EP3331658A1

EP3331658A1 - Replaceable cutting head, tool shank, and shank-mounted tool

Info

Publication number: EP3331658A1
Application number: EP16745402.4A
Authority: EP
Inventors: Christian PAULWEBER; Roland Barbist; Johannes Glätzle
Original assignee: Ceratizit Austria GmbH
Current assignee: Ceratizit Austria GmbH
Priority date: 2015-08-05
Filing date: 2016-06-27
Publication date: 2018-06-13
Also published as: WO2017020051A1; AT15013U1

Abstract

The invention relates to a replaceable cutting head (3), which has a working region (30) and a connecting portion (31) formed integrally with the working region (30) and having an external thread (34). The cutting head (3) has a longitudinal axis (L). Between the working region (30) and the external thread (34) a support surface (35) is formed for support on a corresponding contact surface (25) of a tool shank (2). The support surface (35) is curved in a section in a plane which contains the longitudinal axis (L).

Description

REPLACEABLE CUTTING HEAD, TOOLSCAPE AND

SHAFT TOOL

The present invention relates to a replaceable cutting head, a tool shank for a rotary cutting tool and a rotary shank tool with a replaceable cutting head and a

Tool shank.

For the machining of various materials, in particular metal but also e.g. Composites, e.g.

fiber reinforced plastics, rotating tools are often used which have a plurality of cutting edges. To be as good as possible

To achieve durability of the cutting edges, these are often made of carbide or cermet. Carbide and cermets are particularly hard and wear-resistant materials, where hard materials, such as in particular

Carbides, carbonitrides, carbon oxides and / or Karbooxonitride of particular transition metals are embedded in a ductile metallic matrix, which may in particular predominantly cobalt, nickel and / or iron. In particular, hard metals are often used in which hard

Tungsten carbide grains are embedded in a matrix of cobalt and / or nickel.

On the one hand, it is known, in particular, to produce completely rotating tools such as milling cutters or drills with a relatively small diameter made of hard metal or cermet. On the other hand, it is also known, in particular

Form tools such as larger diameter cutters or drills as tools in which the cutters are formed by a plurality of carbide or cermet cutting inserts interchangeably mounted in respective receptacles on a tool shank which is commonly used e.g. made of tool steel. Furthermore, rotating tools, such as

in particular milling cutters or drills, in which a replaceable cutting head, which consists of hard metal or cermet, at a free end of a tool shank made of a tougher material, such as tool steel, is releasably secured. The replaceable cutting head can be an or have multiple cutting, which can be generated for example by grinding the cutting head.

WO 2013/106875 A1 describes a hard-material threaded connection in which an external thread and an inner thread cooperating therewith have a different thread pitch.

WO 96/06702 A1 describes a shank tool with a tool shank and a replaceable cutting head, which is formed by a one-piece carbide body and a threaded connection with the

Tool shank is connected. The threaded connection is formed by an external thread formed on the cutting head and one therewith

cooperating internal thread at a free end of the

Tool shank formed. On both sides of the external thread and the internal thread cooperating radial support surfaces are provided for a radial support. For the axial support are also

cooperating axial support surfaces provided on the cutting head and on the tool shank. In such an embodiment of a shank tool with a

Tool shank and a replaceable cutting head, it is advantageous that less material of the relatively expensive hard material must be used in comparison with a completely made of carbide or cermet shank tool. On the other hand, in known such

Shank tools having a replaceable cutting head, the problem that a material failure of the cutting head often occurs, in particular in the area between the external thread of the connecting portion and a working area in which the cutting edges are formed. It is an object of the present invention to provide an improved

replaceable cutting head to provide an improved tool shank for a rotating tool and an improved rotating shank tool. The object is achieved by a replaceable cutting head according to claim 1. Advantageous developments are specified in the dependent claims. The cutting head has a working area and an integrally formed with the working area connecting portion with an external thread. The cutting head has a longitudinal axis. Between the working area and the external thread, a support surface for supporting on a corresponding contact surface of a tool shank is formed. The support surface is formed curved in a section in a plane containing the longitudinal axis.

