WO2018187446A1

WO2018187446A1 - End mills having vibration mitigation elements

Info

Publication number: WO2018187446A1
Application number: PCT/US2018/026048
Authority: WO
Inventors: Ian Edward HOLLIDAY; Emil DOBOSZ; Barry Leslie WARD; Antony James THEAKER
Original assignee: Kyocera Sgs Precision Tools, Inc.
Priority date: 2017-04-07
Filing date: 2018-04-04
Publication date: 2018-10-11

Abstract

End mills having vibration reduction elements are disclosed. In one embodiment, an end mill includes a plurality of helical lands that are oriented in a twist direction around a centerline axis, where the helical lands extend to an axial end. The end mill also includes a cutting edge positioned along each of the helical lands. The cutting edge includes a flute portion, a corner portion, and an end cutting portion. The end mill further includes a margin that extends away from the cutting edge in a direction counter to the twist direction. The margin extends along the cutting edge along at least a portion of the flute portion and at least a portion of the corner portion.

Description

END MILLS HAVING VIBRATION MITIGATION ELEMENTS

CROSS-REFERENCE TO RELATED APPLICATION

[0001] This application claims benefit of U.S. Provisional Application No. 62/482,950, filed April 7, 2017, the disclosure of which is incorporated by reference in its entirety.

TECHNICAL FIELD

[0002] The present disclosure is directed to end mills and, in particular, end mills having vibration mitigation elements.

BACKGROUND

[0003] Conventional end mills are used across a variety of industries in material removal operations. Corner radius end mills may be used in material removal operations in which relatively large quantities of material are removed. Corner radius end mills do not include sharp corners that are prone to chipping, but maintain relatively large footprints to maximize material removal rates. Additionally, ball nose end mills may be used to remove large quantities of material and/or introduce contouring into a workpiece. Because high material removal rates are typically desired, a high feed rate and a high depth of cut of the end mill are preferred. High feed rates and high depth of cuts may lead vibration being induced to the end mill during the material removal operation.

[0004] Vibration of an end mill during a material removal operation is undesired, as the end mill may chatter, leading to a poor surface finish on the workpiece and damage to the end mill. It is conventionally known to reduce the material removal rate from the workpiece by reducing the feed rate and/or reducing the depth of cut. Such material removal operation changes, however, increase the time required to complete the material removal operation and reduce the production rate, and therefore may be undesired.

[0005] Accordingly, end mills having vibration mitigation elements that allow for faster production rates may be desired. SUMMARY

[0006] In one embodiment, an end mill includes a plurality of helical lands that are oriented in a twist direction around a centerline axis, where the helical lands extending to an axial end. The end mill also includes a cutting edge positioned along each of the helical lands. The cutting edge includes a flute portion and a tip portion that extends from the flute portion. The end mill further includes a margin that extends away from the cutting edge in a direction counter to the twist direction. The margin extends along the cutting edge along at least a portion of the flute portion and at least a portion of the tip portion.

[0007] In another embodiment, an end mill includes a plurality of helical lands that are oriented in a twist direction around a centerline axis, the helical lands extending to an axial end. The end mill also includes a cutting edge positioned along each of the helical lands. The cutting edge includes a flute portion, a corner portion, and an end cutting portion, where the corner portion includes a corner radius that is tangent to the flute portion and tangent to the end cutting portion of the cutting edge. The end mill further includes a margin that extends away from the cutting edge in a direction counter to the twist direction. The margin extends along the cutting edge along at least a portion of the flute portion and at least a portion of the corner portion.

[0008] These and additional features provided by the embodiments described herein will be more fully understood in view of the following detailed description, in conjunction with the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0009] The embodiments set forth in the drawings are illustrative and exemplary in nature and not intended to limit the subject matter defined by the claims. The following detailed description of the illustrative embodiments can be understood when read in conjunction with the following drawings, where like structure is indicated with like reference numerals and in which:

[0010] FIG. 1 depicts a side perspective view of an end mill according to one or more embodiments shown or described herein; [0011] FIG. 2 depicts a side perspective view of an end mill according to one or more embodiments shown or described herein;

[0012] FIG. 3 depicts a cross-sectional end view of the end mill shown along line A- A of FIG. 2;

[0013] FIG. 4 depicts a side perspective view of an end mill according to one or more embodiments shown or described herein;

