CUTTING INSERT
Technical Field
[0001] This disclosure is related to a cutting insert mountable in a cutting tool.
Background Art
[0002] In general, a machining tool mounted with a cutting insert is used in the field of
cutting machining such as drilling, milling, and turning. A cutting insert used in heavy-
duty machining requiring high depth of cut and feed rate experiences large vibrations
caused by high cutting resistance, leading to decreased tool life. Moreover, the
market nowadays demands higher productivity, so both roughing and finishing
operations need to be conducted simultaneously without changing the insert.
Therefore, there has been wide demand for cutting inserts which have excellent chip
control for high depth of cut and feed rate as well as for small cutting conditions, and
are adaptable for a wide range of machining operations for roughing and finishing,
without excessively increasing the cutting resistance.
Disclosure
Technical Problem
[0003] The present disclosure aims to provide a single sided cutting insert having
excellent chip control for heavy-duty machining and being adaptable for a wide range
of machining operations for roughing and finishing without excessively increasing the
cutting resistance.
Technical Solution
[0004] A cutting insert according to the present disclosure is hexahedral-shaped and
has an upper surface, a lower surface, a plurality of side surfaces connecting the
upper surface and the lower surface and a central hole passing through the upper and
lower surfaces. The lower surface has a flat mounting surface, and the upper surface
is curved concavely over the whole area thereof and is provided with cutting edges
along the borderline to the side surfaces, and corner cutting edge portions formed at
the borders of two adjacent cutting edges. The cutting edges are formed such that the
height is largest at corner cutting edge portions and smallest in the middle portions. A
land portion, a downward inclined surface, a bottom surface, and a seating surface
portion are formed from the cutting edges inwards on the upper surface. A plurality of
semispherical protrusions are formed on border portions between the downward
inclined surface and the bottom surface, and at least one corner cutting edge portion
has a corner bottom surface surrounded by an arc belt protrusion which connects two
adjacent semispherical protrusions.
[0005] In the cutting insert according to the present disclosure, the remaining semi-
spherical shaped protrusions other than those surrounding the corner bottom surface
may be extended inward by an elliptic-semispherical protrusion, of which the height
from the bottom surface is larger so that two-step protrusions are formed.
[0006] In the cutting insert according to the present disclosure, the height of the arc
belt protrusion from the bottom surface may be smaller than that of the adjacent
semispherical protrusions.
[0007] In the cutting insert according to the present disclosure, the depth of the arc
belt protrusion from an imaginary surface extended form the cutting edges may be no
more than twoiimes that of the adjacent semispherical protrusions.
[0008] The cutting insert according to the present disclosure may further comprise a
belt protrusion extension which connects the center of the arc belt protrusion to the
seating surface portion along an imaginary diagonal line in the direction towards the
central hole.
[0009] The cutting insert according to the present disclosure may further comprise a
plurality of supplemental protrusions along the border potion between the bottom
surface and the seating surface portion, wherein the supplemental protrusions and
the semispherical protrusions are placed alternately when viewed along the cutting
edges.
Description of Drawings
[0010] Fig.1 is a perspective view depicting a cutting insert in accordance with the
present disclosure.
[0011] Fig.2 is a side view of a cutting insert in accordance with the present disclosure.
[0012] Fig.3 is a planar view of a cutting insert in accordance with the present
disclosure.
[0013] Figs. 4a to 4d are vertical cross sectional views of the cutting insert cut along
imaginary lines a to d, respectively, shown in Fig. 3.
Mode for Invention
[0014] Hereinafter, a cutting insert according to the embodiments of the present
disclosure is 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.
[0015] A cutting insert according to this disclosure has an upper surface 100, a lower
surface 200, a plurality of side surfaces 300 connecting the upper surface 100 and the
lower surface 200, and has a hexahedral shape. The cutting insert has a central hole
400 passing through the upper and lower surfaces 100,200.
[0016] The lower surface 200 has a flat mounting surface adaptable for heavy duty
machining.
[0017] The upper surface 100 is curved concavely over the whole area thereof, and is
provided with cutting edges 101 along the borderline to the side surfaces 300 and
corner cutting edge portions 102 formed at borders of two adjacent cutting edges.
Since the upper surface 100 has a concave curvature over the whole area, the cutting
edges also have a concave curvature accordingly, such that the height is largest at
corner cutting edge portions and smallest in the middle portions. This concave
curvature of the upper surface 100 allows evacuated chips to break away easily from
the work-piece and lowers cutting resistance while machining.
[0018] A land portion 110, a downward inclined surface 120, a bottom surface 130,
and a seating surface portion 140 are formed consecutively from the cutting edge 101
inwards on the upper surface 100. Since this surface structure is formed over the
overall curvature of the upper surface 100, a uniform chip flow is obtained at various
cutting depths. The seating surface portion 140 serves as an upper supporting
surface when the cutting insert is mounted on a cutting tool.
[0019] A plurality of semispherical protrusions 121,122 are formed on border portions
between the downward inclined surface 120 and the bottom surface 130. These
semispherical protrusions 121,122 allow effective chip control at a small feed rate.
