Abstract:
The present invention relates to a turning insert that comprises a generally rectangularly shaped body having a front end surface with a main cutting edge at the intersection between the front end surface and an upper land area. A chipforming area is provided in the forward portion of the upper surface and is shaped in the form of a number of distinctly provided recesses and ridges in order to promote improved chip control and to obtain narrower chips in grooving operations.

Description:
This application is a continuation of application Ser. No.  08 / 747 , 407 , filed Nov.  12 ,  1996  now abandoned, and a reissue of application Ser. No.  853 , 232 , filed Apr.  28 ,  1993 , now U.S. Pat. No.  5 , 375 , 948 . 
    
    
     BACKGROUND AND SUMMARY OF THE PRESENT INVENTION 
     The present invention relates to a cutting insert for turning and grooving tools, primarily for grooving operations in metal workpieces. The insert could also be useful for cutting off rods, tubes or other rotationally symmetrical details. Such cutting inserts are provided with a cutting edge formed by the transition between the top surface or rake surface of the insert and its forward clearance face. 
     In metal cutting operations, the breaking of the chip and the shape of the chip are often of great importance for an undisturbed production. In modem, high production machines and tools, there is great demand for an efficient chip removal and good chip control. This is of special importance in such high-production machines in which a series of different tools are performing different operations in a continuous sequence. It is not unusual that in such operations the chips may become tangled and wrap around the workpiece or the tool. This creates problems in subsequent operations, especially if automated workpiece handling equipment is involved. These difficulties are compounded when it comes to camshaft or crankshaft turning where several grooves are generated in one operation. The end result is usually high production costs due to expansive machine downtime to clear chips or repair tools. 
     In view of the above and related difficulties with prior art inserts and tools, it is a purpose of the present invention to provide an improved type of turning insert that is formed so as to optimize chip control for the specific demands and conditions of the difficult operations referred to above. 
     In accordance with the present invention, a dimpled chipbreaker and the confining walls thereof are designed so as to form the chip narrower than the groove such that more efficiently manageable safe chips can be obtained. Chip disposal should become safer, more efficient and less costly. With such inserts, it should become possible to generate a finished groove in one pass of the workpiece, such as a crankshaft. 
    