Under a support surface is in the present case a surface to understand that is designed so that the cutting head with this surface on the

corresponding contact surface of a tool shank is supported. In other words, it is a surface which is designed to contact a contact surface touching. The work area can e.g. already be provided with appropriate cutting for a machining. However, it is e.g. also possible that the work area still has a blank shape, in the first still the cutting (for example by a

Grinding machining) must be formed. The curved support surface may e.g. have a convex shape, a concave shape or combinations of these. Due to the curved design of the support surface an embodiment is selected, which is particularly well suited to the special

Material properties of particular carbide or cermet is tuned. These materials, which are usually used for a cutting head, are very sensitive to tensile stresses. Due to the curved design of the support surface tensile stresses are kept low in the material of the cutting head and it will be by the normal force application particular notch effects and concentrations of

Tensile stresses that could lead to cracking, largely avoided. Furthermore, the force is applied in a machining

Processing with the cutting head due to the curved formation of the support surface at least predominantly perpendicular to the support surface, which is has a positive effect on stability. Non-curved surfaces, such as cones or cylinders, can absorb forces perpendicular to the surface only from a certain direction, whereas curved surfaces in forces acting from different directions can absorb these perpendicular to the surface. Perpendicular to the surface means that no dangerous tensile stresses occur. Compared with, for example, the design described in the aforementioned WO 96/06702 A1, in which form between the serving as an axial support surface annular shoulder and serving as a radial support surface cylindrical surface in the corner due to notch forces local stress concentrations, which can lead to material failure , With the solution according to the invention, a significantly more stable configuration is achieved even with larger axial lengths of the cutting head. In particular, instead of two separate support surfaces in the area between the external thread and the working area a

provided by continuous curved support surface which causes both a radial and an axial support. The curved support surface may preferably extend in the radial direction substantially over the entire area between the external thread and the working area. However, it is e.g. It is also possible for one or more further surfaces to be present, which, however, cover significantly smaller partial regions in the radial direction overall. Preferably, the cutting head tapers in the region between the working area and the external thread

continuously. The external thread can in particular be designed as a substantially cylindrical thread. It is e.g. However, also possible that the outer diameter of the external thread tapers with increasing distance from the working area, in particular conically tapered. The

External thread may have the tooth form of a standard thread, e.g. be designed as a metric rule thread, but there are also different tooth shapes possible, such. Round thread, rectangular thread,

Trapezoidal thread, sawtooth thread, reinforced thread, flat thread,

Whitworth pipe thread, UNC, UNF, etc. Preferably, the external thread is designed as a fine thread with low pitch and low thread depth. According to a development, the support surface is curved in such a way that it has a local radius of curvature r _a 1 mm at each point in a section in a plane containing the longitudinal axis,

preferably r _a 1, 5 mm. In this case, a big enough one

Radius of curvature ensured, which allows the occurring

To keep tension low. The radius of curvature can be over the entire support surface, e.g. have the same radius, e.g. can the

Supporting surface may be formed in particular as a partial surface of a tome, or the radius of curvature may also vary. Preferably, the support surface may have the shape of a partial surface of a tire or donut, in particular rotationally symmetrical with respect to the longitudinal axis of the cutting head

be educated.

According to one embodiment, the support surface is concave curved. In this case, the support surface can be produced in a reliable and cost-effective manner and simultaneously allows as a guide surface when screwing the cutting head a particularly good centering and

Positioning. According to a further development, the external thread on his the

Working side facing a diameter d _a and the

Working area on its side facing the male thread one

Diameter D _a and the curved support surface extends between the external thread and the working region in the radial direction over a width A _a 0.75 * (D _a -d _a ) / 2. In this case, the difference in the radial extent between the working area and the external thread is largely bridged by the curved support surface, which allows a particularly reliable positioning and support in both the radial direction and in the axial direction. More preferably, A _a > 0.80 * (D _a -d _a ) / 2, especially Δ ₉ > 0.85 * (D _a -d _a ) / 2.

According to a development, a further support surface for supporting on a further corresponding contact surface of the tool shank is formed on the side remote from the working area of the external thread. In this case, an even better positioning and support is possible, in which the forces are distributed particularly evenly. The further support surface can in particular directly to the

Connect external thread or it can also be provided a transition region between the external thread and the other support surface.

Preferably, the further support surface can taper with increasing distance from the work area. In this case, the further support surface may also be curved, in particular also concavely curved. The further support surface may have a larger radius of curvature than the previously described support surface between the external thread and the working area. Preferably, the further support surface

formed rotationally symmetrical with respect to the longitudinal axis. Preferably, the further support surface may also have the shape of a partial surface of a tire or donut, in particular the shape of a partial surface of a tom.

According to one embodiment, the curved support surface with a

Particle jet blasted. In this case, the curved support surface thus has the properties of a surface blasted with a particle beam, in particular recognizable properties, which are due to the blasting treatment. The blasted support surface can in particular

identifiable local microscopic deformations due to particle collision and a stress gradient in the particle

Have direction perpendicular to the surface. Due to the blasting, which leads to the properties of the particle blasted surface, a mechanical annealing of microcracks and

Achieved surface dislocations, which leads to a further reduction of

Susceptible to breakage of the cutting head. These advantages are particularly evident when the support surface has been ground before the blast treatment so that it has the properties of a ground and subsequently blasted surface. By grinding caused damage to the

Support surface are thus healed in the blasted support surface, so that a significantly higher component safety is achieved. Preferably, the curved support surface in a near-surface region compressive stresses whose formation controlled by the specific design of the blast treatment can be, in particular by the material used of the particles of the particle beam, the shape of the particles, the particle size, the jet pressure and the angle of incidence of the particle beam. In order to preserve the advantageous properties of the ground and then blasted support surface, this is preferably still not sanded after the blast treatment

coated.

