CA2159477A1

CA2159477A1 - Cutting insert

Info

Publication number: CA2159477A1
Application number: CA002159477A
Authority: CA
Inventors: Jose Agustin Paya
Original assignee: Individual
Current assignee: Widia GmbH
Priority date: 1993-03-29
Filing date: 1994-03-11
Publication date: 1994-10-13
Also published as: JPH08508211A; DE4310131A1; WO1994022621A1; EP0691897A1; KR960701718A

Abstract

The invention concerns a cutting insert (10) with a negative face land (14) adjoining the cutting edges (11, 13), designed in particular for radial machining. In order to minimize the resulting overall cutting force, the width of the face land (14), relative to the effective cutting zone, is a maximum in at least one corner (12) of the cutting edge or in the region of a round feed-side cutting edge.

Description

215 94~7 , ., . .. , . . . . . . . . _ FILE, ~ . A'.~ENDE~;i ~E~T TRANSLATION changed ~heet ~pecification C~tting Insert The invention relates to a cuttin~ inse~t in particula~ for radi~l m*ch;n;~ 6uch as tappi~g, turn bro~chin~, turn-turn-broachin~ milling or cutt~ng ~crewth~eads, bu~ als~ for turning, at th~ cutting e~ge6 with a ne~a~ive cutting surfa~e land which width i~ m~lm in at le~st one cutti~y edge corn~r or in the region of a round m4in cutting ~dge.

A cutting inser~ with these f~atur~s i6 known from the US-A-3 279 035. ~ut this cutting insert has in direction of the cutting edge a conVex land which is nei~hboured to ~ cutting edge f~med a~u~tely. By grinding the o~iginally ashlar cu~ting in~ert in the regions of the cutting edges one gets a shape with a land wlder in the cutting edg~ ~orners than in the middle of the cutting edges. By this a convexly arcuated cu~ting ed~e is p~o~uced which is unwe~come at the ob; ect of the presellt invention.

The EP O 4~7 872 Al rela~ to a groove-cutter with a pa~tially ~ounded cutting edge ad]acent to a ne~tive land. Neighboured to th$s l~nd ~he cut~ing surface ha6 circumerentially adjacent recesses as chip forming elements.

Negati~e lands of cut~ing inserts have the advantage of stabilizing the cuttin~ edge ~long with the dis~dv~ntage th~t ~hip outfeed is ~trongly inhibited so that there is substantlal ~riction wh~ch requires con~iderable ~eed ~orce.

It i~ ~n ohject of the invention to improve on the abGve-desc~ibed cutting in~ert so thàt without losing the advant~ges o~ ~ r,egative cutting-sur~ace land tho f~ed force or the resulting overall cutting force is reduced.

~hanged sheet 1~

This object i9 ~chieved by the cutting inser~ de~cr~bed in claim 1 which i~ according to the invention ch~racte~i~ed in tha~ the bord~ be~w~en the cutting surface lAnd ~nd the adjacent cu~ting surface in the dlrection of the cutting ~dge adjacen~ to the cu~tinU sur~ace land and line~r Been in a side view - runs thr~ugh a sole depressi~n ~n the ~hape of a mirimum space per main cutting edge ~nd~or second~ry cutti~ edge or - at cutting lnserts with ~ round o~ ~rtitial rnund cutting edge seen in ~ top ~iew, - there are sPveral depres~ion6 in the shape of a mini~um space whiGh have an angular distance from the neighboured or ~pposite de~ression of 90~ o~ 180'.

So starting from a cTItting edge ~nd ~oing ablong the cutting edge ~he land has a narrowin~ which can ~x~end 60 far that ~he width of the land is z~ro to ths extre~e ca~e. With such a narrowin~ thç height distance o~ the border curve between th~.
cu~ting-su~face l~nd ~nd the cuttin~ surface cau~ed hy ~h~
negative l~nd ~ngle minimi~e~ in relation to the cutting edge.
~his dep~ession of ~he cutting-~ur~ace l~nd ~long the cutting edge cau~es a lower friction of the remo~ing ~hip, fu~ermore the c~tting wed~e i~ released without ab~ndoning the ~dvances o~ a negative wide stable land in the cutting edge ~orners. So t~e cuttin~ ed~e is evidently more supported ir. the cutting edge~ that means in the regions o~ the greatest cutting forccs than in the region~ of the ~econdary cutting edge.

