Blanks for rotary metal cutting tools

Abstract

The present invention relates to a blank for a rotary metal cutting tool, the blank including 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). The body includes a head portion (4), a shaft portion (6), and a chip flute portion (5) having a maximum diameter (7). The chip flute portion (5) includes a longitudinally extending wall (8) surrounding a longitudinally extending internal cavity (9), the wall (8) having an inner wall surface (10) and an outer wall surface that define the cavity (9). The outer wall surface defines a chip flute surface (11). 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). When viewed in cross section at a location along the major length of the chip flute section (5), the wall thickness (14) is constant circumferentially along a portion of the chip flute face (11) and is up to 25% of the maximum diameter (7) of the chip flute section (5), including finish tolerances.

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 technology]

[0002] Rotary metal cutting tools, such as drills and mills, are typically manufactured from blanks. A known type of blank is a cylindrical or conical rod of steel or a sintered powder composition. The rod is machined, for example, by grinding, to form the features of the finished rotary metal cutting tool. Examples of such basic features are chip flutes, clearance surfaces, cutting edges, and / or shafts with dimensions within desired tolerances. Another type of known blank already contains some of these features, such as chip flutes, which roughly correspond to their finished dimensions. After grinding, the blank is often coated to provide the finished rotary metal cutting tool.

[0003] In addition to the problem of time-consuming machining, a problem with these known blanks is the high consumption of blank material for their production. Summary of the Invention

[0004] The object of the present invention is to at least partially eliminate the above-mentioned problems. This object is achieved according to the invention by a blank for a rotary metal cutting tool as set forth in claim 1.

[0005] The present invention relates to a blank for a rotary metal cutting tool, the blank including an elongated unitary body having a front end, a rear end, and a longitudinal axis extending from the front end to the rear end, the body comprising: a head portion extending rearward in the longitudinal direction from the front end portion; a shaft portion extending longitudinally forward from the rear end portion; a tip flute portion extending longitudinally and located between the shaft portion and the head portion, the tip flute portion having a maximum diameter; the chip flute portion includes a longitudinally extending wall surrounding a longitudinally extending interior cavity, the wall having an inner wall surface defining the cavity and an outer wall surface; the 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 an outer wall surface to an inner wall surface; When viewed in cross section at a location along the major length of the chip flute, the wall thickness is constant circumferentially around a portion of the chip flute face and is at most 25%, preferably at most 20%, and more preferably at most 15% of the maximum diameter of the chip flute, including finishing tolerances.

[0006] The blank of the present invention includes a chip flute portion including a longitudinally extending wall. The wall has an inner wall surface surrounding a cavity, an outer wall surface, and a wall thickness. The outer wall can be designed to generally correspond to the final shape of the corresponding feature on the completed rotary metal cutting tool. Specifically, the outer wall surface includes a chip flute surface.

[0007] Manufacturing methods, including additive manufacturing, which builds an object one layer at a time, allow the blank to have almost any desired shape. By designing the cavity's shape, the wall thickness, measured from the outer wall surface to the inner wall surface in a cross section perpendicular to the longitudinal axis, can be freely selected. By selecting a constant wall thickness that is no more than 25% of the maximum diameter of the chip flute, including finishing tolerances, it is ensured that the wall is not thicker than necessary to provide sufficient strength and room for post-processing, such as grinding. This advantageously prevents excessive use of blank material.

[0008] The blank is suitable for producing rotary metal cutting tools, such as milling or drilling tools. Preferably, the rotary cutting tools intended to be produced from the blank of the present invention are of the type sometimes referred to as "solid round tools." These tools are solid in the sense that they are a one-piece, integral part with one or several integral cutting edges. Therefore, the group of tools referred to as solid round tools typically also includes tools with internal cavities, such as coolant channels. Other types of rotary metal cutting tools are those that include a body with an interchangeable cutting insert or an interchangeable head. According to an embodiment of the present invention, the blank is suitable for producing a main tool body for such tools.

[0009] The blank comprises an elongated, monolithic body. Preferably, the body is manufactured by additive manufacturing, e.g., by building the body one layer at a time, e.g., by printing. Preferably, a printable and sinterable powder composition is used, e.g., steel, or a powder comprising tungsten carbide and cobalt. Thus, the blank can 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 completed rotary metal cutting tool. Preferably, the longitudinal axis is a central axis.

