The present invention relates to a tool and corresponding attachment of the type specified in the preamble to the at least one independent claim.

It should be noted that in this document, the term tool identifies a tool for machining operations appropriately for material removal such as, but not limited to, drilling, lapping or preferably milling.

As is well known, in order to use the tools, they must be constrained to a support that can be gripped by the operator, who then either uses the tool manually or preferably to a machine, e.g. a numerically controlled machine.

To this end, the tools have the non-working end provided with a thread of engagement to an attachment proper to said support or machine defining the tool end; and a conical portion adjacent to the thread and located opposite the end from the thread. The conical portion has a ground external surface (i.e., a high surface finish) so as to have no surface inaccuracies.

The attachment has a blind engagement hole to the tool. This bore has a conical seat at the mouth of the bore and an additional engagement thread on the shank thread. The conical seat also has a high surface finish so that there are no surface inaccuracies.

The coupling then involves the non-working end of the tool being inserted into the blind hole, bringing the threads into contact. Tool and attachment are reciprocally rotated engaging the threads and thus advancing the tool into the hole. At the clamping point, the surface of the conical portion and the surface of the conical seat come into contact with each other, ensuring, due to their surface finish, the centring of the tool in relation to the attachment. The known technique described includes some major drawbacks.

In particular, the centring of the tool is not adequately precise.

In fact, the centring is defined by the combination of the conical surfaces ensured by the coupling between the threads which, as is well known, have a low thread surface finish and therefore inherent play.

It should be noted that the presence of such play can also lead to unwanted oscillation/vibration of the tool.

Another drawback is that, in order to reduce backlash and thus have a perfect fit between the conical surfaces, the tool is tightened to the attachment using a high torque, which leads to thread deterioration, accentuating the aforementioned backlash in subsequent uses of the tool.

It can be seen that even the slightest deviation in centring can lead to major errors, which, especially in the case of high-precision machining such as surface finishing, can lead to tool breakage /or rejection of the machined part.

In this situation, the technical task at the heart of the present invention is to devise a tool and attachment capable of substantially obviating at least some of the aforementioned drawbacks.

Within the scope of this technical task, it is an important aim of the invention to obtain a tool and a coupling capable of ensuring perfect centring of the tool.

The specified technical task and purposes are achieved by a tool and a tool attachment as claimed in the independent claims. Examples of preferred embodiments are described in the dependent claims.

The features and advantages of the invention are clarified below by a detailed description of preferred embodiments of the invention, with reference to the accompanying drawings, in which the Fig. 1 shows a tool according to the invention in association with an attachment according to the invention; the Fig. 2 illustrates a tool constrained to an attachment; the Fig. 3 shows a different attachment according to the invention; and the Fig. 4 shows the connection of Fig. 3 in a different position.

In the present document, the measurements, values, shapes and geometric references (such as perpendicularity and parallelism), when associated with words like “about” or other similar terms such as “approximately” or “substantially”, are to be considered as except for measurement errors or inaccuracies due to production and/or manufacturing errors, and, above all, except for a slight divergence from the value, measurements, shape, or geometric reference with which it is associated. For instance, these terms, if associated with a value, preferably indicate a divergence of not more than 10% of the value.

Moreover, when used, terms such as “first”, “second”, “higher”, “lower”, “main” and “secondary” do not necessarily identify an order, a priority of relationship or a relative position, but can simply be used to clearly distinguish between their different components.

Unless otherwise indicated, "perpendicular", "transverse", "parallel" or "normal" or other terms of geometric positioning between geometric elements (e.g. axes, directions and straight lines) are to be understood with reference to their reciprocal geometric position between the corresponding projections. These projections are defined on a single plane parallel to the plane(s) of location of said geometric elements.

The measurements and data reported in this text are to be considered, unless otherwise indicated, as performed in the International Standard Atmosphere ICAO (ISO 2533:1975).

