Cutting insert

Details Cutting insert Cutting insert

1999-06-23

2001-08-07

Wellington, A. L. (Department: 3722)

Cutters, for shaping

Rotary cutting tool

Including holder having seat for inserted tool

C407S048000, C407S113000, C407S114000

Reexamination Certificate

active

06270292

ABSTRACT:

FIELD OF THE INVENTION
The present invention refers to a cutting insert of the type having a front cutting portion associated with an operative cutting edge and a trailing mounting portion for mounting the insert in a cutting tool.
BACKGROUND OF THE INVENTION
The present invention particularly refers to compactly designed cutting inserts for mounting thereof on a cutting tool where the space available for arranging insert receiving pockets therein is limited. This specifically concerns rotary cutting tools of the type used in end milling, drilling and plunging operations and the like, which are formed with a plurality of chip evacuation flutes and which bear cutting inserts on a front face thereof between the flutes.
In order to make efficient use of the space available for mounting the cutting inserts at the front face surface of such cutting tools, it is desirable to optimize the geometry of the cutting inserts so as to enable them to have relatively long cutting edges with trailing mounting portions being of substantially reduced dimensions.
Patent Application No. PCT/IL97/00270 discloses a cutting insert designed to solve the above problem in an end-milling cutter. The cutting insert comprises a front cutting portion having an operative front surface associated with upper and lower arcuate cutting edges and side edges therebetween, and a trailing mounting portion having upper, lower and side walls, all extending away from the respective edges of the front cutting portion, the side walls converging in the direction away from the front cutting portion, and being shorter than a distance between extreme points of each arcuate cutting edge. The insert is formed with a clamping screw bore passing through the upper and lower walls of the trailing mounting portion, and is mounted on the cutter so that an axis of this bore is substantially perpendicular to the rotary axis of the cutter.
U.S. Pat. No. 4,768,901 discloses a cutting insert mounted on a front face of a drilling tool. The cutting insert has a front cutting portion associated with a cutting edge and a trailing mounting portion having upper, lower and side walls, and a rear wall extending therebetween. The cutting insert has a clamping screw bore which passes through the upper and lower walls of the trailing mounting portion, the insert being mounted so that an axis of the clamping screw bore is parallel to a rotary axis of the drilling tool. The rear wall of the trailing mounting portion comprises stepped lateral abutment surfaces disposed adjacent the side walls of the trailing mounting portion relatively close to the cutting edge, and semi-cylindrical central surface disposed between the lateral abutment surfaces and extending around a rear portion of the clamping screw bore.
It is the object of the present invention to provide a new cutting insert which, inter alia, has advantages in respect of its mounting in a cutting tool of the above kind.
SUMMARY OF THE INVENTION
In accordance with one aspect of the present invention, there is provided a cutting insert for mounting on a cutting tool, comprising:
a front cutting portion having an operative front surface associated with at least one cutting edge, and
a trailing mounting portion having upper, lower and side walls extending from said front cutting portion to a rear abutment wall of the trailing mounting portion oriented generally co-directionally with said operative front surface, the side walls of the trailing mounting portion meeting with said rear abutment wall at rear edges;
said rear abutment wall comprising two lateral surfaces and a central surface therebetween, said lateral surfaces converging from said rear edges in the direction towards the front cutting portion, and said central surface protruding outwardly from adjacent portions of the lateral surfaces in the direction away from said front cutting portion, and meeting therewith at merging edge regions.
In accordance with another aspect of the present invention, there is provided a tool holder having a longitudinal axis of rotation and a front face formed with at least one insert receiving pocket for bearing therein a cutting insert having an operative cutting edge;
the insert receiving pocket having a pocket base wall and a pocket rear wall which is disposed at a rear end of the pocket defined with respect to a direction of rotation in which the tool holder is designed to rotate, and is oriented transversely to the pocket base wall and transversely to said direction of rotation;
the pocket rear wall having two lateral portions and a central portion therebetween which is rearwardly depressed relative to adjacent regions of the lateral portions and meets therewith via merging edge regions, said lateral portions of the pocket rear wall converging from outer ends thereof in the direction towards the cutting edge of the cutting insert.
With the design of the rear abutment wall of the cutting insert and the pocket rear wall and, particularly, with the specific orientation of the lateral surfaces of the rear abutment wall of the cutting insert and lateral portions of the pocket rear wall, in accordance with the present invention, there is achieved a favorable direction of reaction forces exerted on the body of the tool holder during a cutting operation. By virtue of this, stress concentration and consequent local deformations may be eliminated in those regions of the tool holder body which are most critical from this point of view.
Preferably, the cutting insert is secured in the insert receiving pocket by means of a clamping screw. In this case, the cutting insert is formed with a clamping screw bore and the pocket base wall is formed with a pocket threaded bore, for receiving therein the clamping screw. The clamping screw bore of the cutting insert passes between the upper and lower walls of its trailing mounting portion substantially perpendicularly thereto.
In one embodiment of the present invention, the pocket threaded bore is directed generally co-directionally with the longitudinal axis of the tool holder. In another embodiment of the present invention, the pocket threaded bore is directed transversely to the longitudinal axis of the tool holder.


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