Patent Description:
Rotary cutting tools can be provided with a threaded coupling mechanism for securely retaining a replaceable cutting head within a tool holder.

The replaceable cutting head can include a male coupling member and the tool holder can include a female coupling member. The male coupling member can include an external thread and at least one abutment surface. The female coupling member can include an internal thread and at least one abutment surface, that each correspond to the external thread and at the least one abutment surface on the male coupling member.

In some such rotary cutting tools, the male coupling member includes one abutment surface which has a conical shape and the external thread is a straight (i.e., "non-tapered") thread. An example of such a rotary cutting tool is disclosed in, for example, <CIT>.

In other such rotary cutting tools, the male coupling member includes one abutment surface which has a conical shape and the external thread is a tapered thread. An example of such a rotary cutting tool is disclosed in, for example, <CIT>.

In still other such rotary cutting tools, the male coupling member includes two abutment surfaces, where one abutment surface has a conical shape, the other abutment surface has a cylindrical shape and the external thread is a straight thread. An example of such a rotary cutting tool is disclosed in <CIT>.

In yet still other such rotary cutting tools, the male coupling member includes two adjacent conical abutment surfaces and the external thread is a tapered thread. An example of such a rotary cutting tool is disclosed in, for example, <CIT>, in which the tapered thread extends in a rearward direction of the coupling member, away from the two adjacent abutment surfaces and towards a spherical supporting region.

It is an object of the subject matter of the present application to provide a coupling of a replaceable cutting head in a tool holder having an improved rigidity.

It is a further object of the subject matter of the present application to provide a rotary cutting tool having threaded coupling mechanism with two conical abutment surfaces that is easy to manufacture compared with other rotary cutting tools having threaded coupling mechanisms with two conical abutment surfaces.

It is a yet further object of the subject matter of the present application to provide a coupling of a replaceable cutting head in a tool holder having improved stability against lateral cutting forces.

In accordance with the invention, there is provided a replaceable cutting head, for rotary cutting operations, having a head longitudinal axis around which the replaceable cutting head rotates in a direction of rotation, the head longitudinal axis extending in a forward to rearward direction, comprising:.

Preferably, there is also provided a rotary cutting tool comprising such a replaceable cutting head and a tool holder, said tool holder having a holder longitudinal axis extending in the forward to rearward direction, comprising a female coupling member extending rearwardly from a forwardly facing holder forward surface, the holder forward surface extending transversely with respect to the holder longitudinal axis, the female coupling member comprising:.

It is understood that the above-said is a summary, and that features described hereinafter may be applicable in any combination within the scope of the claims to the subject matter of the present application, for example, any of the following features may be applicable to the replaceable cutting head, the tool holder or the rotary cutting tool:
The forward head cone angle can be in the range of <NUM>° ≤ α ≤ <NUM>°. The rearward head cone angle can be in the range of <NUM>° ≤ β ≤ <NUM>°.

Preferably, the forward and rearward head cone angles can be equal to exactly <NUM>°.

The external thread can be a straight thread.

The forward head abutment surface lies on an imaginary external forward cone centered about the head longitudinal axis. The plurality of external thread crests define an imaginary external crest cylinder that is axially delimited by the forward and rearward bearing portions. The imaginary external forward cone can intersect the imaginary external crest cylinder.

The rearward head abutment surface lies on an imaginary external rearward cone centered about the head longitudinal axis. The plurality of external thread roots define an imaginary external root cylinder that is axially delimited by the forward and rearward bearing portions. The imaginary external rearward cone can intersect the imaginary external root cylinder.

The major diameter of the external thread closest to the forward bearing portion defines a major external diameter that can be less than a minimum external forward diameter of the forward head abutment surface.

The minor diameter of the external thread closest to the rearward bearing portion defines a minor external diameter that can be greater than a maximum external rearward diameter of the rearward head abutment surface.

A maximum external rearward diameter of the rearward head abutment surface can be less than a minimum external forward diameter of the forward head abutment surface.

The forward head abutment surface has a forward head cone axial height. The rearward head abutment surface has a rearward head cone axial height. The rearward head cone axial height can be greater than the forward head cone axial height.

The head base surface can be perpendicular to the head longitudinal axis.

The forward holder cone angles can be in the range of <NUM>° ≤ γ ≤ <NUM>°. The rearward holder cone angle can be in the range of <NUM>° ≤ δ ≤ <NUM>°.

Preferably, the forward and rearward holder cone angles can be equal to <NUM>°.

The internal thread can be a straight thread.