Unless otherwise specified, as results in the following discussions, terms such as “treatment”, “computing”, “determination”, “calculation”, or similar, refer to the action and/or processes of a computer or similar electronic calculation device that manipulates and/or transforms data represented as physical, such as electronic quantities of registers of a computer system and/or memories in, other data similarly represented as physical quantities within computer systems, registers or other storage, transmission or information displaying devices.

With reference to the Figures, the tool according to the invention is globally indicated by the number 1a.

It is configured to perform at least one machining operation appropriately for material removal such as, but not limited to, drilling, lapping or preferably milling.

The tool 1 a is configured to be constrained to an attachment 1 b identifiable in a spindle of said machine; or a tool holder, for example a morse taper, constrained to said spindle of said machine.

It comprises an active portion 2 configured to perform said machining suitably for material removal. Preferably, the active portion 2 is configured to perform milling and thus the tool 1 a is a milling cutter.

The active portion 2 may comprise an abrasive coating that coats a portion of the tool to define at least the active surface configured to perform material removal. The coating may be diamond coated and comprise diamonds and a bond configured to make said diamonds mutually integral.

The tool 1 a comprises a coupling portion 3 configured to be integrally constrained to the attachment 1 b and said machine. The coupling portion 3 therefore allows the tool 1 a to be constrained to the attachment 1 b. The coupling portion 3 defines a longitudinal axis 3a.

The attachment portion 3 comprises a first sector 31 defining a first external surface 3b of contact with the attachment 1 b and identifiable in the lateral surface of said first sector 31 .

The first sector 31 can have the longitudinal axis 3a as its extension axis.

It may have the form of a solid of revolution. In particular, it may be conical with preferably a maximum cross-section proximal to the active portion 2.

The first sector 31 has an axial extension of at least 1 cm, and in particular of between 3 cm and 5 cm.

In this document the term axial identifies an extension/direction parallel to the axis. In detail if referred to tool 1 a (or a part of it) axial identifies an extension/direction parallel to the longitudinal axis 3a; if referred to attachment 1 b (or a part of it) axial identifies an extension/direction parallel to the axis of preferred extension under introduced.

The first sector 31 may be in the form of a revolution solid of axis 3a. In detail, the first sector 31 may be conical with preferably a maximum cross-section distal from the second sector 32. In this document, the expression "revolution solid" identifies a geometric body formed by rotating a plane surface around a line called an axis and preferably identifiable in the longitudinal axis 3a, at least in the case of tool 1 a, and/or in the sub introduced axis of preferred extension 4a at least in the case of attachment 1 b.

The first external surface 3b is a surface of revolution appropriately about the longitudinal axis 3a. In this document, the expression "surface of revolution" means a surface created by rotating a line (straight or curved and usually referred to as a generatrix) about an axis of rotation preferably identifiable in the longitudinal axis 3a, at least in the case of tool 1 a, and/or in the sub-axis of preferred extension 4a at least in the case of attachment 1 b.

The first external surface 3b can be conical.

The first external surface 3b is configured to contact the attachment 1 b allowing the centring of the tool 1 a to the attachment 1 b (as further detailed below). It has a surface finish and to be precise a surface roughness Ra substantially less than 1 .6 pm in detail at 1 pm and to be precise at 0.5 pm. The first external surface 3b can be performed by grinding or lapping.

The measurement of roughness can be made through well -known instruments of measuring the roughness of the surface profile.

The coupling portion 3 comprises a second sector 32 defining a second external surface 3c in contact with the attachment 1 b and identifiable in the lateral surface of said second sector 32.

The second sector 32 can have the longitudinal axis 3a as its extension axis.

It has an axial extension of at least 1 cm, in detail 3 cm to 5 cm. In some cases, the axial extensions of sectors 31 and 32 may be substantially equal to each other.

The second sector 32 may have the form of a revolution solid of axis 3a. In detail, the second sector 32 may be conical with preferably a maximum cross-section proximal to the first sector 31 . It may have a taper equal to that of the first sector 31 . Alternatively, the sectors 31 and 32 may have a different taper.

