Blank for rotating metal cutting tool
By designing a rotating metal cutting tool blank with optimized wall thickness, the problems of high material consumption and long production time in the prior art are solved, and material saving and production efficiency are improved.
Patent Information
- Application Number
- CN202380074169.9
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Priority Date
- 2022-10-24
- Filing Date
- 2023-10-03
- Publication Date
- 2025-05-16
AI Technical Summary
The blank material consumption of existing rotary metal cutting tools is high, and there are time-consuming problems during the production process.
A blank for rotating metal cutting tools is designed, including an elongated single-piece body, consisting of a cutting head section, a handle section and a chip groove section with a wall thickness of up to 25% of the maximum diameter, and is produced by an additive manufacturing process and suitable for the production of solid body round tools.
By optimizing the blank design and production process, material consumption is reduced, production efficiency is improved, and sufficient strength is provided to avoid excessive grinding and material waste.
Smart Images
Figure CN120018930A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to a blank for a rotary metal cutting tool. Preferably, the blank is a drilling tool blank or a milling tool blank. Background Art
[0002] Rotary metal cutting tools, such as drills and milling cutters, are usually made from blanks. A known type of blank is a cylindrical or tapered bar made of steel or a sintered powder combination. In order to form the features of the finished rotary metal cutting tool, the bar is processed, for example by grinding. Examples of these ground features are chip flutes, clearance surfaces, cutting edges and / or shanks whose dimensions are within the desired tolerance range. Another known type of blank is already provided with some of these features, such as chip flutes that roughly correspond to its finished dimensions. After grinding, the blank is usually subjected to a coating process to provide a finished rotary metal cutting tool.
[0003] A problem with these known blanks, apart from the time-consuming machining, is the high consumption of blank material for their production. Summary of the invention
[0004] It is an object of the present invention to at least partially eliminate the above-mentioned problems. According to the invention, this object is achieved by a blank for a rotating metal cutting tool according to claim 1 .
[0005] The present invention relates to a blank for a rotary metal cutting tool, wherein the blank comprises an elongated one-piece body having a front end, a rear end and a longitudinal axis extending from the front end to the rear end, wherein the body comprises: - a blade head section extending longitudinally rearwardly from the front end, - a handle section extending longitudinally forwardly from said rear end, - a chip flute section extending in the longitudinal direction and located between the shank section and the head section and having a maximum diameter, in, - the chip flute segment comprises a longitudinally extending wall surrounding an inner cavity extending in the longitudinal direction, the wall having an inner wall surface and an outer wall surface, the inner wall surface defining the cavity, - said outer wall surface defines a chip flute surface, - when viewed in a cross section perpendicular to the longitudinal axis, the wall has a wall thickness measured from the outer wall surface to the inner wall surface, and wherein, - said wall thickness is constant along a portion of said chip flute surface in the circumferential direction when viewed in cross-section at multiple locations along a majority of the length of the chip flute segment and is at most 25%, preferably at most 20%, and more preferably at most 15% of the maximum diameter of the chip flute segment, including finishing allowance.
[0006] The blank of the present invention comprises a chip flute section, the chip flute section comprising a wall extending in a longitudinal direction. The wall has an inner wall surface, an outer wall surface and a wall thickness, the inner wall surface surrounding the cavity. The outer wall can be designed to have a final shape that roughly corresponds to a corresponding feature of a finished rotary metal cutting tool. Specifically, the outer wall surface comprises a chip flute surface.
[0007] According to the production method involving additive manufacturing for producing an object by building up one layer at a time, the blank can be given almost any desired shape. By designing the shape of the cavity, the wall thickness measured from the outer wall surface to the inner wall surface when viewed in a section perpendicular to the longitudinal axis can be freely selected. By choosing the wall thickness to be constant and at most 25% of the maximum diameter of the chip flute segment (including finishing allowance), it is ensured that the wall does not exceed the thickness required to provide sufficient strength and that allowance is left for post-processing (such as, for example, grinding). Thus, advantageously, excessive use of blank material is prevented.
[0008] The blank is suitable for producing rotary metal cutting tools, such as milling tools or drilling tools. Preferably, the rotary cutting tools intended to be produced by the blank of the present invention are sometimes referred to as "solid round tools". These tools are solid because they are one-piece, integral components with one or more integral cutting edges. Therefore, tool sets of these tools, which are referred to as solid round tools, typically also include tools with internal cavities (such as coolant channels). Other types of rotary metal cutting tools are types that include a body provided with replaceable cutting blades or replaceable tool heads. According to an embodiment of the present invention, the blank is suitable for producing the main tool body of such a tool.
