CUTTING INSERT FOR THE DUAL PURPOSE OF ROUGHING AND
FINISHING
Technical Field
[0001] This disclosure is related to a cutting insert used for roughing and
finishing.
Background Art
[0002] Since cutting inserts for rough machining large workpieces are placed
under heavy loads, they are relatively large in size and are provided with a
broad supporting surface on the bottom. Generally, since roughing inserts of
this kind have a relatively large depth of cut and feed rate, they are fixed to the
pocket of a tool holder by a lever projected through a pocket sheet, and not by
a clamp coupled from above, to minimize interference.
[0003] However, since conventional roughing inserts are provided with cutting
edges only on the upper surface, they are discarded when the cutting edges
on the upper surface are worn out, which is uneconomical.
Disclosure
Technical Problem
[0004] The present disclosure aims to provide a cutting insert having a
sufficient bottom area for supporting an applied force during roughing, and
also having cutting edges for finishing, thereby allowing the cutting insert to be
used for the dual purpose of roughing and finishing.
Technical Solution
[0005] A cutting insert according to the present disclosure comprises an upper
face and a lower face opposite to each other, a plurality of side faces
connecting the upper face and the lower face, and a through-hole passing
through the upper face and the lower face.
[0006] The upper face comprises an upper cutting edge formed on the outer
periphery thereof, a flat land at the highest level disposed adjacent to and

along the upper cutting edge, and a groove region at a level lower than that of
the upper cutting edge and disposed between the flat land and the
through-hole. The lower face comprises chip breakers formed on parts of
peripheral regions which include each of the corners made by adjacent side
faces, lower cutting edges formed on the outer periphery of the lower face
along the chip breakers, and a flat supporting surface formed on the peripheral
regions between adjacent chip breakers and continuously on regions inward of
the chip breakers.
[0007] The upper face of the cutting insert according to the present disclosure
may comprise a negative land inclined outward and disposed between the
upper cutting edge and the flat land.
[0008] The groove region of the upper face of the cutting insert according to
the present disclosure may be connected by a downwardly inclined surface
extending from the flat land.
[0009] The chip breakers of the cutting insert according to the present
disclosure may comprise groove regions having a level higher than that of the
lower cutting edges and connected by an upwardly inclined surface extending
from the lower cutting edges, and the flat supporting surface may be at the
lowest bottom level.
[0010] The through-hole of the cutting insert according to the present
disclosure may comprise a tapered portion with the diameter increasing
towards the top.
[0011] The through-hole of the cutting insert according to the present
disclosure may comprise a tapered portion with the diameter increasing
towards the top and another tapered portion with the diameter increasing
towards the bottom.
[0012] The flat supporting surface of the cutting insert according to the present
disclosure may extend inwards continuously to the through-hole.
Alternatively, the lower face may have an interior cavity formed around the
through-hole and the flat supporting surface extends inwards continuously to

the interior cavity.
[0013] The lower face may comprise a chip breaker formed along the whole
perimeter of the peripheral region, lower cutting edges formed on the outer
periphery of the lower face along the chip breaker, and a flat supporting
surface formed on the region inward of the chip breaker.
Advantageous Effects
[0014] The cutting insert according to the present disclosure may be used for
the dual purpose of roughing and finishing. The cutting insert according to the
present disclosure has a structure whereby cutting edges for finishing and a
sufficient bottom to support the force during roughing are provided. Also, since
the cutting insert according to the present disclosure is provided with cutting
edges for finishing in addition to cutting edges for roughing, it has an additional
service life over conventional cutting inserts for roughing.
Description of Drawings
[0015] Fig. 1 is a perspective view depicting the upper face of a cutting insert
in accordance with the present disclosure.
[0016] Fig. 2 is a perspective view of the lower face of the cutting insert of Fig.
1.
[0017] Fig. 3 is an altitude profile of the upper face along the line A-A of Fig. 1.
[0018] Fig. 4 is a perspective view of the lower face of another cutting insert in
accordance with the present disclosure.
[0019] Fig. 5 is a planar view of the lower face of a cutting insert in accordance
with the present disclosure.
[0020] Fig. 6 is an altitude profile of the lower face along the line B-B of Fig. 5.
[0021] Fig. 7 is a perspective view depicting a cutting insert mounted on a tool
holder for use in roughing.

