Abstract:
A milling cutter for chip removing machining includes a milling cutter body with a number of cutting insert seats in connection to a chip removing end of the milling cutter body, the milling cutter body being formed to cooperate with a tool attachment at its opposite end in the axial direction, wherein indexable cutting inserts are secured in the cutting insert seats, each the indexable cutting insert having a top surface and a bottom surface substantially parallel with the top surface, wherein side surfaces extend between the top surface and the bottom surface, the indexable cutting insert having the basic shape of a truncated pyramid. The invention also relates to a milling cutter body and an indexable cutting insert, per se. Each indexable cutting insert has its top surface facing against the chip removing end of the milling cutter, and main cutting edges of the indexable cutting insert extend from the top surface of the indexable cutting insert.

Description:
BACKGROUND AND SUMMARY 
   The present invention generally relates to a milling cutter for chip removing machining, a milling cutter body and an indexable cutting insert that is intended to be mounted to a milling cutter body. 
   A milling cutter is previously known, which comprises a milling cutter body that is provided with a number of indexable cutting inserts. Each indexable cutting insert comprises a number of main cutting edges and a minor cutting edge associated with each major cutting edge. A minor cutting edge forms a right angle with an associated major cutting edge. This known milling cutter is especially intended for milling of right-angled corners in a work piece. A drawback that this known milling cutter has is that the cutting depth is limited to the length of the main cutting edge since the minor cutting edge on same edge as the cutting insert is situated radially outside of the main cutting edge when the cutting insert is mounted on the milling cutter body. 
   A face milling cutter is also known which comprises first cutting inserts the center holes of which are essentially axially directed and second cutting inserts the center holes of which are essentially radially directed relative to a holder of the face milling cutter. The first and second cutting inserts are identical. According to a preferred embodiment each cutting insert comprises four cutting insert corners, however different parts of the cutting inserts are used as active cutting edges depending on whether the center holes are oriented axially or radially. In relation to the present invention the cutting inserts with axially directed center hole are most pertinent. In order to activate all four cutting insert corners in one position with axially directed center holes the cutting inserts must be both indexed and flipped. 
   It is desirable to provide a milling cutter and indexable cutting inserts adapted thereto, the milling cutter being able to machine right-angled corners in a work piece to great cutting depths. 
   It is also desirable to provide the indexable cutting inserts according to an aspect of the present invention provided in the milling cutter according to the present invention must be indexable four times during its life-span. 
   It is also desirable to orient indexable cutting inserts such that they can be secured by means of center screws with a relatively long length of anchor. 
   According to an aspect of the present invention, a milling cutter for chip removing machining comprises a milling cutter body with a plurality of cutting insert seats proximate an end of the milling cutter body, the milling cutter body being adapted to cooperate with a tool attachment at an opposite end of the milling cutter body in an axial direction, indexable cutting inserts being secured in the cutting insert seats, each indexable cutting insert having a top surface and a bottom surface substantially parallel with the top surface, wherein side surfaces extend between the top surface and the bottom surface, wherein each indexable cutting insert has a basic shape of a truncated pyramid, and each indexable cutting insert has a top surface facing towards a chip removing end of the milling cutter, and main cutting edges of the indexable cutting insert extend from the top surface of the indexable cutting insert in a direction towards the bottom surface of the indexable cutting insert. 
   According to another aspect of the present invention, a milling cutter body comprises a free end with a plurality of cutting insert seats proximate the free end, the milling cutter body being adapted to cooperate with a tool attachment at an opposite end in the axial direction, each cutting insert seat comprising a plurality of support surfaces, wherein a support surface that is facing towards the free end of the milling cutter body has means for cooperating with a clamping means for an indexable cutting insert having the basic shape of a truncated pyramid. 
   According to another aspect of the present invention, an indexable cutting insert that is intended to be mounted in a cutting insert seat of a milling cutter body comprises a top surface and a bottom surface substantially parallel with the top surface, wherein side surfaces connect the top surface and the bottom surface, wherein the indexable cutting insert has the basic shape of a truncated pyramid and main cutting edges of the indexable cutting insert extend from the top surface in direction towards the bottom surface. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Below follows a preferred embodiment of the invention that is described with reference to the enclosed drawings, wherein: 
       FIG. 1  shows a perspective view of a milling cutter according to the present invention; 
       FIG. 2  shows a side view of the milling cutter according to  FIG. 1 ; 
       FIG. 3  schematically shows the same side view of the milling cutter as in  FIG. 2 , however the milling cutter being provided with only one cutting insert for clarity reasons; 
       FIG. 4  schematically shows another side view of the milling cutter; 
       FIG. 5  shows a cross-section along the line V-V in  FIG. 3 ; 
       FIG. 6  shows a cross-section after the line VI-VI in  FIG. 5 ; 
       FIG. 7  shows a perspective view obliquely from above of an indexable cutting insert according to the present invention, the milling cutter according to the present invention being provided with a number of such indexable cutting inserts; 
       FIG. 8  shows a perspective view oblique from below of the indexable cutting insert according to  FIG. 7 ; 
       FIG. 9  shows a plan view of the indexable cutting insert according to  FIG. 7 ; 
       FIG. 10  shows a side view of the indexable cutting insert according to  FIG. 7 ; and 
       FIG. 11  shows a view of the bottom surface of the indexable cutting insert according to  FIG. 7 . 
