Abstract:
In an embodiment, the invention provides a tool for chip removing machining, including a replaceable cutting insert and a basic body. The basic body includes a rear fixing part, a front supporting part having an insert seat, and a tightening part spaced apart from the front supporting part by a first gap and from the rear fixing part by a second gap. The tightening part is connected to the basic body via a joint around which the tightening part is pivoted to press the cutting insert against the insert seat by a front finger. The rear fixing part includes a first channel having an inlet and an outlet for feed of a fluid toward the cutting insert. The tightening part includes an internal, second channel that extends between an inlet and an outlet. A hollow coupling member extends between the tightening part and one of the rear fixing part and the front supporting part while bridging the respective gap to establish a fluid communication path between the outlet of the first channel and the inlet of the second channel.

Description:
[0001]    This application claims priority under 35 U.S.C. §119 to Swedish Patent Application No. 0602558-9, filed on Nov. 28, 2006, the disclosure of which is incorporated by reference herein in its entirety. 
       FIELD OF THE INVENTION  
       [0002]    The present invention relates generally to a tool for chip removing machining of the type that includes a replaceable cutting insert and a basic body. The basic body includes a rear fixing part, a front supporting part having an insert seat in which the cutting insert is placed, and a tightening part. The tightening part is spaced-apart from the two other parts via two gaps and connected to the rest of the basic body via a joint. The tightening part is pivotable around the joint to press the cutting insert against the insert seat by a front finger. The fixing part includes a channel that has an inlet and an outlet for feed of a fluid toward the cutting insert. The present invention also relates to a basic body for such tools. The invention is particularly applicable and advantageous in connection with turning tools. 
       BACKGROUND OF THE INVENTION  
       [0003]    Turning tools of the above generally mentioned type are usually used for machining workpieces of metal, preferably by parting, grooving and profile turning. For the turning operations, it is desirable to use as slender cutting inserts as possible, in order to generate the thinnest possible grooves, thereby minimizing material losses and energy consumption. This means that the front portion of the support part under the cutting insert, as well as the front finger of the tightening part above the cutting insert have to be designed utmost slender or thin to be accommodated in the groove in the workpiece recessed by the cutting insert. 
         [0004]    As a consequence of, on one hand, the fact that the front portions of the support and tightening parts of the basic body have to be slender, and on the other hand the fact that the movable tightening part is connected to the rest of the basic body via a thin, elastic material portion serving as a joint, difficulties arise in cooling the cutting insert in an efficient way. Thus, the cooling of previously known grooving and parting tools, respectively, has been effected in an inefficient and almost provisional way, more precisely by two pipe conduits routed from the rear fixing part of the basic body (or a tool holder connected with the basic body), situated externally to the basic body, and ending in outlets situated far from the cutting insert. De facto, an upper conduit for cooling the cutting insert from above mouths approximately in flush with the topside of the tightening part, while a lower conduit for cooling the cutting insert from below mouths at a point situated approximately halfway between the cutting insert and the underside of the support part. In order to improve the cooling of the cutting insert and furthermore avoid the need of the space-requiring external pipe conduits and associated problems, attempts have been made to form the requisite cooling-liquid conduits in the form of internal channels in the proper basic body. However, these attempts have had limited success so far that internal channels having a sufficient cross-section area indeed have been producible in the support part stiffly integrated with the fixing part, but not in the pivotably movable tightening part, which, with the exception of the thin, elastic joint, is spaced-apart from the fixing part as well as the support part via open gaps. In other words, it has previously only been practically possible to provide undercooling of the cutting insert via internal cooling-liquid channels, but not overcooling. 
         [0005]    The cooling of the previously known tools has been effected using large quantities of flushing low-pressure cooling liquid (about a pressure of 10 bar), in spite of the development of the cooling technique within the area of cutting machining increasingly being pushed in the direction of using high-pressure liquid. Thus, numerous tools for chip removing machining have recently been designed for cooling-liquid pressures within the range of 400-1000 bar or more. 