The forward holder abutment surface lies on an imaginary internal forward cone centered about the holder longitudinal axis. The plurality of internal thread roots define an imaginary internal root cylinder that is axially delimited by the forward and rearward supporting portions. The imaginary internal forward cone can intersect the imaginary internal root cylinder.

The rearward holder abutment surface lies on an imaginary internal rearward cone centered about the holder longitudinal axis. The plurality of internal thread crests define an imaginary internal crest cylinder that is axially delimited by the forward and rearward supporting portions. The imaginary internal rearward cone can intersect an imaginary internal crest cylinder.

The major diameter of the internal thread closest to the forward supporting portion defines a major internal diameter that can be less than a minimum internal forward diameter of the forward holder abutment surface.

The minor diameter of the internal thread closest to the rearward supporting portion defines a minor internal diameter that can be greater than a maximum internal rearward diameter of the rearward holder abutment surface.

A maximum internal rearward diameter of the rearward holder abutment surface can be less than a minimum internal forward diameter of the forward holder abutment surface.

The forward holder abutment surface has a forward holder cone axial height. The rearward holder abutment surface has a rearward holder cone axial height. The rearward holder cone axial height can be greater than the forward holder cone axial height.

In the released position: the male coupling member can be located outside of the female coupling member. The forward head cone angle can be in the range of <NUM>° ≤ α ≤ <NUM>°. The rearward head cone angle can be in the range of <NUM>° ≤ β ≤ <NUM>°. The forward holder cone angles can be in the range of <NUM>° ≤ γ ≤ <NUM>°. The rearward holder cone angle can be in the range of <NUM>° ≤ δ ≤ <NUM>°.

In the released position: the forward and rearward head cone angles can be greater than the forward and rearward holder cone angles by no more than <NUM>°.

Preferably, in the released position, the forward and rearward head cone angles can be greater than the forward and rearward holder cone angles by <NUM>°.

In the locked position, the forward and rearward supporting portions are elastically deformed so that the forward and rearward head cone angles and the forward and rearward holder cone angles have the same value.

The rotary cutting tool can be further adjustable between the released position and a first pre-locked position, before the locked position, and in the first pre-locked position: the external and internal threads can threadingly engage each other. The head base surface can be spaced apart from the holder forward surface by a first forward distance. The forward head abutment surface can be in initial contact with the forward holder abutment surface. The rearward head abutment surface can be spaced apart from the rearward holder abutment surface by a first rearward distance.

The rotary cutting tool can be further adjustable between the first pre-locked position and a second pre-locked position, before the locked position, and in the second pre-locked position: the external and internal threads can threadingly engage each other. The head base surface can be spaced apart from the holder forward surface by a second forward distance, the second forward distance being less than the first forward distance. The forward head abutment surface can be in contact with the forward holder abutment surface. The rearward head abutment surface can be in initial contact with the rearward holder abutment surface.

The forward head abutment surface has a forward head cone axial height. The rearward head abutment surface has a rearward head cone axial height. The forward holder abutment surface has a forward holder cone axial height. The rearward holder abutment surface has a rearward holder cone axial height. The forward head cone axial height can be greater than the forward holder cone axial height. The rearward head cone axial height can be greater than the rearward holder cone axial height.

For a better understanding of the present application and to show how the same may be carried out in practice, reference will now be made to the accompanying drawings, in which:.

For example, the dimensions of some of the elements may be exaggerated relative to other elements for clarity, or several physical components may be included in one functional block or element. Where considered appropriate, reference numerals may be repeated among the figures to indicate corresponding or analogous elements.

In the following description, various aspects of the subject matter of the present application will be described. For purposes of explanation, specific configurations and details are set forth in sufficient detail to provide a thorough understanding of the subject matter of the present application. However, it will also be apparent to one skilled in the art that the subject matter of the present application can be practiced, within the scope of the claims, without the specific configurations and details presented herein.

Attention is first drawn to <FIG> showing a rotary cutting tool <NUM> of the type used for milling operations, specifically end milling, in accordance with embodiments of the subject matter of the present application. The rotary cutting tool <NUM> includes a replaceable cutting head <NUM> that has a head longitudinal axis A, around which the replaceable cutting head <NUM> rotates in a direction of rotation R. The head longitudinal axis A extends in a forward DF to rearward direction DR. The replaceable cutting head <NUM> can be typically made from cemented carbide. The rotary cutting tool <NUM> also includes a tool holder <NUM>. The tool holder <NUM> can be typically made from steel. In the embodiment shown, the cutting head <NUM> is devoid of a central coolant passage extending along the head longitudinal axis A, though in other embodiments such a coolant passage may be present. The replaceable cutting head <NUM> can be removably retained in the tool holder <NUM> by means of a threaded coupling mechanism. Such a threaded coupling mechanism could possibly be advantageous for other types of rotary cutting operations than that stated hereinabove, such as, for example, reaming or drilling.