[0009] The blank comprises an elongated, one-piece body. Preferably, the body is produced by additive manufacturing, for example by building up the body one layer at a time, for example by printing. Preferably, a printable and sinterable powder component is used, such as, for example, a powder comprising steel or tungsten carbide and cobalt. Thus, the blank may comprise cemented carbide or steel.
[0010] The body has a front end and a rear end, and a longitudinal axis extending from the front end to the rear end. Preferably, the longitudinal axis is the axis of rotation of the finished rotary metal cutting tool. Preferably, the longitudinal axis is a central axis.
[0011] A "section" is to be understood as a longitudinal portion of the body, or in other words, the entire body along a portion of the longitudinal length from a first transverse section or end to a second transverse section or end.
[0012] The main body comprises a cutter head section, which extends longitudinally backward from the front end. Optionally, the cutter head section is a longitudinally shorter end portion, which is configured to be suitable for forming a section of a cutting tool head.
[0013] The shank section extends forward from the rear end, and the chip flute section is located between the head section and the shank section. Preferably, the chip flute section is connected to the shank section and the head section. According to an embodiment, the body includes other sections, such as a transition section, located between the shank section and the head section.
[0014] The chip flute section has a maximum diameter. Optionally, the maximum diameter is located in a cross section at a certain position along the longitudinal length of the chip flute section, or the maximum diameter is the same in all cross sections along the longitudinal length of the chip flute section. The diameter can, for example, decrease or increase from the front end of the chip flute section backwards.
[0015] The chip flute section comprises a wall extending in the longitudinal direction, the wall surrounding the inner cavity extending in the longitudinal direction, the wall having an inner wall surface and an outer wall surface, the inner wall surface defining the inner cavity along the chip flute section.
[0016] The outer wall surface defines the exterior of the chip flute section.
[0017] Optionally, the wall is closed in the circumferential direction so that the cavity does not contact the outside in the radial direction along the longitudinal extension of the chip flute segment. Optionally, the chip flute segment comprises radial channels, which form a fluid connection from the inner cavity extending in the longitudinal direction to the outside of the chip flute segment. These channels can, for example, form openings in the wall for supplying coolant from the inner cavity.
[0018] The wall has a wall thickness measured from the outer wall surface to the inner wall surface when viewed in a cross section perpendicular to the longitudinal axis. The wall thickness at a point of the wall is the shortest length of a straight line intersecting the point, as measured from the inner wall surface to the outer wall surface, when viewed in the cross section.
[0019] The outer wall surface of the chip groove segment defines the chip groove surface. Preferably, the chip groove surface extends radially inward relative to the surface at the maximum diameter and forms a channel that opens radially outward, the channel having a longitudinal extension. In the circumferential direction, the channel is defined by a first edge and a second edge that intersect the radial outer surface. In the finished rotary metal cutting tool, these edges can be the leading edge and the trailing edge seen in the direction of rotation. Optionally, the channel is straight in the longitudinal direction, or extends at a certain angle relative to the longitudinal axis, for example forming a spiral line extending backward, the spiral line having a constant helix angle, an increasing helix angle, a decreasing helix angle, or a helix angle that varies in any other desired manner. In the finished rotary metal cutting tool, the channel can form a chip groove with or without further treatment, such as coating. Preferably, when viewed in a cross section perpendicular to the longitudinal axis, the chip groove surface is concave inward.
[0020] When observed in cross-sections at multiple locations along the majority of the length of the chip flute segment (and preferably along the entire length of the chip flute segment), the wall thickness is constant along a portion of the chip flute surface in the circumferential direction, and the wall thickness is at most 25% of the maximum diameter of the chip flute segment, including finishing allowance. Preferably, the wall thickness is constant, and the wall thickness is at most 20% of the maximum diameter of the chip flute segment, and more preferably at most 15%, including finishing allowance. Although having a smaller wall thickness is beneficial to reduce material consumption, for blanks with a smaller maximum diameter, a larger percentage is sometimes required to obtain a thickness sufficient to provide acceptable strength. The chip flute surface may include several such portions. When observed in these sections, preferably, the one or several portions constitute most of the chip flute surface. The chip flute surface may have an area in which the wall thickness is such a defined wall thickness. The chip flute surface may include several such areas, or the area is a continuous area. Preferably, the area extends over the entire chip flute surface, except at portions along its edges and / or at any internal structures within the cavity. Preferably, the total area is at least 50%, preferably at least 75%, of the chip flute surface.
[0021] According to one embodiment, the chip flute segment further defines a main body clearance surface. Preferably, the main body clearance surface is configured to be suitable for a radially outer surface of a finished rotary metal cutting tool, which extends forward in the rotational direction from a leading edge of the chip flute surface of the finished rotary metal cutting tool in the rotational direction. For example, the main body clearance surface is suitable for a clearance surface located behind the cutting edge in the rotational direction in a milling tool, or is suitable for a clearance surface located behind the boundary surface in the rotational direction in a drilling tool.
