CUTTING INSERT AND CUTTING TOOL COMPRISING THE SAME
TECHNICAL FIELD
[0001] The present invention relates to a cutting insert and a cutting tool
comprising the same, and more particularly, to a cutting insert and a cutting tool
comprising the same, in which a back side face portion of the cutting insert is formed in a
non-symmetric "V" shape for dispersion of a force applied to a clamp screw, thereby
preventing damage to the clamp screw and firmly clamping the cutting insert to a holder.
BACKGROUND ART
[0002] In general, a cutting tool includes a holder made of steel and a cutting insert
made of cemented carbide steel and the cutting insert is indexably mounted to the holder
through a clamp screw.
[0003] Such an indexable cutting tool is advantageous in that the cutting insert
thereof can be replaced with a new one if a cutting edge of the cutting insert is worn out.
However, when coupling between the cutting insert and the holder is defective, problems
such as separation of the cutting insert and damage of the clamp screw may occur.
[0004] In the mean time, the cutting insert is mounted to a tool body, with a back
cross-section thereof being perpendicular to a rotational axis thereof. In this structure, a
longitudinal resistance can be supported stably, but a reaction force with respect to a
lateral cutting resistance is offset only by a clamping force of the clamp screw which fixes
the cutting insert to the tool body.
[0005] During processing of a work-piece in a high-feed condition, a large cutting
resistance acts in a cutting edge of the cutting insert and thus a sufficient clamping force
for the cutting resistance cannot be provided merely by the clamp screw. In this condition,
the clamp screw may be damaged.

DISCLOSURE
Technical Problem
[0006] The present invention is conceived to solve the aforementioned problems,
an object of the present invention is to provide a cutting insert and a cutting tool
comprising the same, in which a back side face portion of the cutting insert is formed in a
non-symmetrical convex "V" shape for dispersion of a force applied to a clamp screw,
thereby preventing damage of the clamp screw and firmly clamping the cutting insert to a
holder.
[0007] In addition, another object of the present invention is to provide a cutting
insert and a cutting tool comprising the same, in which the cutting insert is capable of
reducing manufacturing tolerance by providing easiness in manufacturing and has
superior mounting precision.
Technical Solution
[0008] According to an aspect of the present invention for achieving the objects,
there is provided a cutting tool, which comprises an upper face and a lower face; a front
side face portion and a back side face portion, the front and back side face portions
connecting the upper face and the lower face; and a through-hole passing through the
upper face and the lower face, wherein a cutting edge is formed in the front side face
portion, and the back side face portion is provided with a first inclined face and a second
inclined face which are inclined forwardly at different angles, respectively, with respect to
a plane normal to a rotational axis, and the first inclined face is longer than the second
inclined face so that the back side face portion has a non-symmetrical convex "V" shape.
[0009] According to another aspect of the present invention for achieving the
objects, there is provided a cutting tool, which comprises a holder having a pocket formed
on a front end portion thereof, the pocket having a pair of jaws; and a cutting insert
indexably mounted to the pocket, wherein the cutting insert comprises a upper face and a
lower face corresponding to each of jaws, respectively, a front side face portion and a
back side face portion corresponding to the pocket of the holder, the front and back side
face portions connecting the upper face and the lower face, and a through-hole passing
through the upper face and the lower face, a cutting edge is formed in the front side face

portion, the back side face portion is provided a first inclined face and a second inclined
face which are inclined forwardly at different angles, respectively, with respect to a plane
normal to a rotational axis, and the first inclined face is longer than the second inclined
face so that the back side face portion has a non-symmetrical convex "V" shape.
Advantageous Effects
[0010] As described above, the cutting insert and the cutting tool comprising the
same according to the present invention provide a stable supporting structure with
respect to an axial direction, and prevent damage of the clamp screw and firmly clamp the
cutting insert to the holder by dispersing a force applied to the clamp screw.
[0011] In addition, the cutting insert and the cutting tool comprising the same
according to the present invention are easy to manufacture due to a large manufacturing
tolerance and have superior mounting precision.
DESCRIPTION OF DRAWINGS
[0012] The above and other objects, features and advantages of the present
invention will become apparent from the following description of preferred embodiments
given in conjunction with the accompanying drawings, in which:
[0013] FIG. 1 is a perspective view of a cutting insert according to a first
embodiment of the present invention;
[0014] FIG. 2 is a front view of the cutting insert illustrated in FIG. 1;
[0015] FIG. 3 is a rear view of the cutting insert illustrated in FIG. 2;
[0016] FIG. 4 is a front view of a cutting insert according to a second embodiment
of the present invention;
[0017] FIG. 5 is a front view of a cutting insert according to a third embodiment of
the present invention;