The task is also performed by a tool shank for a rotating

Cutting tool according to claim 7 solved. Advantageous developments are specified in the dependent claims.

The tool shank extends along a longitudinal axis and has a recess formed at a free end with an internal thread for receiving a replaceable cutting head, which has a corresponding external thread. The tool shank points between the

Internal thread and the free end of a contact surface for supporting a corresponding support surface of the cutting head. The contact surface is formed curved in a section in a plane containing the longitudinal axis.

A contact surface is to be understood as meaning a surface which is designed such that a cutting head with a corresponding support surface is supported on it, thus touching it. Due to the curved shape of the

Contact surface is a particularly gentle introduction of force in the

Cutting head allows, in particular, the properties of the typical material of such a cutting head, such as in particular carbide or cermet, taken into account. About the curved contact surface is a

Force application achieved mainly perpendicular to the contact surface. About the curved configuration of the contact surface thereby simultaneously an axial and a radial positioning are achieved and the contact surface also acts when screwing a cutting head as a guide surface. The

curved contact surface may in particular have a convexly curved shape, a concavely curved shape or combinations of these. The curved contact surface may preferably at least substantially of extend the outer circumference of the tool shank in the radial direction up to the diameter of the internal thread on the free end facing side. However, it is also possible that in addition to the curved

One or more additional surfaces are provided contact surface still extending over a smaller partial areas in the radial direction. In particular, the internal thread may be formed as a substantially cylindrical thread, but it is e.g. also possible that the internal thread tapers with increasing distance from the free end, in particular conically tapered. The internal thread can in particular have a standard tooth form, as it is e.g. at a metric

Rule thread, but e.g. also other thread forms such. Round thread, flat thread, sawtooth thread. Reinforced pipe thread, Whitworth pipe thread, UNC, UNF, trapezoidal thread, etc. possible. Preferably, the internal thread is designed as a fine thread with a low thread pitch and low thread depth.

According to a further development, the abutment surface is curved in such a way that, in a section in a plane containing the longitudinal axis, it has a local radius of curvature n 1 mm at each point,

preferably η 1, 5 mm. In this case, the radius of curvature is sufficiently large to avoid too high local stress concentrations. The radius of curvature may be e.g. over the entire extent of the

Bearing surface substantially constant, as it is e.g. in a partial area of a toms is the case. However, it is e.g. also possible that the contact surface has a varying radius. Preferably, however, the contact surface is rotationally symmetrical with respect to the longitudinal axis and has the shape of a partial surface of a tire or donut.

According to a further development, the internal thread on its side facing the free end has a diameter di and the tool shank has a diameter D at its free end, and the curved abutment surface extends between the internal thread and the free end in the radial direction over a width Δ. a 0.75 ^* (D, - dj) / 2. In this case, the

Difference in the radial extent between the outer circumference of the free End and the internal thread clearly predominantly bridged by the curved contact surface, which allows a particularly reliable positioning and support both in the radial direction and in the axial direction. More preferably, A _f > 0.80 * (Dj-dj) / 2, especially

Λ> 0.85 * (D _r di) / 2.

According to a development, the contact surface is convexly curved. In this case, the force is applied to a screwed

Cutting head particularly even and the contact surface is used in the

Screwing in at the same time as a guide surface.

According to a development, the recess has on a side facing away from the free end side of the internal thread on a further contact surface for supporting a further support surface of the cutting head. In this case, an even better positioning and support is possible, in which the forces are distributed particularly evenly. The further support surface may in particular directly connect to the internal thread or it may also be provided an intermediate transition region. When the cross-section of the other bearing surface with increasing

Distance tapered from the internal thread, is a particularly accurate

Positioning and alignment in the radial direction allows and the other contact surface also serves as a guide surface when screwing a cutting head. The further contact surface may preferably also be curved, in particular also convexly curved. The additional contact surface may have a larger radius of curvature than the previously described contact surface between the internal thread and the free end of the tool shank. Preferably, the further contact surface is rotationally symmetrical with respect to the longitudinal axis. Preferably, the further contact surface may also have the shape of a partial surface of a tire or donut, in particular the shape of a partial surface of a torus. The task is also followed by a rotating cutting tool

Claim 13 solved. Advantageous developments are specified in the dependent claims. The rotating shaft tool includes: a replaceable cutting head, a working area and one integral with the work area

formed with a male threaded connection portion, and a tool shank which extends along a longitudinal axis and having an internal thread which is connected to the external thread of the