[0022] Fig. 8 is a perspective view of the lower face of another cutting insert in
accordance with the present disclosure.
[0023] Fig. 9 is a perspective view of the lower face of still another cutting
insert in accordance with the present disclosure.
[0024] Fig. 10 is a side view showing the clamping force by a lever for a cutting
insert mounted on a tool holder for roughing.
[0025] Fig. 11 is a sectional view showing a through-hole of a cutting insert in
accordance with the present disclosure.
[0026] Fig. 12 is a side view showing the clamping force by a lever for a cutting
insert mounted on a tool holder for finishing.
[0027] Fig. 13 is a sectional view showing a through-hole of another cutting
insert in accordance with the present disclosure.
[0028] Fig. 14 is a sectional view showing a through-hole of still another cutting
insert in accordance with the present disclosure.
Mode for Invention
[0029] Hereinafter, cutting inserts according to embodiments of the present
disclosure are described. The figures attached to the present disclosure are
merely for convenience of explanation, and the shapes and the relative scales
may be exaggerated or abridged.
[0030] Fig.1 is a perspective view depicting the upper face of a cutting insert in
accordance with the present disclosure and Fig.2 is a perspective view of the
lower face of the cutting insert of Fig. 1. As a matter of course, although the
upper face and the bottom face can be exchanged depending on the
orientation of the cutting insert, hereinafter the upper face 100 and the lower
face 200 are defined based on Fig. 1 for convenience of explanation. Fig. 3 is
an altitude profile of the upper face along the line A-A of Fig. 1.
[0031] As shown in Fig. 1, the cutting insert in accordance with the present

disclosure comprises an upper face 100 and a lower face 200 opposite to each
other, a plurality of side faces 300 connecting the upper face and the lower
face, and a through-hole 400 passing through the upper face and the lower
face.
[0032] The upper face 100 comprises an upper cutting edge 110 formed on
the outer periphery thereof, a flat land 120 at the highest level disposed
adjacent to and along the upper cutting edge 110, and a groove region 130 at
a level lower than that of the upper cutting edge and disposed between the flat
land 120 and the through-hole 400. The groove region 130 of the upper face
100 is connected by a downwardly inclined surface 140 extending from the flat
land 140.
[0033] The lower face 200 comprises chip breakers 220 formed on parts of
peripheral regions which include each of the corners 230 made by adjacent
side faces 300, lower cutting edges 210 formed on the outer periphery of the
lower face 200 along the chip breakers 220, and a flat supporting surface 260
formed on the peripheral regions 240 between adjacent chip breakers 220 and
continuously on regions 260 inward of the chip breakers 220. The flat
supporting surface 260 may extend inwards continuously to the through-hole
400, or the lower face may have an interior cavity 410 formed around the
through-hole 400 as shown in Fig. 4 to allow closer contact.
[0034] As shown in Fig. 3, the upper face may comprise a negative land 150
inclined outward and disposed between the upper cutting edge 110 and the
flat land 120. Of course, the upper face may lack a negative land. In this
case, the upper cutting edges may have an R-shape formed by honing.
[0035] Fig. 5 is a planar view of the lower face of a cutting insert in accordance
with the present disclosure. Fig. 6 is an altitude profile of the lower face along
the line B-B of Fig. 5.
[0036] As shown in Fig. 6, the chip breakers 220 comprise groove regions 270
having a level lower than that of the lower cutting edges 210 and connected by
a downwardly inclined surface 280 extending from the lower cutting edges 210,

