Shell end mill

Details Shell end mill Shell end mill

1993-11-30

1995-06-20

Terrell, William E.

Cutters, for shaping

Rotary cutting tool

Including holder having seat for inserted tool

407 55, 407 59, B23C 510, B23C 520, B23C 526

Patent

active

054256038

DESCRIPTION:

BRIEF SUMMARY
FIELD OF THE INVENTION

The invention relates to a shell end mill comprising a holder, a cylindrical cutting section connected to the holder, at least two preferably helical chip grooves arranged in the cutting section and spaced from one another in circumferential direction and each one row of insert seats arranged one after the other along one side of a chip groove and each one having an essentially radially aligned base support surface and a side support surface radially defining the same on the side of the base of the groove for receiving cutting inserts, which are preferably designed as indexable inserts and can be fastened on the cutting section by means of a center clamping screw engaging a screw bore in the area of the base support surface, in an arrangement of axially over-lapping pairs. The cutting inserts project radially beyond the cutting section with a main cutting edge and a free surface following the main cutting edge. The frontal outermost cutting inserts of each one row of cutting inserts project with a face cutting edge and a free surface following the face cutting edge axially beyond the cutting section.


BACKGROUND OF THE INVENTION

In shell end mills with full cutting rows of cutting inserts, usually the inner cutting inserts are arranged behind the frontal outermost cutting insert so that the cutting edge arranged on the receiving side is active, whereas the frontally arranged cutting edge is covered up by the adjacent active cutting edge and is therefore inactive. In order to be able to absorb the axial cutting force components acting onto the cutting inserts, the inner cutting inserts were supported frontally against an axial abutment surface. To create an insert seat with an axial abutment surface, however, requires a considerable manufacturing expense. The plate base must be created by an end mill in view of the axial abutment surface to be created at the same time, which end mill, because of the deep machining positions, requires a relatively large cantilever length, and which, to avoid collisions with adjacent interfering edges, can operate only with relatively narrow tool holders. This results in both the machining precision and the machining speed with much to be desired. Furthermore, the cutting section in conventional shell end mills is usually connected in one piece with the holder so that extensive storage is needed for various mill sizes and holder designs.
The basic purpose of the invention is to develop a shell end mill of the above-disclosed type, which can be manufactured easily and economically and in spite of this meets high requirements with respect to function.


SUMMARY OF THE INVENTION

The solution of the invention is essentially based on the thought that the inner cutting inserts of each one row of cutting inserts, which inner cutting inserts are arranged behind the frontal outermost cutting insert, project abutment-free over the associated insert seat with an active cutting edge arranged on the receiving side and a free surface following said cutting edge, and engage abutment-free a free space behind the frontally adjacent cutting insert with their frontally arranged inactive cutting insert and a free surface following said cutting insert. According to a preferred embodiment of the invention, the inner cutting inserts engage abutment-free with their frontal cutting edge and the free surface following the cutting edge, an undercut of the adjacent insert seat. These measures make it possible to create the insert seats by shell end milling not as this has been done up to now by face milling. After the helical chip grooves are created with an end mill, and the groove sides on the insert side are prepared by shell end milling for creating the insert seats, the base support surfaces and the undercuts for receiving the frontal cutting edges are created in a single operation one after the other by an end mill in a shell milling process. With this, the manufacturing speed of the plate seats is increased at least by the factor 3, which, in view of the plurality of in

REFERENCES:
patent: 4714383 (1987-12-01), Shimomura et al.
patent: 4790693 (1988-12-01), Koblesky
patent: 5083887 (1992-01-01), Dotany

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