Connecting portion cooperates. Between the working area and the external thread of the cutting head is a support surface for supporting on a corresponding contact surface of the tool shank, which is arranged between the internal thread and a free end of the tool shank is formed. The support surface and the corresponding contact surface are each formed curved in a section in a plane containing the longitudinal axis. Due to the curved formation of the

Support surface and the corresponding contact surface is a simultaneous radial and axial alignment and positioning of the

Cutting head allows, in particular concentrations of

Tensile stresses are prevented in the material of the cutting head and the forces acting in a machining operation with the shaft tool are introduced substantially perpendicular to the support surface. The

Support surface and the corresponding contact surface preferably have the same curvature, so that a flat support between these two surfaces is guaranteed. In particular, both the support surface and the contact surface are preferably formed rotationally symmetrical with respect to the longitudinal axis. Particularly preferably, the cutting head can be designed such that it tapers continuously from the working area to the external thread. The external thread of the cutting head and the cooperating internal thread of the tool shank can

in particular have a cylindrical outer contour. However, it is e.g. also possible that the thread with increasing distance from the

Rejuvenate working area, for example, in particular taper conically. The threads can be formed in particular, for example, as a standard thread, for example as Metric rule thread, or even have different tooth shapes, eg as a trapezoidal thread, sawtooth thread, armored pipe thread, flat thread, round thread, Whitworth pipe thread, UNC, UNF, etc. be formed.

Preferably, the external thread and the internal thread are each formed as a fine thread with low pitch and small thread depth. In a particularly preferred embodiment, the

External thread and the internal thread while a slightly different

Have thread pitch, as in the cited above

WO 2013/106875 A1 is described.

According to one embodiment, the support surface is concave and formed the contact surface is convexly curved. In this case, a particularly good positioning and centering of the cutting head

ensures and there is a particularly unproblematic introduction of force in the cutting head, are reliably avoided in the high local tensile stresses.

According to a development, the support surface is curved in such a way that, in a section in a plane containing the longitudinal axis, it has a local radius of curvature r _a 2: 1 mm at each point,

preferably r _a ^ 1, 5 mm. The radius of curvature can be constant over the entire support surface, as is the case with a design of the support surface as a partial surface of a torus, or it may for example also be provided a varying radius. The corresponding contact surface preferably has a respective local radius. Preferably, the

Support surface and the abutment surface each having the shape of a partial surface of a tire or a donut, said tire or donut in a plane containing the longitudinal axis of the shank tool does not necessarily have to have an exactly circular or elliptical cross-section.

According to a development, the support surface is blasted with a particle beam. In this case, the curved support surface thus has the

Properties of a blasted with a particle beam surface, in particular recognizable properties caused by the blast treatment are conditional. The blasted support surface can in particular

Surface dislocations, which leads to a further reduction of the

Susceptible to breakage of the cutting head. These advantages are particularly evident when the support surface has been ground before the blast treatment so that it has the properties of a ground and subsequently blasted surface.

According to a development, the cutting head on one of the

Working section facing away from the external thread another

Support surface, which is located on a further contact surface of the

Tool shank is supported on one of the free end of the

Tool shank facing away from the internal thread is formed in the recess. In this case, a particularly stable alignment and positioning of the cutting head is possible. Preferably, the

Cross-section of the further contact surface taper with increasing distance from the internal thread, so that the inner cross section of the recess tapers. In this case, the further contact surface can in particular also be curved in a plane which contains the longitudinal axis, in particular preferably convexly curved. In this case, the other contact surface

in particular have a larger radius of curvature than the abutment surface described above between the free end of the tool shank and the internal thread. Preferably, the further contact surface may also have the shape of a partial surface of a tire or a donut. Of the

Cutting head may be particularly preferably formed of hard metal or cermet. In this case, the cutting head can already be provided with cutting edges, for example, or it can be formed as a blank in which the cutting edges still have to be formed by subsequent processing, such as grinding, for example. The tool shank can in particular be formed of a tougher material, such as tool steel. Further advantages and advantages of the invention will become apparent from the following description of exemplary embodiments with reference to the accompanying figures.

From the figures show:

1 shows a perspective view of a tool shank for a rotating cutting tool according to one embodiment; Fig. 2: a perspective view of a replaceable

Cutting head according to one embodiment;

3: a partially sectioned exploded view of a

Shank tool according to the embodiment;

Fig. 4: a Fig. 3 corresponding further illustration to explain the

Shape of support surfaces and corresponding contact surfaces; 5 is an enlarged sectional view of a part of

Shank tool in assembled condition; and FIG. 6: an enlarged partial cut corresponding to FIG. 5

Representation of the shank power tool.

