CUTTING TOOL ASSEMBLY FOR STABLE COUPLING STRUCTURE
TECHNICAL FIELD
[0001] This disclosure is related to coupling of a cutting tool assembly for
rotation.
BACKGROUND ART
[0002] A conventional rotating tool holder disclosed in CH 692 449 includes a
cutting head and a shank, which has two mating pins. The mating pins transmit
rotational torque with the help of a locking bolt. However, the pins are not easy
to disassemble and may be broken during machining.
[0003] Other conventional modular type boring bars do not have any structural
elements for torque transmission. Therefore, the coupling screws directly bear
the stress resulting from the boring rotation, and are vulnerable to breakage.
CONTENTS OF THE INVENTION
TECHNICAL PROBLEM TO BE SOLVED
[0004] The present disclosure aims to provide a cutting tool assembly having a
stable coupling structure and a longer tool life. The present disclosure also
aims to provide a cutting tool assembly having an interior coolant channel and a
leak- tight contact surface between a cutting head and a shank.
SOLUTION MEANS
[0005] A cutting tool assembly according to the present disclosure comprises a
cutting head having a flat coupling face provided with a multilateral recess, a
shank having a flat coupling face provided with a multilateral recess
corresponding to that of the cutting head, and a multilateral coupling plate fit
complementarily into the interior space created by both of the multilateral
recesses.
[0006] In the cutting tool assembly according to the present disclosure, the
multilateral coupling plate may have a central opening and be secured to the
multilateral recess of the shank by a fixing screw which passes through the
central opening thereof.

[0007] In the cutting tool assembly according to the present disclosure, the
central opening of the multilateral coupling plate is provided with a shoulder on
which the head of the fixing screw rests.
[0008] In the cutting tool assembly according to the present disclosure, the fixing
screw may have a wrench recess in its head.
[0009] In the cutting tool assembly according to the present disclosure, the
shank may have a coolant channel passing through a rotational axis thereof, the
cutting head may have a coolant channel, and the fixing screw may have a
coolant bore passing through the central axis thereof such that a coolant path is
formed all the way through the shank, the coupling plate, and the cutting head.
[0010] In the cutting tool assembly according to the present disclosure, the
wrench recess and the coolant bore may be aligned coaxially.
[0011] In the cutting tool assembly according to the present disclosure, the head
and the shank may be provided with screw holes corresponding to each other so
that coupling screws are engaged to secure the head to the shank.
[0012] In the cutting tool assembly according to the present disclosure, the
shank may be provided with an extra screw hole, which corresponds to a screw
hole of a cutting head for the other handed boring rotation.
TECHNICAL EFFECTS
[0013] The cutting tool assembly in accordance with this disclosure provides a
more stable coupling structure, since rotational torque is transmitted through the
multilateral coupling plate from the shank to the cutting head, whereas in the
prior art coupling screws are used to directly bear the torque force.
[0014] In the present technique in accordance with the present disclosure, the
shank and the head are allowed to be made of more rigid materials so as to
have a longer tool life.

[0015] In the present technique in accordance with the present disclosure,
contact between the shank and the head is made much better so as to be leak-
tight.
[0016] The present technique in accordance with the present disclosure is
adaptable for a shank of a much smaller diameter for small diameter boring.
BRIEF DESCRIPTION OF THE DRAWINGS
[0017] Fig.1 is a perspective view depicting the cutting tool assembly in
accordance with the present disclosure.
[0018] Fig.2 is a disassembled perspective view of the cutting tool assembly of
Fig. 1.
[0019] Fig. 3 is a perspective view of the shank to which the multilateral coupling
plate is secured by a fixing screw in accordance with the present disclosure.
[0020] Fig. 4 is a cross sectional view of the cutting tool assembly cut along the
line A-A shown in Fig. 3
MODES FOR CARRYING OUT THE INVENTION
[0021] Hereinafter, a cutting tool holder assembly according to 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.
[0022] Fig.1 is a perspective view depicting the cutting tool assembly in
accordance with the present disclosure. Fig.2 is a disassembled perspective
view of the cutting tool assembly of Fig. 1. Fig. 3 is a perspective view of the
shank to which the multilateral coupling plate is secured by a fixing screw. Fig.
4 is a cross sectional view of the cutting tool assembly cut along the line A-A
shown in Fig. 3.
[0023] The cutting tool assembly includes a cutting head 100 carrying a cutting