[0014] FIG. 5 depicts an end view of an end mill according to one or more embodiments shown or described herein;

[0015] FIG. 6 depicts a cross-sectional view of a portion of an end mill shown at view C of FIG. 3 according to one or more embodiments shown or described herein;

[0016] FIG. 7 depicts a cross-sectional view of a portion of an end mill shown at view C of FIG. 3 according to one or more embodiments shown or described herein;

[0017] FIG. 8 depicts a cross-sectional view of a portion of an end mill shown at view C of FIG. 3 according to one or more embodiments shown or described herein;

[0018] FIG. 9 depicts a cross-sectional view of a portion of an end mill shown at view C of FIG. 3 according to one or more embodiments shown or described herein; and

[0019] FIG. 10 depicts a side perspective view of an end mill according to one or more embodiments shown or described herein.

DETAILED DESCRIPTION

[0020] Reference will now be made in detail to embodiments of end mills. Various embodiments of end mills will be described in more detail herein.

[0021] Embodiments according to the present disclosure are directed to end mills having a plurality of flutes that are oriented around a centerline axis, a plurality of helical lands between the plurality of flutes, and a cutting edge that is positioned along each of the helical lands that includes a flute portion and a tip portion. Some embodiments according to the present disclosure are directed to corner radius end mills that have a cutting edge that includes a corner portion and an end cutting portion. The corner portion of the cutting edge includes a corner radius that extends from the flute portion to the end cutting portion. Other embodiments according to the present disclosure are directed to ball nose end mills that have a cutting edge that includes a ball nose portion. The end mill further includes a margin that extends from the cutting edge in a direction opposite therefrom, towards a heal of the helical flutes, along at least a portion of the flute portion and at least a portion of the tip portion. When used in a material removal operation, the end mill incorporating the recited elements exhibits reduced vibration, thereby allowing increased material removal rates during the material removal operation.

[0022] By incorporating the elements that mitigate vibration during the material removal operation, the end mill may operate at higher material removal rates than conventional end mills. Further, the elements that mitigate vibration may allow for the end mill to impart an improved surface finish on the workpiece during the material removal process than conventional corner radius end mills. Accordingly, corner radius end mills and ball nose end mills that incorporate vibration mitigation elements may improve production rates and may improve quality of parts produced in production as compared to conventional end mills.

[0023] Referring now to FIG. 1, an end mill 100 is illustrated according to one or more embodiments. The end mill 100 includes a shank portion 102 and a cutting portion 104 extending therefrom. The shank portion 102 may include a shank cylindrical portion 106 and a shank tapering portion 108, the latter of which extending between, and reducing in diameter from, the shank cylindrical portion 106 and the cutting portion 104. The cutting portion 104 includes a cutting edge 110 that is positioned along each of a plurality of helical lands 120. The helical lands 120 extend around a centerline axis 90 in a rearward axial direction 92 and in a twist direction 94 from an axial end 114 of the end mill 100, where the end mill 100 may rotate in an operation direction 96 that is counter to the twist direction 94. The helical lands 120 are oriented at a helix angle 119 relative to the centerline axis 90. The helix angle 119 may be within a range from about 15° to about 60° relative to the centerline axis 90, including being in a range from about 25° to about 35° or in a range from about 40° to about 50° relative to the centerline axis 90. The selection of the helix angle 119 may be determined based on the application needs of sharpness and strength of the cutting edge 110. [0024] The cutting portion 104 may also include a cutting neck portion 116 that extends from flute ends 1 18 to the shank portion 102. In addition, the cutting portion 104 may include a flute segment 112 extending from the flute ends 118 to the axial end 114 of the end mill 100.

[0025] The cutting edge 110 may include a flute portion 124 and a tip portion 117. In the depicted embodiment, the tip portion 117 includes a corner portion 122 and an end cutting portion 121. The end cutting portion 121 may define the axial end 114 of the end mill 100. In some embodiments, the corner portion 122 of the cutting edge 110 may be tangent to the flute portion 124 of the cutting edge 110 and the end cutting portion 121 of the cutting edge 110. In other embodiments, the corner portion 122 of the cutting edge 110 may include a surface that is transverse relative to the flute portion 124 of the cutting edge 110 and may be transverse relative to the end cutting portion 121 of the cutting edge 110. In such an embodiment, the transitions between the corner portion 122 and the flute portion 124 and between the corner portion 122 and the end cutting portion 121 may include rounds, such that the transition between the flute portion 124 and the corner portion 122 and between the corner portion 122 and the end cutting portion 121 are regular and smooth. The transition from the flute portion 124 to the corner portion 122 and from the corner portion 122 to the end cutting portion 121 may provide a high quality surface finish in the corresponding portions of the workpiece on which a material removal operation is performed.

