Indexable insert for thread cutting and slotting

Details Indexable insert for thread cutting and slotting Indexable insert for thread cutting and slotting

1991-11-26

1993-04-20

Bishop, Steven C.

Cutters, for shaping

Including tool having plural alternatively usable cutting edges

407117, B23B 2704, B23B 2716

Patent

active

052036480

DESCRIPTION:

BRIEF SUMMARY
RELATED APPLICATION

This application is related to copending design patent application Ser. No. 07/442688, filed Nov. 29, 1989.


TECHNICAL FIELD

The present invention relates to indexable inserts for thread cutting and slotting to be used, for example, in the threading of workpieces by means of automatically controlled machine tools.


PRIOR ART

There are different methods of producing threads and slots, involving either plastic machining or machining by means of cutting of a blank of, for example, screw or nut type. The most frequent method for producing threads for screws, bolts and nuts is plastic machining by means of thread rolling, in which the thread profile is pressed into the surface of the material. Machining by means of cutting comprises the following methods: use of threading taps and threading dies, thread milling, grinding and chasing. In thread chasing, the thread is cut into the rotating workpiece using a tool edge, such as a cutting insert, suitably of indexable type, clamped in an insert holder. With modern NC and CNC lathes/machine tools, threads can be made quickly and efficiently using cutting inserts and holders for same. The counterpart of the thread cutting of a workpiece is an ordinary turning operation, in which the feeding per revolution corresponds to the thread pitch. The pointed end of an indexable insert is usually cut to a profile intended to correspond to, for example, the space between two thread sides. The chip cutting thickness is determined by the cutting depth. The feeding movement of the tool must be related to the rotary movement of the work spindle. Often, a feeding function as such is provided in the lathe. An operator or computer monitors and controls the actual threading.
Indexable inserts for thread cutting and slotting have been available on the market since the early 1960s. Usually, triangular cutting inserts of positive or negative cut type have been used for horizontal as well as vertical mounting in the cutting insert holder. There are certain disadvantages associated with cutting inserts of this type, since it may be difficult to locate the insert accurately in the holder and there is a risk of insert rupture. As a result of the development as regards equipment, greater demands have to be made as to locating tolerances, and improved built-in safety as regards insert rupture must be demanded, especially in view of the use of unmanned machine tools in continuous operation. Owing to the large investments in equipment required today, cutting economy has become an issue of ever greater importance to companies.


SUMMARY OF THE INVENTION

In order to improve cutting economy, the indexable insert for thread cutting and slotting according to the invention is provided with four cutting edges instead of two or three, which can be done at approximately the same cost. The cutting edge having a substantially square shape with plane contact surfaces on each side, which contact surfaces are located between the cutting edges at right angles to each other, achieves much greater accuracy as regards location and orientation when mounting the insert in the holder. With this design, much closer tolerances are possible than in the case of other types of cutting inserts. Owing to the almost straight corners of the insert and owing to the insert being upended instead of placed in a horizontal position, a much stronger cutting edge is obtained. The cutting forces will act on the corners of the insert within a larger angular area as compared to previously known solutions and the forces will essentially be absorbed by a large part of the entire insert, whereby the risk of insert rupture is considerably reduced. The same cutting insert may be used for right-and left-handed threading and in certain cases also for internal threading. Thanks to the square shape of the insert, two cutting edges of an insert may be ground at the same time, implying an improvement in production technique.


BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross section as seen along line 1--1 of the inve

REFERENCES:
patent: 3613197 (1971-10-01), Stier
patent: 4169690 (1979-10-01), Kendra
patent: 4669925 (1987-06-01), Lowe et al.
patent: 4674925 (1987-06-01), Thornton et al.
patent: 4890961 (1990-01-01), Carl et al.

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