TOOL HOLDER FOR A MILLING CUTTER

FIELD OF THE INVENTION

The present invention relates to a tool holder for a milling cutter having an improved body, characterized by not being provided with threaded holes used for fastening the tools but having guides formed in the mass of a tool holder body, the guides receiving thereon tool support carriages that can be positioned and fastened by means of screws on the tool holder body. The tool support carriages work and act at the same time on an adapted recessed seat formed in the guides of the tool holder body. Such acting blocks the tool between the respective bearing surfaces provided on the tool holder body and on the tool support carriage, also permitting to maintain the diameter swept by the tool when it rotates, even after the tool has been sharpened several times.

The guides are implemented as rectilinear grooved sliding seats formed in the mass of the tool holder body and may be perpendicular or inclined with respect to the central axis of rotation and may be placed at the periphery with any inclination with respect to the tool bearing surface of the tool holder body. Furthermore, the guides are provided, preferably on the center line thereof, with a recessed recessed seat that can be accessed from the outside and that forms a surface inclined with a divergent angle with respect to the entry direction of the guide. The blocking of the tool provided on the tool holder is implemented by using a special tool support carriage that slides in the above-mentioned guides, the tool support carriage having at one end thereof a surface for bearing and/or pressing and/or holding and/or guiding the tool to be fastened. At the same time a screw is provided on the tool support carriage and acting on the recessed seat that is formed on the centerline of the tool holder body. Preferably the recessed seat is linear and planar. The whole construction is blocked into position by tightening the screw, the end of which acts on the recessed seat underneath, thus guaranteeing the blockage of the tool, maintaining of the diameter swept by the rotating tool (even after sharpening of the tool) and preventing the tool from getting dislodged from the fastening unit.

Advantageously, but not exclusively, these milling cutters can be used in working wood, and substitutes thereof, plastics and other similar materials.

PRIOR ART

In the field of manufacturing milling cutters, there are currently known different systems assembling and blocking interchangeable tools by means of fastening wedges acting with screws. All these currently known systems are provided directly on the tool holder body with threaded holes for the screws or holes for centering and fastening the tools.

This involves major machining on the bodies, in particular when several tools have to be provided on the same body, and multiple and repeated operations are required, that affect the final cost of the product.

Furthermore, the currently known fastening systems have drawbacks, particularly when the fastening screws for blocking the tools break inside the body mass either during tightening, unscrewing or even during the use of the milling cutters. Most of the time, this results in the impossibility of using the whole body, which is obviously an economic damage.

The above-mentioned drawback is overcome by the present invention through the use of an adjustment screw operating directly on the tool support carriage and acting on the tool holder body, wherein surface contact of the end of the screw is established with the tool holder body. Therefore, since all the forces acting on the tools are absorbed by the tool holder body, the above mentioned problems are avoided.

OBJECT OF THE INVENTION

It is therefore an object of the invention to provide a tool holder for a milling cutter which avoids the foregoing drawbacks and which can be used with multiple tools.

According to the invention there is provided a tool holder for a milling cutter as defined in the appended claims.

Preferably the tool holder for a milling cutter is adapted to hold multiple tools and uses a system for blocking the tools which may include the following features:

- the tool holder body is free of threaded holes for the insertion of the screws for fastening the tools by using adapted wedges (used in the known systems);

- the tool holder body is provided with rectilinear sliding guides, each being convergent

to the tool bearing surface of the tool holder body in order to receive the adapted supports (tool support carriages) for blocking the tools;

- the tool holder body is provided with sliding guides, preferably with a male-female 'dovetail' coupling or a similar one;

- the tool holder body is equipped with adapted tool support carriages that slide along the coupling guides (also of the male or female type);

- the tool support carriage is provided at one end thereof with a bearing surface to block the tools against the corresponding bearing surface on the tool holder body itself;

- the tool support carriage has on its surface one or more cylindrical pins for coupling with the female seats or connectors provided on the tools, or the vice versa;

- each of the tool support carriages is provided with at least one through-threaded hole to be accessed from the outside, in order to be able to operate with a screw or peg for blocking it into position. In order to guarantee the correct positioning, the end of the screw acts on an recessed seat (on the tool holder body) that is inclined so as to prevent the accidental disengagement of the carriage even when the carriage is subject to the centrifugal force due to the rotation of the tool holder body;

- the bearing surface of the tool holder body and the corresponding bearing surface of the tool support carriage are preferably parallel to one another;

- the direction of the sliding guides and the direction of the respective pins for blocking the tools can be any with respect to the bearing surface of the tool holder body and the rotational axis of the tool holder body;

- the tool holder for a milling cutter according to the invention makes it possible to maintain the diameter swept by the rotating tool even after it has been sharpened several times.