   

   DETAILED DESCRIPTION 
   The milling cutter according to the present invention shown in  FIGS. 1 and 2  comprises a milling cutter body  1 , which has a number of cutting insert seats at the forwardly facing end in  FIG. 1 , in which a corresponding number of indexable cutting insert  3  are received. Each indexable cutting insert  3  has a center hole  4  and is secured in an associated cutting insert seat by means of a center screw  5  received by the center hole  4 . In  FIG. 1  the center axis C-C of the milling cutter is drawn, the center axis C-C also defining the axis of rotation of the milling cutter and its axial direction. The rotational direction R of the milling cutter is depicted with an arrow in  FIG. 1 . 
   The center screws  5  extend along the axial direction of the milling cutter, however the center screws  5  are not parallel with the rotational axis C-C. The indexable cutting inserts  3  are consequently tangentially mounted in the milling cutter body  1 . 
   The milling cutter body  1  is formed for connection with a tool attachment or the like at the rear end in  FIG. 1 . 
   From the side view of the milling cutter that is shown in  FIG. 2  is clearly evident that when the indexable cutting insert  3  is mounted in the milling cutter body the indexable cutting insert incline, i.e. the center axis of the indexable cutting insert, which coincides with the longitudinal direction of the associated center screw, is not parallel with the center axis C-C of the milling cutter. 
   In below-described  FIGS. 3-6  only the cutting insert  3  is drawn for reasons of clarity. At the side view shown in  FIG. 3  the major cutting edge and minor cutting edge of the cutting insert  3  form a right angle. As is evident from  FIG. 3  the bottom surface of the cutting insert seat, symbolized by a first line L 1 , forms a certain angle α with a second line L 2  that extends perpendicularly towards the axis of rotation C-C of the milling cutter. The reason for the seat bottom surface of the cutting insert being angled is that only one corner of the cutting insert should be active, i.e. the remaining three corners should be situated axially rearwardly of the line L 2 . For exemplifying but not limiting purpose can be mentioned that the angle α may be in the magnitude of 5°. In  FIG. 3  is also shown an angle β 1  between the center axis C-C of the milling cutter and the center axis C 1 -C 1  of the cutting insert  3 . In the side view shown in  FIG. 3  this angle is about 8°. 
   The side view shown in  FIG. 4  is taken in a position that is perpendicular to the position for  FIG. 3 . In  FIG. 4  the axial rake angle for the major cutting edge  11  of the cutting insert  3  is drawn in, the angle being depicted by γ. The axial rake angle γ is positive and is about 7° in the shown side view. In  FIG. 4  is also shown an angle β 2  between the center axis C-C of the milling cutter and the center axis C 1 -C 1  of the cutting insert  3 . In the side view shown in  FIG. 4  the angle is about 7°. 
   The cross-section shown in  FIG. 5  is taken along V-V in  FIG. 3 . The clearance angle for the main cutting edge  11  is designated with λ 1 . This angle will lie in the interval of 5°≦λ1≦15°, with a preferred value on λ 1  about 8°. 
   The cross-section shown in  FIG. 6  is taken along VI-VI in  FIG. 5 . The clearance angle for a wiper edge of the cutting insert  3  is designated with λ in  FIG. 6 , wherein this angle lies within the interval of 5°≦λ≦12° with a preferred value at 6°. The indexable cutting inserts  3  according to the present invention that are provided in the milling cutter  1  according to the present invention are shown in more detail in  FIGS. 7-11 . The center axis C 1 -C 1  of the indexable cutting insert  3  is drawn in  FIGS. 7 ,  8 ,  9  and  11 , the center axis C  1  -Cl also defining the axial direction of the indexable cutting insert  3 . Each of the indexable cutting inserts  3  comprises a top surface  7  and a bottom surface  9  parallel thereto. The area for the top surface  7  is bigger than the area for the bottom surface  9 . The top surface  7  and the bottom surface  9  are united by means of four side surfaces  10 A,  10 B,  10 C,  10 D. The center hole  4  of the indexable cutting insert  3  opens into both the top surface  7  and the bottom surface  9 . 