[0011] A cross section is to be understood as a longitudinal portion of the body, in other words the entire body along a portion of its longitudinal length from a first cross section or end to a second cross section or end.

[0012] The body includes a head portion extending rearward from the front end. Optionally, the head portion is a short longitudinal end portion configured to form a cutting head.

[0013] A shaft portion extends forward from the rear end, and a tip flute portion is located between the head portion and the shaft portion. Preferably, the tip flute portion is connected to the shaft portion and the head portion. According to an embodiment, the body includes a further portion, such as a transition portion, between the shaft portion and the head portion.

[0014] The chip flute has a maximum diameter. Optionally, the maximum diameter is located at a cross-section along the longitudinal length of the chip flute or is the same at all cross-sections along the longitudinal length of the chip flute. The diameter may, for example, decrease or increase rearward from the front end of the chip flute.

[0015] The chip flute includes a longitudinally extending wall surrounding a longitudinally extending internal cavity, the wall having an inner wall surface and an outer wall surface, the inner wall surface defining the internal cavity along the chip flute.

[0016] The outer wall surface defines the exterior of the chip flute portion.

[0017] Optionally, the wall is circumferentially closed such that the cavity has no radial exterior contact along the longitudinal extension of the chip flute. Optionally, the chip flute includes radial channels that form fluid connections from the longitudinally extending internal cavity to the exterior of the chip flute. These may, for example, form openings in the wall for supplying coolant from the internal cavity.

[0018] As 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 of a wall at a point on the wall in a cross-sectional view is the length of the shortest straight line intersecting the point when measured from the inner wall surface to the outer wall surface.

[0019] The outer wall surface of the chip flute section defines a chip flute surface. Preferably, the chip flute surface extends radially inward at its maximum diameter to form a radially outward open channel with a longitudinal extension. Circumferentially, the channel is bounded by first and second edges at its intersection with the radially outer surface. In the finished rotary metal cutting tool, these edges may be leading and trailing edges when viewed in the direction of rotation. Optionally, the channel may be straight longitudinally or extend at an angle relative to the longitudinal axis, forming a rearward-extending helix with a helix angle that is constant, increasing, decreasing, or varies in any other desired manner. In the finished rotary metal cutting tool, the channel may form the chip flute with or without further processing, such as a coating. Preferably, the chip flute surface is inwardly concave when viewed in a cross section perpendicular to the longitudinal axis.

[0020] When viewed in cross section along the major length of the chip flute, preferably along the entire length of the chip flute, the wall thickness is constant circumferentially along a portion of the chip flute face and is up to 25% of the maximum diameter of the chip flute, including finish tolerances. Preferably, the wall thickness is constant and is no more than 20%, more preferably no more than 15%, of the maximum diameter of the chip flute, including finish tolerances. While having a small wall thickness is beneficial for low material consumption, a larger percentage may be required for blanks with small maximum diameters to achieve a thickness sufficient to provide acceptable strength. The chip flute face can include several such portions. As viewed in cross section, preferably, one or more portions make up the majority of the chip flute face. The chip flute face can have a region where the wall thickness is as specified. The chip flute face may include several such regions, or the region is a continuous region. Preferably, the region extends across the entire flute face of the chip, except for portions along the edge of the chip and / or any internal structure within the cavity. Preferably, the total area comprises at least 50%, preferably at least 75% of the chip flute surface.

[0021] According to one embodiment, the chip flute portion further defines a body clearance surface. Preferably, the body clearance surface is configured to correspond to a radially outer surface extending rotationally forward from the leading edge of the chip flute surface on the finished rotary metal cutting tool. The body clearance surface may, for example, be suitable for a clearance surface rotating behind a cutting edge on a milling tool or a clearance surface rotating behind a margin surface on a drilling tool.

[0022] According to one embodiment, when viewed in cross section at a location along the major length of the chip flute, preferably along the entire length of the chip flute, the wall thickness is constant circumferentially along a portion of the body clearance surface and is up to 25% of the maximum diameter of the chip flute. Preferably, the wall thickness is constant and is no more than 20%, more preferably no more than 15%, of the maximum diameter of the chip flute. While having a small wall thickness is beneficial for low material consumption, blanks with small maximum diameters may require a larger percentage to achieve a thickness sufficient to provide acceptable strength. The body clearance surface may include several such portions. As viewed in cross section, preferably, one or more portions constitute the majority of the body clearance surface. The body clearance surface may have a region where the wall thickness is as specified. The chip flute surface may include several such regions, or the region may be a continuous region. Preferably, the region extends across the entire body clearance surface, except for portions along its edges and / or any internal structure within the cavity. Preferably, the total area comprises at least 50%, preferably at least 75% of the body clearance surface.