[0022] According to one embodiment, when viewed in a cross section at multiple positions along a majority of the length of the chip flute segment (and preferably along the entire length of the chip flute segment), the wall thickness is constant and is at most 25% of the maximum diameter of the chip flute segment in the circumferential direction. Preferably, the wall thickness is constant and is at most 20% of the maximum diameter of the chip flute segment, and more preferably at most 15%. Although a smaller wall thickness is beneficial for reducing material consumption, for blanks with a smaller maximum diameter, a larger percentage is sometimes required to obtain a thickness sufficient to provide acceptable strength. The main body gap surface may include several such portions. When viewed in the cross section, preferably, the one or several portions constitute a majority of the main body gap surface. The main body gap surface may have an area in which the wall thickness is a defined wall thickness. The main body gap surface may include several such areas, or the area is a continuous area. Preferably, the area extends over the entire main body gap surface, except at a portion along its cutting edge and / or at any internal structure in the cavity. Preferably, the total area accounts for at least 50%, preferably at least 75% of the body interstitial surface.
[0023] According to one embodiment, along said one portion of the chip flute surface and / or along said one portion of the body clearance surface, the inner wall surface substantially follows the contour of the outer wall surface. Preferably, the inner wall surface follows the contour of the outer wall surface along most of it. Preferably, the inner wall surface follows the contour of the outer wall surface, except at a portion along its cutting edge and / or at any internal structure in the cavity.
[0024] According to one embodiment, the wall thickness along the one portion of the main body clearance surface is less than the wall thickness along the one portion of the chip flute surface when viewed in cross-section at a plurality of locations along a majority of the length of the chip flute segment. Preferably, the wall thickness along the one portion of the main body clearance surface has no finishing allowance. Since tolerances are less critical at this portion of the finished tool, a surface within the tolerance range can be produced without grinding allowance. Advantageously, thereby, further blank material can be saved.
[0025] According to one embodiment, the shank segment has a maximum diameter. Optionally, the maximum diameter is located in a cross section at a certain position along the longitudinal length of the shank segment, or the maximum diameter is the same in all cross sections along the longitudinal length of the shank segment. For example, the diameter may decrease or increase from the front end of the shank segment backwards.
[0026] The shank segment comprises a longitudinally extending wall, the wall surrounding an inner cavity extending in the longitudinal direction, the wall having an inner wall surface and an outer wall surface, the inner wall surface defining the cavity, the outer wall surface defining the exterior of the shank segment. When viewed in a cross section perpendicular to the longitudinal axis, the wall has a wall thickness measured from the outer wall surface to the inner wall surface. The wall thickness should be understood and measured corresponding to the wall thickness of the chip flute segment.
[0027] Preferably, the internal cavity of the shank segment is aligned with and in fluid communication with the internal cavity of the chip flute segment.For example, the cavity may be a single continuous cavity.
[0028] Preferably, the outer surface of the shank segment is configured as a surface suitable for producing a finished rotary metal cutting tool for connecting the cutting tool to a machine tool spindle or an adapter for connecting the cutting tool to a machine tool spindle. For example, the outer surface of the shank segment may be a conical or cylindrical surface. The surface may include features such as, for example, grooves or protrusions for producing an element that forms part of an interlocking connection.
[0029] Preferably, the rear end of the handle section, i.e. the rear end of the blank, is open. Thus, excess blank material (in powder form), for example produced by a printing step in an additive manufacturing process, can be removed from the inner cavity. The powder material can be collected and reused in certain applications.
[0030] According to one embodiment, when viewed in cross-section at multiple locations along most of the length of the shank segment (and preferably along the entire length of the shank segment), the wall thickness is constant along a portion of the outer surface of the shank segment in the circumferential direction, and the wall thickness is at most 25% of the maximum diameter of the shank segment, including finishing allowance. Preferably, the wall thickness is constant and is at most 20% of the maximum diameter of the shank segment, and more preferably at most 15%. Although smaller wall thickness is beneficial for reducing material consumption, for blanks with smaller maximum diameters, a larger percentage is sometimes required to achieve a wall thickness sufficient to provide acceptable strength. The outer surface of the shank segment may include several such portions. When viewed in cross-section, preferably, the one portion or several portions constitute the majority of the outer surface of the shank segment. The outer surface of the shank segment may have an area in which the wall thickness is such a defined wall thickness. The outer surface of the shank segment may include several such areas, or the area is a continuous area. Preferably, the area extends over the entire outer wall surface of the handle segment, or the entire outer wall surface of the handle segment except for the portion at any internal structure in the cavity. Preferably, the total area accounts for at least 50%, preferably at least 75% of the outer wall surface of the handle segment.
