Indexable insert and cutting tool

Details Indexable insert and cutting tool Indexable insert and cutting tool

2004-01-15

2004-12-28

Fridie, Jr., Willmon (Department: 3722)

Cutters, for shaping

Including tool having plural alternatively usable cutting edges

With integral chip breaker, guide or deflector

C407S115000

Reexamination Certificate

active

06835028

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an indexable insert (also known in the art as a throwaway tip) for turning use and to a cutting tool configured such that the indexable insert is clamped on a tool holder.
2. Description of the Related Art
Finished-surface roughness (Ry) associated with turning is expressed by Ry≅f
2
/8R, where R is a nose radius, and f is a feed. In principle, an arc assumed by a nose of an indexable insert (the nose radius is usually 0.4 mm to 3.2 mm) is transferred intact to a cut surface, thereby determining finished-surface roughness. Accordingly, for a given feed, the greater the nose radius, the greater the improvement in surface roughness. However, since the width of a portion of a nose cutting-edge in contact with a workpiece increases with the nose radius, an increase in the nose radius can disadvantageously result in chattering. Therefore, an important measure is to determine the nose radius while a balance between improvement in surface roughness and prevention of chattering is achieved.
Turning a workpiece of cast iron involves, in addition to the above problems, the following phenomenon: since cast iron exhibits carbon segregation stemming from its constitution, turning results in digging-up the carbon segregated portions that are cut. Thus, even in finishing in which the depth of cut is small, an open bore, plucking, or the like arises on the finished surface, resulting in a failure to obtain a sufficiently improved finished-surface roughness. In order to improve the roughness of a machined surface of such a workpiece, known indexable inserts are configured such that a minor cutting edge (also called a “sweeper cutting-edge” or a “wiper cutting-edge”) is formed between an arcuate cutting edge having a nose radius and a linear cutting edge (a side portion of a tip). The minor cutting edge assumes the form of a straight line substantially in parallel with the cutting feed direction (in cylindrical turning, the direction of the axis of rotation of a workpiece) or the form of an arc (curved line) having a radius different from the nose radius (See Patent Documents 1 to 3, identified below). An indexable insert having such a minor cutting edge is used to improve the shape transferred to a finished surface, to thereby improve theoretical surface roughness. An indexable insert having such a minor cutting edge is expected to improve surface roughness through the following mechanism: the minor cutting edge is engaged in cutting and burnishing to thereby plastically smooth a rugged machined surface.
In the indexable insert disclosed in Patent Document 1, a linear minor cutting edge having a length of 0.02 mm to 0.2 mm is provided between a nose portion and a linear cutting edge. In the indexable insert disclosed in Patent Document 2, an arcuate minor cutting edge is provided between an arcuate nose portion having a nose radius R and a linear cutting edge so as to satisfy the relation “(nose radius)<(radius of arcuate minor cutting edge).” In the indexable insert disclosed in Patent Document 3, two arcuate cutting edges having radii r
2
and r
3
, respectively, are provided between an arcuate nose portion having a nose radius (r&egr;) and a linear cutting edge as to satisfy the relation “r
2
<r&egr;<r
3
.”
[Patent Document 1]
Japanese Utility Model Registration No. 2556520
[Patent Document 2]
Japanese Kohyo (PCT) Patent Publication No. 8-507976
[Patent Document 3]
Japanese Kohyo (PCT) Patent Publication No. 10-500363
3. Problems to be Solved by the Invention
The results of various cutting tests conducted by the prevent inventors have revealed that use of the indexable inserts described in the above Patent Documents 1 to 3 can cause serious problems as described below. In the case of the indexable insert described in Patent Document 1, the length of the linear minor cutting edge (linear wiper cutting-edge) is as small (short) as 0.2 mm or less, which is too short to effect burnishing in turning a workpiece of cast iron as well as too short to be applied to a high-speed feed. Additionally, the linear minor cutting edge is set such that, when the cutting tool is fed (caused to travel) longitudinally in cylindrical turning, the minor cutting edge angle becomes 1 degree (1 degree in relation to the axis of rotation (hereinafter also referred to as the “axis”) of a workpiece) as measured on the rear side in relation to the direction of the feed.
However, the actual practice of cutting involves an error associated with clamping of the indexable insert in a tip pocket of a holder or an error associated with clamping of the holder on a tool rest. These errors are usually about ±1 degree. In some cases, such an error causes the indexable insert described in Patent Document 1 to assume a condition such that the linear minor cutting edge and the axis become parallel (form an angle of 0 degree) with each other. In such a case, cutting resistance increases, resulting in the occurrence of chattering. In the case where such a error causes the linear minor cutting edge to form an angle of 2 degrees with the axis, the cutting edge angle to a work surface increases, and thus machined-surface roughness (maximum roughness Ry) increases, resulting in impairment in finished-surface condition. That is, because of an unavoidable error in relation to the minor cutting edge angle, the indexable insert described in Patent Document 1 fails to consistently provide highly improved finished-surface roughness.
The indexable insert described in Patent Document 2 is designed to perform cutting such that the lowest point (a point at which a cutting edge is tangent to a line parallel with the axis of rotation) is located on the arcuate minor cutting edge, which assumes the form of a single arc having a radius greater than the nose radius, and thus can basically provide highly improved finished-surface roughness. However, since only the linear cutting edge, which is a portion of a side of the tip, is provided behind the arcuate minor cutting edge, the effect of burnishing a machined surface is not expected. For this reason, in the case of a workpiece of cast iron, a glossy finished surface cannot be obtained. In the case of turning by use of the indexable insert, in order to obtain a glossy finished surface, polishing must be performed after turning, disadvantageously resulting in an increase in machining man-hours.
In the case of the indexable insert described in Patent Document 3, since the nose radius (r&egr;) and the radius r
2
of an arc following the nose have the relation “r
2
<r&egr;,” cutting by the cutting edge having the radius r
2
impairs surface roughness. Thus, in order to improve surface roughness, cutting is performed such that the arcuate cutting edge having the radius r
3
, which is connected to the arcuate cutting edge having the radius r
2
(r
2
<r&egr;<r
3
) on the side opposite the nose (on the side toward the linear cutting edge), includes the lowest point. However, in this case, for a reason similar to that in the case of the indexable insert described in Patent Document 2; i.e., since only the linear cutting edge is provided behind the arcuate cutting edge having the radius r
3
, the effect of burnishing a machined surface is not expected, thus resulting in a problem similar to that in the case of the indexable insert described in Patent Document 2.
SUMMARY OF THE INVENTION
In view of the above-described problems of conventional indexable inserts, an indexable insert of the present invention has been devised on the basis of the results of extensive cutting tests. That is, an object of the present invention is to provide an indexable insert which, in application to turning of a cast iron product, does not cause chattering and can provide a glossy, highly improved, finished surface.
The above object has been achieved by providing the following embodiments and aspects of the invention:
(1) An indexable insert adapted for turning, which comprises a nose cuttin

Affiliated with

Also associated with

Rating

Indexable insert and cutting tool does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Indexable insert and cutting tool, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Indexable insert and cutting tool will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-3278209