Tap with edge transition

Abstract

Tap (2) for machining workpieces, for producing or reworking an internal thread, a) on the circumference of which cutting teeth (3) are arranged, each with a leading end (4) and a trailing end (5), b) wherein the leading end (4) of each tooth (3) forms at least one wedge (8) with at least one wedge edge (9, 9a) and at least one wedge angle (β, β1) between at least one rake face (6, 6a) with at least one rake angle (γ, γ1) and at least one flank (7, 7a) with at least one clearance angle (α, α1), c) wherein at least one wedge edge (9, 9a) forms a peripheral cutting edge of the tap (2), d) wherein the or at least one wedge angle (β) on and / or near the associated wedge edge (9, 9a) is increased by forming an edge transition (10) between the chip surface (6) and the flank surface (7) and e) wherein the or at least one edge transition (10) has at least two planes (11, 12, 13) inclined relative to the chip surface (6) and flank surface (7) and to one another.

Description

[0001] The invention relates to a tap for machining workpieces, for producing or reworking an internal thread.

[0002] In such tools, cutting teeth are arranged around the tool circumference, each with a leading end and a trailing end in a predetermined direction of rotation. The leading end of each cutting tooth forms a wedge with a wedge edge and a wedge angle β between a rake face with a rake angle γ and a flank face with a clearance angle α. The wedge edge forms a peripheral cutting edge (also known as the peripheral cutting edge) of the tool.

[0003] The cutting geometry described above and the terms used are explained below using Fig. 1 explained. Fig. 1 shows a known tool 2 for machining workpieces, namely a cross-section perpendicular to a longitudinal or rotational axis A of the tool 2. Four cutting teeth 3 arranged on the tool circumference can be seen, each with a leading end 4 and a trailing end 5 in a predetermined direction of rotation D.The above-mentioned angles are entered on a cutting tooth 3: a rake angle γ between a rake face 6 at the leading tooth end 4 and the tool radius R (straight line perpendicular to the tool longitudinal axis A, intersecting the tool longitudinal axis A and a wedge edge 9, see below), a clearance angle α between a clearance face 7 tapering towards the trailing tooth end 5 and a perpendicular S to the tool radius R (this perpendicular S corresponds to a tangential surface to the workpiece surface machined by the cutting tooth, accordingly the radius R corresponds to a perpendicular to the workpiece surface machined by the cutting tooth) and a wedge angle β between rake face 6 and clearance face 7. rake face 6 and clearance face 7 enclose a wedge 8 between them, the wedge edge 9 of which forms a peripheral cutting edge 9 or peripheral cutting edge 9 of the tooth 3.

[0004] The sum of the rake angle γ, the wedge angle β, and the clearance angle α is always 90°. Accordingly, the rake angle γ is positive when the rake face 6 is inclined relative to the radius R in the direction of rotation D (viewed toward the peripheral cutting edge 9), and negative when the rake face is inclined opposite to the direction of rotation D.

[0005] JP 2004-291 099 A relates to a disposable end mill comprising a holder and a disposable tip. The disposable tip has a main body shaped like a parallelogram in plan view and includes main cutting edges along long cross ridges formed by side surfaces and an upper surface of the main body, flat drivers along short cross ridges, and rake faces bent at a predetermined rake angle in the upper surface along the main cutting edges.

[0006] US 2006 / 045 638 A1 relates to a rotary end mill. The end mill includes a shank portion and a fluted portion. The fluted portion has a first end integrally connected to the shank portion, a second end, and an outer surface. One or more helical teeth are arranged along the outer surface of the fluted portion. Each helical tooth has a cutting surface and a flank surface that intersect to form an angle defining a helical cutting edge.

[0007] With the known tools, especially at high cutting speeds, there is a risk of damage to the peripheral cutting edge and thus increased tool wear, which reduces the tool life.

[0008] It is an object of the invention to provide a new tool for machining workpieces in which the aforementioned disadvantages are at least partially overcome or at least reduced.

[0009] This problem is solved by the features of patent claim 1. Advantageous embodiments and further developments emerge from the claims dependent on claim 1.

[0010] According to the invention, cutting teeth with a leading and a trailing end are arranged on the circumference of the tool for machining workpieces. The leading end of each tooth forms at least one wedge with at least one wedge edge and at least one wedge angle between a rake face with a rake angle and a flank face with a clearance angle. At least one wedge edge forms a peripheral cutting edge (also: peripheral cutting edge, outer cutting edge) of the tool.

[0011] Furthermore, the invention provides that the wedge angle is increased at and / or near the wedge edge by forming an edge transition between the rake face and flank face. In other words, the peripheral cutting edge is softened by the edge transition. The rake face and flank face do not meet directly at the edge; rather, an edge transition is formed between them. The edge transition can also be referred to as a transition surface or transition region. Strictly speaking, the wedge edge in the tool according to the invention is only a theoretical wedge edge, since it has been replaced by the edge transition. In other words, the wedge angle in the area of ​​the edge transition is thus increased compared to the adjacent tooth areas.