Alternatively, the second sector 32 can be cylindrical.

Thus, the second external surface 3c is a surface of revolution suitably about the longitudinal axis 3a. It may be cylindrical and/or conical (optionally with conicity equal to or preferably different from that of the first surface 3b).

It can be seen that the conicity of the second sector 32 and thus of the second external surface 3c can be extremely reduced and thus have an almost cylindrical shape.

The second external surface 3c is configured to contact the attachment 1 b allowing the centring of the tool 1 a to the attachment 1 b. It has a surface finish and, to be precise, a surface roughness Ra of substantially less than 1 .6 pm in detail at 1 pm and for precision at 0.5 pm. It can be performed by grinding or lapping.

The external surfaces 3b and 3c can have essentially the same finish.

The coupling portion 3 comprises an intermediate sector 33 interposed between sectors 31 and 32 along the longitudinal axis 3a.

The intermediate sector 33 is configured to distance the first sector 31 from the second sector 32 along the longitudinal axis 3a.

The tool 1 a and in particular the coupling portion 3 may comprise means of engagement 34 configured to constrain the tool 1 a to the attachment 1 b by defining an axial constraint imposing a motion along the longitudinal axis between the tool 1 a and the attachment 1 b.

The means of engagement 34 can be obtained/placed at the intermediate sector 33 and thus between sectors 31 and 32.

The means of engagement 34 may comprise a thread, preferably a cylindrical thread, suitably made at the intermediate sector 33. In detail said thread may be a Whitworth thread and to be precise a Gas thread (i.e. a Whitworth thread with a very fine pitch). The said pitch can be substantially between 0.5 mm and 2 mm and in detail between 0.75 and 1 .5 mm.

The attachment 1 b includes a housing 4 for the coupling portion 3.

The housing 4 defines an axis of preferred extension 4a.

It is identifiable in a (preferably blind) hole defining an insertion section of the coupling portion 3 in the housing 4.

The housing 4 and in particular the attachment 1 b comprises a first compartment 41 defining a first internal surface 4b of contact with the tool 1 a and in particular with the first surface 3b and identifiable in the lateral surface of said first compartment 41.

The first compartment 41 can have the axis of preferred extension 4a as its predominant axis of extension.

It has an axial extension of at least 1 cm, in detail between 3 cm and 5 cm. Appropriately, first compartment 41 and first sector 31 have essentially the same axial extension.

The first compartment 41 may be in the form of a solid of revolution. In particular, it may be conical with preferably a maximum cross-section proximal to the insertion section.

In detail, the first compartment 41 can be counter-shaped to the first sector 31 .They can have almost the same conicity.

The first internal surface 4b is a surface of revolution appropriately around the longitudinal axis 3a.

It may be conical. Preferably the first internal surface 4b and the first external surface 3b have essentially the same inclination.

The first internal surface 4b is configured to contact the first external surface 3b allowing centring of the tool 1 a at the attachment 1 b. It may have a surface finish and to be precise a surface roughness Ra substantially less than 1 .6 pm in detail to 1 pm and to be precise to 0.5 pm. It may be performed by grinding or lapping.

The housing 4 comprises a second compartment 42 defining a second internal surface 4c in contact with the tool 1 a and in particular with the second surface 3c and identifiable in the lateral surface of said second compartment 42.

The second compartment 42 can have the axis of preferred extension 4a as its predominant axis of extension.

It has an axial extension of at least 1 cm, in detail between 3 cm and 5 cm. Appropriately, second compartment 42 and second sector 32 have essentially the same axial extension.

The second compartment 42 may have the form of a revolution solid of axis 3a. In detail, it may be conical with preferably a maximum cross-section proximal to the first compartment 41 . The second compartment 42 may have a taper equal to that of the first compartment 41 . Alternatively, the sectors 41 and 42 may have a different taper.

Alternatively, the second sector 42 can be cylindrical.

Thus, the second internal surface 4c is a surface of revolution suitably about the longitudinal axis 3a. It may be cylindrical and/or conical (optionally with conicity equal to or preferably different from the first internal surface 4b).

