IL150012A - Tangential cutting insert and milling cutter - Google Patents

Description

TANGENTIAL CUTTING INSERT AND MILLING CUTTER Iscar Ltd. »"*a The inventors: Amir Satran "pot? ON Daniel Dagan TANGENTIAL CUTTING INSERT AND MILLING CUTTER FIELD OF THE INVENTION The present invention relates to a tangential indexable cutting insert and a milling cutter for use in metal cutting processes in general and for milling a square shoulder in a workpiece in particular.

BACKGROUND OF THE INVENTION Tangential cutting inserts, also known as on-edge, or lay down, cutting inserts, are oriented in an insert holder in such a manner that during a cutting operation on a workpiece the cutting forces are directed along a major (thicker) dimension of the cutting insert. An advantage of such an arrangement being that the cutting insert can withstand greater cutting forces than when oriented in such a manner that the cutting forces are directed along a minor (thinner) dimension of the cutting insert.

There is disclosed in EP 0 769 341 a face milling cutter employing a double-sided indexable tangential cutting insert having a prismoidal shape with two opposed generally rectangular rake surfaces connected by side surfaces. The cutting insert has a basic "negative" geometry and therefore in order to provide the necessary clearance between the cutting insert and the workpiece, when mounted in a face-mill, the cutting insert is oriented with a negative axial rake angle. However, negative axial rake angles are disadvantageous, e.g., they have been found to be deficient in cutting efficiency for applications involving difficult to machine materials.

There is disclosed in WO 96/35536 a double-sided indexable tangential cutting insert which when mounted in a face-mill has a positive axial rake angle, even when the necessary clearance between the cutting insert and the workpiece is provided. This cutting inserts presents two peripheral cutting edges for a right-hand face mill and two peripheral cutting edges for a left-hand face mill.

A double-sided indexable tangential cutting insert for a boring tool head is disclosed in US 5,333,972. The insert is provided at each end with a protruding flat island. Each long cutting edge is inclined at an angle of 3° relative to the protruding flat island, defining an "insert axial rake angle". Rearward of each cutting edge is a descending land surface that merges with an increasing incident angle surface to form a chip breaker groove. Each increasing incident angle surface extends from its associated descending land surface to an adjacent island, at either the top or the bottom of the cutting insert. The cutting insert is left or right handed. It is manufactured to be right-handed and, when flipped around, is left-handed. It will be appreciated that the magnitude of the insert axial rake angle is limited for practical reasons. Any increase in the insert axial rake angle will result in an increase in the "vertical" extent of the increasing incident angle surface (see Fig. 3 of US 5,333,972) that will have an adverse effect on chip development and evacuation.

It is an object of the present invention to provide a double-sided indexable tangential cutting insert that substantially overcomes the above-mentioned problems.

It is a further object of the present invention to provide a double-sided indexable tangential cutting insert having four main cutting edges, for a given direction of rotation of the milling cutter, each main cutting edge having a positive axial rake angle when mounted as an operative cutting edge in a milling cutter.

It is yet a further object of the present invention to provide a double-sided indexable tangential cutting insert capable of milling a square shoulder in a workpiece.

SUMMARY OF THE INVENTION In accordance with the present invention there is provided a tangential cutting insert, for use in a milling cutter, comprising: two identical opposing end surfaces having 180° rotational symmetry about a first axis passing therethrough, a peripheral side surface extending between the two opposing end surfaces, and a peripheral edge fomied at the intersection of each end surface and the peripheral side surface, at least two sections of each peripheral edge constituting cutting edges; the peripheral side surface comprising: two identical opposing major side surfaces having 180° rotational symmetry about a second axis passing therethrough, the second axis being perpendicular to the first axis; two identical opposing minor side surfaces having 180° rotational symmetry about a third axis passing therethrough, the third axis being perpendicular to the first axis and the second axis; a minor plane defined by the first axis and the second axis; a major plane defined by the first axis and the third axis; a median plane being defined by the second axis and the third axis; each end surface having four corners, two lowered corners and two raised corners, the lowered corners being closer to the median plane than the raised corners; each end surface being provided with a projecting abutment member having a projecting abutment surface, wherein in a side view of either major side surface, the projecting abutment surface is concave.