It should be appreciated that use of the terms "forward" and "rearward" throughout the description and claims refer to a relative position in a direction of the head longitudinal axis A towards the left and right, respectively, in <FIG>, and <FIG>.

Reference is now made to <FIG>. The replaceable cutting head <NUM> has a forward portion that forms a cutting portion <NUM> and a rearward portion that forms a mounting portion <NUM>. In accordance with some embodiments of the subject matter of the present application the replaceable cutting head <NUM> can be formed from a unitary integral one-piece construction. This provides an advantage in that the replaceable cutting head <NUM> has no detachable cutting inserts (not shown). Such detachable cutting inserts can be replaced periodically and this can be a time consuming procedure. There is also a possibility that threaded screws (not shown), for example, which can be used to releasably retain the detachable cutting inserts to the replaceable cutting head <NUM> can be mislaid and/or lost during the replacement operation.

Referring to <FIG>, the cutting portion <NUM> includes at least one peripheral cutting edge <NUM>. In this non-limiting example shown in the drawings, the at least one peripheral cutting edge <NUM> can extend helically about the head longitudinal axis A. Moreover, in the non-limiting example shown, there can be exactly four peripheral cutting edges. Each peripheral cutting edge <NUM> is formed at the intersection of a peripheral relief surface <NUM>, and a peripheral rake surface <NUM>. The peripheral relief surface <NUM> is located rotationally behind the peripheral cutting edge <NUM> and the peripheral rake surface <NUM> is located rotationally ahead of the peripheral cutting edge <NUM>, both in respect to the direction of rotation R. The orientation of the peripheral cutting edge <NUM> allows metal cutting operations to be performed. In accordance with some embodiments of the subject matter of the present application the cutting portion <NUM> can include at least one flute <NUM> for evacuating chips (not shown) that are produced during the cutting operation. One flute <NUM> is associated to each peripheral cutting edge <NUM>. The replaceable cutting head <NUM> can include one or more the end cutting edges 30b at an end face <NUM> of the cutting portion <NUM>. In this non-limiting example shown in the drawings, the replaceable cutting head <NUM> can include exactly four end cutting edges 30b.

Making reference now to <FIG> and <FIG>, the mounting portion <NUM> includes a male coupling member <NUM> that protrudes rearwardly from a rearwardly facing head base surface <NUM>. The head base surface <NUM> extends transversely with respect to the head longitudinal axis A and defines a boundary between the cutting portion <NUM> and the mounting portion <NUM>. That is to say, the cutting portion <NUM> is formed forward of the head base surface <NUM> and the mounting portion <NUM> is formed rearward of the head base surface <NUM>. In accordance with some embodiments of the subject matter of the present application the male coupling member <NUM> can be rigid. The head base surface <NUM> can be perpendicular to the head longitudinal axis A. The head base surface <NUM> is intended to abut a corresponding surface on the tool holder <NUM> when the rotary cutting tool <NUM> is in a locked position, as will be described hereinafter.

The male coupling member <NUM> includes an external thread <NUM>. Referring to <FIG>, the external thread <NUM> includes an external thread ridge <NUM> that extends helically about an external thread axis B forming a plurality of external thread crests <NUM> and a plurality of external thread roots <NUM>. The external thread axis B is co-incident with the head longitudinal axis A. Thus, the external thread portion <NUM> and the replaceable cutting head <NUM> are co-axial. The plurality of external thread crests <NUM> define the major diameter and the plurality of external thread roots <NUM> define the minor diameter of the external thread <NUM>, respectively. The external thread has an external thread length LE, measured in a direction of the external thread axis B. In accordance with some embodiments of the subject matter of the present application, the external thread <NUM> can have approximately three turns.

In accordance with some embodiments of the subject matter of the present application the external thread <NUM> can be a straight thread. It should be appreciated that the term "straight thread" throughout the description and claims relates to a thread where the thread ridge extends about a cylinder and thus the thread crests are equidistant from the thread longitudinal axis. Similarly, it should be appreciated that the term "tapered thread" throughout the description and claims relates to a thread where the thread ridge extends about a cone and thus the thread crests decrease in distance from the thread longitudinal axis in the rearward direction. By virtue of the external thread <NUM> being a straight thread, the replaceable cutting head <NUM> is easier to manufacture than if, for example, the external thread <NUM> is tapered.

