Metal tools and implements – making – Blank or process – Drill
Reexamination Certificate
2002-12-18
2004-02-24
Watts, Douglas D. (Department: 3724)
Metal tools and implements, making
Blank or process
Drill
C409S066000
Reexamination Certificate
active
06694847
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a cutting tip which can be manufactured at low cost, and to the manufacture thereof.
2. Description of the Related Art
Generally, cutting tools are made by attaching a hard cutting tip to the end of a tool body. Cutting tip of this kind include for example the “Twist Drill” disclosed in Japanese Utility Model Laid-Open Publication No. HEI-5-63717 and the “Drill” disclosed in Japanese Utility Model Laid-Open Publication No. HEI-3-117520.
In the “Twist Drill” of Japanese Utility Model Laid-Open Publication No. HEI-5-63717, a wedge-shaped very high pressure sintered tip integrated with a cylindrical body part made from cemented carbide is used as the starting blank of a cutting edge body. This starting blank is fixed to a tool body by a method such as brazing, and the shape of an edge is formed to complete the cutting tool. However, in this “Twist Drill”, the starting blank is difficult to manufacture and is expensive. Consequently, as a result of the cost of the cutting tip being high, there has been the problem that the cutting tool is expensive.
In the “Drill” of Japanese Utility Model Laid-Open Publication No. HEI-3-117520, a drill is manufactured by cutting out a pentagonal tip blank from a disc made by surrounding a disc of cemented carbide with a ring-shaped a hard sintered compact. However, in the manufacture of this drill, from a disc of cemented carbide surrounded by a ring of a hard sintered compact, only from one to a few of the pentagonal tip blanks can be cut out, and the yield is poor. Consequently, not much effect of reducing the cost of the cutting tip or the cost of the cutting tool can be expected.
FIGS. 59A through 59C
illustrate a typical thread-cutting method of related art.
FIG.
59
A: A drill
512
is set in a machine tool
510
; the drill
512
is aligned with a cored hole
511
, and machining of a prepared hole is started. The point angle &thgr; of the drill
512
is 120° in general.
FIG.
59
B: Next, the drill
512
is replaced with a tap
514
for thread-cutting. The reference numeral
513
denotes the prepared hole made with the drill
512
, and its depth is D
1
. The tap
514
is aligned with this prepared hole
513
and thread-cutting is started.
FIG.
59
C: The reference numeral
515
denotes a female thread formed by the tap
514
. The tap
514
is replaced with a chamfering tool
516
, and the entrance of the thread
515
is chamfered with the chamfering tool
516
. The reference numeral
517
denotes the chamfer. If the length of the thread
515
including this chamfer
517
is written D
2
, then an unthreaded part of length (D
1
-D
2
) remains.
In this thread-cutting method of related art, to form the thread
515
, a drill, a tap and a chamfering tool are necessary; thus the number of tools required is large, tool supply costs are high and tool management costs are high. Also, it is necessary for tools to be interchanged during the process from the hole-making to the chamfering. Because of this, the cutting work must be stopped for every tool change, the thread-cutting machining operation is troublesome, and there are problems of productivity.
Also, because an unthreaded part of length (D
1
-D
2
) is unavoidable, the unthreaded part must be allowed for in the casting, and consequently there has been the problem that it is not possible to make the casting thin.
Next, as the cutting tool for finishing the hole, generally a reamer is used, to finish the opened hole in advance exactly and obtain a smooth finished surface at the same time. By machining the hole with a reamer, an accurate hole can be obtained. As the procedure for finishing a hole with a reamer, first a small-diameter hole is made with a drill, and then by dragging the wall of the hole with the reamer the hole diameter is finished to the required accuracy (for example, dimensional accuracy H7 (JIS B 0401).
Thus, a reamer is necessary to obtain an accurate hole; however, with this finishing method, the number of tools required is large, numerous tools have to be set on and removed from the machine tool, and preparation is troublesome. Also, hole-finishing with a reamer takes time, and it is necessary for machining with the machine tool to be stopped for the tool change from the drill to the reamer to be carried out. Consequently, the productivity of the hole-machining is low.
SUMMARY OF THE INVENTION
It is therefore a first object of the present invention to provide an inexpensive cutting tip and cutting tool and a method by which this cutting tool can be manufactured.
It is a second object of the invention to provide a thread-cutting method with which it is possible to reduce the number of tools required for thread-cutting and to dispense with an unthreaded part.
It is a third object of the invention to provide a hole-finishing drill which allows good productivity.
According to a first aspect of the present invention, there is provided a cutting tip having a first layer consisting of a cemented carbide tool material, a second layer consisting of a hard sintered compact of CBN or diamond, and a third layer consisting of a cemented carbide tool material; the second layer is sandwiched by the first layer and the third layer to form a three-layer laminate, and a cutting edge is formed in the second layer.
Because the cutting tip as a whole is a three-layer structure, and the second layer is reinforced on both sides by the first layer and the third layer, the rigidity of the tip increases.
According to a second aspect of the present invention, there is provided a method for manufacturing a cutting tip, the method including a preparation step of preparing a three-layer laminate wherein a second layer consisting of a hard sintered compact of CBN or diamond is sandwiched by a first layer and a third layer consisting of a tool material such as cemented carbide, a first cutting step of cutting out a prismatic blank of rectangular cross-section by cutting the first layer, the second layer and the third layer in order substantially perpendicularly to the upper face of the first layer, a second cutting step of cutting out a semi-completed tip including the second layer in the middle thereof by cutting from one cut face of the prismatic blank to the other cut face, and a finishing step of obtaining a completed tip by forming on the semi-completed tip a rake face, a cutting edge and a flank.
Because the three-layer laminate is cut in strips and semi-completed tips are cut out from the prismatic blanks obtained, semi-completed tips can be obtained in large numbers. Consequently yield is good, and the manufacturing cost of the tip can be greatly reduced.
According to a third aspect of the present invention, there is provided a cutting tool made up of a shank and a tip attached to the shank, wherein the tip is made from a three-layer laminate wherein a second layer consisting of a hard sintered compact of CBN or diamond is sandwiched by a first layer and a third layer consisting of a tool material such as cemented carbide, and when the cutting tool is seen in front view, the second layer is a narrow band passing through the center of rotation of the tool, a cutting edge is formed in this narrow band, and the second layer is reinforced on both sides by the first layer and the third layer.
If an oil passage is formed in the shank and another oil passage is formed in the second layer of the tip and the two oil passages connect in a straight line, cutting oil can be injected through the oil passages at the time of cutting. And these holes can be utilized as positioning parts when the tip is attached to the shank.
According to a fourth aspect of the present invention, there is provided a method for manufacturing a cutting tool made up of a shank and a tip attached to the shank, the method including a preparation step of preparing a three-layer laminate wherein a second layer consisting of a hard sintered compact of CBN or diamond is sandwiched by a first layer and a third layer consisting of a tool material such as cemented c
Fukushima Hiroyuki
Hiroyasu Minoru
Isibasi Satomi
Ito Masatomi
Nomura Hiroyuki
Merchant & Gould P.C.
Watts Douglas D.
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