Cutting insert having cylindrically shaped side surface portions

A double-sided reversible and indexable cutting insert has identical opposing first and second end faces and a peripheral side surface extending therebetween. A clamping through-bore extends between, and opens out to, the first and second end faces. The cutting insert has a median plane between the first and second end faces, and a through-bore axis extending perpendicularly through the median plane. The cutting insert also has a Y-fold rotational symmetry about the through-bore axis. The peripheral side surface has Y major side surfaces and Y minor side surfaces, each minor side surface interconnecting two adjacent major side surfaces. Each minor side surface is a section of a single cylindrical surface having a given radius, the given radius being greater than a minor side surface distance of each minor side surface from the through-bore axis.

FIELD OF THE INVENTION

The present invention relates to a double-sided, indexable and reversible cutting insert for metal cutting operations, in general, and for 45° shoulder face-milling operations, in particular.

BACKGROUND OF THE INVENTION

Such cutting inserts are generally provided with curved corners. U.S. Pat. No. 6,196,771 discloses a cutting insert having first and second side faces. Each side face includes a pair of minor cutting edges at each corner of the insert. The two minor cutting edges are located on two opposing sides of a corner bisector B, together forming an obtuse inner angle of about 170°, and are mirror-imaged about the bisector B. Two major cutting edges intersect respective ones of the minor cutting edges whereby each major cutting edge and its associated minor cutting edge together form a cooperating pair of cutting edges. There are two such cooperating pairs at each corner of each side face, whereby the insert has at least sixteen cooperating pairs. During a milling operation the insert is oriented so that only one cutting corner engages a work-piece, and only one of the cooperating pairs of cutting edges of that cutting corner is operative. Only half of the major cutting edge of each cooperating pair is effective. The minor cutting edge of the operative cooperating pair of cutting edges constitutes a wiper edge, by being arranged parallel to the surface of the work-piece, that is perpendicularly to an axis of rotation of a milling tool in which the cutting insert is mounted.

A drawback of these known inserts is that the minor cutting edge of each cooperating pair has a constant setting angle during the machining of the work-piece. Positioning deviation of the cutting insert relative to a cutter body of a milling cutter in which the cutting inserts are mounted, or axial bending of the milling cutter (which may occur under demanding machining conditions) may result in either a wiper corner adjacent the main cutting edge, or a wiper corner distal the main cutting edge of the cooperating pair cutting into the work-piece face, and thereby marring the face of a work-piece being milled.

U.S. Pat. No. 5,032,049 discloses an indexable cutting insert for face milling of engine blocks of cast iron. The insert has two opposing, substantially identical, generally square-shaped upper and lower surfaces which are perpendicularly connected by four side surfaces. Two adjacent side surfaces connect to each other via a smoothly rounded corner. The radius of the corner R is ¼ to ⅛ of the insert, and therefore the setting angle gets close to zero degrees during machining of the engine block when the insert gets close to the border line of the work piece. The corner of the cutting insert serves in machining the shoulder of a work-piece, as well as in finishing the face of the work-piece during the last pass of the milling cutter.

It is an object of the present invention to provide an improved cutting insert. This object is attained with the subject matter in accordance with the claims.

SUMMARY OF THE INVENTION

In accordance with the present invention there is provided a double-sided reversible and indexable cutting insert comprising identical opposing first and second end faces and a peripheral side surface extending therebetween. A clamping through-bore extends between, and opens out to, the first and second end faces. The cutting insert has a median plane extending between the first and second end faces and a through-bore axis extending perpendicularly through the median plane. The cutting insert has a Y-fold rotational symmetry about the through-bore axis. The peripheral side surface comprises Y major side surfaces and Y minor side surfaces, each minor side surfaces interconnecting two adjacent major side surfaces. Each minor side surface is a section of a single cylindrical surface having a given radius; the given radius is greater than a minor side surface distance of each minor side surface from the through-bore axis.

Preferably, each minor side surface has an associated minor surface axis extending parallel to the through-bore axis.

Further preferably, in an end view of the cutting insert, the minor side surface subtends a minor central angle of less than 15°.

Yet further preferably, the minor central angle is less than 5°.

Generally, the peripheral side surface meets the first and second end faces each at a continuous peripheral edge. Each peripheral edge comprises Y major edges and Y minor edges. Each major edge is formed at an intersection of an associated major side surface and a respective one of the first and second end faces. Each minor edge is formed at an intersection of an associated minor side surface and a respective one of the first and second end faces, and interconnects two adjacent major edges.

