CA1229220A - Cutting tool and insert therefor - Google Patents

Abstract

ABSTRACT

A cutting tool, for e?ample a milling cutter, capable of omni-directional machining of a workpiece as disclosed. In a preferred form, the cutting tool is embodied as a ball nosed end mill having a cylindrical shank terminating in a spherically shaped cutting end with recesses shaped for receipt of at least two indexable cutting inserts, each insert mounted in lay-down fashion, and providing a portion of an effective overall arcuate cutting edge, the cutting zones of each insert overlapping each other. Each insert has the form of an equilateral polygon bounded by planar flanks, each flank intersecting a convex portion of a major face of an insert to form an arcuate cutting edge. The convex major face portion forms the clearance face and the planar flank portion the rake face for each associated arcuate cutting edge.

Description

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CIJTTING TOOL AND INSERT TIIE:REFOR
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U/\ ICGROUNI~ Old INV~Nl10i.~1 it field of toe Invc!~tloll:

Iota! i1~velllion relcltes L,cnercllly TV tile Held ox chip Eurlt~ ;, gutting tools utilizing inclexable cUtlillg bits or inserts More partlc-llarly, tile illvelltion pertains to a at USE t lo lo lvil~l, at cyllllclrlcEll slick c11~Ci IT~ecllclllically lleltl, 10 Irlllltil~le easily Cllttilll~ inserts on jar spl~ericEll quietly end will Alcott cuttlnL~ easels for forming a recluses cut )tsclil)lit~ r toe I to 1 L5clll nosed ellcl mills Err kllowll Which can perEorln ornni-tlirectional quietly end contourirlg of irregular shapes on work pieces Ogle class of such prior art fools Iris quietly easels in~e~rcllly [ormecl wltl1 tile cutter clue or celr~entecl carbide quietly elemellls brazed onto lllC' Klutz' booty. Sclcll cJeslC~lls reclUile consitlerable man~liacturill~ erupt end their cutting;, easels can be refound or sllarpeneci only Whitehall Z0 corlsiclerable tli~Iiculty end With tile recluirecl Use of suitable grinclin~ machines Aster re~rinclillg, a loss of clial11etricai size occurs, necessitation;, careful macllille acijustments wren tic Ironical Idol is retulllecl to selvict! 'Isles tools with Intel ally Iolrrletl cutting blushes are ox a sunnily material anti tllelefole are lilniteti to use on certain narrow cottagers of worl~plece materials Ogle suckle Lyle brazed tool is tiisclosetl In U S

I'atenl No, 11,132,rl93 -Isles, Issued Jan~lEIl y 2, 1979.

Jo sequent class owe clown Bali nicety ITllllS Eta en inclexable Quietly;' clelllellts or illserts Scull tools fire (llsCIosetl~ or exEllnlJle~ in Us, i~Ec~tent No- 75,~9G
- lclslllllalTli et at Issued Novel11b~l Z7, 1979 allot U-S- I.'atenl No, ll,252~1100 - Ml7,uno of 311 Elm issllecl l~t~bl hall y 2~1, 19c~ 1 . I tie l<iSIIilIEllrli t t Eli I isle t~llCt~ cliscl(7ses a solute With El Colossal Lotte! old I t~llj,El Jill;, SUI~[EJCC~ wllilt~ toll h~llzlll1o it .11- pal~l1l leaches il1sel to nloulltetl ill a cyclical stanch pOsitioll With equal il1sert~s Mueller tlimemr;loll Iyln;~
It ISSUE lull tot t! Ells Ct~iVilll, -It'll Elk t~llt~lEc~t~ Solute Ells Mix lo . , Jo et at. specifically leaches noll-overlappinp~ of the cutting Jones of each insert employed in the cut. Milling cutters with inserts moulltecl in stand-up position require more mounting room thereby loading to lowered rigidity of the cutter body. Additionally, insole is in Lowe stay us) InoLll)ting alr-1ngell~e1-l ale subjected to Inaximurrl cutting Forces 5 through a minimum dimension of the insert body material. Cutters employing inserts with non-planar Rowley faces produce narrower, stringy chips of non-uniform width which ate snore prone to chip cloggilll7 conditions in the cut.