[0023] According to one embodiment, the inner wall surface substantially follows the contour of the outer wall surface along a portion of the chip flute surface and / or along a portion of the body clearance surface. Preferably, the inner wall surface follows the contour of the outer wall surface along a major portion. Preferably, the inner wall surface follows the contour of the outer wall surface except along its edges and / or any internal structure within the cavity.

[0024] According to one embodiment, the wall thickness along a portion of the body clearance surface is less than the wall thickness along a portion of the chip flute surface when viewed in cross section at a location along the major length of the chip flute section. Preferably, there is no finish tolerance on the wall thickness along the portion of the body clearance surface. Because tolerances are less critical in this portion of the finished tool, it is possible to manufacture the surface within tolerance without allowing for grinding. This advantageously saves additional blank material.

[0025] According to one embodiment, the shaft portion has a maximum diameter. Optionally, the maximum diameter is located at a cross-section along the longitudinal length of the shaft portion or is the same at all cross-sections along the longitudinal length of the shaft portion. The diameter may, for example, decrease or increase from the front end of the shaft portion rearward.

[0026] The shaft portion includes a longitudinally extending wall surrounding a longitudinally extending interior cavity, the wall having an inner wall surface defining the cavity and an outer wall surface defining an exterior of the shaft portion. As 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 relative to the wall thickness of the tip flute portion.

[0027] Preferably, the internal cavity of the shaft portion and the internal cavity of the tip flute portion are aligned and fluidly connected. The cavities may, for example, be a single continuous cavity.

[0028] Preferably, the outer surface of the shaft portion is configured to be suitable for producing a surface of a finished rotary metal cutting tool for connection to a machine spindle or an adapter for connection to a machine spindle. The outer surface of the shaft portion may be, for example, a conical or cylindrical surface. The surface may include features for producing elements that form part of the interlocking connection, such as grooves or protrusions.

[0029] Preferably, the rear end of the shaft portion, which is also the rear end of the blank, is open so that excess blank material, e.g., in the form of powder from production by a printing step in an additive manufacturing process, can be removed from the internal cavity. The powder material can be collected and, in some applications, reused.

[0030] According to one embodiment, when viewed in cross section at a location along the main length of the shaft portion, preferably along the entire length of the tip flute portion, the wall thickness is constant circumferentially along a portion of the shaft portion's outer surface, and is up to 25% of the shaft portion's maximum diameter, including finishing tolerances. Preferably, the wall thickness is constant and is no more than 20%, more preferably no more than 15%, of the shaft portion's maximum diameter. While having a small wall thickness is beneficial for low material consumption, blanks with small maximum diameters may require a larger percentage to achieve a thickness sufficient to provide acceptable strength. The shaft portion's outer surface may include several such portions. Preferably, one or more portions constitute the majority of the shaft portion's outer surface as viewed in cross section. The shaft portion's outer surface may have a region with a specified wall thickness. The shaft portion's outer wall surface may include several such regions, or the region is a continuous region. Preferably, the region extends across the entire shaft portion's outer wall surface, or across the entire shaft portion's outer wall surface, excluding any internal structure within the cavity. Preferably, the total area comprises at least 50%, preferably at least 75% of the outer wall surface of the shaft portion.

[0031] The wall thickness may be measured relative to the wall thickness of the chip flute portion.

[0032] According to one embodiment, the inner wall surface substantially follows the contour of the outer wall surface along a portion of the outer surface of the shaft portion, preferably except along any internal structure within the cavity.

[0033] Preferably, when viewed in cross section along the main length of the shaft portion, the wall thickness along a portion of the outer wall surface is greater than the wall thickness along a portion of the tip flute surface.

[0034] According to one embodiment, when viewed in cross section along a major length of the shaft portion, the wall thickness of a portion of the outer wall surface of the shaft portion is equal to the wall thickness along a portion of the body clearance surface of the tip flute portion, ensuring that along both portions the wall is no thicker than necessary to provide sufficient strength and tolerance for post-processing, such as grinding, which advantageously prevents excessive use of blank material.