    
     BRIEF DESCRIPTION OF THE DRAWING FIGURES 
     These and other objects have been achieved by shaping the insert as described hereinafter in connection with the appended drawings, wherein like members bear like reference numerals and wherein: 
     FIG. 1 is a perspective view of an insert according to the present invention; 
     FIG. 2 is a side view of the insert of FIG. 1; 
     FIG. 3 is a top view of the insert of FIG. 1; 
     FIG. 4 is a front view of the insert of FIG. 1; 
     FIG. 5 is a cross-sectional view along the line A—A in FIG. 3; 
     FIG. 6 is a cross-sectional view along the line B—B in FIG. 3; 
     FIG. 7 is a cross-sectional view along the line C—C in FIG. 3; 
     FIG. 8 is a perspective view of a holder for the insert; 
     FIG. 9 is a partial front view of the insert located in the tip-seat of the holder of FIG. 8; and 
     FIG. 10 is a view of a chip obtained from chipforming by the insert of FIGS.  1 - 7 . 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     An insert  10  according to the invention is shown in the drawing figures. The insert is in the shape of a polygonal body of generally parallepipedic shape. It comprises two mainly plane-parallel side surfaces  11 ,  12 , opposed top and bottom surfaces  14  and  13 , respectively, two end surfaces  15 ,  16 , and a shoulder  17 . The front portion of the insert is provided with a main cutting edge  18  and a chip forming area  19 . The insert is intended to be secured to a holder body  20  (FIG. 8) provided with an integral clamping arm  21 . The top surface  14  is broken at the vicinity of the shoulder  17  so that an upper surface portion  14 a forms an acute angle with the remainder of the surface  14 . 
     With reference to FIG. 8, the insert  10  is intended to be removably held in a holder, which includes the holder body  20  having an integral clamping arm  21  in a front portion  22  of the holder body  20  and an insert receiving recess  23  in which the insert  10  is to be located. The insert receiving recess  23  communicates at an inner end thereof with an elongated slit  24  which terminates in a circular recess  25 . A clamping screw  26  extends into the holder  20  through the clamping arm  21  and through the slit  24 . When the screw  26  is threaded into the holder, the clamping arm  21  flexes downwardly about the recess  23  and urges the clamping arm  21  into firm clamping abutment with the upper surface  14  of the insert. More specifically, a nose portion of the clamping arm  21  is somewhat inclined downwardly so that the nose matches the inclination of the upper surface portion  14 a of the insert  10 . 
     The bottom surface  13  of the insert is intended to be a first support surface for the insert against the holder body and a portion of the bottom surface  13  is parallel with a neutral plane P (FIG. 2) defined by the axial feed direction of the machine. More specifically, the bottom surface  13  includes two distinct flat surface portions  13 a and  13 d, with two inclined surfaces  13 b and  13 c therebetween. The inclined surfaces  13 b and  13 c are intended to abut with correspondingly inclined surfaces in the insert site of the holder as shown in FIG.  9 . As appears from FIG. 9, the surfaces  13 a and  13 d are not active support surfaces. The top surface  14  constitutes a second support surface for the insert against the holder body  20 . The top surface  14  is oriented parallel with the flat bottom surface portions  13   a  and  13   d.    
     The cutting edge  18  is straight and is formed along the intersecting line of a clearance face  16  and a primary land  27 . The clearance face  16 , which is the front end surface of the insert, forms an acute angle α, about 1°-15° with a normal/N drawn to the primary land  27  (FIG.  2 ). The primary land  27  coincides with the neutral plane P. 
     The primary land  27  is bordered radially inwardly by an array of spaced recesses or grooves  28  extending on the rake face of the insert starting from the primary land  27 . The width of the primary land  27  varies along the edge  18  such that the width of the primary land  27  is smaller at those portions located next to the front end portions of each recess  28  whereas the width is larger at inclined rake surface portions  29  located therebetween (FIG.  3 ). The maximum width of each recess  28  is preferably larger than the distance between the depressions. Each recess  28  has a depth initially increasing in a direction away from said primary land and thereafter decreasing in that direction. There are a number of the centrally provided oval-shaped recesses  28  having a longitudinal extension, extending perpendicularly from the cutting edge  18 , that is several times larger than the width of the respective recess  28 . Additionally there is, on each side of the central group of oval-shaped recesses  28 , a recess  30  having a larger width and shorter length than each of the central recesses  28 . 
     Also formed in the top surface  14  of the insert is a recess  31 , which curves inwardly and downwardly from the primary land surface  27  and then curves upwardly to form a rear wall or chip deflector surface  32 . The chip deflector surface  32  terminates in a plateau  33  located approximately at the same level as the neutral plane P. 
     The chipforming area  19  additionally includes a pair of ridges one of which extends from the outer periphery of a respective one of the recesses  30 . More specifically, a front ridge portion  34 a and  34 b are so formed that they converge rearwardly, and they extend rearwardly to the point where they meet with rear ridge portions  35 a and  35 b which are mutually parallel and extend essentially perpendicularly from the cutting edge  18 . Furthermore, the front ridge portions  34 a and  34 b are formed with a top surface that is raised rearwardly until the location where the front ridge portion  34 a,  34 b intersects with the rear, straight rear ridge portions  35 a,  35 b at which intersection the top surface of the rear ridge portion has a level that remains constant further rearwardly. The level of the upper surface of the rear ridge portions  35 a,  35 b is located somewhat above, and generally parallel to, the plane P. 
     By arranging the ridges as aforesaid, it is ensured that the chip remains in contact with the forward ridge portions  34 a,  34 b and that the central portion of the chip is urged deeper into the recess  31 . This arrangement further ensures that the total width of the chip is made narrower and becomes more easily manageable so that no harm is made from the chip to the side wails of the groove which is to be formed by the insert during cutting in a metal workpiece. 
     The forward end of the insert  10  additionally is provided with side cutting edges  36 a and  36 b, which merge rearwardly to an intermediate position along the insert, while intersecting with the primary land surface  27  which extends along both the main cutting edge  18  and along the side cutting edges  36 a,  36 b. The clearance faces of the side cutting edges  36 a,  36 b are designated  11 a and  11 b. Each clearance face  11 a,  11 b intersects with the land surface  27  at an acute angle β (FIG.  6 ). 
     By virtue of the particular construction of the chip forming area as aforesaid, it is possible to obtain desirable clock-shaped chips  37  such as shown in FIG.  10 . These chips  37  can be obtained at a feed rate of 0.30 mm/revolution. If no proper chip deflection area is provided on the upper rake surface of the insert, chips obtained would otherwise be difficult to manage. Also, at moderate feed rates, the chip forming area of this invention effectively contributes to the control and removal of such chips. When large feeds are used, the chip will be pressed against the rear wall  32  of recess  31  which forces the chip to be bent in a favorable manner. 
     The embodiment described above also results in a certain reduction of the cutting forces because the grooves or recesses  28 ,  30  reduce the contact area and increase the positive rake angle. Due to the fact that a reduced contact area is obtained, a relatively low heat generation is obtained. 
     The principles, preferred embodiments and mode of operation of the present invention have been described. Variations and changes may be made and are contemplated within the invention to the extent such variation and changes fail within the scope of the appended claims.