Preferably, in a side view . of either major side surface, the projecting abutment surface is generally V-shaped.

In accordance with the present invention, in an end-view of the cutting insert the projecting abutment surface is generally rectangular in shape having two parallel long edges extending between two short edges, the long edges making an angle of β with the major plane.

In accordance with a specific application, β = 2°.

If desired, the projecting abutment surface comprises three flat portions, two outer flat portions with an inner flat portion therebetween, each outer flat portion extending from a respective short edge to the inner flat portion.

Further if desired, each minor side surface is divided into two minor side sub-surfaces by the major plane along a join where the major plane intersects the minor side surface, each minor side sub-surface extending away from the join at an angle a with respect to a plane passing through the join and parallel to the minor plane.

In accordance with the present invention, each minor side surface merges with an adjacent major side surface at a corner side surface, wherein each corner side surface extends between a given raised corner of one of the two opposing end surfaces and a given lowered corner of the other of one of the two opposing end surfaces.

In accordance with the present invention, each cutting edge comprises a major cutting edge, a minor cutting edge and a corner cutting edge, therebetween.

In accordance with the present invention, major, corner, and minor edges are formed at the intersection of major, corner and minor side surfaces, respectively with an adjacent end surface.

In accordance with the present invention, each corner cutting edge is associated with a given raised corner.

Generally, each major cutting edge extends along substantially the whole length of an associated major edge.

Generally, each minor cutting edge extends along at least half of the length of an associated minor edge.

In accordance with the present invention, the cutting insert further comprises an insert through bore extending between the major side surfaces and having a bore axis coinciding with the second axis.

There is also provided in accordance with the present invention, a milling cutter comprising: at least one cutting insert in accordance with the present invention; and a cutter body having at least one insert pocket in which the at least one cutting insert is retained, the at least one insert pocket comprising adjacent side and rear walls generally transverse to a base, the rear wall being generally convex; the side wall being provided with an axial location surface that abuts a given minor side surface of the at least one cutting insert at a given axial abutment region; the rear wall being provided with two tangential location surfaces, located on either side of a central region of the rear wall, a first of the two tangential location surfaces abuts a first tangential abutment surface located on the projecting abutment surface of the at least one cutting insert, a second of the two tangential location surfaces abuts a second tangential abutment surface located on the projecting abutment surface.

In accordance with the present invention, the given axial abutment region is located on a forward region of a radially outer minor side sub-surface, the forward region being distal the rear wall of the insert pocket.

Further in accordance with the present invention, the lower and upper tangential abutment surfaces are located on opposite sides of the minor plane.

BRIEF DESCRIPTION OF THE DRAWINGS For a better understanding, the invention will now be described, by way of example only, with reference to the accompanying drawings in which: Fig. 1 is a perspective view of a cutting insert in accordance with the present invention; Fig. 2 is a first side view of the cutting insert in Fig. 1 ; Fig. 3 is an end view of the cutting insert shown in Fig. 1 ; Fig. 4 is a second side view of the cutting insert shown in Fig. 1 ; and Fig. 5 is a cross-sectional view of the cutting insert shown in Fig. 1 taken along V-V in Fig. 4.

Fig. 5 is a cross-sectional view of the cutting insert shown in Fig. 1 taken along V-V in Fig. 4.

Fig. 6A is a partial cross section of the cutting insert shown in Fig. 1 taken along VIA- VIA in Fig. 3.

Fig. 6B is a partial cross section of the cutting insert shown in Fig. 1 taken along VIB-VIB in Fig. 3.

Fig. 6C is a partial cross section of the cutting insert shown in Fig. 1 taken along VIC-VIC in Fig. 3.

Fig. 7 is a perspective view of the cutting insert in accordance with the present invention with a ground primary relief surface; Fig. 8 is a perspective view of a milling cutter in accordance with the present invention; and Fig. 9 is a perspective view of a portion of the cutter body of the milling cutter in accordance with the present invention, showing in detail an insert pocket.