Embodiment

An embodiment will be described in more detail below with reference to FIGS. 1 to 6.

The rotary shaft tool 1 according to the embodiment is formed as an end mill, which extends along a longitudinal axis L

extending tool shank 2 and a replaceable cutting head 3 has. According to a modification, however, it is alternatively also possible, for example, to design the rotating shank tool 1 as a drill. In the figures, the cutting head 3 is shown in each case as a blank, which is not yet provided with the cutting edges required for the machining, since it does not depend on the exact configuration of the cutting for the present invention. Unless hereinafter referred to a radial direction or an axial With reference to the direction, these terms always refer to the longitudinal axis L, unless something of the concrete context is concerned

Deviating results. The cutting head 3 has a working area 30 and an integrally formed with the working area 30 connecting portion 31. To the

Work area 30 can be used for machining a

Workpiece necessary cutting e.g. be formed by grinding. The cutting head 3 is formed of a hard and wear-resistant material such as hard metal or cermet in particular. In the embodiment shown in the figures, the working area 30 has an im

Essentially cylindrical shape in which - depending on the desired

Design - one or more cutting edges can be introduced. As can be seen in particular in Figs. 3, Fig. 4 and Fig. 5, the

Cutting head 3 in the illustrated embodiment also has an axial

Bore 32 which extends along the longitudinal axis L. The bore 32 is open on the side of the connecting portion to the outside and is designed as a blind hole, which extends into the work area 30. The bore 32 may be used to supply coolant and / or lubricant to the blades to be formed, e.g. by appropriate grinding, erosion or the like outlets for the cooling and / or

Lubricant can be formed on the outside of the working area 30. Although such a bore 32 is shown with respect to the embodiment, it is e.g. also possible to form the cutting head 3 without such a bore.

In Fig. 2, an optional engagement surface 33 for engagement with a screwing tool is further shown on the cutting head 3, which may be provided to facilitate screwing the cutting head 3. If desired, in particular two such engagement surfaces 33 on

be provided opposite sides of the cutting head 3. Since the provision of these engagement surfaces 33 is optional, these are not shown in the other figures. The connecting portion 31 of the cutting head 3 is designed to connect the cutting head 3 to the tool shank 2, as will be described in more detail below. The tool shank 2 has a first end 20 for connection to a

Receiving a machine tool and this opposite the free end 21. The tool shank 2 is preferably made of a tougher material than the cutting head 3, e.g. made of tool steel, molybdenum or a molybdenum alloy, tungsten or a tungsten alloy. However, it is also conceivable to also produce the tool shank 2 from hard metal, in particular from a tougher hard metal. As can be seen in FIGS. 3 and 4, the tool shank 2 in the illustrated embodiment is provided with a continuous longitudinal bore 22 which makes it possible

Coolant and / or lubricant from a tool holder, in which the first end 20 of the tool shank 2 is clamped to supply to the cutting head 3. The longitudinal bore 22 extends in the illustrated

Embodiment concentric with the longitudinal axis L. Although each such longitudinal bore 22 is shown in the figures, it is e.g. also possible to form the tool shank 2 without such a longitudinal bore 2.

The following are the the connection of cutting head 3 and

Tool shaft 2 serving areas of the cutting head 3 and the

Tool shank 2 described in more detail. Unless hereinafter referred to the cross-section of a component or a

This always refers to the cross section in planes perpendicular to the longitudinal axis L, unless the context clearly dictates otherwise. As can be seen in particular in FIGS. 3 and 4, the cutting head 3 is in the region of

Connecting portion 31 has a smaller cross section than in the

Workspace 30 on.

The connecting portion 31 of the cutting head 3 has an external thread 34, which in the illustrated embodiment as a cylindrical thread with substantially constant over its longitudinal extent

Diameter d _{a is} formed. However, it should be noted that the

External thread 34 can taper in a modification, for example, with increasing distance from the working area 30, in particular conically taper. In the latter case, the diameter d _a denotes the largest diameter of the external thread 34 at its end facing the working area 30. The external thread 34 is shown in the illustrated

Embodiment designed as a metric fine thread, which has a lower thread pitch and a smaller tooth depth compared to a standard metric thread. However, other thread forms are possible.

In the area between the external thread 34 and the working area 30 is a support surface 35 for supporting on a corresponding contact surface of the tool shank 2, which will be described in more detail later,

educated. The support surface 35 is with respect to the longitudinal axis L.

formed rotationally symmetrical. As can be seen in FIGS. 3 to 6, the support surface 35 is formed curved in a section in a plane containing the longitudinal axis L, over its entire extent. In the specific embodiment shown in the figures, the support surface 35 is formed in particular concavely curved. The support surface 35 shown hatched in FIGS. 3 and 4 forms the region between the external thread 34 and the working region 30, which serves to axially and radially support the cutting head 3 on the tool shank 2. Between the support surface 35 and the external thread 34, as can be seen in FIGS. 3 and 4, e.g. still be provided a transitional section.