SUMMARY OF Al lNVl~NTlOI~I
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no improved cutting tool for generating arcuate profiles is disclosed and US ernbocliecl as a bclll nosed end hill having n cylindrical shawl< terminating in a spherically shaped quietly end. rho CUttillg end includes at least two cavities shaped for lay-down mounting receipt of first and second cutting inserts, each insert presenting an 15 acolyte cutting edge with a radius of curvature equal -to the radius of the cut to be taken. The arcuate cutting edge of the first insert extends radially outwardly from the longitudinal axis of the Schick. Lowe cutting zone ox the second insert overlaps that ox the first insert. I ash insert has first and second major faces in the form of equilateral polygons connected by planar flank surfaces. The first major face includes convex 20 portions intersecting each flank< surface in an acute angle to form identical arcuate cutting edges along each stale of the polygon. The second major face is planar and intersects each flank< surface in an obtuse angle. Mounting the fully index able inserts in the so-called "Jay-down" or "on-edge" configuration results in placing the majordimension of the insert body behind the active cutting edge to enable the insert to better 25 withstand the creating forces imposed on it. Additionally, lay-down insert mounting results in shallower rno-1nting cavities in the tool body, thereby providing added strength and rigidity there to .

l5RI~F DESCRIPTION OF THY DRAWING
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the objects and features of the invention will becorne-apparent from a reading ox a detailed description of a preferred embodiment, Tulane in conjunction with the drawing, in which:

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Fig. 1 is a perspective view of a ball nosed end mill designed in accordance with the principles of thy invention;
Fig. 2 is a plan view of the end mill of Fig. 1 taken normal to the lon~ilu<lin.ll axis of Cue tool shank;
lug. 3 is a plan view of the end mill of Fig. 1 taken parallel to the longitudinal axis of the tool shawl< from the CUttillg end;
Fix is a sectional view taker along line I of Fig. 2;
Fig. 5 is a top plan view of an index able cutting insert designed in accor-l.lllce with the pi inciples of toe invelltiol);
Pig. G is a front view of the insert of Pig. S;
Fig. 7 is a side view of the insert of Fig. 5;
lug. PA is a perspective view of the insert of Fig. S; end lucks. 8 and 9 are respectively top and front views owe an alternative body of an insert designed in accordance with the principles of the invention.
DWIGHT ED DESCRIPTION

With reference to jigs. I a ball nosed end mill 100 has a substantially cylindrical shank 101 terminating in a substantially spherical cutting end 110 and a mounting end (not shown) Welch can be fashioned in any of a number of conventional shapes for retention by a machine spindle or tool mounting device.
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In the spherical cutting end 110 are positioned mounting cavities for Index able cutting inserts muon ted in so-called "lowdown" or "on-edge" con figuration -i.e.
with a major dimension of the insert Icing rearwardly of the active cutting edge whereby a major face of the insert acts as a clearance face, while the minor Elan< faces serve as rake or chip engaging surfaces for their respective cutting edges. In the embodiment illustrated, the ball nosed end mill 100 has three cavities for mating lay-down receipt of three inserts 10, 11 and 12. this invention contemplates the use of at least two cutting inserts. Ike number of inserts depend on the size of the inserts used along with the desired radius of the arcu.lte ploEile to be maclljnecl in a worlcpiece in a tool of the invention. Additionally, peripheral inserts (not shown) could be mounted along a portion of the cylindrical shawl< to extend the depth of cut taken by the disclosed cutting tool.

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Chip gullet 102 is provided adjacent arcuate cutting edge 12c of insert 12, while clip gullet 103 lies adjacent arcuate cutting edges 10c and 11c of inserts 10 and 11, respectively. edges 10c, tic and 12c all lie in substantially the same axial plane.
the CUttillg one ox il)sel-t 12 overlaps bottle those of irlsert 10 end insert 11. this is best 5 seen with reference to Fig. 2 where a projection of insert 12 is shown in dashed phantom lines and is desigtlateci 12p. In this manner, inserts 10, 11 and 12 cut a continuous arc-lclte profile having a substantially uniforln racli-ls - i.e. a substantially hemispherical profile with no gaps due to insert spacing.

The radially innermost corner aye of insert 10 intersects or extends just beyond longitudinal axis lo of the cutter body shank. This provides strength and shear cultinls action at the norlnally vulllcrclble center cutting portion of the too.
The radially innermost end of cutting edge 12c lies, as seen from Fig.; 2, at an angle at from axis lo, and angle at is less than angle a, the angle of the radially outermost end of cutting edge 10c with respect to axis Al Hence, the cutting zone of insert 23 overlaps tilt of insert 10 by the angle b - i.e. a _ at l b. Ire purpose of this overlap is twofold. First, it prevents leaving of cusps on toe world surface gel)eratscl, end second, tool life is enhanced. In the area of overlap (angle by, inserts 10 and 12 are subjected to only one half the feed rate encountered where no overlap occurs (angle at).
With no overlap, i.e. with angle at equal to angle a, a minute amount of insert corner wear would cause the cutter body to impact the work surface.