[0035] According to a preferred embodiment, all total areas together constitute at least 50%, preferably at least 75% of the total area of ​​the respective surfaces, which advantageously prevents excessive use of blank material.

[0036] Preferably, the wall thickness along each of a proportion of the chip flute surface and / or body clearance surface is at least 5% of the maximum diameter of the chip flute portion. Preferably, the wall thickness along a proportion of the outer surface of the shaft portion is at least 5% of the maximum diameter of the shaft portion. This ensures that the walls have sufficient strength.

[0037] According to one embodiment, the blank body further includes a central core rod extending along the longitudinal axis through the cavity of the shaft and / or chip flute section. For example, the core rod can extend through the chip flute section and contact the inner wall surface at the deepest point of the channel that will form the chip flute in the finished rotary metal cutting tool. According to one embodiment, the blank body further includes a plurality of longitudinally extending partition walls, each extending from the core rod to the inner wall surface within the cavity of the shaft and / or chip flute section. The core rod and / or partition walls form an internal structure within the cavity. The partition walls may, for example, be radially extending inner walls and may have a wall thickness that is smaller than the wall thickness in the region of the outer wall surface. These embodiments provide improved stability while still significantly reducing blank material compared to prior art blanks. Preferably, the internal structure extends through the shaft section, and the added strength is particularly advantageous in this area, which may be subject to high clamping forces when interconnected with a machine spindle in a finished rotary metal cutting tool manufactured from the blank. In other embodiments, the internal structures additionally or instead extend through the chip flutes, where they add stability such that undesirable twisting and bending during operation of a finished rotary metal cutting tool manufactured from the blank is reduced.

[0038] According to one embodiment, the blank is a drill tool blank, and the outer wall surfaces further define longitudinally extending margin surfaces circumferentially located between the chip flute surfaces and the body clearance surface and intersecting the chip flute surfaces, such that, as viewed in each cross section perpendicular to the longitudinal axis, the margin surfaces form an arc having a radius of curvature equal to half the maximum diameter of the cross section, thereby ensuring that the outer wall surfaces of the chip flute sections correspond as closely as possible to the outer wall surfaces of a finished drill produced from the blank, avoiding unnecessary grinding and material waste.

[0039] Preferably, when viewed circumferentially of the finished drilling tool, the body clearance surface of the drilling tool blank extends rotatably rearward of the margin surface and joins at a trailing edge to the leading edge of the chip flute surface.

[0040] According to one embodiment, the finishing tolerance is 0.1 to 0.5 mm, preferably 0.15 to 0.45 mm. The finishing tolerance may be constant for all relevant outer surfaces of the blank or may be adapted to the amount of post-processing required, for example, in the form of grinding, at each specific location. In particular, the finishing tolerance at the margin may differ from the finishing tolerance of other surfaces, since requirements regarding the support of the finishing tool may require more or less grinding than other surfaces. The finishing tolerance for the chip flute surface and the outer surface of the shaft section may be, for example, 0.15 to 0.45 mm.

[0041] Optionally, the head is solid or includes an internal cavity. Preferably, the head includes at least one internal coolant channel that opens axially forward and / or radially outward.

[0042] In embodiments where the blank is a drill tool blank, the front end of the head is conical with a cone angle of 90 to 150°. Preferably, the axial length of the cone is 0.75 to 1.5 times the maximum diameter of the chip flute. These features are suitable for generating cutting edges for the finished drill tool and reduce the amount of additional blank material required compared to the cylindrical heads of prior art blanks. Optionally, the head includes an insert seat for receiving a cutting insert.

[0043] According to one embodiment, the blank is a milling tool blank including edges for forming cutting edges at the intersections of the chip flute surfaces and the body clearance surface, preferably the body clearance surface having a smooth transition to the chip flute surface at a rotationally forward portion of the chip flute surface.

[0044] Optionally, the milling tool blank includes a head portion in the form of an axially short closed leading end, or a solid head portion having sufficient axial extension to allow grinding of the leading end cutting edge. Optionally, the closed end includes an opening for coolant. Preferably, the head portion of the drilling or milling tool blank includes a surface for forming the leading end start of the chip flute face.

