Abstract:
A cutting insert having a main lip, a rake face and at least one coolant duct, which is formed on the top side of the cutting insert, is disclosed. The at least one coolant duct runs at least partially in the rake face towards the main lip and the width increases towards the main lip.

Description:
CLAIM TO PRIORITY 
     This application is a National entry application of German Application No. 102012111576.1, filed on Nov. 29, 2012, the entire contents of which is incorporated herein by reference. 
     FIELD OF THE INVENTION 
     The invention relates to a cutting insert. Moreover, the 
     invention relates to a cutting tool having a tool holder and a cutting insert. 
     BACKGROUND OF THE INVENTION 
     During the cutting-off and turning of workpieces, friction and forming lead to a strong evolution of heat, as a result of which the workpiece, but also the cutting tool used, is greatly heated. However, the high temperatures of the cutting tool lead to increased wear, resulting in costs. For this reason, the cutting insert is cooled with the aid of a coolant during the machining of the workpiece. To date, it has been conventional for a stream of coolant to be guided to the cutting insert, in particular to the main lip of the cutting insert, through nozzles or ducts in or on the tool holder in which the cutting insert is mounted. This has the problem that the stream of coolant is directed to a strong extent, and therefore merely the portion of the cutting insert which is directly impacted by the stream of coolant is cooled. 
     SUMMARY OF THE INVENTION 
     It is an object of the invention to provide a cutting insert which has a small degree of wear and makes longer service lives possible. 
     This object is achieved by a cutting insert having a main lip, a rake face and at least one coolant duct, which is formed on the top side of the cutting insert, wherein the at least one coolant duct runs at least partially in the rake face toward the main lip and the width thereof increases toward the main lip. By virtue of the invention, the stream of coolant which emerges from a nozzle or opening in the tool holder is guided through the coolant duct in a targeted manner toward the lip. The geometry of the ducts makes it possible to conduct the stream of coolant in such a manner that lips which require cooling are cooled. Moreover, the formation of the coolant ducts on the top side of the cutting insert makes it easier to access the ducts, and therefore, during assembly, it is not necessary to tediously align the openings in the cutting insert and in the tool holder, which guide the coolant, with one another. A further advantage of the ducts formed on the top side is that the production of the cutting insert is made considerably easier compared with those having coolant ducts on the inside. 
     It is preferable that the coolant duct is directed toward the main lip and forms a main coolant duct, making targeted cooling of the main lip possible. 
     The cutting insert preferably has at least one secondary lip, wherein the coolant duct is directed toward the at least one secondary lip and forms a secondary coolant duct. The orientation of the coolant duct toward a secondary lip ensures that the secondary lip, which does not lie directly in the connection between the point at which the coolant emerges in the tool holder and the main lip, is cooled. 
     According to a further embodiment, the rake face has at least one chip breaker, as a result of which it is possible to influence the chip formation. 
     By way of example, the coolant duct is partially delimited by the at least one chip breaker, such that the latter combines the coolant-conducting function of a duct wall with the action of a chip breaker. This makes it possible to achieve a particular space-saving arrangement of chip breaker and coolant duct on the rake face. 
     It is preferable that the at least one chip breaker has a part oriented substantially perpendicular to the main lip and/or a part oriented obliquely to the main lip. As a result of this geometry, the chip breaker can fulfill both its function as a delimitation of the coolant duct and also its chip-breaking function. 
     It is particularly preferable that the secondary coolant duct is arranged on that side of the at least one chip breaker which is remote from the main lip, such that at least some of the stream of coolant is guided without problem into the secondary coolant duct through the height of the chip breaker. 
     In a further embodiment variant, two chip breakers are provided, the main coolant duct extending between the two chip breakers. This geometry makes it possible for some of the stream of coolant to pass directly and unhindered to the main lip. 
     It is preferable that two chip deflectors are provided, between which the coolant duct opens conically, as a result of which the flow of coolant is widened. 
     It is particularly preferable that the distance between the chip deflectors is greater than the distance between the chip breakers, such that the entire stream of coolant does not flow into the main coolant duct. 
     In a further embodiment, the cutting insert has two secondary lips and at least two secondary coolant ducts, and therefore the cutting tool benefits from two cooled secondary lips. 
     By way of example, the coolant ducts have a common portion, which makes it significantly easier to feed the coolant into the various coolant ducts. 
     In one configuration of the invention, the at least one coolant duct is tub-shaped, and therefore the coolant experiences the smallest possible flow resistance. 
     In a further embodiment variant of the invention, the cutting insert is intended for a turning tool. 