[0026] A cutting portion diameter 98 may be evaluated between peripheral extension lines 190, 192 along the flute segment 112. The peripheral extension lines 190, 192 correspond to the swept diameter of the flute portion 124 of the cutting edge 110. In the embodiment depicted in FIG. 1, the extension lines 190, 192 are parallel with one another, reflecting that the flute portion 124 of the cutting edge 110 exhibits a cylindrical shape. In other embodiments (not shown), the flute portion 124 may exhibit a conical shape, such that the extension lines are oriented towards one another as the lines approach the axial end 114 of the end mill 100, or a tapered shape, such that the extension lines are oriented away from one another as the lines approach the axial end 114 of the end mill 100. [0027] Referring now to FIG. 2, a portion of a cutting edge 110 proximate to the axial end 114 is illustrated, according to one or more embodiments. In the depicted embodiment, the cutting edge 110 is positioned along a leading edge of the helical land 120 that extends along the centerline axis 90 in the rearward axial direction 92 helically in the twist direction 94. The end mill 100 may also include a margin 130 formed into the helical land 120 at a location proximate to the cutting edge 110. Here, the margin 130 is formed into the helical land 120 and extends away from the cutting edge 110 in a direction counter to the twist direction 94. In various embodiments, the margin 130 may exhibit a diameter corresponding to the diameter of the cutting edge 110. Referring to FIG. 3, in some embodiments, the margin 130 may exhibit a generally cylindrical configuration when evaluated in cross section. In other embodiments, as described below, the margin 130 may exhibit a generally planar configuration, a concave configuration, a faceted configuration, or an eccentric configuration when evaluated in cross section. FIGS. 6-9, below, describe various embodiments of the margin 130 illustrated at view C in FIG. 3. The end mill 100 may further include a primary relief 140 and, optionally, a secondary relief 142 at positions spaced increasingly further from the cutting edge 110 as evaluated in the twist direction 94. In other non-illustrated embodiments, the lands of end mill 100 may be configured in a double margin or triple margin arrangement.

[0028] Without being bound by theory, the margin 130 may increase the strength and/or durability of the cutting edge 110, while allowing the cutting edge 110 to exhibit a high degree of sharpness. By increasing material that is positioned counter to the twist direction 94 from the cutting edge 110, the margin 130 may reduce the likelihood of the cutting edge 110 chipping during a material removal operation. Further, the margin 130 may perform a burnishing function on the workpiece during a material removal operation, such that the margin 130 modifies the texture of the newly-exposed surfaces of the workpiece as machined by the cutting edge 110 of the end mill 100.

[0029] Referring again to FIG. 2, the margin 130 extends along at least a portion of the flute portion 124 of the cutting edge 110 and along at least a portion of the corner portion 122 of the cutting edge 110. In some embodiments, the margin 130 extends around the entirety of the corner portion 122 of the cutting edge 110. In some embodiments, the margin 130 extends around at least a half of an arclength of the corner portion 122 of the cutting edge 110. In some embodiments, the margin 130 extends around the entity of the corner portion 122 of the cutting edge 110. In some embodiments, the margin 130 extends along at least a portion of the end cutting portion 121 of the cutting edge 110.

[0030] By incorporating the margin 130 that extends around at least a portion of the corner portion 122 of the cutting edge 110, the end mill 100 may exhibit reduced vibration during a material removal operation as compared to a conventional end mill. By extending the margin 130 around at least a portion of the curved corner portion 122, an increasing amount of cutting surfaces of the end mill 100 may include elements that reduce the likelihood of vibration during a material removal operation. Further, because the cutting surfaces positioned proximate to the axial end 114 of the end mill 100, including the corner portion 122 of the cutting edge 110, remove material from the workpiece during a plunge operation of the end mill 100, a cutting edge 110 that exhibits the margin 130 that extends along at least a portion of the corner portion 122 may be subjected to lower vibration than conventional end mills that do not include such elements.