[0018] FIG. 6 is an exploded perspective view of a cutting tool according to an
embodiment of the present invention;
[0019] FIG. 7 is a perspective view illustrating a state of the cutting tool in which
members illustrated in FIG. 4 are coupled with each other; and
[0020] FIG. 8 illustrates axial and radial forces in the state where the members
illustrated in FIG. 4 are coupled with each other.
MODE FOR INVENTION
[0021] Hereinafter, the oil separator according to the preferred embodiment of the
present invention will be described in more detail with reference to the accompanying
drawings. In the drawings, similar symbols typically identify similar components, unless
context dictates otherwise. The drawings are provided for simplicity of description, and
shapes of structural members may be exaggerated or reduced for clarity.
[0022] FIG. 1 is a perspective view of a cutting insert 10 according to a first
embodiment of the present invention, FIG. 2 is a front view of the cutting insert 10
illustrated in FIG. 1, and FIG. 3 is a rear view of the cutting insert 10 illustrated in FIG. 2.
[0023] The cutting insert 10 according to the first embodiment of the present
invention comprises a upper face 11, a lower face 12, and a front side face portion 13
corresponding to a work-piece (not shown) and a back side face portion 14 corresponding
to a pocket of a holder (not shown), the front and back side face portions 13 and 14
connecting the upper face 11 and the lower face 12, and a through-hole 17 passing
through the upper face 11 and the lower face 12.
[0024] Here, the front side face portion 13 is provided with a pair of cutting edges
13-1 and 13-2 which are rotational symmetric to the rotational axis L.
[0025] In addition, the front side face portion 13 of the cutting insert 10 may also
comprise connection sides 15 and 16 which are parallel to the rotational axis L.

[0026] The back side face portion 14 has a first inclined face 14-1 and a second
inclined face 14-2 which are formed upward from a plane S normal to the rotational axis L
at predetermined inclination angles a and Q> respectively. The first inclined face 14-1 is
longer than the second inclined face 14-2.
[0027] That is, the first inclined face 14-1 and the second inclined face 14-2 may
form a non-symmetrical convex "V" shape.
[0028] Here, the inclination angle a of the first inclined face 14-1 of the back side
face portion 14 may be smaller than the inclination angle IS of the second inclined face
14-2, where the first inclined face 14-1 may be inclined at the inclination angle a of
5—15° with respect to the plane S perpendicular to the rotational axis L and the second
inclined face 14-2 may be inclined at the inclination angle β of 35—45° with respect to
the plane S perpendicular to the rotational axis L.
[0029] In the mean time, a portion of an inner circumferential surface of the
through-hole 17 may be a flat plane 18 inclined in an opposite direction to the first inclined
face 14-1.
[0030] An angle 0 of the flat plane 18 is an obtuse angle formed by an extending
line of the flat plane 18, viewed from the upper face 11 of the cutting insert 10 (see FIGs.
2 and 3), with respect to the plane S perpendicular to the rotation axis L
[0031] The cutting insert 10 structured as described above provides superior
engagement precision when being engaged with a holder and remains stably mounted
against the axial and radial cutting resistances.
[0032] FIG. 4 is a front view of a cutting insert 20 according to a second
embodiment of the present invention. The cutting insert 20 according to the second
embodiment of the present invention includes a upper face 21, a lower face (not shown),
and a front side face portion 23 and a back side face portion 24, the front and back side
face portions connecting the upper face 21 and the lower face, and a through-hole 27
passing through the upper face 21 and the lower face.