         [0006]    The present invention aims at obviating the above-mentioned shortcomings of previously known cutting tools, in particular turning tools for, for instance, grooving and parting purposes, and at providing an improved tool. Therefore, an object is to provide a tool having the capability of cooling the cutting insert in an efficient way not only from below but in particular also from above, without the tool needing to be cluttered up with external conduit pipes for the cooling liquid. An additional object is to provide a turning tool having the capability of cooling the topside of the cutting insert by a highpressure liquid jet, which has accurate precision in respect of the point of impact thereof against the cutting insert. In particular, the invention aims at allowing the formation of a so-called hydraulic wedge between the chip surface of the cutting insert and the chip partly broken away, wherein the cooling effect of the jet of liquid even may be of secondary interest in comparison with the chip-breaking effect thereof. A parallel object of the invention is to provide an improved chip evacuation during grooving or parting by the tool. Yet another object of the invention is to provide a tool, the improved cooling and chip-forming capacity of which does not intrude on the capability of the tightening part to distinctly fix the cutting insert in the insert seat. In other words, a high-pressure cooling liquid or fluid should be introducible into the tightening part without detrimentally affecting the delicate joint between the tightening part and the rest of the basic body. 
       SUMMARY OF THE INVENTION  
       [0007]    In an embodiment, the invention provides a tool for chip removing machining, including a replaceable cutting insert and a basic body. The basic body includes a rear fixing part, a front supporting part having an insert seat, and a tightening part spaced apart from the front supporting part by a first gap and from the rear fixing part by a second gap. The tightening part is connected to the basic body via a joint around which the tightening part is pivoted to press the cutting insert against the insert seat by a front finger. The rear fixing part includes a first channel having an inlet and an outlet for feed of a fluid toward the cutting insert. The tightening part includes an internal, second channel that extends between an inlet and an outlet. A hollow coupling member extends between the tightening part and one of the rear fixing part and the front supporting part while bridging the respective gap to establish a fluid communication path between the outlet of the first channel and the inlet of the second channel. 
         [0008]    In another embodiment, the invention provides a basic body for tools for chip removing machining, including a rear fixing part, a front supporting part having a cutting insert seat, and a tightening part spaced apart from the front supporting part by a first gap and from the rear fixing part by a second gap. The tightening part is connected to the basic body via a joint around which the tightening part is pivoted to press a front finger toward the cutting insert seat. The rear fixing part includes a first channel having an inlet and an outlet for feed of a fluid toward the cutting insert seat. The tightening part includes an internal, second channel that extends between an inlet and an outlet. A hollow coupling member extends between the tightening part and one of the rear fixing part and the front supporting part while bridging the respective gap to establish a fluid communication path between the outlet of the first channel and the inlet of the second channel. 
         [0009]    The idea behind the invention is to lead in cooling liquid, in particular high-pressure cooling liquid, into the pivotably movable tightening part of the tool via a hollow coupling member, which intersects either the gap separating the tightening part from the subjacent support part, or the gap separating the tightening part from the fixing part of the basic body. In the coupling member, which advantageously may be a pipe piece, there is a central hole from which the cooling liquid can pass out via radial holes, which mouth in a ring-shaped space between two axially spaced-apart, elastic sealing rings. An internal channel runs inside the tightening part between an inlet mouth between the sealing rings and an outlet mouth in the front tightening finger of the tightening part. 
         [0010]    The liquid pressure may—in a preferred embodiment—apply equally large, but counter-directed forces to the sealing rings. In such a way, the forces are outbalanced so that the coupling member does not apply a compressive force to the tightening part, which could jeopardize the clamping of the cutting insert, in spite of the fact that the liquid pressure may be very high, e.g., of 400 bar or more. However, it is also possible to arrange the sealing rings in such a way that the liquid pressure is utilized to apply a tightening force to the tightening part. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0011]    The accompanying drawings, which are incorporated herein and constitute part of this specification, illustrate the presently preferred embodiments of the invention, and together with the general description given above and the detailed description given below, serve to explain features of the invention. 