[0012] Due to this design, the rake angle and / or clearance angle are reduced at and / or near the (theoretical) wedge edge (alternatively, one could also speak of the edge transition area, which replaces the wedge edge). This results directly from the fact that the sum of the rake angle, wedge angle, and clearance angle is equal to 90°. In some cases, the rake angle and / or clearance angle may assume negative values.

[0013] According to claim 1, the invention further provides that the edge transition has at least two planes inclined relative to the rake face and flank face and to each other.

[0014] The advantages of the invention lie in the fact that tool wear on the peripheral cutting edge is reduced, thus increasing tool life. The proposed new cutting edge geometry also has a beneficial effect on chip formation and chip removal.

[0015] Preferably, the edge transition has three planes inclined relative to the rake face and flank face and to each other.

[0016] According to one embodiment, the mutually inclined planes of the edge transition are straight in cross-section perpendicular to the longitudinal axis of the tool.

[0017] In all of the above embodiments of the invention, the rake angle can be reduced in the area of ​​the edge transition. Alternatively or additionally, the clearance angle can also be reduced in the area of ​​the edge transition.

[0018] When providing mutually inclined planes in the edge transition, in a further development, the rake angle in a first plane of the edge transition adjacent to the rake face can be negative. Furthermore, the rake angle in a second plane of the edge transition adjacent to the first plane can be smaller than in the first plane. When providing additional planes, in particular three planes, the rake angle in a third plane of the edge transition adjacent to the second plane can be smaller than in the second plane.

[0019] In all embodiments of the invention, the edge transition can extend over 1% to 40% of the tooth height or profile height, in particular over 5% to 35% of the tooth height. Tooth height or profile height have already been defined above. The extension of the edge transition here refers to the radial extension of the edge transition, i.e., the difference between the maximum and minimum radial distance of the edge transition from the tool's longitudinal axis.

[0020] The wedge edge(s) with the edge transition, corresponding to the peripheral cutting edge, can be arranged in all embodiments on a tooth tip of the cutting tooth or also on a tooth flank of the cutting tooth and / or on a groove or a skiving cut, etc. Furthermore, the wedge angle or the edge transition can vary on different wedge edges of a tooth or several teeth and / or along at least one wedge edge and / or can vary for different teeth at corresponding wedge edges, in particular being different in a lead-in or starting area than in a full profile area, etc.

[0021] In a further dependent variant of the invention with at least one wedge edge on a tooth flank of a cutting tooth, the or at least one wedge angle on and / or near a or the wedge edge formed on a tooth flank of the associated cutting tooth is increased by forming an edge transition between the rake face and the flank face.

[0022] The invention will be explained in more detail below with regard to further features and advantages based on the description of exemplary embodiments and with reference to the accompanying drawings. They each show a schematic representation Fig. 1 a known tool according to the state of the art for machining workpieces in a cross section perpendicular to the tool longitudinal axis, and Fig. 2 to Fig. 13 different embodiments of a cutting edge geometry of a tool, each showing a cutting tooth in cross section perpendicular to the tool's longitudinal axis. Fig. 12 and Fig. 13 show taps according to the invention, in which Fig. The tools shown in Figures 2 to 11 are not taps according to the invention.

[0023] Corresponding parts, areas or sections are in Fig. 1 to Fig. 13 are provided with the same reference numerals.

[0024] Fig. 1 has already been explained above in the description of the prior art. Fig. Figure 1 shows a known tool according to the state of the art and clarifies the technical terms used.

[0025] Fig. 2 to Fig. 13 schematically show various exemplary embodiments of a cutting edge geometry of a tool. Each shows a cutting tooth 3 in cross-section perpendicular to the tool's longitudinal axis.

[0026] A chip surface 6 can be seen at a tooth end 4 leading in a given direction of rotation and a flank surface 7 at a tooth end 5 trailing. In contrast to the prior art (cf. Fig. 1) no longer directly adjoin each other, but rather an edge transition 10 is formed between them. To clarify the difference to the state of the art, Fig. 2 to Fig. 13 the course of the cutting surface 6a and the flank 7a actually provided for according to the state of the art is shown by dashed lines (compare Fig. 1). According to the state of the art, chip surface 6a and flank surface 7a converge in a wedge edge 9a, which is Fig. 2 to Fig. 13 is also shown. Also shown are the tool radius R and the perpendicular S as well as the rake angle γ1, clearance angle α1 and wedge angle β1 according to the prior art. These angles are also realized in the cutting edge geometry of a tool according to the invention, but only in an area in which the tooth shape corresponds to the shape known from the prior art, i.e. in an area spaced from the (theoretical) wedge edge 9a. Towards the wedge edge 9a, the tooth shape differs from the known tooth shape, the cutting edge geometry is changed. The wedge edge 9a is replaced by an edge transition 10, which in Fig. 2 to Fig. 13 has a different cross-sectional shape.