Overlap b is equal to the angle created by lines extending from the center point 20 of the hemispherical cutting eons 110 over the respective corner radii of insert 10 and of insert 12 projected 180 out of its mounting position as insert 12p. The magnitude of angle b is dependent pun three factors: insert inscribed circle diameter, inter t corner r azaleas, end cut t let booty clime ton .

the stale Celsius of inserts 10, 11 and 12, for example surface 10R ox insert 10 lug. 2), are commonly rerolled to as Elarlks. I-lowever, when the inserts are mounted in lay-down fashion as shown, flank surface 10R becomes the chip engaging or Rowley face. the rays faces of the inserts of this involution are Slat planet surfaces. In I

operacioll~ chips are generated having substantially uniform thickness and flow freely across the unlestlictecl planar rake faces end are expelled via chip gullets 102 end 103.
Arcuate Rowley faces, on the other hand, tend to result in thinner, stringy chips more prone Lo) Lowe In Fig. 4 it will be apparent that by positioning insert 10 angularly inwclrclJy towalcls toe tool axis, C-lttillg clearance lo is obtained. The insert's supporting cavity surface 41 is at a relatively shallow depth, approximately equaling the insert's Thickness, tl)Cleby le.lVilll!, s~ll)stcll~ial lass in body 110 surrounclill~ the insert mounting cavities. Tilts results in strong insert support and cutter body stiffness. The difference between the cutting radius SUE and tool body radius 13R equals cutter body clearance 45.

issue, as seen from Fig. lo, each insert has a countersunk cavity for receipt of an appropria tell headed muon tying screw member I which threadingly engages a tapped hole in booty pox lion 110.

A preferred insert is sol forth ill I its. 5, 6, 7 and I Insert 5 presents three identical arcuate cutting edges 51 and has the form ox an equilateral triangle. It will be apparent Jo those skilled in the art that this invention is not limited to triangular inserts. Any equilateral polygonal shape can be utilized.

The equilateral wrangler shape of insert 5 is formed by three planar flanks Sly, a planar bottom mounting surface SO and a major top cage inducting three arcuate cylindrical surfaces A, B and C. Surfaces A, 13 and C have common boundaries at lines 50, 56 end 58. 'I've intersection of surfaces A, 13 and C with a corresponding adjacent flank surface Al provides three iclenCical arcuate cutting edges 51 each having gutting radius R (Fits. PA).

Surfaces /\, I, and C have respective axes of generation generally transverse to their associated cutting edges end exCendlllg at an acute angle 70 to a plane parallel to the plalle Ox Sirius 55. A preIerrecl range of angle 70 runs from about 5 degrees to about 20 degrees and the value of angle 70 is governed by tile cutter body diameter. Tile larger the cutter body diameter, the smaller is angle 70.

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Faces Al are sloped inwardly Erwin cutting edges 51 to bottom face 55 such that each Rowley face Al intersects its associated surface A, En or C in an acute angle end such that each Rowley face intersects planar surface 55 in an obtuse angle.

PA central hole 53 having countersunk portion 52 is provided for receipt of a suitable insert mounting screw.

Planar surfaces Al function as the rake faces while cylindrical surfaces A, I C EUnC'ti'.)l'l as clecllclllce or relict surfaces for their respective cutting edges when 10insc rut 5 is mounted to body portion 110 of the ball nosed end mill 100 of Figs. 1-4.

no alternative insert designed In accordance with the invention is shown in lugs 8 and 9. Insert 8 has an equilateral triangular shape bounded by three planar flank surfaces 8G sloping inwardly from major top surface 80 to bottom planar mounting 15 surface 83. In this alternative embodiment, top surface 80 Is spherical an intersects each flanlc surface 82 to form three identical arcuate cutting edges 81. A central aperture I with countersunk portion lo is provided for receipt of a suitable mounting screw. When used with the gutting tool of Figs. lo flat surfaces 86 serve as race faces for their respective cutting edges, and spherical surface 80 serves as a clearance or 20 relief surface.

It is to lye understood that specific embodiments of this invention have been described for the sake of example only. Other alternative arrangements within the scope ox the appended claims will be apparent to those skilled in the art.