~ 1 ~ ~ r~ n ~ R ~ r ~- 7 T ~ ~ I . n ~

~A2 1 59477 atod by tho nogativo land anglo of tho bordor botwocn tho cutting urf~3ne~
and the cutting surface relative to the cutting edge. This~g of the cutting-surface land along a cutting edge results in~ of the out-flowing chip and thus takes a load off the c~dge without giving up the advantages of a negative w~fland in the cutting-edge corners. The cutting edge is th~tially better supported in the cutting corners, that is in th~of greatest cutting force, than in the regions of the secondary ~u~g ~dgcs.
Further embodiment of the cutting insert according to the invention are described in the dependent claims.
Thus the border between the cutting-surface land and the cutting surface extends generally arcuately. This is an embodiment wherein the described border runs relative to a straight connecting line of the border points in the cutting corners underneath this connecting line. Preferably the border of the cutting-surface land to the cutting surface or width of the cutting-surface landfrom the cutting edge runs through a minimum in the direction of the cutting edges.
The cutting-surface land angle can have one and the same value along the entire cutting edge, and it can also have different negative land angles to achieve a further compensation of the slope which an outfeeding chip must run up. According to a concrete embodiment the land angle changes continuously along the cutting edge, preferably going continuously toward zero but always staying negative.

CA 21 5 94~7 According to a further embodiment of the invention the border between the cutting-surface land and the cutting surface is of wavy and/or zig-zag shape, at least one of the upper or of the lower containing curves forming an arc with uniform curvature. Unlike in the above-described case it is not strictly necessary that the border have a single curvature from cutting corner to cuttingcorner as it goes through its minimum, instead the border can be irregularly wavy or run as a zig-zag, above all then at least one of the upper or of the lower containing curves fulfills the requirement of an arcuate path with a single curvature.
A preferred embodiment of the invention is a tapping tool with a main cutting edge and two secondary cutting edges with a circumferential cutting-surface land which is larger in the two cutting corners as in the adjacent regions, except if necessary for the rear region of the secondary cutting edge that is irrelevant for the cutting operation. Preferably the main-cutting surface land between the adjacent cutting corners and/orthe secondary cutting-surface lands are formed symmetrically relative to a longitudinal central axis of the tapping tool and/or a perpendicular thereto.
According to a further embodiment of the invention various shapes are particularly advisable for the cutting-surface land seen perpendicular to the cutting edge: The cutting-surface land can be straight, slightly concave or convexly curved and/or formed with one or more chip-forming grooves and/or with one or more chip-forming elements. In this application land means such regions adjacent the cutting edge that are curved with a depth or height of 1/100 --10/100 mm.
According to a further embodiment of the invention a chip-guiding step can be provided adjacent the cutting-surface land or the cutting surface can be provided with a raised chip breaker with a projecting rib-shaped width with seen in top view as well as in longitudinal section a tapering point. All these additional chip-forming means are known in principal from prior-art cutting inserts and can also be used in connection with the embodiments of the 1 0 invention.
According to a further embodiment of the invention the cutting insert is a thread-cutting insert with staggered and stepped cutting corners with the cutting-surface lands each running through a minimum from a projecting cutting corner to a cutting-edge bump.
Preferably with all of the described embodiment the free angle is positive, but it can also be 0.
The cutting insert an according to a further embodiment of the invention be provided with a circularly closed cutting edge. The border between the negative land and the adjacent cutting surface increase to the cutting edge through varying spacings which run through maximum and minimum levels, preferably four maximums and for minimums. Wedge-shaped longitudinal-rib raised chip-forming elements are provided extending radially from the minimum spacings of the border from the cutting edge.

