End mill chucking structure

Details End mill chucking structure End mill chucking structure

2000-01-20

2002-05-28

Bishop, Steven C. (Department: 3722)

Chucks or sockets

Socket type

Friction grip

C029S447000, C403S273000, C409S234000, C408S057000, C279S083000

Reexamination Certificate

active

06394466

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a chucking structure for chucking an end mill having a relatively small diameter and used, for example, for deep milling of a die.
2. Description of the Related Art
FIG. 1
shows a conventional end mill chucking structure. As shown in
FIG. 1
, a straight hole
1
c
is formed in a front cylindrical portion
1
b
of a holder body
1
a
of a tool holder
1
. An end mill
2
includes an end mill body
2
a
, which, in turn, includes a round-rod-shaped shank portion
2
b
. A rear portion of the shank portion
2
b
of the end mill
2
is fitted into the straight hole
1
c
formed in the tool holder
1
. A plurality of side lock members
3
a
and
3
b
are screwed into the front cylindrical portion
1
b
of the tool holder
1
from the outer circumferential surface thereof so as to press the fitted rear portion of the shank portion
2
b
against the wall surface of the straight hole
1
c
, thereby fixedly attaching the end mill
2
to the tool holder
1
.
In the case of the conventional end mill
2
shown in
FIG. 1
, a relatively long front portion of the shank portion
2
b
projects frontward from the tool holder. Thus, the shank portion
2
b
fails to maintain sufficient rigidity, resulting in an impairment in cutting performance and involving vibration, such as pitching, during cutting.
FIG. 2
shows another conventional end mill chucking structure. An end mill
2
includes an end mill body
2
a
of carbide, which, in turn, includes a shank portion
2
b
shorter than that shown in FIG.
1
. An end portion of the shank portion
2
b
is shrink-fitted into a straight hole
1
c
formed in a tool holder
1
. The outer circumferential surface of the end portion of the shank portion
2
b
is gripped by means of the wall surface of the straight hole
1
c
formed in the tool holder
1
; i.e., single-surface restraint is established so as to fixedly attach the end mill
2
to the tool holder
1
.
In the case of the conventional shrink-fitted chucking as shown in
FIG. 2
, the tool holder
1
is heated, and then the shank portion
2
b
of the end mill
2
is fitted to the tool holder
1
. When the shank portion
2
b
is to be removed from the tool holder
1
, the entire tool holder
1
, to which the end mill
2
is attached, is heated so as to be thermally expanded. Then, the shank portion
2
b
is removed from the tool holder
1
. Accordingly, the material of the tool holder
1
has a greater coefficient of thermal expansion than does the material of the end mill
2
; i,e., the tool holder
1
and the end mill
2
must be formed of metals of different coefficients of thermal expansion.
In this connection, the applicant of the present invention filed Japanese Patent Application No. 10-354175 on Dec. 14, 1998 in relation to a shank-integrated end mill. As is disclosed in the patent application, a front portion of a holder body of an end mill holder is formed into a taper portion which tapers down frontward. A small-diameter hole is formed coaxially in the taper portion in such a manner as to extend rearward from a front end. A rear portion of a shank portion of an end mill body is formed into a small-diameter portion. The small-diameter portion of the end mill body is shrink-fitted into the small-diameter hole formed in the holder body, such that a shoulder located at the front end of the small-diameter portion abuts the front end face of the taper portion of the holder body. Cutting means is provided at a front end portion of the end mill body. In the shank-integrated end mill, the shank portion of the end mill body is rendered short to thereby decrease the cost of the end mill. Further, the outer circumferential surface of the small-diameter portion of the shank portion of the end mill body is gripped by means of the wall surface of the small-diameter hole formed in the end mill holder, and the entire face of the shoulder of the shank portion abuts the front end face of the end mill holder; i.e., two-surface restraint is established so as to fixedly attach the end mill body to the holder body. Thus, the rigidity of the end mill becomes considerably high, so that vibration hardly occurs during cutting, resulting in good cutting performance.
FIG. 3
shows still another conventional end mill chucking structure using a collet. The collet includes a taper shank portion
4
A, which is fitted into a taper hole
1
A formed in a tool holder
1
, and a taper arbor portion
4
B, which extends over a predetermined length from the larger-diameter end of the taper shank portion
4
A coaxially with and in opposition to the taper shank portion
4
A while tapering down. A straight hole
4
C having a predetermined length and diameter is formed coaxially in the arbor portion
4
B in such a manner as to extend from the front end thereof toward the taper shank portion
4
A. The arbor portion
4
B is heated to a temperature of about 300° C. to thereby be thermally expanded. A straight shank portion
2
b
of an end mill
2
is fitted into the thermally expanded straight hole
4
C. The end mill
2
is thus chucked in the collet
4
through shrink fit.
The taper shank portion
4
A of the collet
4
to which the end mill
2
is shrink-fitted is inserted into the taper hole
1
A formed in the tool holder
1
. Subsequently, a draw bolt
5
is screwed into a female-threaded hole
4
D formed in an end portion of the taper shank portion
4
A so as to fixedly attach the collet
4
to the tool holder
1
, thereby fixedly attaching the end mill
2
to the tool holder
1
.
In the case of the conventional shrink-fitted chucking as shown in
FIG. 3
, the shank portion
2
b
of the end mill
2
and the hole
4
C, into which the shank portion
2
b
is shrink-fitted, are both straight. Accordingly, when the shank portion
2
b
of the end mill
2
is to be shrink-fitted into the straight hole
4
C formed in the collet
4
or when the end mill
2
is to be removed from the collet
4
through application of heat, the arbor portion
4
B of the collet
4
must be heated to a temperature of 300° C. or higher for smooth shrink-fitting or removal. When shrink-fitting or removal is repeated frequently for replacement of the end mills
2
, the material of the arbor portion
4
B undergoes a change in physical properties due to frequent application of heat, even when the collet
4
is made of special steel having excellent coefficient of thermal expansion and strength. As a result, the collet
4
fails to chuck the end mill
2
reliably.
Since the end mill
2
shrink-fitted to the collet
4
is restrained merely by means of the shank portion
2
b
in contact with the wall surface of the strait hole
4
C formed in the collet
4
, the rigidity of an end portion of the end mill
2
if projecting from the collet
4
becomes relatively low, resulting in a strong likelihood of subtle vibration during cutting.
SUMMARY OF THE INVENTION
An object of the present invention is to solve the above problems involved in the conventional end mill chucking structure, and to provide attend mill chucking structure enabling press-fitting, shrink-fitting, or removal of an end mill through application of heat at relatively low temperature in order to prevent a change in physical properties of material and capable of improving the rigidity of the end mill.
To achieve the above object, the present invention provides an end mill chucking structure comprising an end mill holder, which comprises a holder body, and an end mill, which in turn comprises an end mill body and cutting means provided at a front end portion of the end mill body. The holder body has a taper hole formed in a front portion thereof. The taper hole tapers down rearward and extends rearward from a front end of the holder body. Herein, the term “front” refers to a cutting-end side of the end mill attached to the end mill holder with respect to the axial direction of the end mill holder, and the term “rear” refers to the side opposite the front side. A rear portion of the end mill body is formed into a shank porti

Affiliated with

Also associated with

Rating

End mill chucking structure does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with End mill chucking structure, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and End mill chucking structure will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-2890908