PARTING-OFF CUTTING INSERT

Abstract: A cutting insert of cemented carbide primarily for cutting-off, is provided with a thin wall (7) in its frontal upper part. At its frontal upper edge this wall comprises the cutting edge (8). The wall is supported by a wider reinforcing part (9), whose width suitably coincides with the width of the cutting insert. Suitably, the wall (7) can be substantially shaped as a quarter of a circle. By this reinforcement of the thin wall (7), a large number of cutting-off operations can be effected with a minimal cutting width, which considerably reduces the chip waste.

Description: Parting-off cutting insert The present invention relates to a cutting insert primarily for cutting-off operations. However, if so desired, it may also be used for grooving. Suitably, the insert is made of coated or uncoated cemented carbide, but other hard materials may also be used, such as different ceramic materials and so called cermets. Cutting-off and deep radial and axial grooving are performed with a type of tools which are normally referred to as as parting and grooving tools. Characteristic for inserts and tools of this type is tneir small axial extension. The reason for this is of course that material shall not be unnecessarily wasted, and also to make possible the grooving of grooves of a smaller width. A typical insert for cuttmα-cff is _ιs_lcseα in US- - 4 801 224. However, for some cut mα-c:: :ρer_.: .::. , a_.s__ tr.i- insert is experienced as too wiαe, __.__3_.5- _:" r ._r raicria. fror^ the workpiece s wasted i tr.e :;rr : • ..: . M- _r.scr_- according to this citation are maαe wit: . ?r-_.-.. • ..at... c: _ mm, since even smaller insert widths are not considered to oe safely fastenable. Moreover, the inserts become too fragile. Another cutting insert for cutting-off and grooving is disclosed in SE-C-468 630. This one has a relatively thin, quadrangular basic shape, with a cutting edge provided in each corner. However, the relation between the insert's extension and thickness is too large to make it tenable. Therefore, it is usually made of high speed steel instead of cemented carbide, which of course considerably deteriorates the cutting performance. Thus, a first object of the present invention is to construct a cutting insert primarily intended for cutting-off, which makes possible very small cutting widths, for instance down to 0,4 mm. A second object of the present invention is to provide a cutting-off insert that is as thin as possible but also as strong as possible. Still another object of the present invention is to provide a cutting-off insert that is as thin as possible and does not make necessary any changes of the other equipment, such as for instance the holder blade. These and other objects have oeen achieved in a surprising way by forming a cutting insert according to claim 1. For illustrative but non-limiting purposes, the inventicr. will now be further described with reference t: tr._ appended drawings. These are herewith presentee: Figure 1 shows a cutting insert fir-::::::. : • ■ :.• invention in a perspective view. Figure 2 shows the insert a_ - : :.:. : ' : . : .:• . . : view. Figure 3 shows a partial v: .. : ' : • ." " • : ...: • ; ■ figure 1 straight from above. Figure 4 shows the section 17-17 ir. f α r. 1. Figure 5 shows the section 7-7 in figure 3. Figure 6 shows another embodiment of a cutting insert according to the present invention in a perspective view. Figure 7 shows the cutting insert of figure 6 in a side view. Figure 8 shows a further embodiment of the cutting insert according to figure 1. Figure 9 shows the cutting insert according to figure 8 in a side view. The cutting insert according to the invention is generally designated by reference numeral 1. It comprises a 5 holding part or shaft 2 which can be introduced into and clamped in a corresponding recess in a holder as described in the above mentioned US-A-4 801 224, hereby incorporated by this reference. In order to guarantee a stable fastening, the top side of the shaft 2 and the whole lower side of the cutting insert are 10 shaped as two longitudinal grooves or recesses 3 and 4, respectively. The upper groove 3 is terminated by a portion 3' , which is either substantially parallel to tne groove 4 on the lower side, or forms a very small angle to said groove, the projections of the groove 3' and the groove 4 intersecting at a 15 point in front of the front side 5 of the insert. The insert is pressed into the holder till the upper ciampir.α lever cf the latter abuts against an abutment surface 6 cr. tr.--- upper s c- r : the cutting insert. An essential feature of the rrer-'r.". _ r.v^r._ : : :. :: tr.- • • .' 2. wall wnich according to fig 1 ar.o _ .. _.: • .-.- . — :;rr- . as a sector of a circle and substantial. • _. '. • -: __._..- .. 1:. crj_: to reduce the produced groove width in tne rotating workpiece t: a minimum, it has been made as thin as possible. Thus, it suitably has a thickness of 0,3 to 1,5 mm, preferably from 0,4 25 to 1,2 mm and in particular from 0,5 to 1,0 mm,. Another essential feature of the present invention is that the wall 7 is supported by a considerably thicker reinforcing part 9, whose width substantially corresponds to the thickness of the insert. The whole attachment of wall 7 is 30 accomplished over the reinforcing part 9, preferably via a reinforcing radius transition 10. The thickness of wall 7 suitably amounts to between 1/6 and 2/3 of the thickness of the reinforcing part, preferably between 1/5 and 1/2, and in particular between 1/5 and 1/3. The reinforcing part extends substantially to a vertical line that intersects the cutting edge or at least to a plane that forms maximally 10°, preferably 7°, to said vertical line. It should be pointed out that these values are specific for the cutting insert and do not imply the functional values, when the insert is placed into a holder. Suitably, the cutting edge 8 may be wholly straight or include two short, oblique corner cutting edges 11, below which extend tapering reinforcing chamfers 12. In order to break the created chips and to give a more light-cutting geometry, the rake surface has been formed with a chip-breaking depression or recess 13. This recess begins in immediate connection to the cutting edge 8; according to the illustrated embodiment, however without intersecting it. However, within the frame-work cf tne invention, the recess 13 may aisc ir.tersect the cutting e ge. The cross-section of the recess may ce s eer, n figure 1. Thu_ , the recess may for instance have a trape:: d-snaped cross- section, comprising two longitudinal, .- Γctar.tι_.M y planar :-.::• surfaces 15 and a bottom surface 16 wnich is sucstan lally horizontal and placed centrally between said surfaces 15. The cross-section of recess 13 may also De shaped as a circle segment, the cross-section cf its bottom thus describing a radius. In order to give sufficient clearance, the wall 7 may be shaped in a special way. Thus, the front 14 of the wall 7 may be angled somewhat forwardly relative to the vertical line, which can be most clearly seen in figure 3, the front 5 of the reinforcing part possibly lying in the same inclined plane as the front 14 of the wall, or being wholly vertical. Further, the wall 7 can suitably taper somewhat with an increasing distance from the cutting edge 8, in order to give a certain clearance relative to the walls in the produced groove in the workpiece. Thus, the side surfaces of wall 7 may be inclined by for instance 0,3 to 3° relative to the vertical line in the vertical direction and by about equally much relative to a vertical plane in the longitudinal direction of the cutting insert. The embodiment according to figures 1 and 2 are preferred since the basically quarter-circle-shaped wall 7 gives the smallest possible free over-hang for the cutting edge 8 in all wall-supporting directions, which of course gives a strong and stable wall 7. However, if so desired, for instance because cf production-technical reasons, the wall may also be shaped according to a form as illustrated in fig. 6 and 7, with a substantially straight transition between wall ~* and reinforcing part 9, said transition suitably being shaped as ε reinforcing radius transition 10M The transition is angled ~ ~ tr- octto- side of the cutting insert Dy aoout 3C t: r ~ ° t r:-ι:_:_r_ . r_ - ' • to 50°. Otherwise, tne cutting insert _r s',_r. . .- ._ ~ _s_ the insert as illustrated m figures 1 .: . .. As mentioned above, tne cutting _ .ser- r _ - :asten_ • onto a holαer as shown in US-A-4 801 224, as snowr. ιr figures 1, 2, 6 and 7. However, the combination that s essential for the invention of a thin cutting edge-carrying wall and a supporting part may also be fastened in a number cf other possible ways. Thus, as shown in figures 8 and 9, the cutting insert may be fastened by means of a locking arrangement, such as a locking screw, a locking pin or a levering clamp, which is inserted into a through hole 17 in the holding part of the insert. The thin wall 7 may be produced in at least three different ways: either the whole insert may be directly pressed, or material is taken away on both sides of the wall to-be, either before or after the sintering. The above described cutting inserts do only comprise one cutting edge. However, within the framework of the present invention, cutting inserts are feasible with several thin, reinforced cutting edges, analogously with inserts as disclosed in, e.g., US-A-4 969 779, US-A-4 992 008 or SE-B-450 350. Thus, according to the present invention, cutting edge-carrying, reinforced walls 7 in accordance with the present invention may be formed at both ends of an oblong cutting-off or grooving insert, the two cutting edges either being provided on the same side, i.e., adjacent to the top side, or at different sides, diagonally opposed to each other. In both cases, the intermediate portion functions as a holding part or a shaft. Further, analogously with SE-B-450 350, a cutting insert of a polygonal basic shape, suitably a square basic shape, may be provided with a thin cutting edge-carrying wall part " ' at eacr. operative cutting corner. Cutting inserts cf a triangular can: shape are also feasible. By the cutting insert according t" tr.- :r.v r.ticr., a number of important advantages have oeer_ ac ieveu. Thus, for instance by a cutting insert according to figure 1, which gave __ groove width of 0,8 mm:, it was managed to cut off a roll oearm; blank with a diameter of 8 mm at a feed of 0,2 mm/rev., a large number of times before causing any pronounced wear of the cutting edge.