If desired, each minor edge extends between a raised corner, formed at a meeting of the minor edge with a preceding major edge, and a lowered corner, formed at a meeting of the minor edge with a following major edge. The raised corner is disposed farther from the median plane M than the lowered corner.

If further desired, the through-hole axis and the minor side surface axis define a bisector plane bisecting the minor side surface. The bisector plane and the median plane define a minor axis about which the minor side surface has 180° rotational symmetry.

Generally, two adjacent major median lines formed at intersections of the median plane with each of two adjacent major side surfaces, respectively, meet at an apex located on the minor axis of the minor side surface interconnecting the two adjacent major side surfaces.

Typically, the median plane intersects each minor side surface at a minor median line.

Preferably, each major median line is a straight line.

Further preferably, the minor axis bisects an internal major angle defined by the two adjacent major median lines.

If desired, each major side surface comprises a median surface extending transversely away from a major median line formed at an intersection of the median plane with the major surface, towards the first and second major edges.

If further desired, each major side surfaces comprises first and second support surfaces extending from the median surface towards the respective one of the first and second end faces.

If yet further desired, each major side surfaces comprises first and second primary relief surface extending transversely the major edge adjacent the respective one of the first and second end faces towards the support surface.

Preferably, the first and second support surfaces form each an acute internal support angle with the median plane, the first and second relief surface form each an acute internal relief angle with the median plane, and the internal support angle is equal to, or greater than, the internal relief angle.

Further preferably, the internal relief angle is largest adjacent the lower corner and smallest adjacent the raised corner of the major edge.

Generally, the minor side surface is perpendicular to the median plane.

If desired, in a major side view of the cutting insert, a major side line parallel to the major median line and passing through the lowered corner is longer than the major median line.

If further desired, in a minor side view of the cutting insert, a minor side line parallel to the minor median line and passing through the lowered corner is shorter than the minor median line.

The present invention provides the following preferred advantages:

Because the entire length of each minor edge constitutes a wiper edge, positional deviation of the cutting insert in the insert pocket may not lead to reduced cutting performances, so that the wiper edge may be able to continue machining the work-piece face, substantially without compromising the smoothness of the work-piece face and to the quality of the finished product;

Peripheral surfaces of cutting inserts are often ground to reduce positioning deviation and to achieve a high quality finished product; however, the cutting insert of the present invention is capable of reducing the effects of positional deviation without necessitating grinding of the peripheral side surface.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT

Attention is first drawn toFIG. 1. A cutting insert20in accordance with the present invention is secured to a cutter body22of a rotary milling cutter24by a clamping screw26. The cutting insert20is of a double-sided, indexable and reversible type, and is generally adapted to perform face and 45° shoulder-milling a work-piece (not shown).

Attention is now drawn toFIGS. 2 to 5. The cutting insert20has identical and opposing first and second end faces28,30. In an end view of the cutting insert20, best shown inFIG. 3, each of the identical first and second end faces28,30is of a general form of a square having curved corners. A peripheral side surface32extends between the opposing first and second end faces28,30. The cutting insert is of a negative type and therefore the peripheral side surface32is generally perpendicular to both end faces28,30. The peripheral side surface32has four identical major side surfaces34of a generally parallelogrammatic shape, and four identical minor side surfaces36, also of a general parallelogrammatic shape. Each minor side surface36interconnects two adjacent major side surfaces34.

A given major side surface34has 180° rotational symmetry about given major axis I associated therewith and extending generally perpendicularly therethrough. Similarly, a given minor side surfaces36has 180° rotational symmetry about given minor axis J associated therewith and passing generally perpendicularly therethrough. The major and minor axes I, J are co-planar and intersect at an insert center C to define an insert median plane M. A given major axis I defines an axis angle α of 45° with a given minor axes J.

The cutting insert20is provided with a clamping through-bore38extending between, and opening out to, the first and second end faces28,30. The clamping through-bore38is adapted for receiving the clamping screw26. The clamping through-bore38has a through-bore axis T extending perpendicularly to the median plane M through the insert center C, so that the first and second end faces28,30each have 90° rotational symmetry about the through-bore axis T.

The first and second end faces28,30have each four raised corners40and four lowered corners42. The raised corners40of each of the first and second end faces28,30lie in a first and second end planes EF, ES, respectively. The median plane M is parallel to, and lies midway between, the first and second end planes EF, ES. The lowered corners42are closer to the median plane M than the raised corners40.