As shown in <FIG> and <FIG>, the male coupling member <NUM> includes two bearing portions, a forward bearing portion <NUM> and a rearward bearing portion <NUM> that each face outwardly away from the head longitudinal axis A. That is to say, the forward bearing portion <NUM> and a rearward bearing portion <NUM> face generally radially outwardly. The forward and rearward bearing portions <NUM>, <NUM> are located either side of the external thread <NUM>. Stated differently, the external thread <NUM> is located between the forward and rearward bearing portions <NUM>, <NUM>.

When the external thread <NUM> is a straight thread, an imaginary external crest cylinder <NUM> is defined by the plurality of external thread crests <NUM> of the external thread <NUM> and is axially delimited by the forward and rearward bearing portions <NUM>, <NUM>. Moreover, an imaginary external root cylinder <NUM> is defined by the plurality of external thread roots <NUM> of the external thread <NUM> and is axially delimited by the forward and rearward bearing portions <NUM>, <NUM>.

The forward bearing portion <NUM> includes a forward head abutment surface <NUM> that tapers inwardly in a rearward direction DR to define a forward head cone angle α. That is to say, the forward head abutment surface <NUM> has a conical shape facing generally radially outwards, where the forward head cone angle α is an internal angle. In accordance with some embodiments of the subject matter of the present application, the forward head abutment surface <NUM> can be frusto-conical. The forward head cone angle α can be in the range of <NUM>° ≤ α ≤ <NUM>°. Preferably, the forward head cone angle α can be equal to exactly <NUM>°. Stated differently, forward head abutment surface <NUM> can define an angle of <NUM>° with respect to the head longitudinal axis A. It is noted that the forward head abutment surface <NUM> is intended to abut a corresponding surface on the tool holder <NUM> when the rotary cutting tool <NUM> is in a locked position, as will be described hereinafter.

It should be appreciated that use of the terms "radially inward/inwardly" and "radially outward/outwardly" throughout the description and claims refer to a relative position in a perpendicular direction in relation to the head longitudinal axis A and/or holder longitudinal axis C, towards and away from the respective axis, in <FIG>, and <FIG>. It should further be appreciated that use of the term "cone angle" throughout the description refers to an angle formed by the tapered surfaces of a cone, in a longitudinal cross-section. It is noted that the term "longitudinal cross-section" refers to a cross-section taken in a plane containing the longitudinal axis.

The forward head abutment surface <NUM> lies on an imaginary external forward cone <NUM> centered about the head longitudinal axis A. That is to say, the imaginary external forward cone <NUM> is co-axial with the male coupling member <NUM>. The imaginary external forward cone <NUM> is a right circular cone. In accordance with some embodiments of the subject matter of the present application, the imaginary external forward cone <NUM> can intersect the imaginary external crest cylinder <NUM>.

In accordance with some embodiments of the subject matter of the present application, a forward portion of the forward bearing portion <NUM> can be located adjacent the head base surface <NUM>. The intersection of the forward bearing portion <NUM> and the head base surface <NUM> can be concavely curved. A rearward portion of the forward bearing portion <NUM> can be located adjacent the external thread <NUM>.

The rearward bearing portion <NUM> includes a rearward head abutment surface <NUM> that tapers inwardly in a rearward direction DR to define a rearward head cone angle β. That is to say, the rearward head abutment surface <NUM> has a conical shape facing generally radially outwards, where the rearward head cone angle β is an internal angle. In this non-limiting example shown in the drawings the rearward head abutment surface <NUM> can be frusto-conical. In accordance with some embodiments of the subject matter of the present application, the rearward head cone angle β can be in the range of <NUM>° ≤ β ≤ <NUM>°. Preferably, the rearward head cone angle β can be equal to <NUM>°. Stated differently, the rearward head abutment surface <NUM> can define an angle of <NUM>° with respect to the head longitudinal axis A. It is noted that the rearward head abutment surface <NUM> is intended to abut a corresponding surface on the tool holder <NUM> when the rotary cutting tool <NUM> is in a locked position, as will be described hereinafter.

The rearward head abutment surface <NUM> lies on an imaginary external rearward cone <NUM> centered about the head longitudinal axis A. That is to say, the imaginary external rearward cone <NUM> is co-axial with the male coupling member <NUM>. The imaginary external rearward cone <NUM> is a right circular cone. In accordance with some embodiments of the subject matter of the present application, the imaginary external rearward cone <NUM> can intersect the imaginary external root cylinder <NUM>.