[0031] The wall thickness can be measured corresponding to the wall thickness of the chip flute section.
[0032] According to one embodiment, along said one portion of the outer surface of the shank section, the inner wall surface substantially follows the contour of the outer wall surface.Preferably, the inner wall surface follows the contour of the outer wall surface except at portions along any internal structure in the cavity.
[0033] Preferably, the wall thickness along said one portion of the outer wall surface is greater than the wall thickness along said one portion of the chip flute surface when viewed in cross section along a majority of the length of the shank section.
[0034] According to one embodiment, the wall thickness of said one portion of the outer wall surface of the shank segment is equal to the wall thickness of said one portion of the main body clearance surface of the chip flute segment when viewed in cross-section at multiple locations along a majority of the length of the shank segment. In this way, it is ensured that along both portions the wall is not thicker than required to provide sufficient strength and allowance for post-processing (e.g. grinding). Thus, advantageously, overuse of blank material is prevented.
[0035] According to a preferred embodiment, all of the total areas together account for at least 50%, preferably at least 75%, of the total area of the respective surface. In this way, advantageously, excessive use of blank material is prevented.
[0036] Preferably, the wall thickness of each of the one portion along the chip flute surface and / or the body clearance surface is at least 5% of the maximum diameter of the chip flute segment. Preferably, the wall thickness of the one portion along the outer surface of the shank segment is at least 5% of the maximum diameter of the shank segment. Thus, it is ensured that the wall has sufficient strength.
[0037] According to one embodiment, the body of the blank further comprises a central core rod extending through the cavity of the shank segment and / or the chip flute segment along the longitudinal axis. For example, the core rod may extend through the chip flute segment and contact at the deepest point of the channel (which will form the chip flute in the finished rotary metal cutting tool) to connect to the inner wall surface. According to one embodiment, the body of the blank further comprises a plurality of longitudinally extending partitions, each of which extends from the core rod to the inner wall surface in the cavity of the shank segment and / or the chip flute segment. The core rod and / or the partitions form an internal structure in the cavity. For example, the partitions may be radially extending inner walls, the wall thickness of which may be less than the wall thickness in the region of the outer wall surface. Compared to the prior art blanks, these embodiments provide enhanced stability while still significantly reducing the blank material. Preferably, the internal structure extends through the shank section, where the increased strength is particularly advantageous because this portion may be subject to high clamping forces at the interconnection with the machine tool spindle in the finished rotary metal cutting tool produced from the blank. In other embodiments, the internal structure extends through the chip flute section in addition or as an alternative. In this way, they increase stability, thereby reducing undesirable twisting and bending of the finished rotary metal cutting tool produced from the blank during operation.
[0038] According to one embodiment, the blank is a drilling tool blank, wherein the outer wall surface further defines a boundary surface extending in the longitudinal direction, the boundary surface is located between the chip flute surface and the body clearance surface in the circumferential direction and intersects the chip flute surface, and wherein, when viewed in each cross section perpendicular to the longitudinal axis, the boundary surface forms an arc having a radius of curvature of half the maximum diameter of the cross section. Thereby, it is ensured that the outer wall surface of the chip flute section corresponds as closely as possible to the outer wall surface of the finished drill produced from the blank, thereby avoiding unnecessary grinding and material waste.
[0039] Preferably, the body clearance surface of the drilling tool blank extends behind the boundary surface in the direction of rotation when viewed in the circumferential direction of rotation of the finished drilling tool and is connected to the leading edge of the chip flute surface via a trailing edge.
[0040] According to one embodiment, the finishing allowance is 0.1 - 0.5 mm, preferably 0.15 - 0.45 mm. The finishing allowance can be constant for all relevant outer surfaces of the blank, or can be adjusted according to the amount of post-processing (e.g. in the form of grinding) required at each specific location. In particular, the finishing allowance at the boundaries can be different from the finishing allowance of other surfaces, because the requirements related to the support of the finished tool may require more or less grinding than other surfaces. For example, the finishing allowance in the area of the chip flute surface and the outer surface of the shank section can be 0.15 -0.45 mm.
[0041] Optionally, the cutter head segment is a solid body or comprises an internal cavity.Preferably, the cutter head segment comprises at least one internal coolant channel, which is open axially forward and / or radially outward.
[0042] According to an embodiment in which the blank is a drilling tool blank, the front end of the cutter head section is a cone with a taper angle of 90-150 °. Preferably, the axial length of the cone is 0.75-1.5 times the maximum diameter of the chip flute section. Compared with the cylindrical cutter head section of the prior art blank, these features are suitable for the production of the cutting edge of the finished drilling tool and further reduce the required blank material. Optionally, the cutter head section includes a blade seat for receiving a cutting blade.