[0031] Referring to FIG. 4, an end mill 100 according to the present disclosure may include a gash 160 that extends in the rearward axial direction 92 from the axial end 114 of the end mill 100 and is positioned along the end cutting portions 121. The incorporation of the gash 160 into the end mill 100 may reduce a thickness 162 of the web 164 of the end mill 100, in which the web 164 is formed by the spacing between the helical lands 120 (i.e., the thickness measured across the base of the flutes that are defined between the helical lands 120). In general, the web 164 is a non-cutting surface of the end mill 100. By reducing the thickness 162 of the web 164 along the axial end 114 of the end mill 100, the end mill 100 may present a narrower face to the workpiece during a material removal operation. By presenting a narrower face to the workpiece, an axial force that is applied to the end mill 100 during a plunge movement may be reduced. Instead, the gash 160 reduces contact between non-cutting surfaces of the axial end 114 of the end mill 100 and the workpiece.

[0032] The gash 160 is oriented on the end mill 100 such that the gash 160 has an axial rake angle 166 relative to the centerline axis 90 and the helix angle 119 and, in the illustrated example embodiment, the value of the axial rake angle 166 is less than the value of the helix angle 119. In other embodiments, however, the value of the axial rake angle 166 is greater than the value of the helix angle 119. Moreover, the axial rake angle 166 may be characterized by either a positive, negative, or negative rake angle geometry. By including the gash 160 that is oriented with the axial rake angle 166 at the axial end 114 of the end mill 100, the end mill 100 may exhibit reduced vibration during a plunge movement in a material removal operation.

[0033] Referring now to FIG. 5, illustrated is the axial end 114 of an end mill 100 according to one or more embodiments. According to various embodiments, the end mill 100 may include a wiper portion 150 that is positioned proximate to an intersection between the corner portion 122 and the end cutting portion 121 of the cutting edge 110. In various embodiments, the wiper portion 150 may be transverse to the proximate surfaces of the cutting edge 110. In some embodiments, the margin 130 extends around the entirety of the wiper portion 150 of the cutting edge 110. In some embodiments, the margin 130 extends around at least a half of the wiper portion 150 of the cutting edge 110. In some embodiments, the margin 130 extends along at least a portion of the wiper portion 150 of the cutting edge 110. Without being bound by theory, the wiper portion 150 act as an increase in the size of the cutting edge 110 of the end mill 100, such that the wiper portion 150 removes more material than the material removed by the respective cutting edge 110. The wiper portion 150 may be sized and positioned such that a minimum amount of material is removed by the wiper portion 150, thereby minimizing cutting forces imparted to the end mill 100 through the wiper portion 150 and reducing the likelihood of inducing vibration in to the end mill 100 during the material removal operation and therefore improve surface finish on the component. Further, the wiper portion 150 may improve chip generation at positions of the workpiece that the wiper portion 150 comes into contact with. By managing the formation of chip generation, vibration of the end mill may further be mitigated.

[0034] Reference will now be made to FIGS. 6-9, each of which depict, among other elements, variations in the configuration of the margin at view C in FIG. 3. FIG. 6 depicts a margin 130 that is planar or faceted when evaluated in cross section, according to one or more embodiments. FIG. 7 depicts a margin 230 that is cylindrical when evaluated in cross section, according to one or more embodiments. FIG. 8 depicts a margin 330 that is concave when evaluated in cross section, according to one or more embodiments. FIG. 9 depicts a margin 430 that is eccentric when evaluated in cross section, according to one or more embodiments. Each of the configurations of the shape of the margin 130, 230, 330, 430 may provide different characteristics to the end mill 100 when used in a material removal operation. Accordingly, one of the depicted types of the margin 130, 230, 330, 430 may be incorporated into the end mill 100 based on the parameters of the material removal operation.

[0035] Referring now to FIG. 10, depicted is another embodiment of an end mill 200 according to one or more embodiments. The end mill 200 depicted in FIG. 10 is similar to the end mill 100 of FIG. 1, except the end mill 200 of FIG. 10 includes a cutting edge 210 having a flute portion 221 and tip portion 217 that is a ball nose portion 222.