[0045] According to one embodiment, the outer wall surface of the chip flute section includes a plurality of chip flute surfaces and a plurality of body clearance surfaces, the chip flute surfaces and the body clearance surfaces being circumferentially alternating. Preferably, the number of chip flute surfaces that form channels for the chip flutes in a finished rotary metal cutting tool produced from the blank corresponds to the number of cutting edges that the finished tool will have.

[0046] The present invention further relates to a rotary metal cutting tool manufactured by grinding a rotary metal cutting tool blank as described herein. Preferably, the rotary metal cutting tool is a drilling or milling tool.

[0047] Exemplary embodiments will now be described in more detail with reference to the accompanying drawings. [Brief explanation of the drawings]

[0048] [Figure 1] 1 is a top perspective view of a first embodiment of the present invention in the form of a drilling tool blank; FIG. [Figure 2] FIG. 2 is a bottom perspective view of the first embodiment. [Figure 3] FIG. 2 is a longitudinal cross-sectional view including the longitudinal center axis of the first embodiment. [Figure 4] FIG. 1 is a side view of the first embodiment. [Figure 5A] FIG. 5 is a cross-sectional view of the first embodiment at the axial position shown in FIG. 4. [Figure 5B] FIG. 5 is a cross-sectional view of the first embodiment at the axial position shown in FIG. 4. [Figure 5C]FIG. 5 is a cross-sectional view of the first embodiment at the axial position shown in FIG. 4. [Figure 6] FIG. 10 is a top perspective view of a second embodiment of the present invention in the form of a drill tool blank having an internal structure. [Figure 7] FIG. 10 is a bottom perspective view of the second embodiment. [Figure 8] FIG. 2 is a longitudinal cross-sectional view of the second embodiment, taken along the central longitudinal axis. [Figure 9] FIG. 10 is a side view of the second embodiment. [Figure 10A] FIG. 10 is a cross-sectional view of the first embodiment at the axial position shown in FIG. [Figure 10B] FIG. 10 is a cross-sectional view of the first embodiment at the axial position shown in FIG. [Figure 10C] FIG. 10 is a cross-sectional view of the first embodiment at the axial position shown in FIG. [Figure 11] FIG. 10 is a top perspective view of a third embodiment of the present invention in the form of a milling tool blank. [Figure 12] FIG. 10 is a bottom perspective view of the third embodiment. [Figure 13] FIG. 10 is a longitudinal cross-sectional view of the third embodiment, taken along the longitudinal center axis. [Figure 14] FIG. 10 is a side view of the third embodiment. [Figure 15A] FIG. 15 is a cross-sectional view of the third embodiment at the axial position shown in FIG. [Figure 15B] FIG. 15 is a cross-sectional view of the third embodiment at the axial position shown in FIG. [Figure 15C] FIG. 15 is a cross-sectional view of the third embodiment at the axial position shown in FIG. DETAILED DESCRIPTION OF THE INVENTION

[0049] All figures are schematic, not necessarily to scale, and generally show only those parts necessary to elucidate the respective embodiment, while other parts may be omitted or merely suggested. Unless otherwise indicated, like reference numerals refer to like parts in different figures.

[0050] A first embodiment of a blank for a rotary metal cutting tool according to the present invention in the form of a punch tool blank will now be described with reference to Figures 1 to 5. The punch tool blank comprises an elongated one-piece body having a front end 1 and a rear end 2.

[0051] The drill tool blank is produced by an additive manufacturing process that includes printing a printable and sinterable powder composition including tungsten carbide and cobalt. After printing, the printed green body is sintered to form the drill tool blank. In subsequent manufacturing steps, the drill tool blank can be ground and coated to obtain a type of drill tool sometimes referred to as a solid round tool, which in an exemplary embodiment is a twist drill.

[0052] A longitudinal axis 3 extends from the front end 1 to the rear end 2. The longitudinal axis 3 is the central axis and forms the axis of rotation of the completed drilling tool. The body includes a head portion 4, a chip flute portion 5, and a shaft portion 6 (compare Figure 3). These three portions 4, 5, and 6 form a unitary body.

[0053] The chip flute section 5 is axially located between the head section 4 and the shaft section 6. The chip flute section has a maximum diameter 7 that is constant along the longitudinal extension of the chip flute section 5. In the exemplary embodiment, the maximum diameter 7 is 6.6 mm.

[0054] The chip flute portion 5 includes a longitudinally extending wall 8 surrounding a longitudinally extending internal cavity 9. The wall 8 is circumferentially closed such that the cavity has no radial external contact along the longitudinal extension of the chip flute portion 5.