[0027] The wedge angle β is increased in the area of ​​the edge transition 10 compared to the wedge angle β1 according to the prior art, which continues to apply to the rake face 6 outside the edge transition 10. The rake angle γ is reduced in the area of ​​the edge transition 10 compared to the rake angle γ1 according to the prior art, which also continues to apply to the flank face 7 outside the edge transition 10. This is shown in Fig. 2 is shown as an example for a point P of the edge transition 10 and applies accordingly to the embodiments according to Fig. 3 to Fig. 13. In Fig. 2, the edge transition 10 between rake face 6 and flank face 7 is completely curved, i.e. the curvature extends continuously from rake face 6 to flank face 7, whereby the radius of curvature changes. At the point P of the edge transition 10, a tangent T is entered, which defines a (theoretical) rake face and flank face at this point and thus defines the rake angle γ and the clearance angle α as well as the wedge angle β for this point P. In addition, the radius Rx and the corresponding perpendicular Sx are entered for this point. The (theoretical) wedge angle β in Fig. 2 is a 180° angle and is thus larger than the significantly smaller wedge angle β1 of the state-of-the-art. The rake angle γ and the clearance angle α are now negative and thus smaller than the rake angle γ1 and the clearance angle α1 of the state-of-the-art.

[0028] For the sake of explanation, it should be noted that the edge transition 10 should only extend over a small section of the tooth height, in particular only approximately 1% to 40% of the tooth height. Accordingly, the angles referred to above as rake angle γ1, clearance angle α1 and wedge angle β1 "according to the prior art" can certainly also be regarded as the actual rake angle, clearance angle and wedge angle in a tool according to the invention. The values ​​of these angles are only changed directly at the tooth tip, i.e. at the wedge edge, since this is no longer present in the form known from the prior art due to the formation of the wedge transition.

[0029] As in Fig. 2, the edge transition 10 is also in Fig. 3 is completely curved, with the curvature changing continuously over the edge transition 10, and the transition to rake face 6 and rake face 7 also being continuous, i.e., without a kink. Alternatively, it is of course also conceivable to form the curvature over the entire edge transition 10 with a uniform radius of curvature and, if necessary, to provide a kink at the transition to rake face 6 and flank face 7, which represents a discontinuous surface profile.

[0030] In Fig. 4, the edge transition 10 is continuously curved. The curvature has the shape of a trumpet curve, i.e., the radius of curvature changes continuously; in particular, in the illustrated case, it increases continuously starting from the flank surface 7. At the flank surface 7, the transition to the edge transition is formed as a kink or edge. Symbolically speaking, the trumpet opening of the illustrated trumpet curve is located on the side of the rake face 6. Of course, a reverse configuration is also conceivable, i.e., a continuous increase in the curvature of the edge transition starting from the rake face side.

[0031] Fig. Figure 5 shows a cutting edge geometry in which the edge transition 10 has a first curvature 14 and a second curvature 15 that merge into one another at a kink or edge. The radii of curvature of the respective curvatures can be arbitrary. They can vary within the first curvature 14 or the second curvature 15, or they can be constant within the respective curvature 14, 15. They can have the same value in both curvatures 14, 15, or they can differ.

[0032] In Fig. 6 and Fig. 7, the edge transition 10 has a section 16 which is straight in cross-section and a first curvature 14 adjacent to the chip surface 6 ( Fig. 6) or adjacent to the free area 7 a second curvature 15 ( Fig. 7).

[0033] Fig. 8 and Fig. 9 show embodiments in which the edge transition 10 adjacent to the rake face 6 has a first curvature 14, followed by a straight partial area 16, which finally merges into a second curvature 15 towards the flank face 7. In Fig. 8, the straight section 16 is inclined by approximately 45° relative to the radius R, whereas the inclination to the radius R in Fig. 9 is significantly smaller. The radii of curvature of the first curvature 14 and the second curvature 15 are adjusted accordingly. In particular, the radius of curvature of the first curvature 14 is Fig. 9 significantly larger than in Fig. 8.

[0034] Fig. 10 shows a variant in which the edge transition 10 has a convex curvature 17 in a partial area. Fig. 11 shows a variant with a concave curvature 18 in a partial area of ​​the edge transition 10. In both cases, a first curvature 14 adjacent to the rake face 6 and a second curvature 15 adjacent to the flank face 7 complement the edge transition 10. Of course, the edge transition 10 could also be continuously convex or concavely curved, if necessary with the formation of a corresponding kink or edge at the transition to the rake face 6 and / or flank face 7.