           [0012]      FIG. 1  is a perspective view of a turning tool according to an embodiment of the invention; 
           [0013]      FIG. 2  is a partly sectioned perspective view showing parts of the interior of the tool in  FIG. 1 ; 
           [0014]      FIG. 3  is a central longitudinal section through the basic body of the tool having a cutting insert, a coupling member in the form of a pipe piece, and a tightening screw fitted in the basic body; 
           [0015]      FIG. 4  is a longitudinal section corresponding to  FIG. 3 , in which the cutting insert, the pipe piece, and the tightening screw have been removed; 
           [0016]      FIG. 5  is an enlarged perspective view showing the pipe piece having two pairs of fitted sealing rings; 
           [0017]      FIG. 6  is a corresponding perspective view showing the pipe piece without sealing rings; 
           [0018]      FIG. 7  is a longitudinal section through the pipe piece according to  FIG. 5 ; 
           [0019]      FIG. 8  is a bottom perspective view showing an alternative embodiment of a pipe piece according to the invention; 
           [0020]      FIG. 9  is a top perspective view of the pipe piece according to  FIG. 8 ; and 
           [0021]      FIG. 10  is a schematic section showing an additional alternative embodiment of the invention. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0022]    In  FIG. 1 , a turning tool is shown that in practice can be used for parting, grooving and profile turning. The main components of the tool are a basic body, in its entirety designated  1 , and a replaceable cutting insert  2 . In this case, the cutting insert has an elongate basic shape and is indexable in two positions by including a pair of opposite, circular cutting edges  3 , which are formed on round material portions  4  having a downwardly tapering shape. The intermediate portion  5  of the cutting insert, which extends between the two opposite ends, has a width or thickness that is smaller than the diameter of the cutting edges  3 . 
         [0023]    In this connection, the basic body  1  suitably is manufactured from steel or the like, while the replaceable cutting insert  2  is manufactured from cemented carbide or other hard and wear-resistant materials. 
         [0024]    The basic body  1  includes a rear fixing part  6 , a front supporting part  7 , and a tightening part  8  situated above the support part  7 , and in front of the fixing part  6 . From the support part  7 , the tightening part  8  is spaced-apart by a first, substantially horizontal gap  9 , while a second, vertical gap  10  separates the tightening part from the fixing part  6 . In the fixing part  6 , a rearwardly directed male member  11  is included that is insertable into a co-operating seating in a machine tool to couple together the tool with the machine. In this case, the male member  11  is included in a coupling of the type that is commercially available under the trademark COROMANT CAPTO®. Inside the fixing part  6 , a system of channels is formed to which cooling liquid, in particular high-pressure cooling liquid, can be supplied via one or more inlets  12 . 
         [0025]    Hollow spaces  13 ,  14  extend continuously between the opposite sides of the basic body and, in this case, form inner terminations of the gaps  9 ,  10 , and which are spaced-apart from each other via a material portion  15 , which by virtue of the small thickness thereof (e.g., 2 to 3 mm) to a certain extent is elastically resilient. Due to the elasticity, material portion  15  can serve as a joint around which the tightening part  8  can make moderate pivoting motions. The hollow spaces  13 ,  14  are most suitably cylindrical borings in which the gaps  9 ,  10  mouth. Via inclined side surfaces  16 , the tightening part  8  tapers in the forward direction toward a finger designated  17 , which has the purpose of clamping the cutting insert  2  in the desired position. Via analogous side surfaces  18 , the support part  7  tapers in the forward direction toward a front material portion  19  in the form of a flat, supporting bracket. The bracket  19  is delimited by a pair of opposite side surfaces  20  that suitably are plane and mutually parallel. The topside  21  of the bracket  19  forms an insert seat against which the underside of the cutting insert  2  rests. In front, the bracket  19  is delimited by a front-end surface  22 . The finger  17  is also delimited by a pair of opposite side surfaces  23  that advantageously are plane and mutually parallel. A front end surface designated  24  forms a transition between the topside  25  of the finger and the underside  26  thereof (see  FIG. 4 ), the finger tapering toward the front end surface  24  by the fact that the topside  25  thereof leans obliquely downward/forward. 