Also another object of the invention is that of providing a tool holder for a milling cutter which is adapted to hold multiple tools and which also maintains the position of the tool support carriage when the carriage is slid or advanced on the tool holder body even if the mechanical operation of the coupling between the fixed sliding guide of the tool holder body and the carriage is not very precise, such that a different positioning of the tool is determined due to the mentioned lack of precision.

In accordance with the latter object the tool holder for a milling cutter preferably may include the following features:

- the tool holder body has one or more bearing surfaces for tool support, flat and provided with one or more calibrated protruding pins of the fixed type for each station, on which

the tools are lined up, the tools presenting corresponding female seats or connectors for stable coupling. The tool holder body is equipped, for every tool carrying station, with a rectilinear guide adapted to receive a respective tool support carriage which is slidable and can be fixed in opposition to the bearing surface of the tool holder body;

- the calibrated protruding pins are parallel to each other and to the fastening direction of the tool support carriage for blocking in opposition to the tool;

- the calibrated protruding pins can be of the type of cylindrical, conical, truncated- conical, square, rectangular, hexagonal, star-shaped or any other cross-section, as long as they are adapted to be coupled with the female seats or connectors formed in the tools to be supported;

- the calibrated pins protruding from the bearing surface of the tool holder body can fixed to the tool holder body and arranged parallel to each other and perpendicular and/or inclined to the bearing surface of the tool holder body;

- the calibrated protruding pins, having appropriate lengths, can at the same time also be present on the bearing surface of the tool support carriage; in this case, the female seats or connectors formed in the tool are occupied simultaneously by the pins of the tool holder body and by the pins on the tool support carriage. These pins are parallel to each other, coaxial and have the same center distance, and they all have a direction parallel to the direction of the fixed sliding guide for sliding the tool support carriage on the tool holder body;

- in addition, in one possible variant, the calibrated protruding pins can be present only on the anterior surface of the tool support carriage, and with a direction parallel to the rectilinear sliding direction of the tool support carriage;

- in another possible embodiment, the tool can have more female seats or connectors; some being occupied by the protruding pins of the bearing surface of the tool holder body and others being occupied by the protruding pins of the bearing surface of the tool support carriage;

- on the calibrated protruding pins, the tool may be positioned and coupled by means of appropriate female seats or connectors formed in its surface, the female seats or connectors being inclined and/or perpendicular to the surface of the tool, such that the tool is made to contact with one of its surfaceso the bearing surface of the tool holder body and is then locked into its position with the slidable tool support carriage which can be blocked on the respective guides; accordingly, the tool will be blocked into position, thus preventing any removal from the female seats or connectors, even if it is subjected to mechanical and/or kinematic working forces;

- an analogous result of blocking the tool, maintaining as a reference point the same working radius, can be obtained by means of mobile pins which can be inserted in the female seats or connectors of the tool, protruding from only one or both side(s) of the tool, wherein the ends of the mobile pins are inserted simultaneously in the respective female seats or connectors

in the bearing surface of the tool holder body and/or in the anterior bearing surface of the tool support carriage.

ESSENCE OF THE INVENTION

The present invention provides for an improved tool holder for a milling cutter for blocking the tools thereof, the improved tool holder permitting to maintain the diameter swept by the rotating tool even after repeated sharpening, whose main feature, according to one aspect of the invention, is that the tool holder body is not provided with threaded holes or screws for positioning and fastening the tools.

Moreover, the present invention also provides for an improved tool holder equipped with bearing surfaces for the tools, provided with protruding pins, fixed or removable, as a support and a reference for the tools themselves.