[0055] The wall 8 has an inner wall surface 10 and an outer wall surface. The inner wall surface 10 defines an internal cavity 9 along the chip flute portion 5.

[0056] The outer wall surface defines the exterior of the chip flute portion 5 including a chip flute surface 11 , a body clearance surface 12 , and a margin surface 13 .

[0057] The chip flute faces 11 extend radially inward relative to the maximum diameter 7, forming a radially outward open channel with a longitudinal extension. In the circumferential direction, the channel is bounded by a first edge 15 at the intersection of the chip flute faces 11 and the body clearance surface 12 and a second edge 16 at the margin surface 13. In the completed drilling tool, the first edge 15 is the leading edge of the chip flute faces 11 in the direction of rotation, and the second edge 16 is the trailing edge of the chip flute faces 11 in the direction of rotation. The channel forms a rearward-extending spiral with a constant helix angle. The chip flute faces 11 are concave radially inward.

[0058] As seen in a cross section perpendicular to the longitudinal axis according to FIG. 5B , the wall 8 has a wall thickness 14 measured from the outer wall surface to the inner wall surface. Circumferentially along a portion of the chip flute face 11, the wall thickness 14 is constant and is up to 20% of the maximum diameter 7, including a finishing tolerance. For a drilling tool blank having a maximum diameter 7 of 6.6 mm at the chip flute section 5, a larger wall thickness 14 of up to 20% of the maximum diameter is preferred due to strength requirements. In an exemplary embodiment, the wall thickness is 0.9 mm, with a finishing tolerance of 0.4 mm. In an exemplary embodiment, the wall thickness 14 of the portion of the chip flute face 11 is constant following the chip flute face 11 along the longitudinal spiral. The total area of ​​the chip flute face where the wall thickness 14 is constant covers the entire chip flute face 11, except for first and second edges 15 and 16 where the wall 8 forms angles with the body clearance face 12 and margin face 13, respectively. The total area of ​​the chip flute surface 11 where the wall thickness 14 is constant is a continuous surface that accounts for more than 75% of the entire chip flute surface 11 .

[0059] 5B , the wall thickness 14 is constant circumferentially along a portion of the body clearance surface 12 and is up to 20% of the maximum diameter 7. In the exemplary embodiment, the wall thickness is 0.5 mm and there is no finish tolerance. Thus, the wall thickness 14 along the portion of the body clearance surface 12 is less than the wall thickness 14 along the portion of the chip flute surface 11 by a finish tolerance of 0.4 mm. In the exemplary embodiment, the wall thickness 14 of the portion of the body clearance surface 12 is constant along the longitudinal spiral of the body clearance surface 12. The total area of ​​the body clearance surface 12 with constant wall thickness 14 covers the body clearance surface 12 except for the regions where the wall 8 forms corners with the wall 8 having the chip flute surface 12 and the wall 8 having the margin surface 13. The total area of ​​the body clearance surface 12 with constant wall thickness 14 is a continuous surface that accounts for more than 75% of the entire body clearance surface 12.

[0060] 1 and 2, the margin surface 13 extends longitudinally along the chip flute portion 5 and follows the spiral of the chip flute surface 11 at the second edge 16 of the chip flute surface 11. As a result, the margin surface 13 is located between the chip flute surface 11 and the body clearance surface 12 in the circumferential direction and intersects with the chip flute surface 11 at the second edge 16 of the chip flute surface 11.

[0061] As seen in the cross section of FIG. 5B, the margin surface 13 forms an arc with a radius of curvature that is half the maximum diameter of the cross section. In an exemplary embodiment in which the maximum diameter 7 is constant along the longitudinal length of the chip flute section 5, the maximum diameter 7 of the chip flute section is twice the radius of curvature. The radius of curvature is equal to the desired radius of curvature of the finished drilling tool, including a finishing tolerance. In this and other embodiments, the desired radius of curvature of the finished drilling tool is the radius desired for the support function of the margin surface. The margin finishing tolerance is 0.3 mm in the exemplary embodiment.

[0062] 5B, in the chip flute portion, inner wall surface 10 substantially follows the contour of the outer wall surface along most of chip flute surface 11 and most of body clearance surface 12. Inner wall surface 10 follows the contour of the outer wall surface except for the corners of first edge 15 and second edge 16.

