by the defined circular segment SC V Condition met: 0.10O D V <0.25O D .​ 16. The miniature internal boring tool according to claim 15, further satisfying the condition: 0.12O D V <0.22O D .​ 17. The miniature internal boring tool according to claim 16, further satisfying the condition: 0.14O D V <0.20O D .​ 18. The miniature internal boring tool according to any one of claims 1 to 17, wherein, The flat surface of the handle extends to the rear end.

19. The miniature internal boring tool according to any one of claims 1 to 18, wherein, One of the flat surfaces of each shank and one of the axially aligned front surfaces of each of the teeth form a pair, and the pair extends at right angles to each other.

20. The miniature internal boring tool according to any one of claims 1 to 19, wherein, The cutting tool is rotationally symmetrical at 120°.

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