In accordance with some embodiments of the subject matter of the present application, a forward portion of the rearward bearing portion <NUM> can be located adjacent the external thread <NUM>. A rearward portion of the rearward bearing portion <NUM> can be located adjacent a head rear surface <NUM> of the male coupling member <NUM>. The intersection of the rearward bearing portion <NUM> and the head rear surface <NUM> can be beveled. The head rear surface <NUM> can be perpendicular to the head longitudinal axis A.

The forward and rearward head cone angles α, β have the same value. Thus advantageously, the angle of rotation of a grinding wheel (used for manufacture of the replaceable cutting head <NUM>), does not need to be reconfigured when the forward and rearward head abutment surfaces <NUM>, <NUM> are ground. It should be appreciated that the expression "same value", as applied to the cone angles α, β, means within ± <NUM>°.

The forward head abutment surface <NUM> has a forward head cone axial height H1, as measured in the direction of the head longitudinal axis A. The rearward head abutment surface <NUM> has a rearward head cone axial height H2, as measured in the direction of the head longitudinal axis A. In accordance with some embodiments of the subject matter of the present application, H1 can typically have a value of <NUM> and H2 can typically have a value of <NUM>. The rearward head cone axial height H2 can be greater than the forward head cone axial height H1. The external thread length LE can be greater than the forward head cone axial height H1. The external thread length LE can be greater than the rearward head cone axial height H2.

As further shown in <FIG>, the major diameter of the external thread <NUM> closest to the forward bearing portion <NUM> defines a major external diameter DE1. In accordance with some embodiments of the subject matter of the present application the major external diameter DE1 can be less than a minimum external forward diameter FDE of the forward head abutment surface <NUM>.

The minor diameter of the external thread <NUM> closest to the rearward bearing portion <NUM> defines a minor external diameter DE2. In accordance with some embodiments of the subject matter of the present application the minor external diameter DE2 can be greater than a maximum external rearward diameter RDE of the rearward head abutment surface <NUM>. The maximum external rearward diameter RDE of the rearward head abutment surface <NUM> can be less than the minimum is external forward diameter FDE of the forward head abutment surface <NUM>.

Another aspect of the subject matter of the present application relates to the tool holder <NUM>. Referring now to <FIG> and <FIG>, the tool holder <NUM> has a holder longitudinal axis C that extends in the forward DF to rearward direction DR. The tool holder <NUM> includes a female coupling member <NUM> that extends rearwardly from a forwardly facing holder forward surface <NUM>. The holder forward surface <NUM> extends transversely with respect to the holder longitudinal axis C. In accordance with some embodiments of the subject matter of the present application the holder forward surface <NUM> can be perpendicular to the holder longitudinal axis C.

The female coupling member <NUM> includes an internal thread <NUM>. As shown in a longitudinal cross-sectional view of the female coupling member <NUM> (i.e. <FIG>), the internal thread <NUM> includes an internal thread ridge <NUM> that extends helically about an internal thread axis D forming a plurality of internal thread crests <NUM> and a plurality of internal thread roots <NUM>. The internal thread axis D is co-incident with the holder longitudinal axis C. Thus, the internal thread portion <NUM> is co-axial with the tool holder <NUM>. The plurality of internal thread crests <NUM> define the minor diameter and the plurality of internal thread roots <NUM> define the major diameter of the internal thread <NUM>, respectively. The internal thread has an internal thread length LI, measured in a direction of the internal thread axis D. In accordance with some embodiments of the subject matter of the present application, the internal thread <NUM> can have approximately three turns.

In accordance with some embodiments of the subject matter of the present application the internal thread <NUM> can be a straight thread. By virtue of the internal thread <NUM> being a straight thread, the tool holder <NUM> is easier to manufacture than if, for example, the internal thread <NUM> is tapered.

As shown in <FIG>, the female coupling member <NUM> includes two supporting portions, a forward supporting portion <NUM> and a rearward supporting portion <NUM> that each face inwardly towards the holder longitudinal axis C. That is to say, the forward supporting portion <NUM> and a rearward supporting portion <NUM> face generally radially inwardly. The forward and rearward supporting portions <NUM>, <NUM> are located either side of the internal thread <NUM>. Stated differently, the internal thread <NUM> is located between the forward and rearward supporting portions <NUM>, <NUM>.

When the internal thread <NUM> is a straight thread, an imaginary internal crest cylinder <NUM> is defined by the plurality of internal thread crests <NUM> of the internal thread <NUM> and is axially delimited by the forward and rearward supporting portions <NUM>, <NUM>. Moreover, an imaginary internal root cylinder <NUM> is defined by the plurality of internal thread roots <NUM> of the internal thread <NUM> and is axially delimited by the forward and rearward supporting portions <NUM>, <NUM>.