[0033] Here, the front side face portion 23 has a pair of cutting edges 23-1 and
23-2 having a structure which are rotational symmetric to the rotational axis L.
[0034] Except for a difference in shape between the cutting edge 13-1 of the
cutting insert 10 according to the first embodiment of the present invention and the cutting
edge 23-1 of the cutting insert 20 according to the second embodiment of the present
invention, structures and shapes of other components of the cutting insert 20 are the
same as those of the cutting insert 10.
[0035] In other words, the cutting insert 10 according to the first embodiment of the
present invention is a ball endmill and the cutting insert 20 according to the second
embodiment of the present invention is a corner-radius (R) endmill.
[0036] The front side face portion 23 of the cutting insert 20 may also comprise
connection sides 25 and 26 which are parallel to the rotation axis L.
[0037] The back side face portion 24 has a first inclined face 24-1 and a second
inclined face 24-2 which are formed upward from a plane S perpendicular to the rotation
axis L at predetermined inclination angles a and β, respectively. The length of the first
inclined face 24-1 is larger than that of the second inclined face 24-2.
[0038] That is, the first inclined face 24-1 and the second inclined face 24-2 may
form a non-symmetrical convex "V" shape.
[0039] Here, the inclination angle a of the first inclined face 24-1 of the back side
face portion 24 may be smaller than the inclination angle β of the second inclined face
24-2, where the first inclined face 24-1 may be inclined at the inclination angle a of 5—15°
with respect to the plane S perpendicular to the rotational axis L and the second inclined
face 24-2 may be inclined at the inclination angle β of 35—45° with respect to the plane S
perpendicular to the rotational axis L
[0040] A portion of an inner circumferential surface of the through-hole 27 may be
a flat plane 28 inclined in an opposite direction to the first inclined face 24-1.

[0041 ] For example, an angle θ of the flat plane 28 is an obtuse angle formed by an
extending line of the flat plane 28, viewed from the upper face 21 of the cutting insert 20,
with respect to the plane S perpendicular to the rotation axis L.
[0042] FIG. 5 is a perspective view of a cutting insert 30 according to a third
embodiment of the present invention. The cutting insert 30 according to the third
embodiment of the present invention has the same structure and shape as those of the
cutting insert 10 according to the first embodiment of the present invention or the cutting
insert 20 according to the second embodiment of the present invention, and may further
comprise a recess 38 in at least one of both a upper face 31 and a lower face (not shown)
in order to supply a coolant.
[0043] Both ends of the recess 38 are opened, for example, an inlet portion 38-1 of
the recess 38 may be formed in a boundary portion between a first inclined face 34-1 and
the upper face 31, a outlet portion 38-3 of the recess 38 may be formed in a boundary
portion between a cutting edge 33-1 and the upper face 31, and an intermediate portion
38-2 connecting the inlet portion 38-1 and the outlet portion 38-2 may be formed around a
through-hole 37.
[0044] The recess 38 may also be formed in both the upper face 31 and the lower
face (not shown) in a shape rotationally symmetric with respect to the rotational axis.
[0045] In the mean time, it is preferable that a cross-section area of recess 38 is
gradually reduced from an inlet portion 38-1 (d1: a cross-section area of the inlet portion)
toward an outlet portion 38-3(d2: a cross-section area of the outlet portion). Thus, the
recess 38 is in the shape of a nozzle toward the cutting edge 33-1, thereby increasing the
flow rate of a coolant (cutting oil or air) and effectively injecting the coolant.
[0046] With reference to the accompanying drawings, a detailed description will
now be made of a cutting tool comprising the cutting inserts 10, 20, and 30.
[0047] FIG. 6 is an exploded perspective view of a cutting tool 100 according to an
embodiment of the present invention, FIG. 7 is a perspective view illustrating a state of
the cutting tool 100 in which members illustrated in FIG. 4 are coupled with each other,