The major and minor side surfaces34,38are each intersected by the median plane M to form major and minor median lines LI, LJ, respectively. As best shown inFIG. 4, a major side lines SIlying on the major side surface34and extending from the lowered corner42parallel to the major median line LIis longer than the major median line LI. As best shown inFIG. 5, a minor side lines SJlying on the minor side surface and extending from the lowered corners42parallel to the minor median line LJis shorter than the minor median line LJ.

As is best shown inFIG. 3, imaginary extensions of the major median lines LI′, LI″ of two adjacent major side surfaces34meet at an apex A to define an internal corner angle μ. The apex A lies on the minor axis J associated with the minor side surface36extending between the adjacent major side surfaces34. In a particular embodiment, the corner angle μ is a right angle. A bisector plane B passes through the through-bore axis T and the respective minor axis J extending perpendicularly to the median plane M to bisect the corner angle μ.

Each minor side surface36is a section of a single cylindrical surface extending transversely to the median plane M. Each minor side surface36has a minor surface radius R extending thereto from an associated minor surface axis N lying in the associated bisector plane B parallel to the through-bore axis T. The minor side surface36intersects the associated minor axis J at a minor surface distance D from the insert center C. Generally, the minor surface radius R is two to twelve times as large as the minor surface distance D and more preferably is between three to six times as large. In the particular embodiment shown, the minor surface radius R is approximately four times greater than the minor surface distance D. The minor side surfaces do not all have to conform to the same cylindrical surface. The minor side surface36subtends an acute minor central angle ν, preferably of less than 15°. In a non-binding example, the minor central angle ν is approximately 4° 30′.

The first and second end faces28,30each intersect the peripheral side surface32at a peripheral edge44. The peripheral edges44have each four major edges46associated with the adjacent major side surface34, and four minor edges48associated with the adjacent minor side surface. In the embodiment shown, a given major edge46extends between given lowered corner42and given raised corner40, and a given minor edge extends between given raised corner40and given lowered corner42. Each of the major and minor edges46,48may constitute major and minor cutting edges, respectively. The particular embodiment has four major cutting edges and four minor cutting edges associated with each of the first and second end faces28,30, for a total of eight major and eight minor cutting edges.

The first and second end faces28,30have each a peripheral rake surface50extending in an inward direction of the cutting insert from the respective peripheral edge44towards an end abutment surface52. The end abutment surfaces52may be generally flat, and substantially parallel to each other and to the median plane M. In an end view of the cutting insert, the end abutment surfaces52has a general form of a square having beveled corners, which is rotated relatively to the respective end face28,30. The peripheral rake surfaces50comprise each four major rake surfaces54associated with the major edges46and four minor rake surfaces56associated with the minor edges48. The major and minor rake surfaces54,56have major and minor rake widths WI, WJ, respectively, defined in directions transverse to the associated major and minor edges46,48, respectively. The major rake width WIincreases from a minimal major rake width adjacent the lowered corner42to a maximal major rake width adjacent the raised corner40of the respective major edge46, while the minor rake width WJdecreases from a maximal minor rake width adjacent the raised corner40to a minimal minor rake width adjacent the lowered corner42of the respective minor edge48.

Peripheral rake steps58are formed between the peripheral rake surfaces50and the respective end abutment surface52. The rake step58extends from the end abutment surface52transversely to the median plane M to a step height HS(seeFIG. 6). The step height HSincreases gradually from a minimal step height adjacent the lowered corner42to a maximal step height adjacent the raised corner40. In the particular embodiment, the minimal step height is zero.

As seen inFIG. 6, the major side surfaces34comprise each first and second primary relief surfaces62,64adjacent each of the first and second end surfaces28,30, respectively. Each of the first and second primary relief surfaces62,64extends from the adjacent major edge46towards the major median line LI. First and second side abutment surfaces66,68extend along each major side surface34away from the first and second primary relief surfaces62,64, respectively, towards a substantially planar side median surface70extending therebetween generally perpendicularly to the median plane M.

As seen inFIGS. 6 and 7, in each major cross section of the cutting insert, taken in a plane generally perpendicular to a given major side surface34, the first and second primary relief surfaces62,64may be straight, or they may be convexly curved. The major rake surfaces54may be straight, or they may be concavely curved. First and second primary relief lines FF, FStangent to the first and second primary relief surfaces62,64, respectively, at the respective major edge46form each an acute interior relief angle φ with the median plane M. The relief angle φ may be constant or may vary along the major edge. The variation of the relief angle φ may be in accordance to any desired definition. The first and second side abutment surfaces66,68form each an acute side abutment angle φ with the median plane M. The side abutment angle α may be generally constant along the major side surface34, and is generally equal to, or greater than, the relief angle φ. In the particular embodiment, the primary relief angle φ is equal to the side abutment angle σ adjacent the lower corner42, and decreases along the major edge46towards the raised corner40in such a way so as to define a helically twisting primary relief surface62,64. As is best shown inFIG. 8, in each minor cross section of the cutting insert20, taken in a plane generally perpendicular to a given minor side surface36, the minor side surface36is perpendicular to the median plane M.

