Toolholder and cutting insert used therein

A toolholder at least one cutting insert mounted within a pocket about the peripheral wall of the cutter body. The body includes a pocket having an angled retention ledge which provides acts, in conjunction with a fastener, to securely retain an insert mounted therein. The insert has an angled edge which conforms with and works in conjunction with the toolholder pocket.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to toolholders and inserts used therein and, more specifically, to a milling cutter having angled pockets with a chip clearance groove to permit a greater number of inserts to be mounted within the cutter and the inserts used therein and furthermore to a toolholder having a pocket configured to secure an insert and to the insert secured therein.

2. Description of Related Art

A goal of most metalworking operations is to perform a given machining task in the least amount of time and in a manner that will not result in premature tool failure. As an example, in a milling operation, it is well known that the cutting forces upon, and the tool wear of, individual inserts within a milling cutter will be diminished if the cutting load is evenly distributed among many inserts in the milling cutter. However, in the past, milling cutter body designs have limited the maximum number of cutting inserts to be placed in the body. Utilizing a cutter with the maximum number of inserts is especially important for the machining of cam lobes on camshafts of internal combustion engines.

U.S. Pat. No. 5,820,308 is directed to a milling cutter having a plurality of on-edge inserts mounted about the periphery of the cutter. The orientation of these on-edge inserts limits the number of inserts that will fit within the cutter body.

Additionally, securing inserts within the pockets of a milling cutter or other toolholder in an efficient manner is always a goal in the metalworking industry.

SUMMARY OF THE INVENTION

The present invention is directed to a toolholder comprising a cutter body rotatable about a central axis, a peripheral wall on the cutter body, and insert pockets located in the peripheral wall. Each pocket is spaced from an adjacent pocket by a lug and each pocket has support surfaces including a bottom surface adapted for positioning a rectangular insert within a predefined rectangular envelope within the pocket. Each rectangular envelope has a front and back and four sides therebetween, including a top side, a bottom side and a radially inward side. Each lug has a radial width, a front face extending upwardly from the pocket bottom to the top of the lug, an axial face extending downwardly from the top of the lug to a height below the top of the lug; and a rear face extending from the axial face downwardly to the bottom surface of an adjacent pocket. The support surfaces of the pocket are defined by the lug front face, the bottom surface, and a pocket wall positioned radially inwardly from the peripheral wall and connecting adjacent lugs. The lug axial face is sloped downwardly across the entire lug width from the top of the lug to the lug rear face, thereby providing a chip clearance groove across the entire width of the lug. The lug front face extends over the back of the insert envelope. Furthermore, at least a portion of the bottom surface of the pocket forms a first angle with the front face of the lug to define a first retention ledge and wherein the first angle is acute.

The invention is further directed to a toolholder assembly comprising a toolholder as described above and including inserts within each pocket of the toolholder, which may be a milling cutter.

The invention is not limited to a milling cutter but includes any toolholder having a pocket with features that promote secure retention of a cutting insert within the pocket utilizing a retention ledge within the pocket as described herein.

The invention is further directed to a cutting insert adapted for use within the subject toolholder.

DETAILED DESCRIPTION OF THE INVENTION

For purposes of describing the subject invention, the pockets of a milling cutter will be discussed with the understanding that such a pocket and the insert associated therewith may be utilized for a variety of other toolholder/insert combinations. As an example, the features of the pocket described hereinafter may be applied to a toolholder for a turning operation, threading operation, facing operation, etc. wherein the toolholder secures at least one cutting insert therein.

Directing attention toFIG. 1, a toolholder, or milling cutter10, is illustrated having a cutter body12rotatable about a central axis14. A plurality of cutting inserts16may be mounted about the peripheral wall18within pockets20(FIG. 2) therein. The cutting inserts16are identified as lay-down inserts.

A lay-down cutting insert is one where the cutting face of the insert is located on the largest seating surface of the insert. On the other hand, an on-edge cutting insert is one where the cutting face of the insert is located on a side of the insert perpendicular to the largest seating surface for the insert. A milling cutter with lay-down inserts, not on-edge inserts, is the subject matter of the present application. Using lay-down cutting inserts, the inventors have discovered a design that permits more inserts to be installed in the milling cutter than if they were to use on-edge-cutting inserts.