The invention is particularly suitable for manufacturing milling cutters with all-purpose interchangeable or replaceable tools made of any material, that are capable of accommodating any spatial and geometric arrangement (different thicknesses and shapes) of the tools.

The tool holder can be used mainly in working with chip and stock removal in the field of working wood and substitutes thereof and/or other equivalent materials (such as plastics), as well as in special metal working.

According to one aspect of the present invention, the tool holder body has - in each of the zones provided for blocking the interchangeable tools - a rectilinear guide on which the tool support carriage can slide. The guide extends in a direction that intersects the tool bearing surface of the tool holder body. The guide has a sliding seat having a female or male dovetail shape, or any other shape that is suitable for the purpose, which is capable of mating and blocking, respectively, with the tool support carriage having a complementary sliding seat.

Furthermore, on the outer part of the tool holder body, in the area where the sliding seat is formed, for example on the central axis thereof and in the same direction, an recessed seat is provided which is inclined with respect to the entry and exit point of the sliding seat.

Each of the tool support carriages, besides having its sliding seat coupled to that of the

respective guide in the body, is provided with a tool bearing surface which is substantially parallel to the bearing surface on the tool holder body. In addition, for positioning and blocking it along the guide, a threaded through hole-like seat is provided, so as to use a screw or peg the end of which interferes with the recessed seat formed on the tool holder body.

Thus, the blocking of the tool on the tool holder body occurs with the aid of the tool support carriage, which presses on and keeps the tool in position, precisely because the screw - acting on the tool support carriage and at the same time on the recessed seat of the tool holder body underneath — prevents the tool from sliding out and the tool from getting disengaged.

Since usually the milling cutters have several tools mounted on the same tool holder, in order to ensure that the tools are positioned correctly, according to one exemplary embodiment of the invention, one or more graded pins are provided, that are preferably cylindrical and protrude along the bearing surface of the tool support carriage.

Moreover, according to the above exemplary embodiment, the tool is provided with female seats or connectors having the same center distance for coupling with the pins protruding from the bearing surface of the tool support carriage. Once the tool is pressed against the bearing surface on the tool holder body - after coupling of the female seats with the pins of the bearing surface of the tool support carriage - the tool support carriage is fastened in the closed position with the screw acting on the recessed seat of the tool holder body. This causes the tool to be perfectly blocked in position and kept pressed, precisely because of the action of the screw, which is an integral part of the tool support carriage received on the tool holder body. This in turns prevents the tool from sliding out even when it is subjected to mechanical and/or kinematic stresses during machining.

The present invention advantageously makes it possible to manufacture milling cutter tool holder bodies that are free of threaded holes and/or dowels for fastening the tool, thus avoiding the breaking of fastening screws inside the tool holder body; in fact the screws act on the tool support carriages that are an accessory part separate from the tool holder body and easily replaceable at a low cost.

Furthermore, the versatility of use of the milling cutter tool holder bodies is increased since they can be manufactured identical for different uses, which allows a series production with costs even lower. In fact, it is sufficient to change ad hoc the type of tool or tool support carriage

while using the same tool holder body.

It should be understood that the tool holder body has a tool bearing surface already preset for a given clearance or relief angle. For other values of the clearance angle, other surfaces will have to be provided.

However, in order to maintain the diameter swept by the tools during rotation, even after sharpening of the tool along the bearing surface in a parallel manner, the upper relief face of the tool (top clearance angle) has to be maintained undamaged and parallel to the direction of the feeding of the tool holder.

In addition, the present tool holder for a milling cutter is versatile in use since it can accommodate tools having different thicknesses and/or lengths, both in the axial direction of the body and in the direction perpendicular thereto.

According to a further aspect the present invention provides a fixed support on the bearing surface of the tool holder body functioning as a support and a reference point for the tool. This is done by providing the bearing surfaces of the tool holder body at the tool-carrying station or stations, in case of several stations, with at least one fixed pin, preferably two, protruding from this bearing surface, parallel to each other, in order to permit coupling to the corresponding female seats or connectors formed in the tool and/or in the bearing surface of the tool support carriage, as through holes or blind holes and parallel to the sliding direction of the sliding guide formed in the tool holder body on which the tool support carriage glides. It should be understood that these pins can be of identical height or not and have any cross-sectional geometry, preferably cylindrical or slightly conical.