and the flat supporting surface 250 formed inward of the groove regions 270 is
at the highest level.
[0037] Fig. 7 is a perspective view depicting a cutting insert mounted on a tool
holder for use in roughing. Here, the flat supporting surface 250 functions as a
bottom supporting surface contacting the flat upper surface of the pocket sheet
of a tool holder. Explaining again the structure of the lower face 200 in this
state, the chip breakers 220 comprise groove regions 270 having a level
higher than that of the lower cutting edges 210 and connected by an upwardly
inclined surface 280 extending from the lower cutting edges 210, and the flat
supporting surface 250 formed inward of the groove regions 270 is at the
lowest bottom level.
[0038] When a cutting insert is used for finishing, it is mounted on a tool holder
in a state as shown in Fig. 2, where the flat land 120 of the upper face 100
functions as a supporting surface contacting the flat upper surface of the
pocket sheet of a tool holder. In this case, if a negative land 150 is formed on
the upper face 100 or the edge is honed to an R-shape, they protect the upper
cutting edge 110 from being worn by contact.
[0039] Whereas the lower face provides a chip control function when the
cutting insert is mounted for finishing, it functions as the supporting surface
when the cutting insert is mounted for roughing. For a finishing feed rate in the
range of 0.2~1.0mm/rev, the width (Le) of the chip breaker is set in a range of
0.8~3.5mm. As the width (Le) of the chip breaker increases, the overhang
increases during roughing, resulting in vibrations. Therefore, to prevent
vibrations during roughing, it is desirable to set the width (Le) of the chip
breaker to 1.0~3.0mm for a feed rate of 0.4~0.8mm/rev. Also, the depth of cut
for finishing is within a straight wing length (D) as shown in Fig. 5, which is
preferably in the range of 2~6mm allowing a flat supporting surface 240
between adjacent chip breakers 220.
[0040] The peripheral regions 240 between adjacent chip breakers may be
provided with spacing structures 285 to avoid interference of notch parts by
forming chamfers or grooves of a small width on the outer periphery as shown

in Fig. 8.
[0041] When roughing a workpiece using the upper face for less severe cutting
conditions, or finishing using the lower face for a relatively larger depth of cut,
the chip breaker 290 may be formed along the whole perimeter of the
peripheral region so that lower cutting edges are provided on the outer
periphery along the whole perimeter of the lower face as shown in Fig. 9.
[0042] The chip breaker area is preferably no more than 50% of the whole
area of the lower face except for the through-hole so that the flat supporting
surface 260 provides a sufficient supporting area for roughing.
[0043] If roughing is performed prior to finishing, a harsh cutting condition may
damage the flat land 120 which is to be used as the supporting area for
finishing. Therefore it is preferred that the cutting insert according to the
present disclosure is used for finishing first, and then for roughing. In other
words, the first cutting insert is used only for roughing and then discarded, and
the subsequent cutting inserts are used for finishing first and then roughing,
consecutively.
[0044] Fig. 10 is a side view showing the clamping force imparted by a lever
on a cutting insert mounted on a tool holder for roughing. If the through-hole of
a cutting insert has a tapered portion with the diameter increasing towards the
top as shown in Fig. 11, the direction of the clamping force is downwardly
inclined toward the inside corner of the pocket as shown by the arrow in Fig.
10, thereby fastening the cutting insert more firmly to the pocket. If the cutting
edge of Fig. 11 is mounted to a tool holder for finishing, the clamping force
from the lever is directed laterally as shown by the arrow in Fig. 12. In order
for the clamping force to be inclined downwardly toward the inside corner of
the pocket even for the case of mounting the cutting insert for finishing, the
through-hole is preferably made to comprise two tapered portions with the
diameter increasing towards the top and with the diameter increasing towards
the bottom as shown in Fig. 13. Of course, it is still possible to fasten a cutting
insert with a lever even with a straight through-hole as shown in Fig. 14.