r~2159~771 Embodiments of the invention are shown in the drawings. In the drawing:
FIG.1 is a perspective view of a tapping insert;
FIG. 2 is a side view taken in the direction of arrow x of FIG. 1;
FIG. 3 is a partial perspective side view of a further cutting insert;
FIG. 4 is a perspective view of a cutting insert with a front rounded cutting edge;
FIG. 5 is a top view of a cutting insert;
FIGS. 5a -- 5c are sections taken along lines A--A, B--B,and C--C of FIG.
5;
FIG. 6 is a partial perspective view of a screwthread cutting insert;
FIG. 7 is a top view of a further cutting insert;
FIG. 8 is a side view of the cutting insert according to FIG. 7; and FIGS. 9a -- 9k are respective embodiments of different lands.
The tapping insert 10 according to FIG. 1 has a main cutting edge 11 that is bounded by two cutting corners 12 from which extend respective secondary cutting edges 13 that extend at an acute angle to each other.
Immediately adjacent the main and secondary cutting edges there is a land 14 which is of maximum width at the cutting corners 12 and which has restrictions 15 in CA2~ 594~

regions adjacent the main cutting edge 1 1 and the secondary cutting edges 13.
At the rear the cutting land 14 is again wider. If the borders between the cutting land 14 and the cutting surface 16 are joined by straight lines 17, the extent of the restriction, that is the reduction of the cutting-surface land width, becomes evident. The cutting insert has with a negative land angle ~ (see FIG.

2) a positive free-surface angle,t~. The cutting surface 16 can be shaped as a recess 18 (see FIG. 2). In addition the cutting surface 16 can also have a chip-shaper 19 which has the shape of a wedge 20 directed perpendicular toward the main cutting edge 11. The cutting insert shown in FIG. 3 is correspondingly constructed where the perspective representation makes it clear that the cutting-land width in the rear where it is not important for the cut is larger than the width of the cutting-surface land in the cutting-corner region.
The cutting-surface width in the rear region depends on how much the cutting-surface land or the descending region 21 extends in toward the cutting-surface recess 22 as a chip-forming element.
The main cutting edge 11 is rounded in a further embodiment of a tapping insert according to FIG. 4 and merges smoothly into the secondary edge 13. In this embodiment the main cutting edge 1 1 takes over the function of a cutting corner so that the cutting-surface land 14 has in the region of themain cutting edge a constant thickness. Immediately adjacent in the region of the secondary cutting edge the border between the cutting-surface land and the cutting surface 16 of the respective CA21 5~7 ramp part is arcuately recessed, that is the cutting-surface land width is smaller in this region of the restriction. Even this cutting insert has an elongated forwardly tapering raised chip-forming element 19 with respective wedge-shaped rib parts 20 that are arranged symmetrically to the longitudinal central axis of the cutting insert. The construction of these edges or longitudinal ribsis the subject of German patent 4,136,471 to which reference is made.
The cutting insert shown in top view in FIG. 5 corresponds generally to the cutting insert according to FIG. 1 (except for the central chip former) but has different land angles a1 to a'3 with the land angle decreasing along the secondary edge 13 with increasing spacing from the cutting edge 1 1.
Decreasing the land angle to small absolute values takes place in any case up to the region of the restriction whereupon the angle can stay the same or even increase or go much further negative.
FIG. 6 shows a thread-cutting insert 23 with several cutting edges 24 than are staggered and adjacent which the cutting-surface land 14 has a maximum width relative to the remaining regions. In addition the same parts have the same references as in the above-discussed figures.
FIG. 7 shows a top view of a cutting insert with a closed circular cutting edge which has a negative cutting-surface land 27. The cutting-surface land 27 has a varying width such that it assumes maximum width (in the drawing above and below as well as right and left) on opposite sides and runs through a C~21 59~7~

minimum in the regions therebetween. As particularly visible from FIG. 8 the border between the negative land 27 and the remaining cutting surface sinks relative to the surrounding regions. The negative land ends at a chip-guiding groove 23 into which project wedge-shaped radially outwardly direction chip-forming elements 29. These chip-forming elements point to a low parts of the border 15 between the negative land 27 and the remaining cutting surface.
Even these wedges or longitudinal ribs are described in German patent 4,136,417 to which reference is made.
FIGS. 9a through 9k show that with the cutting inserts according to the invention different shapes for the cutting-surface lands can be provided.
The land according to FIGS. 9 and 9b has a planar flat shape 141 whereas the cutting-surface land according to FIG. 9c and 9d has a lightly convexly curved shape 142 (the curvature is shown exaggerated and in practice has 1/100 to 10/100 mm height differential). The cutting-surface land according to FIGS. 9e and 9f has a concave shape 143 with a convexity of 1/100 to 10/100 mm depth. The above-named cutting-surface shaped can be combined with grooves 25 in the region of the cutting-surface land. In addition according to FIG. 9i and 9k it is possible to use raised chip-forming elements 26 on the cutting surface land 14, preferably perpendicular or at an acute angleto the cutting edge and shaped as elongated wedge-shaped ribs.