The tool holder body provided in every zone of the tool-carrying station has, for the purpose of blocking the replaceable tool, a guide for rectilinear gliding whose direction intersects the bearing surface of the tool on the tool holder body. The guide has a gliding seat, preferably in a "dovetail" shape of the male or female type or any other geometrical shape suitable to achieve the above function, able to be coupled with and locked to the slidable tool support carriage having a corresponding gliding seat.

In addition, externally to the tool holder body, in the zone where the sliding guide is formed, e. g. in its median strip and in the same direction, an recessed seat in contrast to the point

of entrance and exit of the guide seat is embedded in the mass of the tool holder body. This recessed seat is designed to lock the tool support carriage in position on the tool holder body and in contrast to the base surface of the tool holder body, with one screw or one dowel whose end interferes with the recessed seat formed in the tool holder body.

Every tool support carriage, in addition to providing the sliding seat coupled to the one of the respective guide of the tool holder body, is equipped with an anterior bearing surface for holding and fastening the tool, in a position substantially parallel to the bearing surface on the tool holder body. The same is flat and smooth, but in one possible embodiment, it can also present protruding pins parallel to each other and to the sliding direction of the sliding guide, which can be coupled to female seats or connectors, in through holes or not, of the tool in which the pins protruding from the bearing surface of the tool holder body are already operative or to other female seats or connectors different from the first ones. The purpose of this is that of improving the blocking action and preventing decoupling of the tool.

According to another feature of the present invention, the bearing surfaces on the tool holder body and the bearing surfaces of the tool support carriages are flat and/or flat and knurled, in order to improve the fastening action of the tool. Furthermore, the bearing surface can also be profiled so as to follow the shape of the tool.

As known in the art, the sharpening of the tools results in the thinning of the same. Therefore, according to one advantageous aspect of the invention, in order to permit constant and safe closing of the blocking, one can predefine suitable recesses or female seats or connectors in one of the bearing surfaces in order to permit insertion of the protruding ends of the pins of the other bearing surfaces. Such female seats or connectors are located in a position opposite to and corresponding to the fastening direction of the pins. The purpose of this is that of utilizing the same pins, with appropriate lengths, for tools of different thicknesses.

It will be appreciated by the person skilled in the art that the bearing surface of the tool holder body with the protruding pins of the tool is already preset by a defined lower clearance angle; for other angular values, corresponding bearing surfaces have to be arranged.

In a further embodiment, both the bearing surfaces on the tool holder body and the anterior bearing surfaces of the tool support carriages can have holes or calibrated female seats or connectors whose direction is parallel to the sliding direction of the respective guides disposed

on the tool holder body. In this case, the female seats or connectors of the tool are parallel to each other and parallel to the direction of the guide of the tool holder body. The positioning and fixing of the tool takes place simply by the insertion of cylindrical (or having other shapes suitable to the objective) pins of the loose and removable type whose protruding ends can be inserted in both female seats or connectors. In the latter case, accordingly, no pins are formed in the bearing surface of the tool holder body or in the anterior bearing surface of the tool support carriage. Nevertheless, the tool is blocked, as is the case with the pins fixed to the bearing surface of the tool holder body and/or to the anterior bearing surface of the tool support carriage.

Advantageously, the pins or elements which protrude from the bearing surface of the tool holder body and/or from the anterior surface of the tool support carriage, or which can be inserted in the hollow seats formed in the bearing surface of the tool holder body or in the bearing surface of the tool support carriage, permit exact positioning of the tool during the phases of interchangeability and prevent removal of the tool, even if it is subjected to mechanical and kinematic actions; which serves to improve working security.

*

In summary, some of the advantages of the present invention are as follows:

- the construction of the tool holder body has no threaded holes and/or protruding dowels or screws for fastening the tools thereto, yet maintaining the possibility of maintaining the diameter swept by the rotating tool even after repeated sharpening;

- the tools can be readily sharpened even without employing special equipment;

- the interchangeability of the tools is improved and simplified;

- the interchangeability of the tool support on the same tool holder body is ensured;

- the possibility is provided of mounting tools of different geometry and materials (such as for example steel, sintered materials, industrial diamond, etc.) on the same tool holder;

- the simplicity of maintenance and cleaning if compared with the prior art solutions is improved.