     The invention also relates to a cutting tool having a tool holder and a cutting insert. Here, the cutting insert is inserted into a recess in the tool holder, the coolant duct being defined at least partially between the surface of the cutting insert and a surface of the recess in the tool holder. The assembly of a cutting insert in the tool holder is thereby made easier and can be carried out without additional alignment steps. In the case of the tool holder according to the invention there are a total of at least three positions for the lever tool. Along with the insertion portion which enables the insertion of the lever tool, it is possible to push out the groove insert directly in a direction proceeding from the insertion portion by the ejector portion pushing directly against the groove insert in order to release it from the support. The expanding portion proceeds from the insertion portion in the opposite direction, the slot tapering in this case. When the ejector continuation is moved out of the insertion portion into the expanding portion or when it is moved along the expanding portion, the ejector continuation presses against the bottom surface of the clamping jaw in order to pivot up said clamping jaw. The tool holder according to the invention consequently allows for either the groove insert to be pushed out directly or, as an alternative to this, the clamping jaw to be raised. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Further features and advantages of the invention become apparent from the following description and from the accompanying drawings, to which reference is made. In the drawings: 
         FIG. 1  shows a perspective view of the cutting insert according to the invention, 
         FIG. 2  shows a plan view of the cutting insert shown in  FIG. 1 , 
         FIG. 3  shows a section through the cutting insert according to the invention along the plane III-III, and 
         FIG. 4  shows the cutting insert as shown in  FIG. 1  inserted in a tool holder. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       FIGS. 1 to 3  show a cutting insert  12  intended for a cutting tool  10 . Here, the cutting insert  12  can be divided into two regions: an insertion region  16  for mounting the cutting insert in the cutting tool  10  and a cutting region  18 , with which the workpiece to be machined (not shown) can be machined. 
     A coolant duct  20  extends virtually over the entire length of the cutting insert  12 . An inlet region  22  of the coolant duct  20  is located in the insertion region  16  and runs along a central axis A of the cutting insert  12 . The inlet region  22  is surrounded by a U-shaped duct wall  24 , which is open toward the cutting region  18 . 
     On that side of the cutting region  18  which faces toward the insertion region  16 , the duct wall  24  forms, at the ends of the legs of its U shape, chip deflectors  25 , between which the coolant duct  20  extends and opens conically in this region. The surface of the cutting region  18  is configured as a rake face  26  and forms lips at the intersection with the circumferential faces of the cutting insert  12 . A main lip  28  is formed at the edge of the rake face  26  with the end face  30  of the cutting insert  12 . Two secondary lips  32  are formed by the rake face  26  and in each case one of the opposing side faces  34 . The main lip  28  forms approximately a right angle with each of the two secondary lips  32 . However, the internal angles α, β between the main lip  28  and in each case one of the secondary lips  32  are preferably smaller than 90°. 
     The rake face  26  has two chip breakers  36 , which divide the rake face  26  into three ducts. The distance perpendicular to the central axis A between the chip breakers  36  is in this case smaller than that between the chip deflectors  25 . A main coolant duct  38  extends between the two chip breakers  36  along the central axis A. Proceeding obliquely from the central axis A, secondary coolant ducts  40  extend in the direction of the secondary lips  32  in front of the chip breakers  36 . These are delimited in each case at least partially by a chip deflector  25  and a chip breaker  36 . 
     The main coolant duct  38  is configured as a tub-shaped depression  42  at least between the chip breakers  36  and here is delimited partially by parts of the chip breakers  36  which are oriented perpendicularly to the main lip. Thereafter, the main coolant duct  38  rises rapidly toward the main lip  28  and ends as soon as the base thereof has reached the level of the main lip  28 . 
     Each of the secondary coolant ducts  40  runs toward a secondary lip  32  at an angle. Proceeding from the central axis A, the secondary coolant ducts  40  widen in the direction of the secondary lips  32 . This is achieved by parts of the chip breakers  36 , which delimit the secondary coolant ducts  40 , oriented obliquely to the main lip  28 . In a manner similar to the main coolant duct  38 , the secondary coolant ducts  40  rise slightly before they reach the respective secondary lips  32 , until the base thereof has reached the level of the secondary lips  32 . 
       FIG. 4  shows sections of a cutting tool  10 , consisting of the cutting insert  12 , which has been inserted into a tool holder  44 . For this purpose, the tool holder has a recess  46 , which is delimited toward the top by a nose  48 . A nozzle (not shown), which can also be configured as a duct or bore, is formed inside the tool holder  44  and opens out into the recess  46 . 
     For assembly, the cutting insert  12  is introduced into the recess  46  in the tool holder  44 . The insertion region  16  of the cutting insert  12  is then located completely in the recess  46 , the cutting region  18  protruding in front of the nose  48 . Here, the bottom side of the nose  48  of the tool holder  44 , together with the duct wall  24 , forms the inlet region  22  of the coolant duct  20 . The nozzle then opens out into the inlet region  22 . 
     For cooling the cutting insert  12 , coolant flows out of the nozzle into the inlet region  22  of the coolant duct  20 . The coolant then passes through the opening between the chip deflectors  25  and consequently impinges on the chip breakers  36 . Since the opening between the chip breakers  36  is smaller than the opening between the chip deflectors  25 , the stream of coolant is split into three at this point. The quantity of coolant which passes through the opening between the chip breakers  36  is guided by the main coolant duct  38  to the main lip  28 , and can accordingly cool the main lip  28 . 
     As seen in the direction of flow along the central axis A, the rest of the coolant is conducted by the chip breakers  36  to the left or right into the secondary coolant ducts  40 , through which the coolant passes to the secondary lips  32  and cools the latter. All three lips of the cutting insert  12  are therefore cooled in a targeted manner.