[0036] The end mill 200 includes a shank portion 202 and a cutting portion 204 extending therefrom. The shank portion 202 may include a shank cylindrical portion 206 and a shank tapering portion 208, which extends between, and reducing in diameter from the shank cylindrical portion 206 and the cutting portion 204. The cutting portion 204 includes a cutting edge 210 that is positioned along each of a plurality of helical lands 220. The helical lands 220 extend around a centerline axis 90 in a rearward axial direction 92 and in a twist direction 94 from an axial end 214 of the end mill 200. The helical lands 220 are oriented at a helix angle 219 relative to the centerline axis 90. The helix angle 219 may be within a range from about 15° to about 60° relative to the centerline axis 90, including being in a range from about 25° to about 35° or in a range from about 40° to about 50° relative to the centerline axis 90. The selection of the helix angle 219 may be determined based on the application needs of sharpness and strength of the cutting edge 210.

[0037] The cutting edge 210 may include the flute portion 221 and the tip portion 217. In the depicted embodiment, the tip portion 217 includes a ball nose portion 222. The ball nose portion 222 may define the axial end 214 of the end mill 200. In some embodiments, the ball nose portion 222 may be tangent to the flute portion 221 of the cutting edge 210.

[0038] A cutting portion diameter 98 may be evaluated along peripheral extension lines 290, 292 at the axial end 214. The peripheral extension lines 290, 292 correspond to the swept diameter of the flute portion 221 of the cutting edge 210. In the embodiment depicted in FIG. 10, the extension lines 290, 292 are parallel with one another, reflecting that the flute portion 221 of the cutting edge 210 exhibits a cylindrical shape. In other embodiments (not shown), the flute portion 221 may exhibit a conical shape, such that the extension lines are oriented towards one another as the lines approach the axial end 214 of the end mill 200, or a tapered shape, such that the extension lines are oriented away from one another as the lines approach the axial end 214 of the end mill 200.

[0039] Still referring to FIG. 10, the cutting edge 210 is positioned along a side of each of the helical lands 220 positioned in the twist direction 94. The end mill 200 also includes a margin 130 that extends away from the cutting edge 210 in a direction counter to the twist direction 94. In various embodiments, the margin 130 may exhibit a diameter corresponding to the diameter of the cutting edge 210. In various embodiments, the margin 130 may exhibit a generally cylindrical configuration, a generally planar configuration, a concave configuration, a faceted configuration, or an eccentric configuration when evaluated in cross section, as described hereinabove. The end mill 200 may further include a primary relief 240 and, optionally, a secondary relief (not shown) at positions spaced increasingly further from the cutting edge 210 as evaluated in the twist direction 94.

[0040] The margin 130 extends along at least a portion of the flute portion 221 of the cutting edge 210 and along at least a portion of the ball nose portion 222 of the cutting edge 210. In some embodiments, the margin 130 extends around the entirety of the ball nose portion 222 of the cutting edge 220. In some embodiments, the margin 130 extends around at least a half of an arclength of the ball nose portion 222 of the cutting edge 210. In some embodiments, the margin 130 extends around the entity of the ball nose portion 222 of the cutting edge 210.

[0041] End mills according to the present disclosure may be made with a variety of conventionally known materials that are suitable for a material removal operation. Such materials may include, without limitation, cemented tungsten carbide, including cemented cobalt tungsten carbide, cermets, ceramics, diamond, including polycrystalline diamond (PCD) and chemical vapor deposition (CVD) diamond, polycrystalline cubic boron nitride (PCBN), and various grades of tool steel and high speed steel (HSS). Surfaces of the end mill 100 may be coated with dissimilar materials to improve certain properties of the end mill 100. Such coatings may include, without limitation AlTiSiN, AlTiCrN, TiB₂, diamond, TiN, TiC, and TiAIN, which may be applied through CVD or physical vapor deposition (PVD) processes.

[0042] End mills according to the present disclosure may have any number of features or combinations of different features. For example, end mills according to the present disclosure may include a tip portion that comprises a corner portion and an end cutting portion. In such embodiments, the end mill may include a margin that extends along at least a portion of a flute portion and, in some of those embodiments, the margin may extend around the corner portion. In embodiments where the margin extends onto the corner portion, the margin may extend along any arclength of the corner portion. For example, the margin may extend at least half an arclength of the corner portion, but in other examples, the margin may extend at least three quarters of an arclength of the corner portion. In even other embodiments, the margin may extend less than a half arclength of the corner portion, or less than a quarter arclength of the corner portion.