The milling cutter10may be used for milling operations and, more particularly, may be used for the machining of cam lobes on camshafts used for automotive equipment.

Reference will be made to top and bottom with respect to the elements ofFIG. 2, however it should be understood that these terms are used only to describe the relative location of these elements.

For clarity reference will also be made to a single pocket20and a single lug25with the understanding that each pocket and lug is identical to other pockets and lugs in the cutter body12. However, separate reference will be made to adjacent pockets20A,20B and adjacent lugs25A,25B to better describe pocket20and lug25.

Directing attention toFIG. 2, insert pocket20is spaced from an adjacent pocket20B by a lug25and is defined, in large part, by two lugs25,25A.

Each pocket20has support surfaces including a bottom surface27. Furthermore, the pocket20is adapted for positioning a rectangular insert16conforming to a predefined rectangular envelope30in the pocket20. Although the insert envelope30is actually located within the pocket20, for clarity in illustration, the envelope30has been extracted as shown inFIG. 2.

The rectangular envelope30has a front surface32, a back surface34, and four sides including a top side36A, a bottom side36B, a radially inward side36C, and a radially outward side36D. Additionally the cutting insert16has a front132, a back134, and four sides including a top side136A, a bottom side136B, a radially inward side136C, and a radially outward side136D. At the intersection of the front132and each of the sides136A,136B,136C and136D of the insert16there are cutting edges137A,137B,137C and137D respectively. However, it is possible for certain insert designs to include only cutting edges137A and137B.

Each lug25has a radially outward surface40and a radially inward surface42defining therebetween a radial width W which for clarity is shown on an adjacent lug25B. Each lug25furthermore has a front face45extending upwardly from the pocket bottom27to the top47of the lug25. Each lug25furthermore has an axial face49extending downwardly from the top47of the lug25to a height H (See lug25B) which is less than the height L of the lug. Each lug25furthermore has a rear face51extending downwardly from the axial face49of an adjacent lug25A to the bottom surface27of pocket20.

The support surfaces of pocket20are defined by the lug front face45, the pocket bottom surface27, and a pocket wall53positioned radially inwardly from the peripheral wall18whereby the pocket wall53connects adjacent lugs25,25A. The lug axial face49is sloped downwardly across the entire lug width W from the top47of the lug25to the lug rear face51. By doing so, a chip clearance groove55is provided across the entire width W of the lug25.

To provide maximum support to the cutting insert16within the pocket20, the lug front face45extends over the back side134of the insert16.

To maximize the size of the clearance groove55, the lug rear face51preferably extends from the bottom surface27to a distance H which is no higher than half way up the side of the insert16, when the insert is mounted within the pocket20. To further enhance the chip clearance groove55, the lug axial face49has a planar portion57which may be generally perpendicular to the lug front face45.

Each lug front face45has a bore60therethrough to accept a mounting screw62that is designed to extend within a mounting bore70through the cutting insert16and to secure the insert16within the pocket20. Furthermore, each pocket20is angled about the central axis14(FIG. 1) by an axial rake angle X which may be between −20° and 20° and preferably is between −5° and 5° to permit multiple inserts16to be mounted in the cutter body12and furthermore to provide access for inserting and for removing the mounting screw62. Each lug25furthermore has an access groove64(FIG. 2) within the lug front face45and the lug axial face49to permit greater access to the mounting screw62secured within the lug front face45. Although the access groove64is illustrated as curved, this is only a matter of convenience.

The lug rear face51, as previously mentioned, extends upwardly from the bottom surface27. This not only determines the size of the chip clearance groove55but furthermore, in conjunction with the bottom surface27, protects the bottom edge137B of the cutting insert16that is mounted within the pocket20.

To protect the side cutting edge137C of a cutting insert16, the pocket wall53may further include at least one recessed groove66parallel to the lug front face45. It is entirely possible that the cutting insert16has a cutting edge on side136C but opposite cutting edge137C. Under the circumstances, a second recessed groove68may exist such that, together, recessed grooves66,68protect the cutting edge137C and a cutting edge on the opposite side of136C. These recesses66,68also provide relief for the cutting edges positioned within the recesses66,68.