[0043] According to one embodiment, the blank is a milling tool blank, the milling tool blank comprising a cutting edge for forming a cutting edge at the intersection of the chip flute surface and the main body clearance surface. Preferably, at the front portion of the chip flute surface in the rotational direction, the main body clearance surface has a smooth transition to the chip flute surface.
[0044] Optionally, the milling tool blank comprises a head section in the form of an axially short and closed front end, or comprises a solid head section with sufficient axial extension to allow grinding of the front cutting edge. Optionally, the closed end comprises an opening for a coolant. Preferably, the head section of the drilling tool blank or the milling tool blank comprises a surface for forming the front start of the chip flute surface.
[0045] According to one embodiment, the outer wall surface of the chip flute segment comprises a plurality of said chip flute surfaces and a plurality of said main body clearance surfaces, wherein said chip flute surfaces and said main body clearance surfaces are arranged alternately in the circumferential direction. Preferably, in the finished rotary metal cutting tool produced from the blank, the number of chip flute surfaces (which form the channel for the chip flute) corresponds to the number of cutting edges that the finished rotary metal cutting tool will have.
[0046] The invention also relates to a rotary metal cutting tool produced by grinding a blank for a rotary metal cutting tool as described herein. Preferably, the rotary metal cutting tool is a drilling tool or a milling tool. BRIEF DESCRIPTION OF THE DRAWINGS
[0047] In the following, exemplary embodiments will be described in more detail with reference to the accompanying drawings, in which:
[0048] Figure 1 is a perspective top view of a first embodiment of the present invention in the form of a drilling tool blank;
[0049] Figure 2 is a perspective bottom view of the first embodiment;
[0050] Figure 3 is a longitudinal section containing the central longitudinal axis of the first embodiment;
[0051] Figure 4 is a side view of the first embodiment;
[0052] Figure 5A - 5C is in Figure 4 A cross section of the first embodiment in the axial position indicated in;
[0053] Figure 6 is a perspective top view of a second embodiment of the present invention in the form of a drilling tool blank with an internal structure;
[0054] Figure 7 is a perspective bottom view of a second embodiment;
[0055] Figure 8 is a longitudinal section containing the central longitudinal axis of the second embodiment;
[0056] Fig. 9 is a side view of a second embodiment;
[0057] Fig. 10A - 10C is at Fig. 9 A cross section of the first embodiment in the axial position indicated in;
[0058] Fig.11 is a perspective top view of a third embodiment of the present invention in the form of a milling tool blank;
[0059] Fig.12 is a perspective bottom view of a third embodiment;
[0060] Fig.13 is a longitudinal section containing the central longitudinal axis of the third embodiment;
[0061] Fig.14is a side view of a third embodiment;
[0062] Fig.15A - 15C is at Fig.14 Cross section of the third embodiment in the axial position indicated in FIG.
[0063] All the figures are schematic, not necessarily to scale, and generally show only parts which are necessary to elucidate the various embodiments, while other parts may be omitted or merely suggested. Unless otherwise indicated, similar reference numerals in different figures denote similar components. DETAILED DESCRIPTION
[0064] See also Figure 1 5 , depicts a first embodiment of a blank for a rotary metal cutting tool according to the invention in the form of a drilling tool blank. The drilling tool blank comprises an elongated single-piece body having a front end 1 and a rear end 2.
[0065] The drilling tool blank is produced by an additive manufacturing process, which includes the following steps: printing a printable and sinterable powder component, which contains tungsten carbide and cobalt. After printing, the printed green body is sintered to form the drilling tool blank. In subsequent production steps, the drilling tool blank can be ground and coated to obtain a drilling tool of the type sometimes referred to as a solid round tool, which in this example embodiment is a twist drill.
[0066] The longitudinal axis 3 extends from the front end 1 to the rear end 2. The longitudinal axis 3 is the central axis and will form the axis of rotation in the finished drilling tool. The body comprises a head section 4, a chip flute section 5 and a shank section 6, see Figure 3 The three sections 4 , 5 , 6 together form the one-piece body.
[0067] The chip flute segment 5 is located axially between the head segment 4 and the shank segment 6. The chip flute segment has a maximum diameter 7 which is constant along the longitudinal extension of the chip flute segment 5. In the present exemplary embodiment, this maximum diameter 7 is 6.6 mm.
[0068] The chip flute segment 5 comprises a longitudinally extending wall 8 which surrounds a longitudinally extending inner cavity 9. The wall 8 is closed in the circumferential direction, so that the cavity has no contact with the outside in the radial direction along the longitudinal extension of the chip flute segment 5.