[0043] The margin may also be arranged to extend along at least a portion of the end cutting portion of the cutting edge, regardless of whether the margin extends along any portion of the corner portion. Thus, the margin may extend along the end cutting portion while not extending along the corner portion. Moreover, without departing from the present disclosure, the margin may (i) extend along the flute portion and the corner portion, but not the end cutting portion, (ii) extend along the flute portion and the end cutting portion, but not the corner portion, or (iii) extend along the flute portion, the corner portion, and the end cutting portion.

[0044] Regardless of the configuration of the margin and/or whether it extends onto the flute portion, the corner portion, and/or the end cutting portion (and regardless of the length onto which it extends on any or all of the flute portion, the corner portion, and/or the end cutting portion), in some embodiments the corner portion may comprise a corner radius that is tangent to the flute portion of the cutting edge. In the same or other embodiments, the corner portion may comprise a corner radius that is tangent to the end cutting portion of the cutting edge. [0045] Regardless of the configuration of the margin and/or whether it extends onto the flute portion, the corner portion, and/or the end cutting portion (and regardless of the length onto which it extends on any or all of the flute portion, the corner portion, and/or the end cutting portion) and regardless of whether the corner portion comprises a radius that is tangent to either the end cutting portion or the flute portion, the corner portion may comprise a surface having various geometries. For example, the corner portion may comprise a surface that is transverse relative to the flute portion of the cutting edge and, in these examples, the corner portion may comprise a surface that is transverse relative to the end cutting portion of the cutting edge. In even other embodiments, the corner portion may comprise a surface that is transverse relative to the end cutting portion of the cutting edge in lieu of the corner portion surface that is transverse relative to the flute portion of the cutting edge.

[0046] In addition to or in lieu of the above, the cutting edge may comprise a wiper portion. In some embodiments, the wiper portion is positioned proximate to an intersection between the corner portion and the end cutting portion of the cutting edge; however, it may be positioned differently without departing from the present disclosure. In these or other embodiments, the wiper portion of the cutting edge may be arranged transverse to the surrounding cutting edge. In addition or instead, the margin may be arranged to extend along a portion of the wiper portion, regardless of whether the margin extends along any other portion of the end mill (i.e., regardless of the length onto which the margin may extend (if at all) on any or all of the flute portion, the corner portion, and/or the end cutting portion).

[0047] Regardless of the arrangement of the margin (if any), the arrangement of the corner portion (if any), and regardless of whether the end mill includes a wiper portion, the tip portion of the cutting edge may be configured as a ball nose portion. In such embodiments, the ball nose portion may be tangent to the flute portion of the cutting edge. In these embodiments, a margin me be arranged to extend along any length of the ball nose portion. In one embodiment, the margin is arranged to extend at least one half an arc length of the ball nose portion; however, the margin may be arranged to extend less than one half an arc length of the ball nose portion. [0048] In some embodiments, the end mill includes a margin having a cross-sectional shape selected from the group consisting of cylindrical, planar, faceted, eccentric, or concave. The margin may include any of these shapes, regardless of which portions of the end mill onto which the margin is arranged to extend and the length thereon which the margin may extend.

[0049] Irrespective of the above, the end mill of the present disclosure may include one or more gashes positioned in respective helical lands and extending away from the axial end of the end mill. These one or more gashes may be provided regardless of any other characteristic or geometry of the end mill detailed above. In one embodiment where the end mill includes one or more gashes, the helical lands are positioned at a helix angle relative to a centerline axis of the end mill, and, in in some of these embodiments, the gashes are oriented at an axial rake angle. The axial rake angle may comprise any number of angles without departing from the present disclosure, and may be characterized by either a positive, negative, or negative rake angle geometry. In at least some embodiments, the axial rake angle is less than the helix angle relative to the centerline axis; however, it may be greater or equal to in other embodiments.

[0050] It should now be understood that end mills according to the present disclosure include cutting edges having a flute portion, a corner portion, and an end cutting portion, and margins that extend along at least a portion of the flute portion and along at least a portion of the corner portion. The end mills may also include a wiper portion that is positioned proximate to an intersection between the corner portion and the end cutting portion of the cutting edges, and a gash oriented at a positive, neutral, or negative axial rake angle relative to a helix angle of the helical lands. These elements may reduce the propensity of the end mill to vibrate when subjected to aggressive material removal rates in a material removal operation. The incorporation of these elements may enhance the sharpness and/or strength of the cutting edge of the end mill, and may reduce forces imparted to the end mill during the material removal operation.