The forward supporting portion <NUM> includes a forward holder abutment surface <NUM> that tapers inwardly in a rearward direction DR to define a forward holder cone angle γ. That is to say, the forward holder abutment surface <NUM> has a conical shape facing generally radially inwards, where the forward holder cone angle γ is an external angle. In accordance with some embodiments of the subject matter of the present application, the forward holder abutment surface <NUM> can be frusto-conical. The forward holder cone angle γ can be in the range of <NUM>° ≤ γ ≤ <NUM>°. Preferably, the forward holder cone angle γ can be equal to <NUM>°. Stated differently, the forward holder abutment surface <NUM> can define an angle of <NUM>° with respect to the holder longitudinal axis C.

The forward holder abutment surface <NUM> lies on an imaginary internal forward cone <NUM> centered about the holder longitudinal axis (C). That is to say, the imaginary internal forward cone <NUM> is co-axial with the female coupling member <NUM>. The imaginary internal forward cone <NUM> is a right circular cone. In accordance with some embodiments of the subject matter of the present application, the imaginary internal forward cone <NUM> can intersect the imaginary internal root cylinder <NUM>.

In accordance with some embodiments of the subject matter of the present application, the forward supporting portion <NUM> can include a forward annular groove <NUM> and the forward holder abutment surface <NUM> can be spaced apart from the internal thread <NUM> by the forward annular groove <NUM>. A forward portion of the forward supporting portion <NUM> can be located adjacent the holder forward surface <NUM>. The intersection of the forward supporting portion <NUM> and the holder forward surface <NUM> can be beveled.

The rearward supporting portion <NUM> includes a rearward holder abutment surface <NUM> that tapers inwardly in a rearward direction DR to define a rearward holder cone angle δ. That is to say, the rearward holder abutment surface <NUM> has a conical shape facing generally radially inwards, where the rearward holder cone angle δ is an external angle. In accordance with some embodiments of the subject matter of the present application, the rearward holder abutment surface <NUM> can be frusto-conical. The rearward holder cone angle δ can be in the range of <NUM>° ≤ δ ≤ <NUM>°. Preferably, the rearward holder cone angle δ is equal to <NUM>°. Stated differently, the rearward holder abutment surface <NUM> can define an angle of <NUM>° with respect to the holder longitudinal axis C.

The rearward holder abutment surface <NUM> lies on an imaginary internal rearward cone <NUM> centered about the holder longitudinal axis C. That is to say, the imaginary internal rearward cone <NUM> is co-axial with the female coupling member <NUM>. The imaginary internal rearward cone <NUM> is a right circular cone. In accordance with some embodiments of the subject matter of the present application, the imaginary internal rearward cone <NUM> can intersect the imaginary internal crest cylinder <NUM>.

In accordance with some embodiments of the subject matter of the present application, a forward portion of the rearward supporting portion <NUM> can be located adjacent the internal thread <NUM>. The rearward supporting portion <NUM> can include a rearward annular groove <NUM> and the rearward holder abutment surface <NUM> can be spaced apart from a rear end <NUM> of the female coupling member <NUM> by the rearward annular groove <NUM>.

The forward and rearward holder cone angles γ, δ have the same value. Thus advantageously, when the forward and rearward holder abutment surfaces <NUM>, <NUM> are formed, for example via turning operations, during manufacture of the tool holder <NUM>, the turning tool does not need to be reconfigured. It should be appreciated that the expression "same value", as applied to the cone angles γ, δ, means within ± <NUM>°.

The forward holder abutment surface <NUM> has a forward holder cone axial height H3, as measured in the direction of the holder longitudinal axis C. The rearward holder abutment surface <NUM> has a rearward holder cone axial height H4, as measured in the direction of the holder longitudinal axis C. In accordance with some embodiments of the subject matter of the present application, H3 can typically have a value of <NUM> and H4 can typically have a value of <NUM>. The rearward holder cone axial height H4 can be greater than the forward holder cone axial height H3. The internal thread length LI can be greater than the forward holder cone axial height H3. The internal thread length LI can be greater than the rearward holder cone axial height H4.

As shown in <FIG>, the major diameter of the internal thread <NUM> closest to the forward supporting portion <NUM> defines a major internal diameter DI1. In accordance with some embodiments of the subject matter of the present application the major internal diameter DI1 can be less than a minimum internal forward diameter FDI of the forward holder abutment surface <NUM>.