[0063] The shaft portion 6 includes a longitudinally extending wall 8 surrounding a longitudinally extending internal cavity 9. The internal cavity 9 of the shaft portion 6 is continuous with the internal cavity 9 of the tip flute portion 5. The wall 8 has an inner wall surface 10 that defines the cavity and an outer wall surface 17. The shaft portion 6 in this and other embodiments has a hollow cylindrical shape, with the outer wall surface 17 and the inner wall surface 10 being circles having different diameters when viewed in cross section along the longitudinal extension of the shaft portion 6. The diameter of the outer wall surface 17 constitutes the maximum diameter 7 of the shaft portion 6 and is constant along the longitudinal length of the shaft portion 6. Thus, the wall thickness 14 is constant along the circumferential and longitudinal major portions. The total area of ​​the outer wall surface 17 of the shaft portion 6 over which the wall thickness 14 is constant is a continuous surface that accounts for more than 75% of the entire outer wall surface 17 of the shaft portion 6.

[0064] In the exemplary embodiment, the maximum diameter 7 of the shaft portion is 6.6 mm. The constant wall thickness 14 of the shaft portion 6 is no greater than 20% of the maximum diameter of the shaft portion, including finish tolerances. In the exemplary embodiment, the wall thickness 14 of this major portion of the shaft portion 6 is 0.9 mm, with a finish tolerance of 0.4 mm. Thus, the wall thickness and finish tolerance of the wall thickness 14 at the outer wall surface 17 of the shaft portion 6 are equal to the wall thickness and finish tolerance, respectively, at the chip flute surface.

[0065] At the rear end, the shaft portion 6 includes a beveled portion 18 and a circular opening 19 that connects to the internal cavity 9. The internal cavity 9 is in fluid communication with the outside by means of the opening 19.

[0066] The head portion 4 is solid and includes two internal coolant channels 20 that open axially forward.

[0067] The forward end of the head portion 4 includes a conical surface having a cone angle α of 120°. The axial length of the cone is approximately 0.9 times the maximum diameter 7 of the chip flute portion 5, which is 6.6 mm in the exemplary embodiment. The head portion 4 further includes a surface for forming the forward start 21 of the chip flute face 11.

[0068] The conical head portion 4 is configured to provide two cutting edges on the finished drilling tool. The outer wall surface of the chip flute portion 5 of the drilling tool blank includes, as described above, two chip flute surfaces 11, two body clearance surfaces 12, and two margin surfaces 13. These surfaces alternate circumferentially according to their associated cutting edges.

[0069] 6 to 10 show a second embodiment of the blank according to the present invention.

[0070] The second embodiment in the form of a drilling tool blank differs from the first embodiment only in that it includes an internal structure within the internal cavity 9. A central core rod 22 extends longitudinally through the chip flute section 5. The core rod 22 contacts and connects with the inner wall surface 10 at the deepest point of the channel that will form the chip flute in the finished rotary metal cutting tool. The channel is defined by the chip flute surface 11.

[0071] The core rod 22 also passes through the shaft portion 6. The core rod 6 of the shaft portion 6 is continuous with the core rod 22 of the tip flute portion 5. A plurality of longitudinally extending partitions 23 (four in the exemplary embodiment) each extend from the core rod 22 to the inner wall surface 10 within the cavity 9.

[0072] The third embodiment is a milling tool blank, shown in Figures 11-15. The milling tool blank differs from the first embodiment in that it lacks a margin surface 13 and instead has an edge 24 for forming a cutting edge at the intersection of the chip flute surface 11 and the body clearance surface 12. Preferably, the body clearance surface 12 has a smooth transition to the chip flute surface 11 at the forward portion of the chip flute surface in the direction of rotation. The head portion 4 is solid with sufficient axial extension to allow grinding of the leading end cutting edge. The leading end is closed toward the internal cavity 9.