         [0026]    The finger  17 , as well as the bracket  19  positioned under the finger  17 , has a width or thickness (determined as the distance between the pairs of opposite side surfaces  20  and  23 , respectively) that is smaller than the diameter of the cutting edges  3 . In other words, the finger, as well as the bracket, is housed in a groove generated by the cutting insert, the width of which is determined by the diameter of the cutting edge  3 . 
         [0027]    In order to press and clamp the cutting insert  2  against the insert seat  21 , a tightening element  27  is included in the tool, which in this case is a pressure screw. The pressure screw is fitted with the male thread thereof in engagement with a female thread in a through hole in the upper portion  28  of the tightening part  8 , the free end of the screw being pressed against a shoulder surface  29  on the fixing part  6 . Upon tightening of the screw, a force is applied to the tightening part  8 , which forces the tightening part  8  to pivot around the joint  15  so that the finger  17  distinctly presses the cutting insert  2  against the insert seat  21 . 
         [0028]    With reference to  FIGS. 2-7 , inside the basic body  1 , a coupling member is fitted in the form of a pipe piece  30 , which has the purpose of allowing transfer of high-pressure cooling liquid to the pivotably movable tightening part  8 . In this case, the pipe piece is fitted in two co-operating cavities  31 ,  32  (see  FIG. 4 ) formed in the tightening part  8  and the support part  7 , respectively. Advantageously—but not necessarily—the pipe piece  30  as well as the two cavities  31 ,  32  have a cylindrical basic shape, the cavities being drilled bores. The first cavity  31  in the tightening part  8  is closed at the upper end thereof by an end wall  33  and opens in the underside of the tightening part via a lower opening  34 . However, the second cavity  32  extends all the way through the support part  7 , viz. from an upper opening  35  adjacent to the horizontal gap  9 , and a lower opening  36  in the underside of the support part  7 . When the tightening part  8  is unloaded, the cylindrical inner surfaces of the two cavities are concentric with a common axis C. Thus, in the example shown, the space formed by the cavities  31 ,  32  opens in the downward direction, wherein the pipe piece  30  can be inserted from below. In order to keep the pipe piece in place after the installation, a stopping element  37  (see  FIG. 2 ) is used, which in this case is a screw, the male thread of which is tightened in a threaded hole in the basic body and the head of which is accessible from outside. 
         [0029]    As illustrated in  FIGS. 3 and 4 , an internal channel  38  extends between an inlet  12  in the rear fixing part of the basic body and the front support part  7 , and mouths in the cavity  32  in an outlet designated  39 . This channel  38  has the purpose of feeding cooling liquid to the cavity  32  to be forwarded to the interior of the pipe piece  30 . Between the upper cavity  31  inside the tightening part  8  and the free end  24  of the finger  17 , a second channel extends, which is generally designated  40  and which is composed of two bores drilled at an angle to each other, one of which is sealed by means of a plug  41  and the other of which includes a high-pressure nozzle  42  in the immediate vicinity of the free end of the finger  17 . The nozzle is situated in the outlet of the channel  40 . Via an inlet  43 , the channel  40  mouths in the cylindrical inner surface of the cavity  31 . 
