Cutting by use of rotating axially moving tool – Tool-support
Reexamination Certificate
1999-06-02
2001-06-05
Wellington, A. L. (Department: 3722)
Cutting by use of rotating axially moving tool
Tool-support
C279S075000, C279S083000, C408S226000, C408S23900A, C408S23900A
Reexamination Certificate
active
06241434
ABSTRACT:
This application is based on Japanese patent applications, namely JP 10-194514, JP 10-305905, JP 10-370467, and JP 1131277 filed in Japan, the contents of which are incorporated hereinto by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a drill bit comprising a drill and a drill holder for holding the drill, a drill tool provided with the drill bit, and a manufacturing method of the drill bit.
2. Description of the Related Art
A drill bit is known, for instance as disclosed in Japanese Examined Patent Publication No. 8-18213/1996, comprising a drill part formed with a spiral bit on a circumference thereof and a holding part with a larger diameter than the drill part. The drill bit is drivingly rotated in a state that the holding part is held by, for instance, an electric drive source.
There has been a common practice, when manufacturing the drill bit, to shape the drill part and the holding part as one-piece unit by machining one metallic material with a lathe or the like.
However, the above machining process is cumbersome and requires a lot of processing, leading to a remarkable production cost rise.
As a means to solve the above problem, several drill bits have been proposed, as shown in
FIGS. 16A
to
16
C. In any of these prior art drill bits, the drill bit comprises a drill corresponding to the drill part and a holder corresponding to the holding part and is constructed such that a shank formed at a base end of the drill is inserted into an insertion hole formed in the holder to joint the drill together with the holder. The specific construction of these drill bits is described one by one with reference to
FIGS. 16A
to
16
C.
A drill bit
100
shown in
FIG. 16A
has a drill
200
including a main part
201
formed at a lead end thereof and a cylindrical shank
202
formed at a base end thereof. The drill main part
201
and the shank
202
are integrally formed. A spiral bit
203
is formed on the drill main part
201
, and an external thread
204
is formed at an end of the shank
202
.
The drill bit
100
has a holder
300
shaped into a cylinder with a larger diameter than the drill
200
. A screw hole
301
is formed inside a lead end of the holder
300
concentrically with an axis of rotation of the drill
200
. Screwing the external thread
204
of the shank
202
into the screw hole
301
enables mounting the drill
200
onto the holder
300
.
The drill bit
101
shown in
FIG. 16B
is constructed by inserting a shank
202
into an insertion hole
311
formed in a holder
310
and adhering the joint part of the shank
202
and the insertion hole
311
with a brazing filler metal
312
including silver and nickel alloy, in place of providing the external thread
204
and the screw hole
301
.
A drill bit
102
shown in
FIG. 16C
is constructed such that a flat part
204
is formed on an outer circumference of a shank
202
, and a press fit hole (screw hole)
322
is formed extending from an outer circumference of a holder
320
toward a shank insertion hole
321
to communicate with the flat part
204
. In this arrangement, inserting the shank
202
into the shank insertion hole
321
so as to set the flat part
204
in the press fit hole
322
and press fitting a metal piece
400
into the press fit hole
322
(or screwing an external thread
400
into the screw hole
322
) enables preventing relative rotation of a drill
200
to the holder
320
.
The drill bit
100
shown in
FIG. 16A
is constructed by screw joint of the drill
200
with the holder
300
. Accordingly, the joint state may be loosened due to vibration during working with a result that the drill
200
unnecessarily vibrates in spite of holding of the holder
300
and in a worst case, the drill
200
may come out from the holder
300
.
In the case of the drill bit
101
shown in
FIG. 16B
, if a large torque acts upon the drill bit
101
during working, adhesion of the joint part may be weakened, leading to breakage of the joint part. In such a case, the drill
200
may idly rotate relative to the holder
310
(namely, the torque is not transmitted to the drill
200
), making the drill bit
101
usable. Particularly, filling of the filler
312
between the shank
202
and the insertion hole
311
is insufficient (poor filling state), even application of a small torque may break the joint part. This is not desirable when seeking for reliability of the drill bit.
The construction of the drill bit
102
shown in
FIG. 16C
also does not provide an effective solution to prevent relative rotation of the drill
200
to the holder
320
because there is a possibility that the metal piece (or external thread)
400
may be loosened and come out from the press fit hole (or the screw hole)
322
due to vibration and centrifugal force generated during working.
Other fixation means such as close fitting the shank
202
in the insertion hole
311
by shrinkage fit or press fit can be applied. However, such fixation by a close fit cannot sufficiently resist a large torque generated when start the drill bit starts rotating, and the problem that the drill rotates relative to the holder cannot be avoided.
SUMMARY OF THE INVENTION
In view of the aforementioned problems residing in the prior art, it is an object of the invention to provide a drill bit, a drill tool provided with the drill bit, and a drill bit manufacturing method that can securely prevent rotation of a drill relative to a drill holder with a simplified construction and in a simplified manner.
To solve the above problems, this invention adopts the following arrangements.
A drill bit, according to an aspect of this invention, comprises a drill including a bit and a shank, and a drill holder formed with an axial insertion hole to fit the shank. The shank is formed with an engaging part, the drill holder is formed with a hole with a closed bottom extending from an outer circumference thereof in such a way as to intersect the insertion hole, and a stopper is inserted in the bottom of the hole, whereby a top of the stopper engages the engaging part to restrict relative rotation of the drill to the drill holder.
In this arrangement, fittingly inserting the shank of the drill into the insertion hole of the drill holder to engage the engaging part of the shank with the top of the stopper inserted in the hole securely prevents relative rotation of the drill with respect to the drill holder. Accordingly, simply mounting the thus constructed drill holder onto a certain drive source for rotation secures integral rotation of the drill bit for drilling.
Further, the top of the stopper engages the engaging part of the shank in a state that the stopper is inserted in the bottom of the hole. In this arrangement, even if an external force such as vibration is exerted on the drill bit, the possibility that the stopper comes out from the hole is eliminated, and thus secures prevention of a relative rotation of the drill and the drill holder for a long span of time.
A drill bit, according to another aspect of this invention, comprises a drill including a bit and a shank, and a drill holder formed with an insertion hole to fit the shank. The drill holder is formed with a hole extending radially halfway through the insertion hole in such a way as to intersect a bottom end of the insertion hole to thereby form a restricting part at the bottom end of the insertion hole. The shank is formed with an engaging part at an end thereof to engage the restricting part. Thereby, an engagement of the restricting part and the engaging part restricts relative rotation of the drill with respect to the drill holder.
In this arrangement, fitting the shank of the drill into the insertion hole of the drill holder to engage the engaging part of the shank with the restricting part formed at the bottom end of the insertion hole securely prevents a relative rotation of the drill to the drill holder. Accordingly, simply mounting the thus constructed drill holder onto a certain drive source for rotation secures integral rotation of the drill bit for dri
Carter Monica
House B.M. Co., Ltd.
Smith Patent Office
Wellington A. L.
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