The support surface 35 has in a section in a plane which the

Longitudinal axis L contains, at each point a local radius of curvature r _a , which is at least 1 mm, preferably at least 1, 5 mm. Of the

Radius of curvature may vary in the direction from the external thread 34 to the working area 30 or, for example, also be formed constant, as shown schematically in Fig. 4. In the embodiment shown schematically in Fig. 4, the radius of curvature r _{a of} the support surface 35th For example, constant, so that the support surface 35 extends along a partial surface of a torus, which allows a particularly precise and simple production.

The support surface 35 bridges the majority of the ring

Difference in diameter between the diameter d _a of

External thread 34 and the diameter D _{a of} the working area 30 on the external thread 34 facing side. In this way, a reliable support in both the radial and in the axial direction is made possible. In the embodiment shown specifically, the support surface 35 extends up to the outer edge of the working area 30 on the outer thread 34 side facing. However, it is also possible, for example, that the support surface does not bridge the entire difference in diameter between the diameter d _{a of} the external thread 34 and the diameter D _{a of} the working region 30. In order to enable a reliable positioning and advantageous introduction of force, however, the annularly extending support surface 35 has at least one width A _a in the radial direction, for which the following applies: A _a ^ 0.75 * (D _a -d _a ) / 2. In other words, this means that the support surface bridges at least 75% of the radial distance between the working area 30 and the external thread 34.

The support surface 35 is further blasted in the embodiment with a particle beam so that it has the properties of a blasted surface. In particular, the support surface 35 is formed such that it

Achieving a high geometric accuracy with low tolerances ground and then blasted to mechanically annihilate microcracks and surface dislocations. The blast treatment in the preparation of the support surface 35 may preferably in one

Compressed jet method by dry blasting, wherein as particles of the particle beam, e.g. Glass beads, zirconium oxide and / or corundum can be used. During the production, the blast treatment may preferably take place such that the support surface 35 has compressive stresses in a region near the surface. The targeted introduction of

Compressive stresses can be controlled in a simple manner via the parameters of the jet treatment, in particular the jet pressure, the Material of the particles, the size of the particles, the angle of incidence, the shape of the particles, etc. In order to obtain the advantageous properties of the ground and then blasted support surface 35, the support surface 35 is not ground or coated after blasting.

As can be seen in particular in FIGS. 3 and 4, FIG

Connecting portion 31 of the cutting head 3 on the of the

Working area 30 facing away from the external thread 34 still another support surface 36 on. In the illustrated embodiment, the further support surface 36 also extends rotationally symmetrical about the longitudinal axis L. The connecting portion 31 has a smaller diameter in the region of the further support surface 36 as in the region of

External thread 34 on. In the embodiment, the tapered

Diameter of the further support surface 36 thereby with increasing distance from the external thread 34. The hatched in Figs. 3 and Fig. 4 shown further support surface 36 is adapted to engage another

Support contact surface of the tool shank 2, which will be described in more detail. In the embodiment, the further support surface 36 is also concavely curved in a plane containing the longitudinal axis L. In this case, the further support surface 36 has a radius of curvature R _a , which is greater than the radius of curvature r _{a of} the support surface 35 described above. Although with respect to the embodiment, a constant radius of curvature R _{a of} the further support surface 36 is shown, so that the other

Supporting surface 36 extends along a partial surface of a tome, the radius of curvature R _a, for example, also vary in the axial direction. In the illustrated embodiment, the connecting portion 31 to the external thread 34 throughout the same radius of curvature R _a , which allows a particularly simple and reliable production.

The tool shank 2 has at its free end 21 a recess 23 which extends from the free end 21 in the direction of the longitudinal axis L into the tool shank 2. The recess 23 is (apart from the Teeth of the internal thread 24 described below) with respect to the longitudinal axis L formed substantially rotationally symmetrical. The

Recess 23 is provided with an internal thread 24 to the

is formed with the above-described external thread 34 of the

Collaborate cutting head 3. Consequently, the internal thread 24 is also formed in the embodiment as a metric fine thread. According to an advantageous development, however, it may be provided that the internal thread 24 and the external thread 34 have a slightly different thread pitch, as described in the aforementioned prior art, in order to achieve an improved force distribution.