It can be seen that in some cases the taper of the second compartment 42 and thus of the second internal surface 4c can be extremely small and thus have an almost cylindrical shape.

The second internal surface 4c is configured to contact attachment 1 b allowing the centring of tool 1 a at attachment 1 b. It has a surface finish and to be precise a surface roughness Ra substantially less than 1 .6 pm in detail to 1 pm and to be precise to 0.5 pm. It can be performed by grinding or lapping.

The surfaces 4b, 4c, 3b and 3c can have essentially the same finish.

Preferably, the second compartment 42 can be counter-shaped to the second sector 32. Accordingly, second compartment 42 and second sector 32 may be cylindrical or have the same conicity, therefore, the second surfaces 4c and 3c have a cylindrical shape and substantially the same inclination, respectively.

The housing 4 comprises an intermediate compartment 43 interposed between compartments 41 and 42 along the axis of preferred extension 41 a.

The intermediate compartment 43 is configured to distance the first compartment 41 from the second compartment 42 along the axis of preferred extension 4a.

The attachment 1 b and in particular the housing 4 may comprise constraint means 44 configured to constrain the tool 1 a to the attachment 1 b by defining an axial constraint imposing a motion along the longitudinal axis between the tool 1 a and the attachment 1 b.

The constraint means 44 can be obtained/placed at the intermediate compartment 43 and thus between compartments 41 and 42.

In particular, they are configured to constrain themselves to the means of commitment 34 defining said axial constraint.

The constraint means 44 may comprise a thread, preferably a cylindrical thread. In detail, said thread may be a Whitworth thread and to be precise a Gas thread (i.e. a Whitworth thread with a very fine pitch). This pitch can basically be between 0.5 mm and 2 mm and in detail between 0.75 and 1 .5 mm.

Preferably, the means 44 and 34 include threads (e.g. gas threads) that can be reciprocally engaged.

It should be noted that when the tool 1 a is engaged, i.e. constrained, to the attachment 1 b, the means 44 and/or 34 engage with each other by opposing, preferably exclusively, axial forces and thus an axial motion between the tool 1 a and the attachment 1 b; any transverse motions to the axes 2a and 4a are prevented by the contact between the external surfaces 3b 3c against the attachment 1 b and the internal surfaces against the tool 1 a. In detail, when the tool 1 a is engaged at the attachment 1 b the first surfaces 3b and 4b and the second surfaces 3c and 4c define two contact zones between the tool 1 a and the attachment 1 b axially spaced apart suitably avoiding any transverse motions to the axes 2a and 4a between the tool 1 a and the attachment 1 b.

Preferably the means 44 and/or 34 represent the unique axial constraint between attachment 1 b and tool 1 a.

Finally, the invention introduces an assembly 1 comprising the tool 1 a and the attachment 1 b individually described above.

The assembly 1 , preferably when the tool 1 a is engaged to the attachment 1 b and thus the engagement portion is in the housing, has the first internal surface 4b in contact with the first external surface 3b and simultaneously the second internal surface 4c in contact with the second external surface 3c so as to align the axis of preferred extension 4a with the longitudinal axis 3a preventing a reciprocal motion between tool 1 a and attachment 1 b transverse to said axes 4a and 3a; and the intermediate compartment 43 constrained to the intermediate sector 33 (to be precise, the mutually engaged means 44 and 34) preventing a motion along axes 4a and 3a between tool 1 a and attachment 1 b.

The installation of assembly 1 and in particular the constraint of tool 1 a and the attachment 1 b described above in structural terms is as follows.

The coupling portion 3 is inserted into the housing 4. In particular, the first sector 31 is inserted into the first compartment 41 by bringing the first external surface 3b into correspondence with the first internal surface 4b and, at the same time, particular the second sector 32 is inserted into the second compartment 412 by bringing the second external surface 3c into correspondence with the second internal surface 4c.