[0020] At least one corner cutting edge portion 102 has a corner bottom surface 130a
surrounded by an arc belt protrusion which connects two diagonally
symmetrical and adjacent semispherical protrusions 121 as shown in Figs 1 and 3.
The cutting insert generally has a rhombus shape and the corner cutting edge
portions 102 are formed at both diagonal corners forming an acute angle. The height
of the arc belt protrusion 131 from the bottom surface 130 is preferably smaller than
that of the adjacent semispherical protrusions 121. When an imaginary surface is
drawn by extending from the cutting edges 101 with the overall curvature of the upper
surface 100, the depth of the arc belt protrusion 131 from the imaginary surface is
preferably no more than two times that of the adjacent semispherical protrusions 121,
[0021] The surrounded corner bottom surface 130a allows effective :Chip control at
small depths of cut and small feed rates. Since bending stress to the chip becomes
large at higher feed rates, the lower arc belt protrusion 131 can make chips curl
without excessively increasing cutting resistance and so provides good chip control.
If the height of the arc belt protrusion 131 is too small, curls are not formed, whereas
if the height is too large, curls remain in the surrounded corner bottom surface 130a
too long and cutting resistance becomes large.
[0022] The remaining semispherical shaped protrusions 122 other than those
surrounding the corner bottom surface 130a may be extended inward by elliptic-
semispherical protrusions 123 of which the height from the bottom surface 130 is
larger so that two-step protrusions 124 are formed. While the semispherical
protrusions 121,122 allow effective chip control at small feed rates, the higher elliptic-
semispherical protrusions 123 of the two-step protrusions allow effective chip control
at high feed rates. The two-step protrusions reduce contact area with chips and so
reduce the cutting resistance and increase heat radiation through evacuated chips.
[0023] The cutting insert may include a belt protrusion extension 132 which connects
the center of the arc belt protrusion 131 to the seating surface portion 140 along an
imaginary diagonal line in the direction towards the central hole 400. The belt
protrusion extension 132 prevents chip flow over the arc belt protrusion 131 from
contact with the bottom surface 130 of the insert and so further increases the
possibility of heat radiation through evacuated chips.
[0024] The cutting insert may include a plurality of supplemental protrusions 141 in a
semispherical shape along the border potion between the bottom surface 130 and the
seating surface portion 140, wherein the supplemental protrusions 141 and the
semispherical protrusions 122 are preferably placed alternately when viewed along
the cutting edges as shown in Figs. 1 and 3. The supplemental protrusions 141 allow
better chip control by making bigger waves of the chips at higher feed rates.
[0025] Therefore, the cutting insert according to this disclosure has excellent chip
control for high depths of cut and feed rates as well as for small cutting conditions,
and are adaptable for a wide range of machining operations without excessively
increasing the cutting resistance.
[0026] The cutting insert 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.
Industrial Applicability
[0027] The cutting insert in accordance with this disclosure allows evacuated chips to
break away easily from the work-piece and lowers cutting resistance while machining.
[0028] The cutting insert in accordance with this disclosure allows effective chip
control at a small feed rate as well as under heavy duty cutting conditions, without
excessively increasing cutting resistance. The cutting insert in accordance with this
disclosure reduces the contact area with chips and so reduces the cutting resistance
and increases heat radiation through evacuated chips.
CLAIMS:
1. A hexahedral-shaped cutting insert having an upper surface, a lower surface,
a plurality of side surfaces connecting the upper surface and the lower surface and a
central hole passing through the upper and lower surfaces, wherein
the lower surface has a flat mounting surface,
the upper surface is curved concavely over the whole area thereof, and is provided
with cutting edges along the borderline to the side surfaces and corner cutting edge
portions formed at borders of two adjacent cutting edges, the cutting edges formed
such that the height is largest at corner cutting edge portions and smallest in the
middle portions, and
a land portion, a downward inclined surface, a bottom surface, and a seating surface
portion are formed from the cutting edges inwards on the upper surface,
a plurality of semispherical protrusions are formed on border portions between the
downward inclined surface and the bottom surface, and
at least one corner cutting edge portion has a corner bottom surface surrounded by
an arc belt protrusion which connects two adjacent semispherical protrusions.
2. The cutting insert according to claim 1, wherein the remaining semi-spherical
shaped protrusions other than those surrounding the corner bottom surface are
extended inward by an elliptic-semispherical protrusion, of which the height from the
bottom surface is larger so that two-step protrusions are formed.
3. The cutting insert according to claim 1 or 2, wherein the height of the arc belt
protrusion from the bottom surface is smaller than that of the adjacent semispherical
protrusions.
4. The cutting insert according to claim 3, wherein the depth of the arc belt
protrusion from an imaginary surface extended form the cutting edges is no more than
two times that of the adjacent semispherical protrusions.
5. The cutting insert according to claim 1 or 2, further comprising a belt
protrusion extension which connects the center of the arc belt protrusion to the
seating surface portion along an imaginary diagonal line in the direction towards the
central hole.
6. The cutting insert according to claim 1 or 2, further comprising a plurality of
supplemental protrusions along the border potion between the bottom surface and the
seating surface portion, wherein the supplemental protrusions and the semispherical
protrusions are placed alternately when viewed along the cutting edges.