Cutters – for shaping – Rotary cutting tool – Including holder having seat for inserted tool
Reexamination Certificate
2002-05-03
2004-09-14
Fridie, Jr., Willmon (Department: 3722)
Cutters, for shaping
Rotary cutting tool
Including holder having seat for inserted tool
C407S047000, C407S049000
Reexamination Certificate
active
06789983
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a mechanism for clamping a cutting insert used in a rotary cutting tool such as a face milling cutter. It also relates to a cutting insert to be clamped by the mechanism.
BACKGROUND ART
Researchers and engineers have been improving the cutting method for soft materials such as aluminum alloys in order to increase machining precision and productivity. In particular, in the field of the milling of soft aluminum alloys, the cutting efficiency has increased notably by employing high-speed rotation in comparison with the cutting of ordinary steel materials. In other words, cutting tools have been rotated at increasingly high speeds. Cutting tools for milling aluminum alloys usually use cemented-carbide inserts and coated inserts. However, the use of polycrystalline-diamond (PCD) inserts has been increasing in recent years. PCD inserts can prevent the aluminum component from welding onto the cutting edge, improving the finishing precision. Consequently, PCD inserts can have sufficient resistance to high-speed cutting.
When a cutting tool is operated at high rotational speeds to increase efficiency, considerable centrifugal force is applied to the peripheral portion of the cutting tool. The force may scatter cutting inserts and insert-holding parts to the outside, and become a serious safety hazard. Therefore, it is necessary to solve this potential problem prior to the application of high-speed operation. A number of proposals to prevent scattering have been disclosed thus far.
FIG. 7
is an example of the prior art for securing a cutting insert (hereinafter referred to as insert) with a wedging member. This example has been disclosed by the published Japanese patent application Tokukaihei 5-138426. In
FIG. 7
, the individual members are denoted by the following numbers:
1
: a tool body;
2
: an insert;
3
: a wedging member;
4
: a clamping bolt;
5
: a holding member;
6
: a recess; and
7
: a projection. The insert
2
is held by fitting the projection
7
provided on the front face of the holding member
5
into the recess
6
provided on the rear face of the insert
2
. This patent application has also disclosed another structure in which the insert
2
is directly held by fitting the projection
7
provided directly on the tool body into the recess
6
without using the holding member
5
.
The wedging member
3
is held such that the turning of the clamping bolt
4
can move the wedging member
3
back and forth in the radial direction of the tool body
1
. Thus, one side of the wedging member
3
presses the front face of the insert
2
to prevent it from springing out. When loosened, the wedging member
3
and the clamping bolt
4
can move in the axial direction of the tool body
1
, facilitating the attaching and detaching of the insert
2
.
Another published Japanese patent application, Tokukai 2000-15503, has disclosed another method for preventing the spring-out of an insert by using a wedging member. In this application, the fitting of the insert is performed by replacing the recess of the insert shown in
FIG. 7
with a through hole and concurrently replacing the projection of the holding member with a pinning member. Yet another published Japanese patent application, Tokukaihei 11-10435, has disclosed another method. This method not only prevents the spring-out of an insert by pressing the slanted face of the insert or a holding member with a wedging member but also enables the draw-out of the insert or the holding member in the axial direction of the tool body. This structure allows easy attachment and detachment of the insert or the holding member merely by slightly loosening the wedging member.
In the above description, when an insert is attached by the fitting of the recess and the projection or by the fitting of the through hole and the pin, a clearance must be provided at the fitting portion for enabling easy attachment and detachment of the insert. This clearance, however, allows the insert to shift by the amount of the clearance when centrifugal force is applied during high-speed rotation. This shift disturbs, the balanced amounts of the cutting among the inserts, causing uneven thicknesses of the metal chips produced by the cutting operation. As a result, an excessive load is applied to the shifted insert. This load may cause a fracture and subsequent spring-out of the insert.
Although the fixing of the insert with the wedging member can prevent the shift and spring-out of the insert, the centrifugal force may cause the wedging member itself to spring out because the wedging member is attached without restriction in the direction of the centrifugal force. Furthermore, the use of the wedging member is unavoidably accompanied by the reduction in the stiffness of the tool body. The intense tightening force broadens the groove that houses the insert and wedging member, generating distortion and strain in the tool body. When centrifugal force is applied due to high-speed rotation of the tool, the distortion and strain will be released, increasing the risk of the spring-out of the wedging member.
Yet another published Japanese patent application, Tokuhyouhei 10-508259, has disclosed another method shown in FIG.
8
. This method attaches an insert without using a recess-projection fit or a pin fit and yet without using a wedging member. In
FIG. 8
, the individual members are denoted by the following numbers:
11
: a tool body;
12
: an insert;
13
: a cartridge (holding member);
14
: an insert-attaching screw;
15
: a cartridge-receiving recess;
16
: a holding screw;
17
: an adjusting screw;
18
: a threaded hole; and
19
: a set screw.
As shown in
FIG. 8
, the insert
12
is attached to the tool body
11
through the cartridge
13
. The insert
12
is positioned in a pocket
13
a
of the cartridge without being turned and is fixed by the insert-attaching screw
14
. The cartridge
13
is fixed in the cartridge-receiving recess
15
of the tool body
11
with the holding screw
16
and the set screw
19
.
A cartridge hole
13
b
into which the holding screw
16
is inserted has a diameter slightly larger than that of the holding screw
16
so that the position of the cartridge
13
can be adjusted upward and downward and leftward and rightward. The upward and downward adjustment of the cartridge
13
is performed by inserting the adjusting screw
17
into an inclined hole
13
c
provided at an upper portion of the cartridge
13
. This adjustment controls the amount of the front protrusion of the insert
12
.
The cartridge-receiving recess
15
has an inner wall
15
a
that is parallel to its position's tangent on the peripheral circle of the tool body
11
and a side wall
15
b
that is slanted to the normal direction of the inner wall
15
a
by an angle of about 10 degrees. The cartridge
13
to be mated with these walls has a back face
13
d
and a side face
13
e
between which the same angle as above is provided. The threaded hole
18
is provided from the peripheral surface of the tool body
11
to the cartridge-receiving recess
15
. The set screw
19
is screwed into the threaded hole
18
to press the other side face
13
f
of the cartridge
13
, so that the back face
13
d
and the side face
13
e
of the cartridge
13
are strongly mated with the inner wall
15
a
and the side wall
15
b
of the recess
15
, respectively. Thus, the cartridge
13
is fixed.
The side face
13
f
of the cartridge
13
has an indentation (not shown in
FIG. 8
) into which the end of the set screw
19
is fitted. The spring-out of the cartridge
13
due to the centrifugal force is prevented by fitting the set screw
19
into the indentation and by pressing the side face
13
e
of the cartridge against the side wall
15
b
having an acute angle to the inner wall
15
a.
Unlike the structure shown in
FIG. 7
, the one shown in
FIG. 8
is designed to attach an insert without using a recess-projection fit or a pin fit and yet without using a wedging member. This design therefore can prevent the shift of the insert due
Fridie Jr. Willmon
Greenblum & Bernstein P.L.C.
Sumitomo Electric Industries Ltd.
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