The minor diameter of the internal thread <NUM> closest to the rearward supporting portion <NUM> defines a minor internal diameter DI2. In accordance with some embodiments of the subject matter of the present application the minor internal diameter DI2 can be greater than a maximum internal rearward diameter RDI of the rearward holder abutment surface <NUM>. The maximum internal rearward diameter RDI of the rearward holder abutment surface <NUM> can be less than the minimum internal forward diameter FDI of the forward holder abutment surface <NUM>.

Another aspect of the subject matter of the present application relates to a rotary cutting tool <NUM> that includes the replaceable cutting head <NUM> and tool holder <NUM> as defined herein above. The rotary cutting tool <NUM> is adjustable between a released position and a locked position. In the released position of the rotary cutting tool <NUM>, as shown in <FIG>, the rotary cutting tool <NUM> is unassembled and the male coupling member <NUM> is located outside of the female coupling member <NUM>. In accordance with some embodiments of the subject matter of the present application, in the released position, the forward and rearward head cone angles α, β can be greater than the forward and rearward holder cone angles γ, δ by no more than <NUM>°. Preferably, forward and rearward head cone angles α, β can be greater than the forward and rearward holder cone angles γ, δ by <NUM>°.

Assembly of the rotary cutting tool <NUM> is accomplished by performing the following steps. The male coupling member <NUM> is inserted into the female coupling member <NUM>. The external thread <NUM> is turned in a direction against the direction of rotation R within the internal thread <NUM>, so that the external and internal threads <NUM>, <NUM> threadingly engage each other, until the forward head abutment surface <NUM> comes into initial contact with the forward holder abutment surface <NUM>, attaining a first pre-locked position of the rotary cutting tool <NUM> (see <FIG>). Clearly, once the external and internal thread portions <NUM>, <NUM> threadingly engage, any further rotation of the external thread <NUM> in a direction against the direction of rotation R draws the replaceable cutting head <NUM> towards the tool holder <NUM>. As seen in a longitudinal cross-sectional view of the rotary cutting tool in the first pre-locked position of the rotary cutting tool <NUM> (i.e. <FIG>), the head base surface <NUM> is spaced apart from the holder forward surface <NUM> by a first forward distance F1. As shown in <FIG>, the rearward head abutment surface <NUM> is spaced apart from the rearward holder abutment surface <NUM> by a first rearward distance R1. According to one embodiment of the present application, when the forward head cone angle α of the forward head abutment surface <NUM> is greater than the forward holder cone angle γ of the forward holder abutment surface <NUM>, it is ensured that the initial contact between the forward head abutment surface <NUM> and the forward holder abutment surface <NUM> is made at the forward portion of the forward holder abutment surface <NUM>, thereby increasing the rigidity of the coupling between the male and female coupling members <NUM>, <NUM> at the forward bearing and supporting portions <NUM>, <NUM> when the locked position of the rotary cutting tool <NUM> is attained.

The replaceable cutting head <NUM> is rotated further in a direction against the direction of rotation R, until the rearward head abutment surface <NUM> comes into initial contact with the rearward holder abutment surface <NUM>, attaining a second pre-locked position of the rotary cutting tool <NUM> (see <FIG>, showing a longitudinal cross-sectional view of the rotary cutting tool <NUM> in a second pre-locked position). In the second pre-locked position of the rotary cutting tool <NUM>, the head base surface <NUM> is spaced apart from the holder forward surface <NUM> by a second forward distance F2, the second forward distance F2 being less than the first forward distance F1. Clearly, the forward head abutment surface <NUM> remains in contact with the forward holder abutment surface <NUM>. According to one embodiment of the present application, when the rearward head cone angle β of the rearward head abutment surface <NUM> is greater than the rearward holder cone angle δ of the rearward holder abutment surface <NUM>, it is ensured that the initial contact between the rearward head abutment surface <NUM> and the rearward holder abutment surface <NUM> is made at the forward portion of the rearward holder abutment surface <NUM>, thereby increasing the rigidity of the coupling between the male and female coupling members <NUM>, <NUM> at the rearward bearing and supporting portions <NUM>, <NUM> when the locked position is attained. Since the replaceable cutting head <NUM> is made of a harder material than the tool holder <NUM>, and also in view of the conical abutment surfaces, during the rotation of the replaceable cutting head <NUM> relative to the tool holder <NUM>, from the first pre-locked position to the second pre-locked position of the rotary cutting tool <NUM>, the forward head abutment surface <NUM> urges the forward holder abutment surface <NUM> in a radially outward direction, so that the forward supporting portion <NUM> deforms.