In the region between the internal thread 24 and the free end 21 of the tool shank 2, a contact surface 25 is in the recess 23

formed, which is adapted to the support surface 35 of the

Collaborate head. In the illustrated embodiment, the contact surface 25 extends up to the free end 21 of the

Tool shank 2. As can be seen in FIGS. 3 and 4, in the embodiment between the abutment surface 25 and the internal thread 24 a transition surface is still formed. The contact surface 25 extends rotationally symmetrically about the longitudinal axis L and is in a section in a

Level containing the longitudinal axis L, formed curved over its entire extent. In the specific embodiment shown is the

Bearing surface 25 in particular convex curved, as shown in Figs. 3 and Fig. 4 can be seen.

The contact surface 25 has in a section in a plane that the

Longitudinal axis L, at each point a local radius of curvature η, which is at least 1 mm, preferably at least 1, 5 mm. The contact surface 25 is preferably in shape exactly to the shape of the support surface 35 of the

Cutting head 3 adapted to achieve a flat support.

In particular, the radius of curvature n of the contact surface 25 may be at least substantially equal to the radius of curvature r _{a of} the support surface 35

to match. Even with the contact surface 25 thus the local

Radius of curvature n vary in the axial direction. In the illustrated However, in a special embodiment, the contact surface 25 has a constant radius of curvature n, so that it extends along a partial surface of a torus, as can be seen in particular in FIG. 4. In the embodiment, the abutment surface 25 is formed to cover substantially the entire difference between the diameter d,

Internal thread 24 and the diameter D, the free end 21 of the

Tool shank 2 bridged. However, it is e.g. also possible that the contact surface 25 does not bridge the entire difference in diameter between the diameter d, the internal thread 24 and the diameter D, the free end 21. In order to enable reliable positioning and advantageous introduction of force, the annularly extending

Bearing surface 25 but at least one width Δ, in the radial direction, for which applies: Δ, 0.75 ^* (Drdi) / 2. In other words, this means that the

Bearing surface bridged at least 75% of the radial distance between the free end 21 and the internal thread 24.

As can be seen in particular in FIGS. 3 and 4, a further contact surface 26 is formed in the recess 23 on the side remote from the free end 21 of the tool shank 2. The further contact surface 26 is designed to support the further support surface 36 of the cutting head 3. The further contact surface 26 is dimensioned such that it is in contact with the further support surface 36 of the cutting head 3 when the

Connecting portion 31 of the cutting head 3 in the recess 23rd

is screwed. The other contact surface 26 is in the

Embodiment rotationally symmetrical with respect to the longitudinal axis L.

educated.

In the specific embodiment shown, the further abutment surface 26 is also curved, in particular in a section in a plane containing the longitudinal axis L, formed convexly curved over its entire axial extent. In the special case shown in FIGS. 3 and 4, the further contact surface 26 has a constant radius of curvature Rj over its entire radial extension, so that the further Bearing surface 26 extends along a partial surface of a tome. In this case, the radius of curvature R, the other bearing surface 26 in particular to the radius of curvature R _{a of} the further support surface 36 of the cutting head adapted so that the radii of curvature at least substantially coincide. But it is also possible that the

Radius of curvature R, varies in the axial direction.

As can be seen in FIGS. 3 and 4, the other side closes on the side facing away from the free end 21 of the tool shank 2

Contact surface 26 is still a substantially cylindrical portion 27 of the recess 23, which is adapted to accommodate, inter alia, manufacturing tolerances. At the transition from the further contact surface 26 to the internal thread 24, a substantially step-like cross-sectional widening 28 is formed in the embodiment. Instead of such a stepped cross-sectional enlargement 28, e.g. also a continuous one

Cross-sectional enlargement with e.g. be provided a conical shape. The provision of a cross-sectional widening between the others

Bearing surface 26 and the internal thread 24 allows reliable production of the curved contour of the other contact surface 26th

In the following, with reference to FIGS. 5 and 6, the composite state of the rotary shaft tool 1 will be described, in which the connecting portion 31 of the cutting head 3 in the

Recess 23 of the tool shank 2 is received.

In the assembled state, the external thread 34 of the acts

Cutting head 3 so together with the internal thread 24 in the recess 23 that the support surface 35 of the cutting head 3 is pressed against the corresponding contact surface 25 of the tool shank 2, so that sets a substantially flat contact. In particular, it may be provided that further intermediate surfaces, e.g.

between the external thread 34 and the support surface 35 and between the internal thread 24 and the contact surface 25 are provided, something are free to each other so that they do not contact. On the side facing away from the free end 21 of the tool shank 2 side of the threaded connection, the further support surface 36 is pressed against the corresponding further contact surface 26 in the assembled state, so that sets a substantially flat contact between them.

Due to the described configuration of the cutting head 3 and the tool shank 2, the power transmission takes place during machining with the rotating shank tool 1 in the area between the threaded connection and the working area 30 over the curved surfaces, which are pressed against each other, i. the support surface 35 and the

Corresponding contact surface 25. In this way, a good distribution of the forces is achieved, in particular concentrations of tensile stresses in the material of the cutting head 3 are reliably prevented.