Claims

Patent claims

1. A cutting insert (10, 23) in particular for radial machining such as tapping, turn broaching, turn-turn-broaching, milling or cutting screwthreads, but also for turning, at the cutting edges (11, 13) with a negative cutting surface lane (14, 141, 142) which width is maximum in at least one cutting edge corner or in the region of a round main cutting edge, characterized in that the border (15) between the cutting surface land (14, 27, 141, 142, 143) and the adjacent cutting surface (16) in the direction of the cutting edge (11, 13, 18) adjacent to the cutting surface land and linear seen in a side view - runs through a sole depression in the shape of a minimum space per main cutting edge (11) and/or secondary cutting edge (13) or - at cutting inserts with a round or partitial round cutting edge (28) seen in a top view, - there are several depressions in the shape of a minimum space which have an angular distance from the neighboured or opposite depression of 90° or 180°.

2. The cutting insert according to claim 1, characterized in that the border (15) between the cutting-surface land (14, 141 through 143, 27) and the cutting surface (16) extends generally arcuateley.

3. The cutting insert according to one of claims 1 or 2, characterized in that the cutting-surface land angle (.alpha.) from one cutting corner (12, 24) out toward the cutting edge (13) has different negative land angles (.alpha.1 through .alpha.3).

8a

4. The cutting insert according to claim 3, characterized in that the land angle (.alpha., .alpha.2 through .alpha.3) changes continuously, preferably continuously toward zero, but always negatively.

5. The cutting insert according to one of claims 1 through 4, characterized in that the border (15) between the cutting surface (14) and the cutting surface (16) is of wavy and/or zig-zag shape, at least one of the upper or of the lower containing curves forming an arc with uniform curvature.

6. The cutting insert according to one of claims 1 through 5, characterized in that in a tapping tool (10) the main cutting edge (11) and/or the secondary cutting edge (13) has cutting-surface lands (14).

7. The cutting insert according to claim 6, characterized in that the main cutting-surface land (14) is formed symmetrically between the adjacent cutting corners (12) and the secondary cutting-surface lands (13) relative to the longitudinal central axis of the tapping tool (10) and/or a perpendicular thereto.

8. The cutting insert according to one of claims 1 through 7, characterized in that the cutting-surface lands (14, 141, 142, 143) are formed perpendicular to the cutting edge (11, 13) straight, convex, concave, with one or more chip-forming grooves (25) and/or with one or more chip-forming elements (26).

9. The cutting insert according to one of claims 1 through 8, characterized in that a chip-guiding step is arranged immediately at the cutting-surface land (14, 141, 142, 143).

10. The cutting insert according to one of claims 1 through 9, characterized in that the cutting surface (16) has a raised chip breaker (19) with a projecting rib-shaped wedge (20) with a tapering point directed in the longitudinal direction.

11. The cutting insert according to one of claims 1 through 6 and 8 through 10, characterized in that the cutting insert is a thread-cutting insert (23) with staggered and stepped adjacent cutting edges (24) with the cutting-surface lands (14) each running through a minimum of a projecting cutting corner to the cutting-edge bump.

12. The cutting insert according to one of claims 1 through 11, characterized in that the free angle (.beta.) is positive or 0°.

13. The cutting insert according to one of claims 1 through 6, 8 through 10, and 12 characterized in that the cutting insert has a closed circular cutting edge (28) and that the border (15) between the negative land (27) and the adjacent cutting surface runs through maximum and minimum spacings from the cutting edge (28).

14. The cutting insert according to claim 13, characterized in that the border runs through at leat four maximum levels and four minimum levels.

15. The cutting insert according to claim 13 or 14, characterized in that wedge-shaped longitudinal-rib raised chip-forming elements are provided extending radially from the minimum spacings of the border (15) from the cutting edge (28).