At this point, the means 34 and 44 engage each other by realising the axial constraint between tool 1 a and attachment 1 b. In detail, when the intermediate sector 33 is in the intermediate compartment 43 the means 34 and 44 engage each other by realising the axial constraint. More in detail, the threads defining the means 34 and 44 are engaged with each other by pressing the external surfaces 3b and 3c against the respective internal surfaces 4b and 4c.

The assembly 1 and in particular tool 1 a and attachment 1 b achieve important advantages.

In fact, the coupling/contact between the first surfaces 3b and 4b and between the second surfaces 3c and 4c, the axes 3a and 4a being axis revolution surfaces, allows a simple and particularly precise alignment between the same axes 3a and 4a and thus of tool 1 a to attachment 1 b.

Furthermore, this contact between the first surfaces 3b and 4b and between the second surfaces 3c and 4c defines two unloading zones between tool 1 a and attachment 1 b axially spaced apart capable of absorbing any forces that would lead to a misalignment between axes 3a and 4a and therefore to an incorrect operation of tool 1 a. In fact, as the axes 3a and 4a are axes of revolution, the coupling between the first surfaces 3b and 4b and between the second surfaces 3c and 4c allows for the absorption of the loads transversal/normal to the axis 3a/4a that represent the main loads normally afflicting tool 1 a and attachment 1 b.

It is clear that these advantages result in greater machining precision and at the same time increased life of the tool 1 a.

It should also be emphasised that these advantages are especially pronounced in the case of conical surfaces 3b, 4b, 3c and 4c, even if they have an extremely small taper (i.e. almost cylindrical).

Another advantage is the fact that the first surfaces 3b and 4b and the second surfaces 3c and 4c, by defining two contact zones between tool 1 a and attachment 1 b that are spaced apart, make it possible to prevent fluid and/or dust from entering the area where the media 34 and 44 are present, for example by ruining the threads. The invention is susceptible to variations within the inventive concept as defined by the claims.

In a first example, means 34 and 44 can be obtained from the second sector 32 and the second compartment 42 respectively.

In a second example (alternative or additional to the first), the tool 1 a is configured to be constrained to a graspable support identifiable the attachment 1 b described above.

In a third example (Figs. 3 and 4), the attachment 1 b and, in particular, the housing 4 may comprise a main body 45 and an auxiliary body 46 that may be constrained to said main body 45.

The main body 45 comprises the first compartment 41 (and thus the first internal surface 4b), the intermediate compartment 43 and the constraint means 44. Preferably the constraint means 44 are identifiable in a thread made at the intermediate compartment 43.

The auxiliary body 46 comprises a second compartment 42 and thus the second interior surface 4c.

The auxiliary body 46 is constrained to the main body 45 on the opposite side of the first compartment 41 from the intermediate compartment 43 so as to arrange the intermediate compartment 43 between the first compartment 41 and the second compartment 42. For this purpose, it may comprise additional constraint means 47 configured to engage the main body and preferably the constraint means 44.

Accordingly, the constraint means 44 are pledged at the same time as the means of engagement 34 and said additional constraint means 47. In particular, in the case of constraint means 44, of engagement 34 and additional constraint means identifiable in threads; the engagement means 34 are pledged to a first portion of the thread of the constraint means 44 and the additional constraint means 47 are pledged to a second portion of the thread of the constraint means 44. Said first portion is proximal to the first compartment 41 and said second portion is distal from the first compartment 41 .

The auxiliary body 46 may be hollow and thus comprise a cavity defining said second compartment 42. Preferably said cavity is passing along the axis 4a thus defining a passage channel for a fluid such as for example a lubricant and/or coolant for the tool 1 a.

In order to control the constraint of the additional constraint means 47 to the constraint means 44 the auxiliary body 46 may comprise a gripping surface of the same auxiliary body 46. For example, the gripping surface may be an engagement surface of a socket made at said cavity.

These examples are mutually implementable with each other and/or with any of the other features described above.

Here, all details can be replaced by equivalent elements and materials, shapes and sizes can be any.