         [0030]    Reference is now made to  FIGS. 5-7 , which illustrate the nature of the pipe piece  30 . Inside the pipe piece, there is a central, cylindrical hole  44 , which extends from a permanently closed wall  45  at the one end of the pipe piece to an opening sealed by a dismountable plug  46  at the opposite end of the pipe piece. In practice, the hole  44  is accomplished by drilling. Between the central hole  44  and the outside of the pipe piece, a number of radial holes extend, which are arranged in two axially spaced-apart sets. In a first set, a plurality of (in this case four) holes  47  are included in the vicinity of the permanently closed end of the pipe piece, while a second set of holes  48  is situated closer to the opposite end of the pipe piece. Adjacent to the radial holes  47 , ring-shaped grooves  49   a ,  49   b  are formed in the envelope surface of the pipe piece for the receipt of a sealing ring  50   a ,  50   b  each. Correspondingly, grooves  51   a ,  51   b  are formed adjacent to the radial holes  48  for the receipt of sealing rings  52   a ,  52   b . Although the individual sealing ring could be applied alone in a groove of a suitable width, in this case the individual sealing ring is fitted together with a particular support ring  53  (see  FIG. 7 ), which gives the sealing ring a good capability of resisting high pressure. In practice, the individual sealing ring may include rubber (or a rubber-like material) having a relatively great stiffness (e.g., 70-90 Shore), while the support ring  53  may be a plastic material having a greater hardness. In this connection, it should be pointed out that the proper pipe piece suitably consists of metal, such as steel, which easily can be machined by turning and drilling. 
         [0031]    In  FIG. 6 , it is seen that two flanges  54   a ,  54   b  adjacent to the grooves  49   a ,  49   b  delimit an intermediate groove  55  in which the radial holes  47  mouth. In an analogous way, an intermediate groove  56  is delimited by flanges  57   a ,  57   b  adjacent to the grooves  51   a ,  51   b , the radial holes  48  mouthing in the intermediate groove  56 . The outer diameter of the flanges  54 ,  57  is smaller than the outer diameter of the sealing rings  50 ,  52  and should not exceed the outer diameter of the support rings serving as an abutment for the sealing rings. In each pair of co-operating sealing rings, the rings should, in this case, be uniform to afford equally large contact areas to the cooling liquid fed out into the ring-shaped space between the rings. 
         [0032]    When the tightening part  8  (refer again to  FIGS. 1-4 ) is unloaded in order to allow insertion of the cutting insert  2  between the underside  26  of the tightening finger  17  and the insert seat  21  on the topside of the bracket  19 , the vertical distance between the surface  26  and the insert seat  21  is maximal. When the cutting insert has been brought in between the tightening finger and the insert seat, the play between the topside of the cutting insert and the underside of the clamping finger is limited and may in practice be within the range of 0.2-0.5 mm. When the tightening part  8  after that is brought to pivot around the elastic joint  15  by the tightening screw  27 , the free end of the clamping finger  17  will move a corresponding distance to be pressed against the cutting insert and clamp the same against the insert seat  21 . In other words, the motion between the tightening part and the support part is very limited already out at the free end of the tightening finger. This motion is further reduced in the direction inward toward the joint  15 . For this reason, the pipe piece  30  has been placed as near the joint  15  as possible. Therefore, in the area where the pipe piece is situated, the relative motion between the tightening part and the support part is limited to a few tenths of a millimeter, which means that the angle divergence between the upper and lower cavities  31 ,  32  will be very small. Nevertheless, the outer diameter of the pipe piece  30  (or of the support rings  52 ) should be somewhat smaller than the inner diameter of the cavities  31 ,  32 . Thus, the outer diameter of the pipe piece and/or of the individual support ring should be 0.1-0.8 mm smaller than the inner diameter of the cavities. 