Claims: Claims 1. A cutting insert of a hard material for cutting-off and grooving operations, comprising at least one part provided with a cutting edge, and one holding part (2) for the fastening of the cutting insert in a holder, characteri zed in tha t each part provided with a cutting edge comprises a cutting edge- carrying wall (7) and a reinforcing part (9), said wall (7) being thinner than the width of the cutting insert and the reinforcing part (9) , respectively, and being supported by the reinforcing part (9) . 2. Cutting insert according to claim 1, chara cteri zed in tha t the width of the wall (7) amounts to between 1/6 and 2/3 of the width of the reinforcing part (9) . 3. Cutting insert according to claim 1 or 2, cha ra ct eri zed i n tha t tne width of tne reinforcing part (9) suostantially coincides with tne width cf the cutting insert. 4. Cutting insert according to claims 1 to 3, cha ra cteri zed in tha t the wall (7) is substantially circle segment-shaped. 5. Cutting insert according to any of the preceding claims, chara cteri zed in tha t the thickness of the wall (7) diminishes in the direction away from the cutting edge (8) , in order to give sufficient clearance. 6. Cutting insert according to any of the preceding claims, characterized in tha t the rake side of the wall (7) is provided with a chip-breaking recess (13) . 7. Cutting insert according to any of the preceding claims, characterized in tha t it comprises one, two, three or four cutting edges.

Inventors: JONSSON ANDERS, OVASKA PEKKA, JONSSON, ANDERS, OVASKA, PEKKA
Applicants: JONSSON ANDERS, OVASKA PEKKA, SANDVIK AB, JONSSON, ANDERS, OVASKA, PEKKA
Application year: 1995
Main classification: B23B27
IPC codes: B23B27