DETAILED DESCRIPTION OF THE INVENTION Attention is first drawn to Figs. 1 to 6C, showing a cutting insert 10 in accordance with the present invention there. The cutting insert 10 is tangential and indexable. The cutting insert 10 is typically manufactured by form-pressing and sintering carbide powders. The cutting insert 10 is generally rectangular in an end view and has two identical opposing end surfaces 12. Each end surface 12 has 180° rotational symmetry about a first axis Al passing through the two end surfaces 12.

A peripheral side surface 14 extends between the two opposing end surfaces 12 and comprises two opposed identical minor side surfaces 16, two opposed identical major side surfaces 18, and four opposed corner side surfaces 22. Adjacent minor and major side surfaces 16, 18 merge at a common corner side surface 22. The two identical opposing major side surfaces 18 each have 180° rotational symmetry about a second axis A2 passing through the opposing major side surfaces 18. The second axis A2 is perpendicular to the first axis Al. Similarly, the two identical opposing minor side surfaces 16 each have 180° rotational symmetry about a third axis A3 passing through the opposing minor side surfaces 16. The third axis A3 is perpendicular to the first axis Al and to the second axis A2. A minor plane PI defined by the first axis Al and the second axis A2, a major plane P2 defined by the first axis Al and the third axis A3 and a median plane M is defined by the second axis A2 and the third axis A3.

Each end surface 12 has four corners, two lowered corners 24 and two raised corners 26. The lowered corners 26 being closer to the median plane M than the raised corners 24. Each corner side surface 22 extends between a given raised corner 26 of one of the two opposing end surfaces 12 and a given lowered corner 26 of the other of one of the two opposing end surfaces 12. Each end surface 12 is provided with a projecting abutment member 28 having a projecting abutment surface 30, wherein in a side view of either major side surface 18, the projecting abutment surface is generally concave in form. The projecting abutment surface 30 comprises three generally flat portions, two outer portions 32 with an inner portion 34 therebetween. Therefore, in a side view of either major side surface 18, the projecting abutment surface 30 appears generally V-shaped.

Referring to Fig. 3, it can be seen that in an end-view of the cutting insert 10 the projecting abutment surface 30 is generally rectangular in shape having two parallel long edges 36 extending between two short edges 38. Therefore, each outer flat portion 32 of the projecting abutment surface 30, extends from a respective short edge 38 to the inner flat portion 34.

A peripheral edge 40 is formed at the intersection of each end surface 12 and the peripheral side surface 14. For each end surface 12, the peripheral edge 40 comprises two major edges 42, formed by the intersection of the major side surfaces 18 with the end surface 12; two minor edges 44, formed by the intersection of the minor side surfaces 16 with the end surface 12; and two corner edges 42, formed by the intersection of the corner side surfaces 22 with the end surface 12.

In the cutting insert 10 of the present invention at least two sections of each peripheral edge 40 constitute cutting edges 52. Each cutting edge 52 comprises a major cutting edge 54, extending along substantially the whole length of its associated major edge 42; a minor cutting edge 56, extending along at least half of the length of its associated minor edge 44; and a corner cutting edge 58, associated with a raised corner 24 and at which the major and minor cutting edges 54, 56 merge. Adjacent each cutting edge 52 in the end surfaces 12 is a rake surface 60 along which chips, removed from a workpiece during a milling operation, flow. Between the rake surface 60 and the projecting abutment member 28 there is a chip groove 62. The portion of the projecting abutment member 28 adjacent the chip forming groove 62 constitutes a chip deflector 64.

Referring to Fig. 3, it is seen that each minor side surface 16 is divided into two minor side sub-surfaces 70 by a join 72 where the major plane P2 intersects the minor side surface 16. Each minor side sub-surface 70 extends away from the join 72 at an angle a with respect to a plane P3 passing through the join 72 and parallel to the minor plane PI. In accordance with a specific application this angle is approximately 1.5°. The cutting insert is provided with a through bore 74 extending between the major side surfaces 18 and having a bore axis B coinciding with the second axis A2.