It should be noted that the pocket wall53extends only partially to the top47of the lug25. In one embodiment the pocket wall53extends no more than a distance of at least fifty-percent of the length of an insert that would be mounted within the pocket20. The purpose of this shortened height is to provide clearance during a cam lobe milling operations such that the cutter body12does not interfere with adjacent lobes on a cam shaft that are not currently being machined by the cutter10.

From inspection ofFIG. 1, one corner17of each of the inserts16is protruding and foremost in the cutter body12such that during a milling operation this corner will be the first to engage a workpiece. The bottom surface27of the pocket20is oriented to position the rectangular insert16such that this corner17of the insert16protrudes beyond the cutter body12. In particular, the pocket bottom surface27is angled to provide a bevel angle Y of between 0° and 90° and preferably between 40° and 90°.

Finally, the lug front face45may be oriented at a radial rake angle relative to a radial line extending from the central axis14to form an angle of between −10° and 20° and is preferably of between −5° and 5°. Radial rake angles are well known by those skilled in the art of metalworking and for that reason the radial rake angle is not illustrated inFIG. 1.

It should be appreciated that the insert16suitable for the pockets20discussed herein has been described as rectangular and it is entirely possible that such a rectangle may be a square.

Furthermore, while the insert300has been illustrated as double-sided, i.e. cutting edges on both sides of the insert300, and the insert300has been illustrated as indexable, it is entirely possible to have an insert without these features.

While the subject invention so far has been directed to a milling cutter10having a body12with reference to a cutting insert16mounted within a pocket20, it should be appreciated that the invention may be directed to the milling cutter body12alone without cutting inserts16mounted therein. However, under these circumstances, the insert envelope30, which is a predetermined shape based upon an insert for which the cutter body12was designed, will define the shape of the pocket20.

A second embodiment is illustrated with milling cutter200inFIG. 3. With the exception of the details discussed hereinafter, all of the other details of the milling cutter200are identical to those previously discussed for milling cutter10. Briefly referring toFIG. 2, a pocket20was essentially rectangular in shape with straight sides adapted to support a generally rectangular insert16.

It has been determined that additional support may be provided to an insert within a pocket by modifying the sides of the insert and the walls of the pocket. In particular, as illustrated inFIG. 4and as further illustrated inFIGS. 5 and 5A, at least a portion of the bottom surface227of the pocket220forms a first angle A with the front face245of the lug225to define a first retention ledge280. As illustrated inFIGS. 5 and 5A, the first angle A is acute and may be between 45° and 85°. Additionally, the bottom surface227has a length L between lug225and lug225A and the first retention ledge280extends along at least one fourth of the length L at a location spaced from the lug front face245.

For clarity,FIG. 5Ain the region of the cutting insert300has certain contour lines removed, which exist inFIG. 5, to more clearly illustrate the gap that exists between the front surface325of the insert300and the rear face251of the lug225A. The fastener370(FIG. 4) is recessed within the bore372of the insert300so that the head of the fastener370is recessed or at least flush with the front surface325of the insert300. It should be noted, as illustrated inFIG. 5A, there is no contact between the front surface325of the insert300and the rear face251of the lug225A.

As illustrated inFIG. 4the pocket220has a pocket wall253. Directing attention toFIGS. 6 and 6A, at least a portion of the pocket wall253may form a second angle B with the front face245of the lug225to define a second retention ledge290. The second angle is acute and may be between 45° and 85°. Additionally, the second retention ledge290extends along at least one fourth of the length L at a location spaced from the front face245of the lug225. In one embodiment the first angle A and the second angle B are equal.

Just as withFIG. 5A, for clarity,FIG. 6Ain the region of the cutting insert300has certain contour lines removed, which exist inFIG. 6, to more clearly illustrate the gap that exists between the front surface325of the insert300and the rear face251of the lug225A. The fastener370(FIG. 4) is recessed within the bore372of the insert300so that the head of the fastener372is recessed or at least flush with the front surface325of the insert325. It should be noted, as illustrated inFIG. 6, there is no contact between the front surface325of the insert300and the rear face251of the lug225A.