insert 101 and having a flat coupling face 110 provided with a multilateral recess
120, a shank 200 having a flat coupling face 210 provided with a multilateral
recess 220 corresponding to that of the cutting head 100, and a multilateral
coupling plate 300 fit complementarily into the interior space created by both of
the multilateral recesses 120,220. The multilateral coupling plate 300 and the
multilateral recesses 120,220 above generally have polygonal shapes such as
trilateral or quadrilateral, but also include other torque transmittable shapes such
as a star or shapes having a curved or undulating periphery.
[0024] The multilateral coupling plate 300 has a central opening 301 and is
secured to the multilateral recess 220 of the shank 200 by a fixing screw 320
which passes through the central opening 301 of the multilateral coupling plate
300.
[0025] The central opening 301 of the multilateral coupling plate 300 is provided
with a shoulder 302 on which the head of the fixing screw 320 rests. The fixing
screw 320 may have a wrench recess 322 in its head. The wrench recess
herein includes a driver groove.
[0026] The shank 200 has a coolant channel 230 passing through a rotational
axis thereof, and the cutting head 100 also has a coolant channel 103
corresponding to that of the shank 200. The fixing screw 320 has a coolant
bore 303 passing through the central axis thereof so that a coolant path is
formed all the way through the shank 200, the coupling plate 300, and the
cutting head 100. The wrench recess 322 and the coolant bore 303 are aligned
coaxially in the fixing screw 320.
[0027] The head 100 and the shank 200 are provided with screw holes 106, 206
corresponding to each other. When the head 100 is matched to the shank 200
with the coupling plate 300 interposed there between, coupling screws 105 are
engaged into the screw holes 106, 206 to secure the head 100 to the shank 200.
[0028] Figs. 1 and 2 depict a right-handed rotational cutting head. The shank
200 may be provided with an extra screw hole 209 on the flat coupling face 210,

which does not correspond to any of the screw holes 106 of the head 100.
However, this extra screw hole 209 may be used for a left-handed rotational
cutting head which has a screw hole corresponding to the extra screw hole 209.
The shank 200 with this extra screw hole 209 allows ambidextrous adaptability
for right-handed and left-handed cutting heads.
[0029] In the cutting tool assembly in accordance with this disclosure, rotational
torque is transmittable through the multilateral coupling plate 300 from the shank
200 to the head 100 so that coupling screws 105 do not directly bear the torque
force and the coupling is much more stable structurally.
[0030] Since the coupling plate is replaceable when it wears out, the shank and
the head are allowed to be made of more rigid materials than that of the
coupling plate so as to have a longer tool life.
[0031] Since the multilateral coupling plate 300 is detachable, the flat coupling
faces of the shank 200 and the head 100 can be machined flat with ease and
contact between the shank 200 and the head 100 is much better so as to be
leak- tight.
[0032] Since the coolant path is formed through the central axis of the fixing
screw 320, the multilateral coupling plate 300, and the shank 200, the present
technique is adaptable for a shank of a much smaller diameter for small
diameter boring.
[0033] The cutting tool assembly 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 tool assembly comprising,
a cutting head having a flat coupling face provided with a multilateral recess;
a shank having a flat coupling face provided with a multilateral recess
corresponding to that of the cutting head; and
a multilateral coupling plate fit complementarily into the interior space created by
both of the multilateral recesses.
2. The cutting tool assembly according to claim 1, wherein the multilateral coupling
plate has a central opening and is secured to the multilateral recess of the shank
by a fixing screw which passes through the central opening thereof.
3. The cutting tool assembly according to claim 2, wherein the central opening of
the multilateral coupling plate is provided with a shoulder on which the head of
the fixing screw rests.
4. The cutting tool assembly according to claim 2, wherein the fixing screw has a
wrench recess in its head.
5. The cutting tool assembly according to claim 2, wherein the shank has a coolant
channel passing through a rotational axis thereof, the cutting head has a coolant
channel, and the fixing screw has a coolant bore passing through the central
axis thereof such that a coolant path is formed all the way through the shank,
the coupling plate, and the cutting head.
6. The cutting tool assembly according to claim 5, wherein the fixing screw has a
wrench recess in its head, and the wrench recess and the coolant bore are
aligned coaxially.
7. The cutting tool assembly according to claim 1, wherein the cutting head and the
shank are provided with screw holes corresponding to each other so that
coupling screws are engaged to secure the cutting head to the shank.

8. The cutting tool assembly according to claim 7, wherein the shank is provided
with an extra screw hole, which corresponds to a screw hole of a cutting head
for the other handed rotation.

A cutting tool assembly is disclosed which comprises a cutting head having
a flat coupling face provided with a multilateral recess, a shank having a flat
coupling face provided with a multilateral recess corresponding to that of the
cutting head, and a multilateral coupling plate fit complementarily into the interior
space created by both of the multilateral recesses. The cutting tool assembly
in accordance with this disclosure provides a more stable coupling structure,
since rotational torque is transmitted through the multilateral coupling plate from
the shank to the cutting head, whereas in the prior art coupling screws are used
to directly bear the torque force.