Cutters – for shaping – Including tool having plural alternatively usable cutting edges
Patent
1991-11-27
1993-07-27
Bishop, Steven C.
Cutters, for shaping
Including tool having plural alternatively usable cutting edges
407107, 407117, B23B 2716
Patent
active
052305902
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to indexable inserts for thread cutting and slotting to be used, for example, in internal thread cutting of workpieces by means of automatically controlled machine tools.
PRIOR ART
There are different methods of making 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 by means of a tool edge such as a cutting insert, suitably of indexable type, clamped in an insert holder. With modern NC and CNA 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 the 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 a computer monitors and controls the actual threading.
Indexable inserts for thread cutting and slotting have been available on the market since the early 1960s. Mainly, triangular cutting inserts of positive or negative cut type have been used for horizontal as well as vertical mounting in the insert holder. There are certain disadvantages associated with a cutting insert 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 converting machines in continuous operation. Owing to the large investments in equipment required today, cutting economy has become an issue of ever greater importance to companies.
DESCRIPTION OF THE INVENTION
In order to improve cutting economy, the indexable insert according to the invention for internal thread cutting and slotting is provided with two cutting edges at the ends of a bevelled cutting body. A cutting column with symmetrical cross section relative to an axial section through the central axis of the column is connected with the cutting body, thus allowing the cutting insert to be reversed half a turn, if required, for continued use of the cutting insert. The cutting column has a plurality of limiting surfaces with parallel intersecting lines, which contributes towards great accuracy as regards location and orientation when mounting the cutting 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 cutting body between the cutting edges having been given an elongated shape, the cutting forces will act on the cutting insert within a larger angular area as compared to previous solutions, and the forces and the heat will be absorbed more efficiently in the whole of the cutting insert including the cutting body and column, whereby the risk of a cutting insert rupture is considerably reduced. Further, since the cutting body supports two cutting edges in a line which can be ground at the same time, an improvement in production technique is achieved.
DESCRIPTION OF THE FIGURES
FIG. 1 shows different views of a cutting insert comprising a cutting body and a cutting column according to the invention, FIG. 1A being a longitudinal side view, FIG. 1B being a longitudin
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Bohannan Richard D.
Schmidt Reinar
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