[0069] The wall 8 has an inner wall surface 10 and an outer wall surface. The inner wall surface 10 delimits the inner cavity 9 along the chip flute section 5.
[0070] The outer wall surface defines the exterior of the chip flute segment 5 , which includes a chip flute surface 11 , a body clearance surface 12 , and a boundary surface 13 .
[0071] The chip flute surface 11 extends radially inwards relative to the maximum diameter 7 and forms a channel opening radially outwards, which has a longitudinal extension. In the circumferential direction, the channel is defined by a first edge 15 at the intersection of the chip flute surface 11 and the body clearance surface 12 and by a second edge 16 at the boundary surface 13. In the finished drilling tool, the first edge 15 is the leading edge of the chip flute surface 11 in the rotational direction, and the second edge 16 is the trailing edge of the chip flute surface 11 in the rotational direction. The channel forms a helix extending backwards, which has a constant helix angle. The chip flute surface 11 is radially concave inwards.
[0072] When in Figure 5B The wall 8 has a wall thickness 14 measured from the outer wall surface to the inner wall surface when viewed in the cross section shown perpendicular to the longitudinal axis. The wall thickness 14 is constant along a portion of the chip flute surface 11 in the circumferential direction and is at most 20% of the maximum diameter 7, including finishing allowance. For a drilling tool blank with a maximum diameter 7 of 6.6 mm in the chip flute section 5, it is preferred to have a greater wall thickness 14 of at most 20% of the maximum diameter due to strength requirements. In the present exemplary embodiment, the wall thickness is 0.9 mm, wherein the finishing allowance is 0.4 mm. In the present exemplary embodiment, the wall thickness 14 of the portion of the chip flute surface 11 is constant in the longitudinal direction along a helical line following the chip flute surface 11. The total area of the chip flute surface 11 in which the wall thickness 14 remains constant covers the entire chip flute surface 11, except at the first edge 15 and the second edge 16, where the wall 8 forms a corner with the body clearance surface 12 and the boundary surface 13, respectively. The total area of the chip flute surface 11 in which the wall thickness 14 remains constant is a continuous surface, which exceeds 75% of the total chip flute surface 11.
[0073] In addition, see Figure 5B, along a portion of the main body clearance surface 12 in the circumferential direction, the wall thickness 14 is constant and is at most 20% of the maximum diameter 7. In the present exemplary embodiment, the wall thickness is 0.5 mm, wherein there is no finishing allowance. Therefore, the wall thickness 14 of the portion along the main body clearance surface 12 is smaller than the wall thickness 14 of the portion along the chip groove surface 11 by a finishing allowance of 0.4 mm. In the present exemplary embodiment, the wall thickness 14 of the portion of the main body clearance surface 12 is constant in the longitudinal direction along the spiral line following the main body clearance surface 12. The total area of the main body clearance surface 12 in which the wall thickness 14 remains constant covers the main body clearance surface 12, except in the area in which the wall 8 (the wall 8 and the chip groove surface 12, and the wall 8 and the boundary surface 13) form a corner. The total area of the main body clearance surface 12 in which the wall thickness 14 remains constant is a constant, continuous surface, which exceeds 75% of the total main body clearance surface 12.
[0074] See also Figure 1 , 2 , the boundary surface 13 extends in the longitudinal direction along the chip groove section 5 and follows the helix of the cutting groove surface 11 at the second edge 16 of the chip groove surface 11. Therefore, the boundary surface 13 is located between the chip groove surface 11 and the main body clearance surface 12 in the circumferential direction and intersects with the chip groove surface 11 at the second edge 16 of the chip groove surface 11.
[0075] When Figure 5B When viewed in a cross section of the embodiment of the present invention, the boundary surface 13 forms an arc whose radius of curvature is half the maximum diameter of the cross section. In the present exemplary embodiment, in which the maximum diameter 7 is constant along the longitudinal length of the chip flute segment 5, the maximum diameter 7 of the chip flute segment is twice the radius of curvature. The radius of curvature is equal to the desired radius of curvature of the finished drilling tool, including the finishing allowance. In this and other embodiments, the desired radius of curvature of the finished drilling tool is the radius required for the support function of the boundary surface. In the present exemplary embodiment, the finishing allowance of the boundary is 0.3 mm.
[0076] As in Figure 5B It can be seen that in the chip flute section, the inner wall surface 10 substantially follows the contour of the outer wall surface along most of the chip flute surface 11 and along most of the body clearance surface 12. The inner wall surface 10 follows the contour of the outer wall surface except at the corner portions at the first edge 15 and the second edge 16.