   Generally, the indexable cutting insert  3  has the shape of a truncated pyramid, wherein the top surface  7  corresponds to the great base surface while the bottom surface  9  corresponds to the little base surface. When the milling body according to the present invention is equipped with indexable cutting inserts  3 , the bottom surface  9  of each indexable cutting insert  3  abuts a supporting surface of each cutting insert seat, the supporting surface generally extending laterally to the axial direction C-C of the milling cutter. 
   Four main cutting edges  11 A,  11 B,  11 C,  11 D are formed at the intersection of two adjacent side surfaces, which generally extend along the axial direction C 1 -C 1  of the indexable cutting insert, however not parallel with the axial direction C 1 -C 1 . An alternative way of expressing this is that the main cutting edges  11 A,  11 B,  11 C,  11 D extend from the top surface  7  in direction towards the bottom surface  9 . Analogous with the truncated pyramid the side edges of the truncated pyramid, i.e. the intersection of two adjacent side surfaces, comprises the main cutting edges  11 A- 11 D of the indexable cutting insert  3  according to the present invention. However, in the shown embodiment each major cutting edge is provided radially inside the intersection. At the intersection of the top surface  7  and the side surfaces  10 A,  10 B,  10 C,  10 D are formed minor cutting edges  12 A,  12 B,  12 C,  12 D, which generally extend laterally to the axial direction C 1 -C 1  of the indexable cutting insert  3 . The indexable cutting insert  3  according to the present invention shown in  FIGS. 7-11  comprises four pairs of cutting edges. 
   In the side surface  10 A,  10 B,  10 C,  10 D that is associated with a major cutting edge  11 A,  11 B,  11 C,  11 D is provided a rake face  13 A,  13 B,  13 C,  13 D associated with the main cutting edge, which generally has a concave shape. In the shown embodiment of the indexable cutting insert  3  each rake face  13 A,  13 B,  13 C,  13 D opens into the bottom surface  9  but not into the top surface  7 . More exactly, the rake face  13 A,  13 B,  13 C,  13 D connects to the top surface  7  via the minor cutting edge  12 A,  12 B,  12 C,  12 D. A support surface  14 A,  14 B,  14 C,  14 D is situated at one and the same side surface  10 A,  10 B,  10 C,  10 D adjacent to the rake face  13 A,  13 B,  13 C,  13 D. Of the four support surfaces  14 A,  14 B,  14 C,  14 D of an indexable cutting insert  3  three cooperate with a surface of the cutting insert seat wherein the indexable cutting insert  3  is received. The fourth support surface connects to the active the main cutting edge  11 A,  11 B,  11 C,  11 D and comprises clearance surface for this active major cutting edge. 
   A line L 3  is drawn in  FIG. 10 , which extends from the main cutting edge  11 D to the minor cutting edge  12 D. Therein can be noted that this line L 3  does not intersect the plane of the support surface  14 D. In  FIGS. 9 and 10  is also the greatest diagonal measure D and thickness T of the indexable cutting insert  3  marked, wherein the relationship T/D&gt;0.4. In the shown embodiment T/D is about 0.5. In this connection shall be noted that the indexable cutting insert  3  is intended to be clamped in the milling cutter body  1  in its thickness direction, and consequently the bottom surface  9 /“little the base surface” abuts against a supporting surface of the cutting insert seat. 
   As pointed out above a primary function of the milling cutter according to the present invention is to mill right-angled corners, and in this connection is referred to  FIGS. 2 and 3 . At the lower right end of  FIG. 2  is shown an indexable cutting insert  3  according to the present invention, wherein the side view in  FIG. 2  shows a major cutting edge  11  and a minor cutting edge  12  of this indexable cutting insert  3 . This view illustrates how the milling cutter according to the present invention achieves right-angled corners in a work piece. Through study of  FIG. 2  is also perceived that the cutting depth that the milling cutter according to the present invention can take does not have any limitations that depend on the milling cutter geometry. 
   The embodiment shown in  FIGS. 1 and 2  of a milling cutter according to the present invention machines the work piece with a positive axial angle, i.e. the in axial direction extremely positioned part of the main cutting edge  11 A,  11 B,  11 C,  11 D comes first in engagement with the work piece. 
   In the above described embodiment the indexable cutting insert  3  has four main cutting edges and four associated minor cutting edges. However, within the scope of the invention each indexable cutting insert may have three main cutting edges and three associated minor cutting edges. 
   The shown embodiment of the milling cutter according to the present invention machines the work piece under a positive axial angle. This angle can also be chosen negative. 
   The disclosures in Swedish patent application No. 0502134-0, from which this application claims priority are incorporated herein by reference. 
   The invention is in no way limited to the above-described embodiment but can be freely varied within the limits of the appended claims.