Cutting by use of rotating axially moving tool – Tool or tool with support – Having peripherally spaced cutting edges
Reexamination Certificate
2000-10-04
2003-05-27
Howell, Daniel W. (Department: 3722)
Cutting by use of rotating axially moving tool
Tool or tool with support
Having peripherally spaced cutting edges
C076S108100, C408S0010BD, C408S181000, C408S23900A
Reexamination Certificate
active
06568883
ABSTRACT:
TECHNICAL FIELD
The present invention relates in general to a method of finishing inner circumferential surfaces of a plurality of holes, which are arranged along a line and spaced apart from each other in the axial direction of the holes, and a reamer suitable for the same method.
BACKGROUND ART
There is a demand for finishing inner circumferential surfaces of a plurality of holes, such as camshaft holes of an engine, which are arranged along a line and axially spaced apart from each other, with a high degree of concentricity between the holes and a high degree of dimensional accuracy of each hole. To satisfy such a demand, there has been conventionally employed a single-blade reamer having a cutting tip fixedly attached to the tool body, or a cutting tip slidably attached to the tool body such that the position of the cutting tip relative to the tool body is finely adjustable by an adjusting mechanism which is built in the tool body. It is preferable that the single-blade reamer has a plurality of land surfaces formed in an outer circumferential surface thereof and axially extending from a distal end thereof toward a proximal end thereof, and that the cutting tip having major and minor cutting edges is positioned in one of the land surfaces. Further, it is desirable that the cutting tip is constituted by a sintered-compact cutting tip or other cutting tip which has a hardness higher than that of cemented carbide.
However, where the demand is very severe, namely, where the required degrees of concentricity and dimensional accuracy are considerably high, it is not easy to satisfy such a severe demand even by using the above-described reamer.
DISCLOSURE OF INVENTION
The present invention was made under this situation, and the object of the invention is therefore to provide a method of finishing inner circumferential surfaces of a plurality of holes which are arranged along a line and spaced apart from each other in the axial direction of the holes, and a reamer suitable for practicing the same method, which assure a required degree of concentricity between the holes and a required degree of dimensional accuracy of each hole even where the required degrees of concentricity and dimensional accuracy are considerably high.
The present invention provides an inner-circumferential-surface finishing method or a reamer according to each of the following modes of the invention, which are numbered and dependent from each other like the appended claims, where appropriate. It is to be understood that the following modes are provided to facilitate the understanding of possible combinations of features recited in the following modes, and that the technical features and the combinations of the technical features disclosed in the present specification are not limited to the following modes.
(1) A method of finishing inner circumferential surfaces of a plurality of holes which are arranged along a line and spaced apart from each other in an axial direction of the plurality of holes by using a reamer, the method being characterized in that:
the reamer comprises at least one land surface which is formed in an outer circumferential surface of the reamer and which extends from an axially distal end of the reamer toward an axially proximal end of the reamer, an axially-distal-end small-diameter portion which extends over a predetermined axial distance from the axially distal end toward the axially proximal end, a guide portion which is axially adjacent to the axially-distal-end small-diameter portion, and major and minor cutting edges which are formed in at least one of the at least one land surface in the axially-distal-end small-diameter portion, the at least one land surface having a turning radius which is smaller in the axially-distal-end small-diameter portion than in the guide portion, the minor cutting edge having a turning radius which is larger than the turning radius of the at least one land surface in the axially-distal-end small-diameter portion and which is smaller than the turning radius of the at least one land surface in the guide portion;
and wherein the plurality of holes are finished in order of the arrangement of the plurality of holes in the line, such that an inner circumferential surface of an outermost one of the plurality of holes is first finished by the major and minor cutting edges of the reamer, and such that an inner circumferential surface of each of the other of the plurality of holes is then finished by the major and minor cutting edges, with the guide portion being fitted in at least one of the plurality of holes whose inner circumferential surface has been finished by the major and minor cutting edges.
The major and minor cutting edges may be formed integrally with the land surface, or alternatively may be formed in a cutting tip which is removably fixed to the reamer. Further, the reamer may have an adjusting mechanism built therein which permits fine adjustment of position of the cutting tip (turning radius of the minor cutting edge).
In the finishing operation to the holes positioned in a line and axially-spaced apart from each other by the present method, a first one of the holes is machined as in a case where a hole is machined by an ordinary reamer, and then a second one of the holes is machined with the guide portion being interference-fitted or transition-fitted in the first hole which has been machined. Thus, while the second hole is machined, the guide portion of the reamer is guided by the first hole and is accordingly substantially unmovable in the radial direction. Since the second hole is machined by the major or minor cutting edge which is comparatively near from the guide portion accurately guided by the first hole, a sufficiently high degree of concentricity of the second hole with respect to the first hole and a sufficiently high degree of dimensional accuracy of the second hole are assured. In a process of manufacturing the reamer, if the major and minor cutting edges are formed integrally with the guide portion in a single step, it is possible to easily establish a minute difference between the turning radius of the land surface in the guide portion and the turning radius of the minor cutting edge. This eliminates a necessity of the fine adjustment of position of the cutting tip by the above-described adjusting mechanism which adjustment is not so easy for an ordinary operator and requires a skilled operator to be achieved.
The turning radius of the land surface in the axially-distal-end small-diameter portion and that in the guide portion may be determined such that the second and later holes are machined with the guide portion being interference- or transition-fitted in the hole or holes which has been machined, for assuring considerably high degrees of concentricity and machining accuracy. However, it is not essential that the guide portion is interference-fitted in the machined holes. That is, as long as the turning radius of the minor cutting edge is smaller than the turning radius of the land surface in the guide portion, the concentricity and machining accuracy can be improved as compared with the prior art.
(2) A method according to claim
1
, wherein the number of the plurality of holes is at least three, and an inner circumferential surface of at least one of the plurality of holes is finished by the major and minor cutting edges, with the guide portion being fitted in at least two of the plurality of holes whose inner circumferential surfaces have been finished by the major and minor cutting edges.
Where the number of the holes to be machined is at least three, the first and second holes are machined as described above, and a third hole is then machined with the guide portion of the reamer being fitted in the first and second holes which have been machined. The third hole is thus machined while the guide portion is guided by the two points which are spaced apart from each other in the axial direction, thereby assuring a high degree of concentricity between the three holes. A fourth and later holes are also machined while the guide po
Fukui Akio
Iwahori Atsushi
Miyazaki Kunitoshi
Nakamura Motoshi
Nakanose Tetsuro
Fuji Seiko Limited
Howell Daniel W.
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