SHORT DESCRIPTION OF THE DRAWINGS

A solution according to the present invention is represented in exemplary, preferable, but non-limiting manner in the enclosed figures, wherein:

Figure 1 shows, in a front view, a tool holder for a milling cutter according to a first embodiment of the invention and with four equidistant positions for the tools, emphasizing the sliding guides formed in opposed positions on the bearing surfaces of the tools;

Figure 2 shows, in a lateral view, the tool holder of Figure 1 , emphasizing the inclined surface formed on the median strip with respect to the sliding guide;

Figure 3 shows, in a partial exploded front view of the first embodiment of the invention emphasizing the parts of interest, the supporting zone of the tool of the tool holder body, the tool, the tool support carriage and the dowel or screw;

Figure 4 shows, in a partial sectional front view, the same parts as Figure 3, however in mounted position, with the tool locked to the tool holder body and coupled to the pins protruding from the bearing surface of the tool holder body, and with the tool support carriage closed;

Figure 5 shows a perspective view of the first embodiment of the invention in a disassembled state;

Figure 6 shows a perspective view of the first embodiment of the invention in an assembled state;

Figure 7 shows a view similar to Figure 4, however, with the tool in a first locked position prior to sharpening and in a second locked position after sharpening, wherein the sharpening occurs at the surface of the tool resting on one of the bearing surfaces;

Figure 8 shows, in a front view, a tool holder for a milling cutter according to a second embodiment of the invention;

Figure 9 shows, in a lateral view, the tool holder of Figure 8;

Figure 10 shows, in a partial exploded front view of the second embodiment of the invention emphasizing the parts of interest, the supporting zone of the tool of the tool holder body, the tool, the tool support carriage and the dowel or screw;

Figure 11 shows, in a partial sectional front view, the same parts as Figure 10, however in mounted position, with the tool locked to the tool holder body and coupled to the pins protruding from the bearing surface of the tool holder body, and with the tool support carriage closed;

Figure 12 shows, in a partial exploded front view, the parts of interest, in a third embodiment of the invention, with protruding pins of the bearing surface of the tool holder body of shorter length than in the second embodiment, but with protruding pins present simultaneously on the anterior bearing surface of the tool support carriage;

Figure 13 shows, in a partial sectional front view, the parts of Figure 12 in a locked position of the tool between the bearing surfaces, emphasizing that both pins enter the female seats or connectors of the tool;

Figure 14 shows, in a partial exploded front view, a fourth embodiment, with the pins on the anterior bearing surface of the tool support carriage, wherein the pins can be coupled with the respective female seats or connectors of the tool and of the bearing surface of the tool holder

body ;

Figure 15 shows, in a partial sectional front view, the parts of Figure 14, in locked position and in blocking position of the tool;

Figure 16 shows, in a partial exploded perspective view, the tool holder body of the second embodiment, emphasizing the cylindrical pins protruding from the bearing surface of the tool holder body and the tool with the female seats or connectors; and

Figure 17 shows, in a transverse sectional view, a series of possible protruding pins suitable for use in any of the embodiments of the invention.

With reference to Figures 1 through 7, according to a first embodiment of the invention, there is provided a tool holder for a milling cutter with a plurality of tool-carrying stations, four in the specific example.

Each tool-carrying station is includes a tool holder body 1 having a base 2 on which a bearing surface 6 for a tool 9 is provided which has, for instance, a prismatic shape. The tool holder body 1 is further provided with respective lateral lightening holes 7 on both sides thereof and a cavity or opening 8 to enable insertion of the tool 9. Opposite to the bearing surface 6 of the tool holder body 1, there is arranged a sliding guide 3, preferably in the shape of a "dovetail", of the male type and rectilinear, the sliding guide 3 being provided on the median strip on its outside with a recessed seat 5. Preferably the recessed seat 5 is linear and inclined and has an inclination α, in respect to an exit or entry portion of the sliding guide 3.