[0077] The shank segment 6 comprises a wall 8 extending in the longitudinal direction, which surrounds an inner cavity 9 extending in the longitudinal direction. The inner cavity 9 of the shank segment 6 is continuous with the inner cavity 9 of the chip flute segment 5. The wall 8 has an inner wall surface 10 and an outer wall surface 17, which define the cavity. In this embodiment and other embodiments, the shank segment 6 has the shape of a hollow cylinder, wherein the outer wall surface 17 and the inner wall surface 10 are circular, and when viewed in a cross section at multiple positions along the longitudinal extension of the shank segment 6, these circles have different diameters. The diameter of the outer wall surface 17 constitutes the maximum diameter 7 of the shank segment 6 and remains constant along most of the longitudinal length of the shank segment 6. Therefore, the wall thickness 14 is constant in the circumferential direction and in the longitudinal direction along most of the area. The total area of the outer wall surface 17 of the shank segment 6, in which the wall thickness 14 remains constant, is a continuous surface, exceeding 75% of the total outer wall surface 17 of the shank segment 6.
[0078] In the present exemplary embodiment, the maximum diameter 7 of the shank segment is 6.6 mm. The constant wall thickness 14 of the shank segment 6 is at most 20% of the maximum diameter of the shank segment, including the finishing allowance. In the present exemplary embodiment, the wall thickness 14 of the majority of the shank segment 6 is 0.9 mm, wherein the finishing allowance is 0.4 mm. Thus, at the outer wall surface 17 of the shank segment 6, the wall thickness 14 and the finishing allowance of the wall thickness 14 are respectively equal to the wall thickness 14 and the finishing allowance at the chip flute surface 11.
[0079] At the rear end, the shank section 6 comprises a bevel portion 18 and a circular opening 19, which is connected to the inner cavity 9. The inner cavity 9 is fluidically connected to the outside through the opening 19.
[0080] The cutter head section 4 is a solid body and comprises two internal coolant passages 20 which open forward in the axial direction.
[0081] The front end of the tool head segment 4 includes a cone surface with a cone angle α of 120°. The axial length of the cone is about 0.9 times the maximum diameter 7 of the chip groove segment 5, and is 6.6 mm in this embodiment. The tool head segment 4 also includes a surface for forming the front end starting part 21 of the chip groove surface 11.
[0082] The tool head section 4 with a cone surface is configured to provide two cutting edges in a finished drilling tool. The outer wall surface of the chip flute section 5 of the drilling tool blank includes the two chip flute surfaces 11, the two body clearance surfaces 12 and the two boundary surfaces 13 as described above. These surfaces are alternately arranged in the circumferential direction according to their respective associated cutting edges.
[0083] Figure 6 – Figure 10 shows a second embodiment of a blank according to the invention as described.
[0084] The second embodiment is in the form of a drilling tool blank which differs from the first embodiment only in that it includes an internal structure in the internal cavity 9. In the chip flute section 5, a central core rod 22 extends longitudinally. The core rod 22 contacts and connects to the inner wall surface 10 at the deepest point of the channel which will form the chip flute in the finished rotary metal cutting tool. The channel is defined by the chip flute surface 11.
[0085] The core rod 22 also extends through the shank section 6. The core rod 6 of the shank section 6 is continuous with the core rod 22 of the chip flute section 5. A plurality of longitudinally extending partitions 23 (four in this embodiment) each extend from the core rod 22 to the inner wall surface 10 located in the cavity 9.
[0086] The third embodiment is a milling tool blank, and Fig.11 – shown in FIG. 15 . The milling tool blank differs from the first embodiment in that it has no boundary surface 13, but a cutting edge 24 for forming a cutting edge is provided at the intersection of the chip groove surface 11 and the main body clearance surface 12. Preferably, at the front of the chip groove surface 11 in the rotational direction, the main body clearance surface 12 has a smooth transition to the chip groove surface 11. The head section 4 is a solid body with sufficient axial extension to allow grinding of the front cutting edge. The front end is closed toward the internal cavity 9.
Claims
1. A blank for a rotary metal cutting tool, the blank comprising an elongated one-piece body having a front end (1), a rear end (2) and a longitudinal axis (3) extending from the front end (1) to the rear end (2), wherein the body comprises: - a blade head section (4), the blade head section (4) extending longitudinally rearward from the front end (1), - a shank section (6), said shank section (6) extending longitudinally forward from said rear end (2), - a chip flute section (5), which extends in the longitudinal direction and is located between the shank section (6) and the cutter head section (4) and has a maximum diameter (7), in, - the chip flute segment (5) comprises a longitudinally extending wall (8), the wall (8) surrounding an inner cavity (9) extending in the longitudinal direction, the wall (8) having an inner wall surface (10) and an outer wall surface, the inner wall surface (10) defining the cavity (9), - the outer wall surface defines a chip flute surface (11), and wherein, - when viewed in a cross section perpendicular to the longitudinal axis (3), the wall (8) has a wall thickness (14) measured from the outer wall surface to the inner wall surface (10), It is characterized in that The wall thickness (14) is constant along a portion of the chip flute surface (11) in the circumferential direction when viewed in cross-section at multiple locations along a majority of the length of the chip flute segment (5), and is at most 25%, preferably at most 20%, and more preferably at most 15% of the maximum diameter (7) of the chip flute segment (5), including finishing allowance.