As will become apparent below, with reference to the milling cutter in accordance with the present invention, the section of the major cutting edge 54 adjacent the raised corner 24 constitutes a leading end 66 of the major cutting edge 54 whereas, the section of the major cutting edge 54 adjacent the lowered corner 26 constitutes a trailing end 68 of the major cutting edge 54. As can be seen in Fig. 4, in a side view of the cutting insert 10, the projecting abutment member 28 in the region of the leading end of the major cutting edge 54 and up to and a little beyond the region of the minor plane PI, does not protrude by much above the major cutting edge 54. As a consequence, chips in this region are completely formed during a milling process. However, in the region of the trailing end 68 of the major cutting edge 54, the chip deflector 64 protrudes much further than it does in the region of the leading end 66, which can disturb the development of the chips. In order to reduce the influence of the protruding chip deflector 64 in the region of the trailing end 68, the chip deflector 64 is designed to be more distant from the major cutting edge 54 in the region of the trailing end 68 than it is in the region of the leading end 66. Consequently, as can be seen in Fig. 3, in an end-view of the cutting insert 10 the long edges 36 of the projecting abutment member 28 are oriented at a small angle β with respect to the major plane P2. In accordance with a specific application this angle is 2°. Although the shape of the major cutting edge 54 is shown in Fig. 4 to be generally straight in a side view, apart from section adjacent the trailing end 68, the major cutting edge 54 can have any desired shape. Further with reference to Fig. 4, it can be seen that in a side view of the major side surface 18, the major cutting edge 54 generally slopes downwardly from the raised corner 24 to the lowered corner 26. With reference to Fig. 2, it can be seen that in a side view of the minor side surface 16, the minor edge 44 is clearly divided into two sections, a first section 46 extending from the raised corner 24 to approximately the major plane P2 and a second section 48 extending from the major plane to the lowered corner 26. The first section 46 is approximately straight and is perpendicular to the major side surface 18 in a side view, see Fig. 2, and is oriented at the angle a with respect to a plane P3 in an end view, see Fig. 3. The second section 48 extends from approximately the major plane P2 slopingly towards the lowered corner 26 in an end view, see Fig. 2, and is oriented at the angle a with respect to a plane P3 in an end view, see Fig. 3. It is the first section 46 of the minor edge 44 that forms the minor cutting edge 56.

Attention is now drawn to Fig. 7, showing the cutting insert 10 in accordance with the present invention, in which the major side surface comprises a primary relief surface 76 adjacent the major cutting edge 54 and a secondary relief surface 78 adjacent the primary relief surface 76. This arrangement gives more flexibility in the design of the major cutting edge 54 and is particularly important when designing the major cutting edge 54 to mill a true 90° shoulder in a workpiece. The primary relief surface 76 can have a constant relief angle along the major cutting edge 54, or a variable relief angle along the major cutting edge 54.

