Cutters – for shaping – Including tool having plural alternatively usable cutting edges – With integral chip breaker – guide or deflector
Patent
1983-02-24
1986-10-14
Husar, Francis S.
Cutters, for shaping
Including tool having plural alternatively usable cutting edges
With integral chip breaker, guide or deflector
407116, B23B 2722, B26D 100
Patent
active
046169636
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a cutting tip, especially a ceramic cutting tip for cutting-tools having top and bearing surfaces, which is provided with an encircling bevel and a shaping stage for the chip.
Cutting tips of the type mentioned above are known, for example, from DE-AS 15 52 360 and from DE-OS 22 52 349. The first specification describes a cutting tip having a negative rake angle and the second describes a cutting tip having a positive rake angle. In the case of the cutting tip having a negative rake angle, the bevel is formed by making a chip-breaking groove in the cutting tip, that is to say that the bevel lies in one plane with the top or bearing surface of the cutting tip. Although, therefore, the term bevel is used in DE-AS 15 52 360, the plate is not, in fact, bevelled, rather an edge remains which is retained when the chip-breaking groove is made in the cutting tip. An edge of this type, however, especially if the cutting tip is manufactured from sintered oxide ceramic, is very susceptible to break-outs which result in premature failure of the cutting tip.
The chip-breaking groove has a cross-section which increases continuously from the cutting edge to the middle of the face and is to permit the cutting of chips of different thicknesses. The chip-breaking groove itself, however, lies in the plane of the top or bearing surface, that is to say that at high cutting speeds of more than 250 m/min the chip shaping cannot be influenced or can be influenced only very unsatisfactorily. In the case of the cutting tips represented in DE-OS 22 52 349, the encircling chip-breaking groove forms a positive cutting angle in those cases in which it adjoins the cutting edge directly. If a bevel is provided in front of the groove, a negative rake angle is produced in this case also, the chip-breaking groove running substantially in the plane of the top or bearing surface as it does in the case of DE-AS 15 52 360. Thus, the same disadvantage occurs in the case of the cutting tip described in DE-OS 22 52 349, that is to say that at high cutting speeds the problem of chip shaping is not solved or not in optimum manner, and, in addition, there remains the danger that the edge will break at the cutting edge.
The article "Spanform beim Drehen" (Chip shapes when turning) makes known a classification of the individual chip shapes into disadvantageous, useful and good, the formation of these chips depending on very different factors. These factors are determined, substantially, by the properties of the material to be machined, the conditions of the machining operation including the design of the cutting edge and the cutting material itself. When using the same material to be machined and retaining the same tool, however, the chip changes if the feed rate and/or delivery are altered to such an extent that, possibly, the removal of the chips is no longer ensured and the matching operation therefore has to be broken off or interrupted.
The cutting speeds customary hitherto, such as those that can be achieved with hard metals, are below 250 m/min if uncoated hard metals are used. With the increase in the cutting speed, the problem arises of controlling the shaping of the chip when finishing, since in a unit of time a relatively large volume of chips occurs which must be removed. Disadvantageous chip shapes constitute considerable dangers for the quality of the surface of the workpiece, the tool, the machine-tool and, not least, for the operating staff. The damage results in periods of machine stoppage and the occurrence of rejects and pieces having reduced surface quality.
The problem underlying the present invention is therefore to influence the shaping of chips during finishing in such a manner that a plurality of materials can be machined in the case of a plurality of machining conditions using one tool, without disadvantageous shaping of chips occurring which would require the machining unit to be stopped.
This problem is solved by a cutting tip, especially a ceramic cutting tip for cutting-tools having top and bearing
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Habert Guy
Kraft Harald
Feldmuhle Aktiengesellschaft
Husar Francis S.
Kearns Jerry
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