Claims (13)

WHAT IS CLAIMED IS:

1. A cutting tool comprising:
a cylindrical shank terminating in a spherical cutting end, the cutting end including first and second indexable cutting inserts each comprising first and second equilaterial polygonal major faces, three identical planar flank surfaces forming the sides of the polygon with two of the flank surfaces intersecting at each corner thereof, the first major face including upwardly sloping convex portions intersecting each flank surface to form identical arcuate cutting edges along each side of the polygon, said convex portions including corresponding clearance face portions extending along said first major face rearwardly from said cutting edges, said second major face intersecting each flank at an obtuse angle forming identical rake edges; first and second mounting cavities shaped for respective receipt, in lay-down fashion of the first and second indexable cutting inserts; and means mounting the first and second indexable cutting inserts respectively to the first and second mounting cavities, the first cavity oriented such that an active arcuate cutting edge of the first insert placed in lay-down fashion in the first cavity will extend radially outwardly from a corner arc of the insert passing through a longitudinal axis of the shank, and the second cavity positioned on the cutting end with respect to the first cavity such that the second insert placed in lay-down fashion therein presents an active arcuate cutting edge whose cutting zone partially overlaps that of the first insert's cutting edge and extends the arcuate cutting action of the first insert substantially in a common plane passing through the shank axis, thereby enabling the cutting tool to generate an arcuate cut of substantially uniform radius.

2. The cutting tool of claim 1 further comprising first and second chip gullets respectively intersecting the first and second cavities such that chips formed by the first and second active arcuate cutting edges are directed by the planar flank surfaces into the first and second chip gullets.

3. The cutting tool of claim 1 wherein said rake edge forms an angle with respect to an imaginary plan drawn from the cutting edge to a center point on the spherical cutter's rotational axis.

4. The cutting tool of claim 1 wherein said sloped convex portions form a maximum angle with respect to a plane parallel with said second major face so to reduce contact between said clearance face portion and work surface during radial cutting.

5. The cutting tool of claim 4 wherein said maximum angle is between about 5 degrees to about 20 degrees.

6. The cutting tool of claim 4 wherein the second major face of each insert is planar and rests upon a correspondingly planar mounting floor of its respective mounting cavity.

7. The cutting tool of claim 6 wherein each planar mounting floor is intersected by a threaded cavity in the spherical cutting end for receipt of an insert mounting screw.

8. The cutting tool of claim 7 wherein said first and second major faces are minimally spaced at the intersection of said flank surfaces.

9. A cutting tool comprising:
a cylindrical shank terminating in a spherical cutting end, the cutting end including first and second indexable cutting inserts each comprising first and second equilateral polygonal major faces, three identical planar flank surfaces forming the sides of the polygon with two of the flank surfaces intersecting at each corner thereof, the first major face including upwardly sloping convex portions intersecting each flank surface to form identical arcuate cutting edges along each side of the polygon, said sloped convex portions form an angle with respect to a plane parallel with said second major face between about 5 degrees to about 20 degrees, said convexed portions including corresponding clearance face portions extending along said first major face rearwardly from said cutting edges, said second major face intersecting each flank at an obtuse angle forming identical rake edges, said rake edges form an angle with respect to an imaginary plane drawn from the cutting edge to the center point on the spherical cutters rotational axis, first and second mounting cavities shaped for respective receipt, in lay-down fashion of the first and second indexable cutting inserts, and means mounting the first and second indexable cutting inserts respectively to the first and second mounting cavities, the first cavity oriented such that an active arcuate cutting edge of the first insert placed in lay-down fashion in the first cavity will extend radially outwardly from a corner arc of the insert passing through a longitudinal axis of the shank, and the second cavity positioned on the cutting end with respect to the first cavity such that the second insert placed in the lay-down fashion therein presents an active arcuate cutting edge whose cutting zone partially overlaps that of the first insert's cutting edge and extends the arcuate cutting action of the first insert substantially in a common plane passing through the shank axis, thereby enabling the cutting tool to generate an arcuate cut of substantially uniform radius.

10. The cutting tool of claim 9 further comprising first and second chip gullets respectively intersecting the first and second cavities such that chips formed by the first and second active arcuate cutting edges are directed by the planar flank surfaces into the first and second chip gullets.

11. The cutting tool of claim 10 wherein the second major face of each insert is planar and rests upon a correspondingly planar mounting floor of its respective mounting cavity.

12. The cutting tool of claim 11 wherein each planar mounting floor is intersected by a threaded cavity in the spherical cutting end for receipt of an insert mounting screw.

13. The cutting tool of claim 12 wherein said first and second major faces are minimally spaced at the intersection of said flank surfaces.