and FIG. 8 illustrates axial and radial forces in the state where the members illustrated in
FIG. 4 are coupled with each other.
[0048] Methods of engaging each of the cutting inserts 10, 20, and 30 illustrated in
FIGs. 1 to 5 with a holder 120 are the same, and thus a description will be made by using
the cutting insert 10 according to the first embodiment of the present invention as an
example for convenience of explanation. A cutting insert 110 illustrated in FIG. 6 is the
same as the cutting insert 10 according to the first embodiment of the present invention.
[0049] The cutting tool 100 according to an embodiment of the present invention
comprises the holder 120 in which a pocket 121 having a pair of jaws 122 and 123 at a
front end portion thereof is formed, and the cutting insert 110 mounted on the pocket 121
in a replaceable manner.
[0050] The cutting insert 110 and the holder 120 may be engaged through a clamp
screw 130.
[0051] The cutting insert 110 comprises a upper face and a lower face which
correspond to each of jaws 122 and 123, respectively, and a front side face portion
corresponding to a work-piece and a back side face portion corresponding to the pocket
121 of the holder 120, the front and back side face portions connecting the upper face and
the lower face, and a through-hole passing through the upper face and the lower face.
[0052] A first contact face 124 contacting a first inclined face and a second contact
face 125 contacting a second inclined face may be formed in the pocket 121 of the holder
120.
[0053] The first inclined face and the second inclined face of the cutting insert 110
form a non-symmetrical convex "V" shape, and the first contact face 124 and the second
contact face 125 of the pocket 121 of the holder 120 form a non-symmetrical concave "V"
shape.
0054] When a recess for supplying a coolant is formed in the upper face and the
lower face of the cutting insert 100, a coolant guide hole (not shown) may be formed in the

holder 120 to supply the coolant to the pocket 121 of the holder 120.
[0055] Referring to FIG. 8, P4 represents a rotational force generated by contact
between the circumferential sides of the clamp screw 130 and the inner side of the
through-hole of the cutting insert 110 when the holder 120 and the cutting insert 110 are
engaged through the clamp screw 130, P3 represents an axial adhesive force exerted by
an elastic force of the clamp screw 130 supported by both jaws 122 and 123 from the
cutting insert 110 toward the holder 120 along the axial direction when the clamp screw
130 is engaged, and P1 and P2 represent a component force exerted in a direction
normal to P3 and a component force exerted in a tangential direction, respectively.
[0056] As illustrated in FIG. 8, the large normal component force P1 provides firm
adhesive force between the first inclined face and the pocket 121 (the first contact face
124) of the holder 120 and the relatively small tangential component force P2 induces
close adhesion between the second inclined face and the pocket 121 (the second contact
face 125) of the holder 120.
[0057] When the clamp screw 130 is engaged, the rotational force P4 is exerted
such that the first inclined face slides with maintaining surface-contact with the first
contact face 124 of the pocket portion 121 until the second inclined face contacts the
second contact face 125 of the pocket 121, thereby securing a firm and stable engaging
structure even if the "V" shape of the cutting insert 110 and the "V" shape of the pocket
portion 121 are not exactly identical to each other, and thus allowing a relatively large
manufacturing tolerance.
[0058] Herein, a flat plane inclined in an opposite direction to the first inclined face
is formed on a some portion of an inner circumferential surface of the through-hole of the
cutting insert 110, whereby an elastic force of the clamp screw 130 is oriented in a
direction normal to the flat plane toward the second inclined face. Thus, P1 to P3 bring
the cutting insert 110 into contact with the first contact face 124 in a good condition, even
when the first inclined face of the cutting insert 110 slides on the first contact face 124 due
to the rotational force P4 of the clamp screw 130, firm support can be guaranteed by
contact between the second inclined face and the second contact face 125 of the pocket
121, thus improving firmness and stability of the engaging structure.

[0059] The first inclined face of the cutting insert 110, which is a main mounting
surface, maintains stable mounting by providing resistance against the axial cutting force
through surface-contact with the first contact face 124 of the holder 120, and also
provides resistance against the lateral cutting force.
[0060] The second inclined face of the cutting insert 110, which is a supplementary
mounting surface, resists the radial cutting force through line-contact or surface-contact
with the second contact face 125 of the holder 120, and the first contact face 124 and the
second contact face 125 of the holder 120 absorb the radial cutting force, thereby
reducing the radial cutting force delivered to the clamp screw 130.
[0061] As such, the cutting inserts 10, 20, 30, and 110 and the holder 120 are easy
to process, have large manufacturing tolerances, and prevent precision degradation
caused by engagement of the cutting insert 110 with the holder 120 in a wrong direction
by providing apparent orientation through the asymmetric structures. The cutting tool 100
prevents damage of the clamp screw 130 and firmly clamps the cutting insert 110 to the
holder 120 by dispersing a force applied to the clamp screw 130.
[0062] Although embodiments have been described with reference to a number of
illustrative embodiments thereof, it should be understood that numerous other
modifications and embodiments can be devised by those skilled in the art that will fall
within the spirit and scope of the principles of this disclosure. More particularly, various
variations and modifications are possible in the component parts and/or arrangements of
the subject combination arrangement within the scope of the disclosure, the drawings and
appended claims. In addition to variations and modifications in the component parts
and/or arrangements, alternative uses will also be apparent to those skilled in the art.