In addition, via the also in pairs curved surfaces on the side facing away from the free end 21 side of the threaded connection, i. the further support surface 36 and the further contact surface 26, an additional support, which also contributes to an advantageous force distribution and relief of the threaded connection. Furthermore, an additional centering and alignment of the cutting head 3 is provided via the further support surface 36 and the further contact surface 26.

Claims

claims

Interchangeable cutting head (3) having a working area (30) and integrally formed with the working area (30)

Connecting portion (31) having an external thread (34), wherein the cutting head (3) has a longitudinal axis (L),

wherein between the work area (30) and the external thread (34) a support surface (35) for supporting on a corresponding contact surface (25) of a tool shank (2) is formed,

wherein the support surface (35) is formed curved in a section in a plane containing the longitudinal axis (L).

A cutting head according to claim 1, wherein the support surface (35) is curved so as to be local in each point in a section in a plane containing the longitudinal axis (L)

Radius of curvature r _a > 1 mm, preferably r _a > 1, 5 mm.

Cutting head according to claim 1 or 2, wherein the support surface (35) is concavely curved.

Cutting head according to one of the preceding claims, wherein the external thread (34) has a diameter d _a on its side facing the working region (30) and the working region (30) has a diameter D _a on its side facing the external thread (34) and the curved one Support surface (35) between the

External thread (34) and the work area (30) in the radial direction over a width A _a > 0.75 ^* (D _a -d _a ) / 2 extends.

Cutting head according to one of the preceding claims, wherein on the side remote from the working area (30) of the external thread (34), a further support surface (36) for supporting on a further corresponding bearing surface (26) of the tool shank (2) is formed.

6. Cutting head according to one of the preceding claims, wherein the curved support surface (35) is blasted with a particle beam.

A tool shank (2) for a rotary cutting tool extending along a longitudinal axis (L) having a recess (23) formed at a free end (21) with an internal thread (24) for receiving a replaceable cutting head (3)

has corresponding external thread (34),

wherein the tool shank (2) between the internal thread (24) and the free end (21) has a contact surface (25) for supporting a

corresponding support surface (35) of the cutting head (3), wherein the abutment surface (25) is formed curved in a section in a plane which contains the longitudinal axis (L).

Tool shank according to claim 7, wherein the abutment surface (25) is curved so as to be local in each point in a section in a plane containing the longitudinal axis (L)

Curvature radius n> 1 mm, preferably n> 1, 5 mm. 9. Tool shank according to claim 7 or 8, wherein the internal thread (24) on its free end (21) facing side has a diameter dj and the tool shank (2) at its free end (21) a

Diameter D, and the curved abutment surface (25) extends between the internal thread (24) and the free end (21) in the radial direction over a width Δ,> 0.75 * (D, -d,) / 2.

10. Tool shank according to one of claims 7 to 9, wherein the

Contact surface (25) is convexly curved. 11. Tool shank according to one of claims 7 to 10, wherein the

Recess (23) on a side remote from the free end (21) side of the internal thread (24) has a further contact surface (26) for supporting a further support surface (36) of the cutting head (3).

12. Tool shank according to one of claims 7 to 11, wherein the cross section of the further contact surface (26) tapers with increasing distance from the internal thread (24).

13. Rotating shank tool (1) with:

a replaceable cutting head (3) having a working area (30) and integrally formed with the working area (30)

Connecting portion (31) having an external thread (34), and a tool shank (2) extending along a longitudinal axis (L) and having an internal thread (24), which with the

External thread (34) of the connecting portion (31) cooperates, wherein between the working area (30) and the external thread (34) of the cutting head (3) has a support surface (35) for supporting on a corresponding contact surface (25) of the tool shank (2) between the internal thread (24) and a free end (21) of the

Tool shank (2) is arranged, is formed,

wherein the support surface (35) and the corresponding abutment surface (25) are each formed curved in a section in a plane containing the longitudinal axis (L).

14. Shank tool according to claim 13, wherein the support surface (35) is concavely curved and the contact surface (25) is formed convexly curved.

15. Shank tool according to claim 13 or 14, wherein the support surface (35) is formed curved so that in a section in a plane containing the longitudinal axis (L), in each point a local

Radius of curvature r _a- 1 mm, preferably r _a 2: 1, 5 mm.

16. Shank tool according to one of claims 13 to 15, wherein the

Support surface (35) is blasted with a particle beam. Shank tool according to one of claims 13 to 16, wherein the

Cutting head (3) on a side facing away from the working portion (30) side of the external thread (34) has a further support surface (36), which is supported on a further bearing surface (26) of the tool shank (2) on one of the free end (21) of the tool shank (2) facing away from the internal thread (24) in the recess (23) is formed.