The bearing surface 6 on the tool holder body 1 is arranged on a surface parallel to or passing through the axis of rotation of milling cutter, but the bearing surface 6 can also be arranged with an inclination respect to the axis of rotation of the milling cutter.

A tool support carriage 11 is provided to be slidable on the sliding guide 3 and presents, preferably a female "dovetailed" seat 12, connectible to the above-mentioned male "dovetail" sliding guide 3, whereas on the upper part of the tool support carriage 11 there is a threaded hole 13 receiving a dowel or screw 14 whose lower end is wedged tight against the surface of the recessed seat 5 of the sliding guide 3 during the tightening phase, as best seen in Figure 4. The anterior part of the tool support carriage 12 has a bearing surface 16 with the same inclination β as the bearing surface 6 on the tool holder body 1 with respect to the sliding direction of the sliding guide 3.

The bearing surface 16 of the tool support carriage 11 is provided with at least two protruding calibrated pins 15, preferably of cylindrical shape, which are adapted to be inserted into corresponding female seats or connectors 10 provided in the tool 9. The female seats or connectors 10 may be implemented as through holes or non-through holes, are parallel to each other and to the directions of the pins 15, and have the same center distance of the pins 15 to which they are coupled.

The calibrated pins 15 protrude preferably in a perpendicular manner in respect to the bearing surface 16. The coupling of the pins 15 to the female seats or connectors 10 ensures the centering of the tool 9 and hinders at the same time its accidental disengagement from the tool holder during the operation of the milling cutter. As an alternative, however, the pins 15 may also extend in a non-perpendicular (inclined) manner in respect to the bearing surface 16.

Thus, the locking of the tool 9 onto the tool holder body 1 occurs by the contact of the lateral support surface 17 of the tool 9 with the bearing surface 6 of the tool holder body 1 and by the contact of the opposing lateral support surface 18 of the tool 9 with the bearing surface 16 of the tool support carriage 11 ,whereby the protruding pins 15 are inserted in surface into the female seats or connectors 10 of the tool 9. The final locking of the tool 9 occurs by means of the screw 14 threadingly engaging the threaded hole 13 of the tool support carriage 11 and by the end of the screw 14 contacting externally the inclined recessed surface 5, such as to hinder the displacement of the tool support carriage 11 with respect to the tool holder body 1.

The invention thus maintains the working diameter of the tool 9 even after sharpening of the lateral support surface 17 of the tool 9 which contacts the bearing surface 6 (lower clearance angle δ) maintaining unchanged the upper relief face 19 (upper clearance or angle γ) of the tool 9, as shown in Figure 7. The upper relief face 19 of the tool 8 is parallel to the advancement direction of the tool support carriage 11 determined by the sliding guide 3 and the female seat 12. In other words, the sliding direction of the sliding guide 3 is inclined with an angle equal to the clearance or angle γ of the tool 9 in respect to the tangent 23 passing through the contact point 22 of the tool 9.

With reference to Figures 8 through 11 and 16, according to a second embodiment of the present invention, there is provided a tool holder for a milling cutter with a plurality of tool- carrying stations, four in the specific example.

The second embodiment is identical to the first embodiment except for the calibrated pins 15.1 protruding now from the bearing surface 6 of the tool holder body 1. As shown in Figures 8 through 11 no pins are provided on the bearing surface 16 of the tool support carriage 11.

Moreover, the protruding pins 15.1 of the second embodiment extend an inclined manner in respect to the bearing surface 6, such that the axis of the pins 15.1 is parallel to the sliding direction defined by the sliding guide 3. As shown in Figures 10 and 11 the pins 15.1 are insertable into respective recesses 21 provided in the bearing surface 16 of the tool support carriage 11, the recesses 21 also extending parallel to the sliding direction defined sliding guide 3.

Advantageously a clearance is left between the pins 15.1 and the respective bottom of the recesses 21 in the locked state of a new tool on the tool holder, in order to provide for safe locking of the tool even after repeatedly sharpening of the lateral support surface 17 thereof.

As shown in Figure 10 and 11, the pins 15.1 protruding from the bearing surface 6 are of the fixed type, but they can also be of the type which can be extracted and inserted in the tool holder body 1. The same variation is applicable to all embodiments described herein.