In the previous embodiment of the milling cutter10the pocket wall53was integral with the milling cutter body12. However, as illustrated infigure 3the pocket wall253of milling cutter200, which includes the second retention ledge290may be part of an annular ring295which conforms to the contour of each pocket wall (253for example) wherein when the annular ring295is secured to the cutter body210, the pocket wall253is positioned at the pocket220and the pocket walls associated with other pockets are also simultaneously positioned. The annular ring295may be secured to the body210utilizing threaded bolts297secured to the cutter body210or using any other conventional technique. The annular ring295is removable which improves access to inserts that may be within the pockets. Use of this annular ring295furthermore simplifies the manufacturing process.

An insert300that is suitable for retention in the pocket220(FIG. 4) is illustrated in detail inFIGS. 7-9. In particular, the insert300is a polygonal body320comprising a front surface325and back surface330opposing the front surface325.

The insert300has a peripheral wall335between the front surface325and the back surface330with sides340a,340b,340c,340d. Cutting edges350a,350b,350c,350dare formed at the intersection of the peripheral wall335and the front surface325. Additional cutting edges (not labeled) are formed at the intersection of the peripheral wall335and the back surface330of the insert300.

Each side, for example side340a, has two opposing beveled surfaces360,365thereupon. A first beveled surface360is proximate to the front surface325and a second beveled surface365is proximate to the back surface330. Together, the beveled surfaces360,365extend over at least fifty percent of the length L1of the side340a. In a preferred embodiment, the beveled surfaces360,365extend over at least ninety percent of the length L1of the side340a.

Directing attention toFIG. 8, the first beveled surface360forms a bevel angle C with the front surface325and the second beveled surface365forms a second bevel angle D with the back surface330. Each angle C and angle D is acute angles and are between 45° and 85°.

While only two beveled surfaces360,365have been discussed, it should be appreciated that each side340a340b,340c,340dof the insert300has a similar pair of opposing beveled surfaces. As an example, the two beveled surfaces associated with side340aas illustrated inFIG. 8are beveled surface360and beveled surface365, while the two beveled surfaces associated with side340bare beveled surface366and beveled surface367. Furthermore, for each side340a,340b,340c,340dthe two opposing beveled surfaces thereon extend over at least fifty percent of the length of the respective side.

The cutting insert300illustrated inFIGS. 7-9has a generally square shape and may be indexed to present a different cutting edge to the workpiece. Since there are four separate cutting edges associated with both the top surface and the bottom surface of the insert, a total of eight cutting edges may be selected for a machining operation.

Directing attention toFIG. 4andFIGS. 7-9, the shape on the insert300and the shape of the pocket220are compatible with one another. In particular, the back surface330of the insert300rests against the front face245of the lug225while the beveled surface365on side340bof insert300contacts the first retention ledge280. Furthermore, the beveled surface360on side340aof the insert300contacts the second retention ledge290on the pocket wall253of the cutter body210. Just as before, a fastener370extending through a bore372of the cutting insert300may be used to secure the cutting insert300within a bore372extending within the front face245of the lug225. The front surface325and the back surface330are generally planar and each include grooves380a,380b,380c,380dalong the cutting edges350a,350b,350c,350d, The grooves380a,380b,380c,380dextend downwardly and inwardly away from the cutting edge350a,350b350c,350dtoward the centerline385and then upwardly to meet the planar front surface325to form chip breaking grooves and also to retain the planar front surface325and the planar rear surface330as mounting surfaces.

The embodiment so far described has been directed to a milling cutter, which is one type of a toolholder. The invention generally is directed to a toolholder having a body210with a peripheral wall218on the body210. A pocket220is recessed within the peripheral wall218. The pocket220has support surfaces for positioning a generally rectangular insert within a predefined rectangular envelope within the pocket220including a bottom surface227and a front face245, also referred to as a lug front face245, extending upwardly from the pocket bottom surface227to a top side236of the body210. A pocket wall253is positioned inwardly from the peripheral wall218. At least a portion of the bottom surface227of the pocket220forms a first angle A with the front face245of the pocket220to define a first retention ledge280. The first angle A is acute. At least a portion of the pocket wall253may form a second angle B with the front face245of the body210to define a second retention ledge290. The second angle B is acute.