The cutting inserts and the tool holder mounted with the cutting inserts
disclosed above may have various other embodiments without departing from
the basic concept of the present disclosure. Accordingly, all the disclosed
embodiments must be understood as being exemplary only and must not be
construed to be the limit of the present disclosure. Accordingly, the range of
protection for the present disclosure must be determined not by an
embodiment described hereinabove, but by the attached claims. An alternative
that is equivalent to the attached claims is included in the range of protection
of the attached claims.

CLAIMS:
1. A cutting insert comprising an upper face and a lower face opposite to each
other, a plurality of side faces connecting the upper face and the lower face,
and a through-hole passing through the upper face and the lower face;
wherein
the upper face comprises an upper cutting edge formed on the outer periphery
thereof, a flat land at the highest level disposed adjacent to and along the
upper cutting edge, and a groove region at a level lower than that of the upper
cutting edge and disposed between the flat land and the through-hole; and
the lower face comprises chip breakers formed on parts of peripheral regions
which include each of the corners made by adjacent side faces, lower cutting
edges formed on the outer periphery of the lower face along the chip breakers,
and a flat supporting surface formed on the peripheral regions between
adjacent chip breakers and continuously on regions inward of the chip
breakers.
2. A cutting insert comprising an upper face and a lower face opposite to each
other, a plurality of side faces connecting the upper face and the lower face,
and a through-hole passing through the upper face and the lower face;
wherein
the upper face comprises an upper cutting edge formed on the outer periphery
thereof, a flat land at the highest level disposed adjacent to and along the
upper cutting edge, and a groove region at a level lower than that of the upper
cutting edge and disposed between the flat land and the through-hole; and
the lower face comprises a chip breaker formed along the whole perimeter of
the peripheral region, lower cutting edges formed on the outer periphery of the
lower face along the chip breaker, and a flat supporting surface formed on the
region inward of the chip breaker.
3. The cutting insert according to claims 1 or 2, wherein the upper face
comprises a negative land inclined outward and disposed between the upper
cutting edge and the flat land.
4. The cutting insert according to claims 1 or 2, wherein the groove region of

the upper face is connected by a downwardly inclined surface extending from
the flat land.
5. The cutting insert according to claims 1 or 2, wherein the chip breakers
comprise groove regions having a level higher than that of the lower cutting
edges and connected by an upwardly inclined surface extending from the
lower cutting edges, and the flat supporting surface is at the lowest bottom
level.
6. The cutting insert according to claims 1 or 2, wherein the through-hole
comprises a tapered portion with the diameter increasing towards the top.
7. The cutting insert according to claims 1 or 2, wherein the through-hole
comprises a tapered portion with the diameter increasing towards the top and
another tapered portion with the diameter increasing towards the bottom.
8. The cutting insert according to claims 1 or 2, wherein the flat supporting
surface extends inwards continuously to the through-hole.
9. The cutting insert according to claims 1 or 2, wherein the lower face has an
interior cavity formed around the through-hole and the flat supporting surface
extends inwards continuously to the interior cavity.
10. The cutting insert according to claims 1 or 2, wherein the width (Le) of the
chip breaker is in the range 1.0~3.0mm, and the total chip breaker area is no
more than 50% of the whole area of the lower face except the through-hole.
11. The cutting insert according to claim 1, wherein the peripheral regions
between adjacent chip breakers are provided with spacing structures.

A cutting insert is disclosed herein. The cutting insert comprises an upper face
and a lower face opposite to each other, a plurality of side faces connecting
the upper face and the lower face, and a through-hole passing through the
upper face and the lower face. The upper face comprises an upper cutting
edge formed on the outer periphery thereof, a flat land at the highest level
disposed adjacent to and along the upper cutting edge, and a groove region at
a level lower than that of the upper cutting edge and disposed between the flat
land and the through-hole. The lower face comprises chip breakers formed at
least on parts of peripheral regions which include each of the corners made by
adjacent side faces, lower cutting edges formed on the outer periphery of the
lower face along the chip breakers, and a flat supporting surface formed on the
peripheral regions between adjacent chip breakers and continuously on
regions inward of the chip breakers.