CLAIMS
1. A cutting insert comprising:
an upper face and a lower face;
a front side face portion and a back side face portion, the front and back side face
portions connecting the upper face and the lower face; and
a through-hole passing through the upper face and the lower face,
wherein a cutting edge is formed in the front side face portion, and the back side
face portion is provided with a first inclined face and a second inclined face which are
inclined forwardly at different angles, respectively, with respect to a plane normal to a
rotational axis, and the first inclined face is longer than the second inclined face so that
the back side face portion has a non-symmetrical convex "V" shape.
2. The cutting insert of claim 1, wherein the front side face portion comprises a pair
of cutting edges which are rotational symmetric to the rotational axis.
3. The cutting insert of claim 1, wherein an inclination angle of the first inclined face
is smaller than that of the second inclined face.
4. The cutting insert of claim 1, wherein the first inclined face of the back side face
portion is inclined at an angle of 5 to 15 degrees with respect to the plane perpendicular to
the rotational axis, and the second inclined face of the back side face portion is inclined at
an angle of 35 to 45 degrees with respect to the plane perpendicular to the rotational axis.
5. The cutting insert of claim 1, wherein a portion of an inner circumferential
surface of the through-hole is a flat plane which is inclined in an opposite direction to the
first inclined face.
6. The cutting insert of claim 1, wherein a recess for supplying a coolant is formed
in at least one of both the upper face and the lower face, an inlet portion of the recess is
formed in a boundary portion between the first inclined face and at least one of both the
upper face and the lower face, an outlet portion of the recess is formed in a boundary

portion between the cutting edge and at least one of both the upper face and the lower
face, and an intermediate portion for connecting the inlet portion and the outlet portion is
formed around the through-hole.
7. A cutting tool comprising:
a holder having a pocket formed on a front end portion thereof, the pocket having a
pair of jaws; and
a cutting insert indexably mounted to the pocket,
wherein the cutting insert comprises a upper face and a lower face corresponding
to each of jaws, respectively, a front side face portion and a back side face portion
corresponding to the pocket of the holder, the front and back side face portions
connecting the upper face and the lower face, and a through-hole passing through the
upper face and the lower face,
a cutting edge is formed in the front side face portion,
the back side face portion is provided a first inclined face and a second inclined
face which are inclined forwardly at different angles, respectively, with respect to a plane
normal to a rotational axis, and
the first inclined face is longer than the second inclined face so that the back side
face portion has a non-symmetrical convex "V" shape.
8. The cutting tool of claim 7, wherein an inclination angle of the first inclined face is
smaller than that of the second inclined face.
9. The cutting tool of claim 7, wherein the pocket of the holder is provided with a
first contact face and a second contact face which contact the first inclined face and the
second inclined face, respectively.

10. The cutting tool of claim 7, wherein the first contact face and the second
contact face form a non-symmetrical concave "V" shape.
11. The cutting tool of claim 7, wherein a portion of an inner circumferential surface
of the through-hole is a flat plane which is inclined in an opposite direction to the first
inclined face.

12. The cutting tool of claim 7, wherein a recess for supplying a coolant is formed in
at least one of both the upper face and the lower face, an inlet portion of the recess is
formed in a boundary portion between the first inclined face and at least one of both the
upper face and the lower face, a outlet portion of the recess is formed in a boundary
portion between the cutting edge and at least one of both the upper face and the lower
face, and an intermediate portion for connecting the inlet portion and the outlet portion is
formed around the through-hole.

The cutting insert according to the present invention comprises an upper face and
a lower face; a front side face portion and a back side face portion, the front and back side
face portions connecting the upper face and the lower face; and a through-hole passing
through the upper face and the lower face, wherein a cutting edge is formed in the front
side face portion, and the back side face portion is provided with a first inclined face and a
second inclined face which are inclined forwardly at different angles, respectively, with
respect to a plane normal to a rotational axis, and the first inclined face is longer than the
second inclined face so that the back side face portion has a non-symmetrical convex "V"
shape.