Attention is now drawn to Fig. 8, showing a milling cutter 80 with an axis of rotation R, having a cutter body 82 provided with a plurality of insert pockets 84. In each insert pocket 84 a cutting insert 10 in accordance with the present invention is clamped by means of a clamping screw (not shown). The axial rake angle will generally be in the range of 5° to 20°. As can be seen, each cutting insert is seated so that there will be a clearance between a workpiece (not shown) and the cutting insert's minor side surface 16 adjacent the milling cutter's face 86. The structure of the insert pocket 84 is shown in detail in Fig. 9. The insert pocket 84 comprises adjacent side and rear walls 88, 90 generally transverse to a base 92. The rear wall 90 is generally convex and the side wall 88 is provided with an axial location surface 94 for abutting a given minor side surface 16 of the cutting insert 10 at an axial abutment region 96. The rear wall 90 is provided with two tangential location surfaces, a upper tangential location surface 98, adjacent the pocket side wall 88 and a lower tangential location surface 100. The two tangential location surfaces are located on either side of a central region 102 of the rear wall 90. The upper tangential location surface 98 abuts an upper tangential abutment surface 104 located on the projecting abutment surface 30 of the cutting insert 10. The lower tangential location surface 100 abuts a lower tangential abutment surface 106 located on the projecting abutment surface 30. Clearly, the terms "lower" and "upper" used here with respect to the projecting abutment surface 30 are used only when the cutting insert 10 is mounted in the milling cutter 80, and with respect to the orientation shown in Figs. 8 and 9. Similarly, with respect to Figs. 8 and 9, the axial abutment region 96 is located on a forward region 108 of a radially outer minor side sub-surface 110, the forward region being distal the rear wall of the insert pocket 90. As can be seen in Fig. 3, the two tangential abutment surfaces 104, 106 on each projecting abutment surface 30 are located on opposite sides of the minor plane. As can be seen in Fig. 2, each minor side sub-surface 70 is provided with one axial abutment region 96 adjacent a lowered corner 26. The base 92 of the insert pocket 84 is provided with a threaded bore 112 for receiving a clamping screw in order to secure the cutting insert 10 in the insert pocket 84. When the cutting insert 10 is secured in the insert pocket 84, a radially inner major side surface 20 will abut the base 92 of the insert pocket 84. Preferably, the major side surfaces 18 of the cutting insert 10 are ground. Further preferably, the minor side sub-surfaces 70 are ground. With these surfaces ground, good positioning of the cutting insert 10 in the insert pocket 84 is ensured.

Although the present invention has been described to a certain degree of particularity, it should be understood that various alterations and modifications could be made without departing from the spirit or scope of the invention as hereinafter claimed.

Claims (6)

150012 / 2 -12- tangential cutting insert comprising: two identical opposing end surfaces having 180° rotational symmetry about a first axis passing therethrough, a peripheral side surface extending between the two opposing end surfaces, and a peripheral edge formed at the intersection of each end surface and the peripheral side surface, at least two sections of each peripheral edge constituting cutting edges; the peripheral side surface comprising: two identical opposing major side surfaces having 180° rotational symmetry about a second axis passing therethrough, the second axis being perpendicular to the first axis; two identical opposing minor side surfaces having 180° rotational symmetry about a third axis passing therethrough, the third axis being perpendicular to the first axis and the second axis; a minor plane defined by the first axis and the second axis; a major plane defined by the first axis and the third axis; a median plane being defined by the second axis and the third axis; each end surface having four corners, two lowered corners and two raised corners, the lowered corners being closer to the median plane than the raised corners; each end surface being provided with at least one projecting abutment member having a projecting abutment surface, wherein in a side view of either major side surface, the projecting abutment surface lies on a concave surface.

2. The cutting insert according to claim 1, wherein in a side view of either major side surface, the projecting abutment surface is generally V-shaped.

3. The cutting insert according to claim 1, wherein in an end-view of the cutting insert the projecting abutment surface is generally rectangular in shape having two parallel long edges extending between two short edges, the long 150012 / 2 -13- edges making an angle of β with the major plane.

4. The cutting insert according to claim 1, wherein β = 2°.

5. The cutting insert according to claim 2, wherein the projecting abutment surface comprises three flat portions, two outer flat portions with an inner flat portion therebetween, each outer flat portion extending from a respective short edge to the inner flat portion.

6. A milling cutter comprising: at least one cutting insert in accordance with claim 1 ; and a cutter body having at least one insert pocket in which the at least one cutting insert is retained, the at least one insert pocket comprising adjacent side and rear walls generally transverse to a base, the rear wall being generally convex; the side wall being provided with an axial location surface that abuts a given minor side surface of the at least one cutting insert at a given axial abutment region; the rear wall being provided with two tangential location surfaces, located on either side of a central region of the rear wall, a first of the two tangential location surfaces abuts a first tangential abutment surface located on the at least one cutting insert, a second of the two tangential location surfaces abuts a second tangential abutment surface located on the at least one cutting insert.