Claims

1. A blank for a rotary metal cutting tool, said blank comprising an elongated unitary body having a front end (1), a rear end (2) and a longitudinal axis (3) extending from said front end (1) to said rear end (2), said body comprising: a head portion (4) extending rearward in the longitudinal direction from the front end portion (1); a shaft portion (6) extending longitudinally forward from the rear end portion (2); a tip flute portion (5) extending longitudinally and located between the shaft portion (6) and the head portion (4), the tip flute portion having a maximum diameter (7); the chip flute portion (5) includes a longitudinally extending wall (8) surrounding a longitudinally extending internal cavity (9), the wall (8) having an inner wall surface (10) and an outer wall surface that define the cavity (9); The outer wall surface defines a chip flute surface (11); 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); 1. A blank, characterized in that when viewed in cross section along the circumferential direction of a portion of the chip flute surface (11) and at a position along a major length of the chip flute section (5), the wall thickness (14) is constant and is at most 25%, preferably at most 20%, more preferably at most 15% of the maximum diameter (7) of the chip flute section (5) including finishing tolerances.

2. 2. A blank according to claim 1, wherein the outer wall surface of the chip flute section (5) further defines a body clearance surface (12), and when viewed in cross section at a position along a major length of the chip flute section (5), the wall thickness (14) is constant circumferentially along a portion of the body clearance surface (12) and is at most 25%, preferably at most 20%, more preferably at most 15% of the maximum diameter (7) of the chip flute section (5).

3. 3. The blank of claim 2, wherein, when viewed in cross section at a location along a major length of the chip flute portion, the wall thickness (14) along the portion of the body clearance surface (12) is less than the wall thickness (14) along the portion of the chip flute surface (11).

4. The shaft portion (6) has a maximum diameter (7), the shaft portion (6) includes a longitudinally extending wall (8) surrounding a longitudinally extending interior cavity, the wall (8) having an inner wall surface (10) and an outer wall surface (17) defining the cavity; 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); 4. A blank according to any one of claims 1 to 3, wherein the wall thickness (14) is constant circumferentially along a portion of the outer surface of the shaft portion (6) when viewed in cross section at a position along the main length of the shaft portion (6) and is at most 25%, preferably at most 20%, more preferably at most 15% of the maximum diameter (7) of the shaft portion (6) including finishing tolerances.

5. 4. A blank according to claim 4, wherein, when viewed in cross section at a position along a main length of the shaft portion, the wall thickness (14) of the portion of the outer wall surface (17) of the shaft portion (6) is equal to the wall thickness (14) along the portion of the chip flute surface (11) of the chip flute portion (5).

6. 6. A blank according to any one of claims 1 to 5, wherein the chip flute surface (11), the body clearance surface (12) or the outer wall surface (17) of the shaft portion (6) each has an area within which the wall thickness (14) is defined, and the total area of ​​each respective surface constitutes at least 50%, preferably at least 75%, of the respective surface.

7. 7. The blank of claim 6, wherein all of said total areas together constitute at least 50%, preferably at least 75% of said total area of ​​said face.

8. A blank according to any one of claims 1 to 7, wherein the finishing tolerance is between 0.1 and 0.5 mm, preferably between 0.15 and 0.45 mm.

9. 9. The blank according to any one of claims 1 to 8, further comprising a central core rod (22) extending along the longitudinal axis (3) through the cavity of the shaft portion (6) and / or the chip flute portion (5).

10. 10. The blank of claim 9, further comprising a plurality of longitudinally extending partitions (23) each extending from the core rod to an inner wall surface (10) within the cavity of the shaft portion (6) and / or the chip flute portion (5).

11. The blank of any one of claims 1 to 10, wherein the blank is a printed and sintered component comprising a cemented carbide composition.

12. the blank is a punch tool blank; the outer wall surface further defines a longitudinally extending margin surface (13), the margin surface being circumferentially located between the chip flute surface (11) and the body clearance surface (12) and intersecting the chip flute surface (11); 12. A blank according to any one of claims 2 to 11, wherein when viewed in a cross section perpendicular to the longitudinal axis (3), the margin surface (13) forms an arc of a circle having a radius of curvature equal to half the maximum diameter of the cross section.

13. 13. A blank according to claim 12, wherein the head portion (4) is solid and includes at least one internal coolant channel (20).

14. 12. The blank according to any one of claims 2 to 11, wherein the blank is a milling tool blank including an edge (24) at the intersection of the chip flute surface (11) and the body clearance surface (12) for forming a cutting edge.

15. 15. The blank according to claim 2, wherein the outer wall surface of the chip flute portion includes a plurality of chip flute surfaces and a plurality of body clearance surfaces, the chip flute surfaces and the body clearance surfaces being alternately arranged in the circumferential direction.

16. A rotary metal cutting tool manufactured by grinding the blank for a rotary metal cutting tool according to any one of claims 1 to 15.

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