Cutters – for shaping – Rotary cutting tool – Face or end mill
Reexamination Certificate
2002-01-25
2004-04-06
Fridie, Jr., Willmon (Department: 3722)
Cutters, for shaping
Rotary cutting tool
Face or end mill
C407S057000
Reexamination Certificate
active
06715966
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates in general to a rotary cutting tool, and more particularly to improvements in such a rotary cutting tool having at least one peripheral cutting edge each of which includes a corrugated edge portion in the form of a roughing cutting edge portion or a nicked cutting edge portion.
2. Discussion of the Related Art
As one type of a rotary cutting tool which is to be rotated about its axis for machining or cutting a workpiece with its peripheral cutting edges, there is known a tapered end mill in which the diameter of the peripheral cutting edges is changed gradually in the axial direction. Such a tapered end mill is widely used for formation of a rib slot in a die or mold, cutting of a side face in a die or mold, or other kinds of machining works. There is proposed an end mill having, in each of its cutting edges, a corrugated edge portion which serves for breaking a cutting chip into small pieces and accordingly reducing a cutting resistance so as to improve cutting performance and cutting efficiency of the end mill, as disclosed in JP-A-H7-299635 (publication of unexamined Japanese Patent Application laid open in 1995) and JP-A-H9-29530 (publication of unexamined Japanese Patent Application laid open in 1997). The corrugated edge portion takes, for example, the form of a roughing cutting edge portion having sinuous shape in which the diameter is gradually changed in the axial direction, or the form of a nicked cutting edge portion in which a plurality of nicks are formed to be arranged with a constant spacing interval in the axial direction. Whichever the corrugated edge portion takes the form of the roughing cutting portion or the form of the nicked cutting edge portion, it can be said that the corrugated edge portion has, in its cross section taken in a plane containing a rake face which cooperates with a flank face to define the corresponding cutting edge, a corrugated shape consisting of a succession of protrusions and recesses which are alternately arranged. The pitch, depth and other dimension of the corrugated shape of the roughing cutting edge portion or nicked cutting edge portion are determined to have suitable amounts, commonly, in view of the diameter of a body portion in which the cutting edges are formed. When the diameter of the body portion is generally small, such dimensions of the corrugated shape of the roughing or nicked cutting edge are adapted to be small, so that the pieces into which the cutting chip is broken by the roughing or nicked cutting edge portion is sufficiently small. This is because the rigidity of the end mill is relatively small when the diameter of the body portion is relatively small.
The pitch, depth and other dimensions of the corrugated shape of the roughing or nicked cutting edge are held constant throughout the entire length of the corrugated edge portion of the cutting edge, even where the end mill is of a tapered end mill in which the diameter of the body portion is changed in the axial direction. That is, the dimensions of the corrugated shape of the corrugated edge portion of a tapered end mill are determined, for example, on the basis of the diameter of an axially intermediate portion of the body portion of the tapered end mill. However, the thus determined dimensions of the corrugated shape do not necessarily enable, particularly, axially opposite end portions of the body portion to exhibit a sufficient improvement in their cutting performance, in spite of the provision of the corrugated edge portion in the cutting edge. Namely, where the dimensions of the corrugated shape are determined on the basis of the diameter of the axially intermediate portion of the body portion, a sufficiently improved cutting performance is not necessarily exhibited by the axially opposite end portions of the body portion in which the diameter is increased and reduced, thereby undesirably reducing a degree of freedom in determining number of revolutions, feed rate and other cutting conditions which are applicable to the end mill.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a rotary cutting tool which has a corrugated edge portion in the form of a roughing cutting edge portion or a nicked cutting edge, and which exhibits a sufficiently improved cutting performance in the entire axial length of each cutting edge irrespective of the change of diameter of the cutting edge. The object may be achieved according to any one of first through ninth aspects of the invention which are described below.
The first aspect of this invention provides a rotary cutting tool which is to be rotated about an axis thereof for cutting a workpiece, comprising: a generally cylindrical body portion having (a) at least one flute each of which is formed in the cylindrical body portion and each of which extends from an axially distal end of the cylindrical body portion toward an axially proximal end of the cylindrical body portion, and (b) at least one cutting edge each of which is provided by one of widthwise opposite edges of the flute, wherein each of the above-described at least one cutting edge includes a corrugated edge portion having a corrugated shape, and wherein at least one of a pitch and a depth of the corrugated shape is increased with an increase in a diameter of the cylindrical body portion whose outer circumferential surface is defined by a rotary trajectory of an envelope passing through crests of the corrugated shape.
The above-described corrugated shape may consist of a succession of protrusions and recesses which are alternately arranged. Each of the crests or peaks is defined as the highest point of a corresponding one of the protrusions. The pitch is defined as a distance between the crests or peaks of two successive protrusions, or between roots or bottoms of two successive recesses. The depth is defined as a distance between the crest and root which are adjacent to each other. It is noted that the cylindrical body portion includes a diameter changing portion whose diameter is changed in the axial direction.
According to the second aspect of the invention, in the rotary cutting tool defined in the first aspect of the invention, the generally cylindrical body portion includes a tapered body portion, so that the diameter of the cylindrical body portion is increased in a direction away from one of the axially distal and proximal ends of the body portion toward the other of the axially distal and proximal ends of the body portion. In the rotary cutting tool of this second aspect of the invention, the cylindrical body portion includes the above-described diameter changing portion in the form of the tapered body portion.
According to the third aspect of the invention, in the rotary cutting tool defined in the first or second aspect of the invention, the pitch of the corrugated shape is increased with the increase in the diameter of the cylindrical body portion such that the following expression (1) is satisfied:
0.5+(3/100)×
D≦P≦
2+(3/25)×
D
(1);
wherein D represents the diameter of the cylindrical body portion; and P represents the pitch of the corrugated shape. It is noted that the pitch represents a distance measured along a generating line of the diameter changing portion or tapered body portion, between the crests or peaks of two successive protrusions, or between the roots or bottoms of two successive recesses, whichever each of the above-described at least one flute consist of a straight flute or a helical flute.
The fourth aspect of this invention provides a rotary cutting tool which is to be rotated about an axis thereof for cutting a workpiece, comprising: a generally cylindrical body portion having (a) at least one flute each of which is formed in the cylindrical body portion and each of which extends from an axially distal end of the cylindrical body portion toward an axially proximal end of the cylindrical body portion, and (b) at least one cutting edge each of which is provided by one o
Kamata Satoru
Tatebe Naomi
Tsuzuki Kiyoshi
Fridie Jr. Willmon
Oliff & Berridg,e PLC
OSG Corporation
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