The replaceable cutting head <NUM> is rotated further in a direction against the direction of rotation R, until the head base surface <NUM> abuts the holder forward surface <NUM>, attaining the locked position of the rotary cutting tool <NUM> (see <FIG>, showing a longitudinal cross-sectional view of the rotary cutting tool <NUM> in a locked position). In the locked position of the rotary cutting tool <NUM>, the male coupling member <NUM> is removably retained in the female coupling member <NUM>. The head longitudinal axis A is co-incident with the holder longitudinal axis C. The external and internal threads <NUM>, <NUM> threadingly engage each other. The forward head abutment surface <NUM> abuts the forward holder abutment surface <NUM>. The rearward head abutment surface <NUM> abuts the rearward holder abutment surface <NUM>. The head base surface <NUM> abuts the holder forward surface <NUM>. Again, since the replaceable cutting head <NUM> is made of a harder material than the tool holder <NUM>, and also in view of the conical abutment surfaces, during the rotation of the replaceable cutting head <NUM> relative to the tool holder <NUM>, from the second pre-locked position to the locked position of the rotary cutting tool <NUM>, the forward head abutment surface <NUM> urges the forward holder abutment surface <NUM> further in a radially outward direction, and further deformation of the forward supporting portion <NUM> occurs.

Moreover, the rearward head abutment surface <NUM> urges the rearward holder abutment surface <NUM> in a radially outward direction, so that the rearward supporting portion <NUM> deforms. The deformation at the rearward supporting portion <NUM> is less than the deformation at the forward supporting portion <NUM>. By virtue of the rearward head and holder abutment surfaces <NUM>, <NUM> having a conical shape the adjustment of the cutting tool <NUM> from the second pre-locked position to the locked position is smooth and gradual.

By virtue of the threaded engagement located between two conical abutment regions the rotary cutting tool <NUM> as improved stability against lateral cutting forces.

Advantageously, the design of the forward and rearward head cone angles α, β being greater than the forward and rearward holder cone angles γ, δ by no more than <NUM>° (in the released position) ensures conical abutment between the forward head abutment surface <NUM> and the forward holder abutment surface <NUM>, and the rearward head abutment surface <NUM> and the rearward holder abutment surface <NUM> after deformation has occurred (i.e. in the locked position of the rotary cutting tool <NUM>). In accordance with some embodiments of the subject matter of the present application, in the locked position, by virtue of the deformation at the forward and rearward supporting portions <NUM>, <NUM>, the forward and rearward head cone angles α, β and the forward and rearward holder cone angles γ, δ can have the same value. The forward head cone axial height H1 can be greater than the forward holder cone axial height H3. Thus, an interference fit is attained along the full axial extent of the forward holder abutment surface <NUM>. Likewise, the rearward head cone axial height H2 can be greater than the rearward holder cone axial height H4. Thus an interference fit is attained along the full axial extent of the rearward holder abutment surface <NUM>.

In the locked position of the rotary cutting tool <NUM> a tight fit between the replaceable cutting head <NUM> and the tool holder <NUM> is accomplished. The coupling mechanism described herein above provides a quick, self-lock coupling between the replaceable cutting head <NUM> and the tool holder <NUM>.

Claim 1:
A replaceable cutting head (<NUM>), for rotary cutting operations, having a head longitudinal axis (A) around which the replaceable cutting head (<NUM>) rotates in a direction of rotation (R), the head longitudinal axis (A) extending in a forward (DF) to rearward direction (DR), comprising:
a forward portion forming a cutting portion (<NUM>) and a rearward portion forming a mounting portion (<NUM>), wherein;
the mounting portion (<NUM>) comprises a male coupling member (<NUM>) protruding rearwardly from a rearwardly facing head base surface (<NUM>), the head base surface (<NUM>) extending transversely with respect to the head longitudinal axis (A), and defining a boundary between the cutting portion (<NUM>) and the mounting portion (<NUM>), the male coupling member (<NUM>) comprising:
outwardly facing forward and rearward bearing portions (<NUM>, <NUM>) and an external thread (<NUM>) located therebetween wherein;
the forward bearing portion (<NUM>) comprises a conically shaped forward head abutment surface (<NUM>) that tapers inwardly in a rearward direction (DR) defining a forward head cone angle (α); and
the rearward bearing portion (<NUM>) comprises a conically shaped rearward head abutment surface (<NUM>) that tapers inwardly in a rearward direction (DR) defining a rearward head cone angle (β);
characterised in that
the forward and rearward head abutment surfaces (<NUM>, <NUM>) are ground, and
the forward and rearward head cone angles (α, β) are within ± <NUM>° of each other.