Attention is now drawn toFIGS. 9 to 12. The milling cutter24is rotatable about an axis of rotation X defining a front-to-rear direction and a direction of rotation Z, and has four cutting inserts20in accordance with the present invention mounted each in an insert pocket72provided at a cutter front end74of the cutter body22. It should be noted that directional terms appearing throughout the specification and claims, e.g. “front”, “rear”etc., (and derivatives thereof) are for illustrative purposes only, and are not intended to limit the scope of the appended claims. The insert pocket72comprises adjacent inner and outer walls76,78, generally transverse to a pocket base80. The outer wall78is provided with an outer location surface82and the inner wall76is provided with spaced apart front and rear location surfaces84,86located on either side of a central recessed region88of the inner wall76. The pocket base80is provided with a threaded bore90for receiving the clamping screw26in order to secure the cutting insert20in the insert pocket72.

When the cutting insert20is secured in the insert pocket72, one of the first and second end faces28,30, e.g., the first end face28, is positioned to face generally tangentially forwardly in the direction of rotation Z of the milling cutter, and constitutes an operative end face92. The second end face30constitutes a supporting end face (not shown), and is positioned with the respective end abutment surface52abutting the pocket base80. A front outer major edge96of the operative end face92constitutes an operative major cutting edge98, while a front minor edge100of the operative end face92constitutes an operative minor cutting edge102associated with the operative major cutting edge98. The first side abutment surface66of an inner rear major side surface (not shown), located adjacent the operative end face92and opposite the operative major cutting edge98, abuts the front and rear location surfaces84,86. The first side abutment surface66of an outer rear major side surface (not shown) located adjacent the operative end face92and adjacent the operative major cutting edge98abuts the outer location surface82of the insert pocket72.

The cutting insert20and the milling cutter24shown in the figures may be used to face-mill a work-piece (not shown), machining a 45° shoulder on the work-piece face, and therefore the cutting insert20is located in the insert pocket72so that, when the milling cutter24is rotated about the axis of rotation X, the operative major cutting edge98describes a frustoconical envelope having a generator line G forming a generator angle γ of generally 45° with the axis of rotation X. In order to provide a high-quality work-piece face relatively free from machining marks or blemishes, the operative minor cutting edge102functions as a wiper edge106. The wiper edge106is adapted to machine a substantially flat face on the work-piece at 90° to the axis of rotation X of the milling cutter24. The operative major cutting edge98forms a positive major axial rake angle γA with a radial plane P passing through a raised corner40thereof and through the axis of rotation X of the milling cutter24(best shown inFIG. 12).

The cutting insert20shown in the figures may be indexed in the insert pocket72about its through-hole axis T in four steps of 90°, each indexing step positioning a fresh major edge46as the operative major cutting edge98. The cutting insert20may additionally be reversed so that the first end face28may become the supportive end face (not shown) and the second end face30may become the operative end face92, providing four additional fresh major edges46which can be indexed to the position of the operative major cutting edge98. Generally, each of the major and minor edges46,48constitutes “full effective” cutting edges, i.e., the entire extent of each of the major and minor edges is capable of performing machining operations in a given position of the cutting insert20.

The cutting insert20in accordance with the present invention is preferably manufactured by form-pressing or injection molding and sintering of metallurgical, ceramic or cermet powders. The peripheral side surface32of the cutting insert20may be ground to increase positioning accuracy thereof in the insert pocket72, which may be desirable in milling a smooth, high-quality face of the work-piece. However, in accordance with the present invention, it may not be necessary to grind the peripheral side surfaces32while maintaining desired smoothness and quality of the milled face of the work-piece.

Attention is directed toFIGS. 13 and 14, showing the cutting insert in accordance with the present invention machining the work-piece face108while being secured in the milling cutter in a correct position (FIG. 13) and in a deviated position (FIG. 14). In the correct position (FIG. 13), the wiper edge106of the cutting insert machines the work-piece face108at a first wiping region K1located on a first wiper portion110extending between the bisector plane B and the associated operative major cutting edge98. However, even when mounted in the deviated position (FIG. 14), the wiper edge106still machines the work-piece face108, albeit at a second wiping region K2located on a second wiper portion112extending from the bisector plane B away from the operative major cutting edge98.

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.