2. A blank according to claim 1, wherein the outer wall surface of the chip flute segment (5) further defines a main body clearance surface (12), wherein the wall thickness (14) is constant along a portion of the main body clearance surface (12) in the circumferential direction when viewed in cross-section at multiple locations along a majority of the length of the chip flute segment (5) and is at most 25%, preferably at most 20%, and more preferably at most 15% of the maximum diameter (7) of the chip flute segment (5).
3. The blank according to claim 2, wherein: When viewed in cross-section at multiple locations along a majority of the length of the chip flute segment (5), the wall thickness (14) along the one portion of the body clearance surface (12) is less than the wall thickness (14) along the one portion of the chip flute surface (11).
4. A blank according to any preceding claim, wherein - the shank section (6) has a maximum diameter (7), - the handle section (6) comprises a longitudinally extending wall (8), the wall (8) surrounding an inner cavity extending in the longitudinal direction, the wall (8) having an inner wall surface (10) and an outer wall surface (17), the inner wall surface (10) defining the cavity, and, - when viewed in a cross section perpendicular to the longitudinal axis (3), the wall (8) has a wall thickness (14) measured from the outer wall surface (17) to the inner wall surface (10), - when viewed in cross-section at multiple locations along a majority of the length of the shank segment (6), the wall thickness (14) is constant along a portion of the outer surface of the shank segment (6) in the circumferential direction, and the wall thickness (14) is at most 25%, preferably at most 20%, and more preferably at most 15% of the maximum diameter (7) of the shank segment (6), including finishing allowance.
5. A blank according to claim 4 and any one of claims 2-3, wherein the wall thickness (14) of the portion of the outer wall surface (17) of the shank segment (6) is equal to the wall thickness (14) of the portion of the chip groove surface (11) along the chip groove segment (5) when observed in cross-section at multiple positions along a majority of the length of the shank segment (6).
6. A blank according to any preceding claim, wherein the chip groove surface (11), the body clearance surface (12) or the outer wall surface (17) of the shank section (6) each has an area in which the wall thickness (14) is a defined wall thickness, wherein the total area of each respective surface accounts for at least 50%, preferably at least 75%, of the respective surface.
7. A blank according to claim 6, wherein all of said total areas together account for at least 50%, preferably at least 75% of the total area of said surface.
8. A blank according to any preceding claim, wherein the finishing allowance is 0.1 - 0.5 mm, preferably 0.15 - 0.45 mm.
9. The blank according to any preceding claim, further comprising a central core rod (22) extending along the longitudinal axis (3) through the cavity of the shank section (6) and / or the chip flute section (5).
10. The blank according to claim 9, further comprising a plurality of longitudinally extending partitions (23), each partition (23) extending from the core rod to an inner wall surface (10) in the cavity of the shank section (6) and / or the chip flute section (5).
11. A blank according to any preceding claim, wherein the blank is a printed and sintered component comprising a cemented carbide component.
12. A blank according to any one of claims 2 to 11, wherein the blank is a drilling tool blank, wherein - the outer wall surface further defines a boundary surface (13) extending in the longitudinal direction, the boundary surface (13) being located between the chip groove surface (11) and the main body clearance surface (12) in the circumferential direction and intersecting with the chip groove surface (11), and wherein, - When viewed in a cross section perpendicular to the longitudinal axis (3), the boundary surface (13) forms an arc having a radius of curvature that is half the maximum diameter of the cross section.
13. The blank according to claim 12, wherein the cutter head segment (4) is a solid body comprising at least one internal coolant channel (20).
14. A blank according to any one of claims 2 to 11, wherein the blank is a milling tool blank, the milling tool blank comprising a cutting edge (24) for forming a cutting edge at the intersection of the chip flute surface (11) and the body clearance surface (12).
15. The blank according to claims 2 - 14, wherein the outer wall surface of the chip flute segment (5) comprises a plurality of the chip flute surfaces (11) and a plurality of the body clearance surfaces (12), wherein: The chip groove surfaces (11) and the main body gap surfaces (12) are arranged alternately in the circumferential direction.
16. A rotary metal cutting tool produced by grinding a blank for a rotary metal cutting tool according to any one of the preceding claims.