[0051] It is noted that the terms "generally" and "substantially" may be used herein to represent the inherent degree of uncertainty that may be attributed to any quantitative comparison, value, measurement, or other representation. These terms are also used herein to represent the degree by which a quantitative representation may vary from a stated reference without resulting in a change in the basic function of the subject matter at issue.

[0052] While particular embodiments have been illustrated and described herein, it should be understood that various other changes and modifications may be made without departing from the spirit and scope of the claimed subject matter. Moreover, although various aspects of the claimed subject matter have been described herein, such aspects need not be utilized in combination. It is therefore intended that the appended claims cover all such changes and modifications that are within the scope of the claimed subject matter.

Claims

1. An end mill comprising:

a plurality of helical lands that are oriented in a twist direction around a centerline axis, the helical lands extending to an axial end;

a cutting edge positioned along each of the helical lands, the cutting edge comprising a flute portion and a tip portion that extends away from the flute portion; and a margin that extends away from the cutting edge in a direction counter to the twist direction, the margin extending along the cutting edge along at least a portion of the flute portion and at least a portion of the tip portion.

2. The end mill of claim 1, wherein the tip portion comprises a corner portion and an end cutting portion.

3. The end mill of claim 2, wherein the margin extends along at least a portion of the flute portion and around the corner portion.

4. The end mill of claim 2, wherein the margin extends along at least half an arclength of the corner portion.

5. The end mill of claim 2, wherein the margin extends along at least a portion of the end cutting portion of the cutting edge.

6. The end mill of claim 2, wherein the corner portion comprises a corner radius that is tangent to the flute portion of the cutting edge.

7. The end mill of claim 2, wherein the corner portion comprises a corner radius that is tangent to the end cutting portion of the cutting edge.

8. The end mill of claim 2, wherein the corner portion comprises a surface that is transverse relative to the flute portion of the cutting edge.

9. The end mill of claim 2, wherein the corner portion comprises a surface that is transverse relative to the end cutting portion of the cutting edge.

10. The end mill of claim 2, wherein the cutting edge further comprises a wiper portion that is positioned proximate to an intersection between the corner portion and the end cutting portion of the cutting edge.

11. The end mill of claim 10, wherein the wiper portion of the cutting edge is transverse to the surrounding cutting edge.

12. The end mill of claim 10, wherein the margin extends along at least a portion of the wiper portion.

13. The end mill of claim 1, wherein the tip portion of the cutting edge comprises a ball nose portion that is tangent to the flute portion of the cutting edge.

14. The end mill of claim 13, wherein margin extends along at least half an arclength of the ball nose portion.

15. The end mill of claim 1, wherein the margin has a cross-sectional shape selected from the group consisting of: cylindrical, planar, faceted, eccentric, and concave.

16. The end mill of claim 1, further comprising a plurality of gashes positioned in respective helical lands and extending away from the axial end of the end mill, wherein:

the helical lands are positioned at a helix angle relative to a centerline axis of the end mill, and

the gashes are oriented at an axial rake angle.

17. The end mill of claim 16, wherein the axial rake angle is less than the helix angle relative to the centerline axis.

18. The end mill of claim 16, wherein the axial rake angle is characterized by a geometry selected from the group consisting of: positive, neutral, and negative.

19. An end mill, comprising:

a plurality of helical lands that are oriented in a twist direction around a centerline axis, the helical lands extending to an axial end; a cutting edge positioned along each of the helical lands, the cutting edge comprising a flute portion, a corner portion, and an end cutting portion, wherein the corner portion comprises a corner radius that is tangent to flute portion and tangent to the end cutting portion of the cutting edge; and

a margin that extends away from the cutting edge in a direction counter to the twist direction, the margin extending along the cutting edge along at least a portion of the flute portion and at least a portion of the corner portion.

20. The end mill of claim 19, wherein the margin extends along at least a portion of the end cutting portion of the cutting edge.

21. The end mill of claim 19, further comprising a wiper portion that is positioned proximate to an intersection between the corner portion and the end cutting portion of the cutting edge.

22. The end mill of claim 21, wherein the margin extends along at least a portion of the wiper portion.

23. The end mill of claim 19, wherein the margin has a cross-sectional shape selected from the group consisting of: cylindrical, planar, faceted, eccentric, and concave.