         [0033]    When the cutting insert has been fixed in the way described above by tightening the tightening screw  27 , supply of cooling liquid to the cutting insert can be commenced. Thus, from the machine in which the tool is fitted, cooling liquid can be fed via the channel  38 , more precisely from the inlet  12  thereof to the outlet  39  and further into the ring-shaped space, which is delimited by the groove  56  and the inside of the cavity  32 , and which is sealed by the sealing rings  52   a ,  52   b . From this ring space, the liquid is led into the central hole  44  of the pipe piece via the lower radial holes  48  to be fed out again via the upper radial holes  47 . Upper radial holes mouth in an additional ring-shaped space formed by the groove  55  and the inside of the cavity  31 . From here, the liquid is fed further via the channel  40  formed in the tightening part  8 , more precisely from the inlet  43  thereof to the outlet in which the nozzle  42  is fitted. In practice, the pressure in the liquid may be very high, e.g., of the order of 400-1000 bar. However, in spite of the fact that the pressure may be high, no compressive forces, which could jeopardize the fixation of the cutting insert, is applied to the tightening part  8 . Thus, the liquid pressure in the ring space between the sealing rings  50   a ,  50   b  will act in two opposite directions against the same. Because the sealing rings and the shoulders in the form of the support rings  53  co-operating with the same are uniform, i.e., have the same dimensions, the downwardly directed force acting against the lower sealing ring  50   b  will become as great as the upwardly directed force acting against the upper sealing ring  50   a . In other words, the compressive forces will outbalance each other so that no forces of any consequence caused by the liquid pressure are applied to the proper pipe piece  30 . 
         [0034]    The same condition as has been described above in respect of the pressure in the upper groove  55  also applies in respect of the pressure in the lower groove  56 . 
         [0035]    The high-pressure liquid can be transferred from the support part  7  of the basic body to the movable tightening part  8 , without the pipe piece  30  or the two parts  7 ,  8  being subjected to liquid-pressure forces, which could alter the compressive force by which the tightening part  8  keeps the cutting insert  2  pressed against the appurtenant insert seat. Expressed in other words, the pipe piece  30  may be said to be free-flowing in the appurtenant cavities  31 ,  32 , although the same of course is kept in place mechanically. 
         [0036]    The tool according to the invention includes a lower channel system (a part of which is outlined at  58  in  FIGS. 3 and 4 ) by which the cutting insert can be cooled also from below, more precisely via a nozzle that is fitted in the front-end surface  22  and points up at a steep angle toward the cutting insert. However, such undercooling of the cutting insert is of secondary importance in comparison with the improved overcooling allowed by the invention. Thus, the nozzle  42  fitted centrally in the front end of the tightening finger  17  can direct a distinct liquid jet toward the topside of the cutting insert adjacent to the cutting edge. By locating the nozzle in a suitable position, the liquid jet can be brought to impinge on the cutting insert at an ideal impact angle, which in practice is within the range of 12-15°. In such a way, a hydraulic wedge is formed between the chip and the cutting insert, which contributes to loosen the chip and counteracts sticking to the cutting insert. The high pressure of the liquid also contributes to make the chip evacuation more effective from the generated groove in the workpiece. 
         [0037]    The above-mentioned impact angle of the liquid jet may of course deviate from the given interval. However, the angle should be within the range of 5-30°, suitably 10-20°. 
         [0038]    In  FIGS. 8 and 9 , an alternative embodiment of a pipe piece  30 A according to the invention is shown. In this case, the pipe piece is at one end thereof formed with a pin  59  having a male thread  60 . Simultaneously, the opposite end of the pipe piece is formed with a ring-shaped shoulder or flange  61 , besides which a key grip  62  is formed in the end surface of the pipe piece. In a modified embodiment of the tool, the pipe piece  10 A shown in  FIGS. 8 and 9  could replace the pipe piece  30  described above while fulfilling the function as a tightening element. Thus, the male thread  60  could be tightened in a hole that is formed with a female thread and mouths in the end surface of the upper cavity  31 , besides which the flange  61  can be pressed against a co-operating support surface in the lower part of the cavity  32 . In this connection, the pipe piece  30 A may serve as a tension screw by which the tightening part  8  can be forced to pivot and press the cutting insert against the insert seat. In other words, the previously described pressure screw  27  can be spared. 