[0035] Fig. Figure 11 shows a variant in which the edge transition 10 is formed from a first plane 11 and a second plane 12, which are inclined relative to each other and relative to the rake face 6 and the flank face 7, i.e., they have a different angle to the radius R. Accordingly, a kink 19 or edge 19 is formed between the first plane 11 and the second plane 12. A kink 20, 21 (also called an edge) is also formed at the transition to the rake face 6 and the flank face 7. The second plane 12 is inclined more sharply relative to the radius R than the first plane 11.

[0036] Fig.13 shows an embodiment in which the edge transition 10 has a first plane 11 adjacent to the rake face 6, followed by a second plane 12, and a third plane 13 adjacent to the flank face 7. The three planes 11, 12, 13 are in turn inclined relative to each other and relative to the rake face 6 and flank face 7, which leads to the formation of the kinks or edges 19, 20, 21, 22.

[0037] Overall, the invention thus provides a new cutting edge geometry in which an edge transition is formed between the rake face and the flank face. This increases the wedge angle in the area of ​​the edge transition and reduces the rake angle and / or the clearance angle. This reduces wear at the tooth tip and extends tool life.

[0038] The specific design of the edge transition is always adapted to the intended tool use.

[0039] The edge transition can be created, for example, by filing or grinding the tool accordingly. List of reference symbols 2 tools 3 cutting teeth 4 leading tooth end 5 trailing tooth end 6 chip surface 6a Cutting surface profile according to the state of the art 7 open space 7a Open space layout according to state of the art 8 wedge 9 Wedge edge, peripheral cutting edge (also: peripheral cutting edge) 9a Wedge edge or peripheral cutting edge according to the state of the art 10 Edge transition 11 first level 12 second level 13 third level 14 first curvature 15 second curvature 16 straight section 17 convex curvature 18 concave curvature 19 Bend, edge 20 crease, edge 21 Bend, edge 22 crease, edge α clearance angle β wedge angle γ rake angle α1 clearance angle according to the state of the art β1 wedge angle according to the state of the art γ1 rake angle according to the state of the art A Tool longitudinal axis, rotation axis D Direction of rotation P point R tool radius Rx radius at point P S Vertical Sx Perpendicular at point P T Tangent

Claims

[1] Taps (2) for machining workpieces, for producing or reworking an internal thread, a) on the circumference of which cutting teeth (3) are arranged, each with a leading end (4) and a trailing end (5), b) wherein the leading end (4) of each tooth (3) forms at least one wedge (8) with at least one wedge edge (9, 9a) and at least one wedge angle (β, β1) between at least one rake face (6, 6a) with at least one rake angle (γ, γ1) and at least one flank (7, 7a) with at least one clearance angle (α, α1), c) wherein at least one wedge edge (9, 9a) forms a peripheral cutting edge of the tap (2), d) wherein the or at least one wedge angle (β) on and / or near the associated wedge edge (9, 9a) is increased by forming an edge transition (10) between the chip surface (6) and the flank surface (7) and e) wherein the or at least one edge transition (10) has at least two planes (11, 12, 13) inclined relative to the chip surface (6) and flank surface (7) and to one another. [2] Tap according to claim 1, characterized by that the edge transition (10) has three planes (11, 12, 13) inclined relative to the chip surface (6) and flank surface (7) and to each other. [3] Tap according to claim 2, characterized by that the mutually inclined planes (11, 12, 13) of the edge transition (10) are straight in cross-section perpendicular to the longitudinal axis of the tap (2). [4] Tap according to one of the preceding claims, characterized by that the rake angle (γ) is reduced in the area of ​​the edge transition (10). [5] Tap according to one of the preceding claims, characterized by that the clearance angle (α) is reduced in the area of ​​the edge transition (10). [6] Tap according to claim 4, characterized bythat the rake angle (γ) is negative in a first plane (11) of the edge transition (10) adjacent to the rake face (6). [7] Tap according to claim 6, characterized by that the rake angle (γ) in a second plane (12) of the edge transition (10) adjacent to the first plane (11) is smaller than in the first plane (11). [8] Tap according to claim 7, characterized by that the rake angle (γ) in a third plane (13) of the edge transition (10) adjacent to the second plane (12) is smaller than in the second plane (12). [9] Tap according to one of the preceding claims, characterized by that the edge transition (10) extends over 1% to 40% of the tooth height, in particular over 5% to 35% of the tooth height. [10] Tap according to one of the preceding claims, in which the wedge angle or the edge transition varies at different wedge edges of a tooth or several teeth and / or along at least one wedge edge and / or varies at different teeth at corresponding wedge edges, in particular is different in a lead-in or starting area than in a full profile area, etc.

Images