The tool 9 is inserted onto the pins 15.1, coupled with the female seats or connectors 10 and therefore locked in position with the anterior bearing surface 16, which can be flat and/or knurled, of the slidable tool support carriage 11. The bearing surface 16 provides for the back pressure, fastening the tool 9 safely to the tool holder body 1 by threading the screw 14 into the recessed seat 5.

A third embodiment of the invention is shown in Figures 12 and 13, and this third embodiment differs from the second one in that both the bearing surface 6 of the tool holder body 1 and the bearing surface 16 of the tool support carriage are provided with respective protruding pins, namely pins 15.1 protruding from the bearing surface 6 and pins 15 protruding from the bearing surface 16. Both pins 15 and 15.1 must be sized such as to allow a close contact of the bearing surfaces 6 and 16 with the respective lateral support surfaces 17 and 18 of the tool 9 in order lock the tool 9 on the tool holder.

Preferably, as in the case of the second embodiment, a clearance remains between the

pins 15 and 15.1 in the locked state of a new tool on the tool holder, in order to provide for safe locking of the tool even after repeatedly sharpening of the lateral support surface 17 thereof.

As in the previous embodiments the pins 15 and 15.1 according to the third embodiment parallel to and coaxial with each other, also having their center distance equal with that of the female seats or connectors 10 of the tool 9.

According to a fourth embodiment of the invention, as illustrated in Figures 14 and 15, the pins 15 supporting the tool 9 are located on the anterior bearing surface 16 of the tool support carriage 11 and parallel to the sliding direction of the sliding guide 3. In this case, no protruding pins 15 are not located on the bearing surface 6 of the tool holder body 11. Fastening the tool 9 to the tool holder body 1 takes place by means of the insertion of the pins 15 of the tool support carriage 11 into the female seats or connectors 10 of the tool 9, which rests its lateral support surface 17 on the bearing surface 6 and rests the opposite lateral support surface 18 against the surface 16 of the tool support carriage 11 and further by inserting the pins 15 into the recesses 20 provided in the bearing surface 6 of the tool holder body 1. Finally, threading of the screw or dowel 14 against the inclined recessed surface 5 of the fixed sliding guide 3 takes place, which will prevent removal of the tool carriage support 11 and of the tool itself.

As in the second and third embodiments all axes of the pins, female seats and recesses are parallel to the direction of advancement of the tool support carriage 11.

Yet again, as in the case of the previous embodiments, after repeated sharpening of the prismatic tools 9, the thickness of the fastening zone or of the shaft of the tool 9 along the lateral support surface 17 is reduced. Therefore, in order to always guarantee perfect connection of the support surfaces to the tool for varying thicknesses, forming of a recess 20 of adequate depth on the bearing surface 6 opposed to the end of each pin 15 is envisaged, such that in the locked state of a new tool on the tool holder a clearance remains between the tip of the pins 15 and the bottom of the recess 20.

Various cross-sections of the calibrated pins are shown in Figure 17 which depicts cross-sections applicable to all embodiments of the present invention as herewith described and claimed.

The proposed examples are equivalent, and all achieve the proposed objectives; i. e.

security of fastening of the tool and the prevention of removal of the tool support carriage. In addition, the main advantage is maintenance of the references for centering, in particular of the tool tip, at the same radial dimension, even if the tool is repeatedly sharpened along the lateral support surface 17 during its normal maintenance. The fixed or removable pins promote inter- changeability of the tools on the tool holder body.

Moreover, the solution according to the second, third and fourth embodiments of the invention advantageously maintains the position of the tool support carriage when the carriage is slid or advanced on the tool holder body, even if the mechanical operation of the coupling between the fixed sliding guide of the tool holder body and the carriage is not very precise, by the additional guiding effect provided by the pins insertable into the respective recesses of the bearing surfaces or by the effect of the pins extending from both bearing surfaces and insertable into the respective female seats of the tool.

Naturally, the invention is not limited to the embodiment described above, in deviation from which other forms and types of embodiment can be implemented, and in any case, the particulars of the embodiment can vary without departing from the essence of the invention, as it is explained and claimed in the following.