         [0039]    The invention is not limited only to the embodiments described above and shown in the drawings. Thus, the invention may be applied to any tools of the type that makes use of a tightening part pivotable around a joint for the fixation of a cutting insert. Among other things, the invention may advantageously be applied to such tools intended for parting and grooving operations, the tightening and support parts of which in their entirety are comparatively thin plates that project from a rear fixing part having an arbitrary shape. In addition to turning tools and other fixed tools, the invention may be applied to certain rotatable tools, such as slitting cutters. Furthermore, instead of genuine liquids, other fluids for chip breaking and/or cooling of the cutting insert may be used, e.g., different types of gas, or mixtures of gas and liquid. Furthermore, the fluid-transferring pipe piece or the coupling member could be arranged between the tightening part and the fixing part, instead of between the tightening part and the support part, such as has been exemplified above. In such cases, the pipe piece would intersect the vertical gap instead of the horizontal gap. In this connection, it should be emphasized that the pipe piece does not necessarily have to be made with two pairs of axially spaced-apart sealing rings. Thus, a pair of pressure-balancing sealing rings is generally only required in the pivotably movable tightening part, while the supply of cooling fluid to the section of the pipe piece positioned in the support part (or the fixing part) may be effected in another way. However, for reasons of manufacturing technique, the exemplified solution is preferred, because the manufacture and installation of the pipe piece will be easy when two pairs of sealing rings are used. It should also be pointed out that the provided solution does not require that the two sealing rings in co-operating pairs of sealing rings are fitted on the outside of the pipe piece. Thus, it is possible to delimit and seal the ring-shaped space, through which the cooling fluid should pass out into the outlet channel of the tightening finger, by sealing rings fitted on the inside of the cavity in the tightening part. Thus, importantly, the counter-directed forces against the sealing rings that are generated by the pressure in the ring space balance out each other in such a way that no forces of any consequence caused by the liquid pressure are applied to the tightening element. It should also be mentioned that the tightening part may be formed with more than one channel to allow jetting of cooling fluid in a plurality of jets directed at different angles to the cutting insert. 
         [0040]    In  FIG. 10 , an embodiment is schematically illustrated according to which the liquid pressure may be utilized to apply a tightening force to the tightening part  8 . In this case, one of the sealing rings, viz. the upper sealing ring  50   a , is fixedly fitted in the inside of the cavity  31 , while the other sealing ring  50   b  is fitted in the envelope surface of the pipe piece  30  in the way previously described. Furthermore, the pipe piece  30  is formed with a driver  63 , which in this case is in the form of an upper, piston-like flange, which is pressable against a shoulder surface  64  formed adjacent to the cavity. When high-pressure cooling liquid is led into the ring-shaped space  55  between the sealing rings  50   a ,  50   b , the sealing ring  50   b  will be subjected to a downwardly directed force (see the arrow) that aims to pull the pipe piece in the downward direction. In this connection, the driver  63  applies a downwardly directed force to the tightening part  8 . This force may be utilized either as a complement to the tightening force generated by the traditional tightening element, e.g., the shown tightening screw, or to alone provide the pivoting of the tightening part requisite for the clamping of the cutting insert. In other words, also in this case, the pipe piece could alone serve as a tightening element in analogy with the embodiment according to  FIGS. 8 and 9 . 
         [0041]    Furthermore, the invention is applicable to such tools that in one and the same basic body includes more than one tightening part, e.g., two diametrically opposed tightening parts for the fixation of a cutting insert each, which are located in opposite insert seats on a common support part. 
         [0042]    While the invention has been disclosed with reference to certain preferred embodiments, numerous modifications, alterations, and changes to the described embodiments are possible without departing from the sphere and scope of the invention, as defined in the appended claims and their equivalents thereof. Accordingly, it is intended that the invention not be limited to the described embodiments, but that it have the full scope defined by the language of the following claims.