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Guidelines for Choosing PCBN Inserts With Chip Breaker

The chip breaker represents an important advancement in cutting technology. Before chip breakers were included in cutting tool inserts, chip formation posed a major challenge to many machining processes, especially turning. In particular, when unattended machining was required to meet up with high demand, formation of chips would clog the conveyor belt and other sections of the machine. This would require the machinist to stop the operation and spend precious time clearing away the chips. But with the addition of chip breakers to tool inserts, the formation of the chips can be controlled and heat can be transfered away from the tool and workpiece more efficiently. The following is a brief description of the factors to consider when choosing polycrystalline cbn turning inserts with chip breaker.

Chip Shape of Various Workpiece Materials
The kind of chip formed during cutting is determined by the workpiece material. For example, cast iron produces very short chips. These grayish red chips usually come off in small particles and sometimes form cast iron dust. Steel chips, however, form longer curly chip segments. During turning, which is usually a continuous operation, these chips may curl into very long spiral shapes if they are not properly controlled. Ideally, the chips produced by turning need to be broken off into a helical shape that looks like figure 6 and is not more than 2 1/2 inches long. If you are turning a steel shaft, you should select a polycrystalline cbn turning inserts with a positive rake and a chip breaker that will produce this kind of chip size and shape.

Cutting Data: Feed Rate and Lead Angle
Chip formation is normally affected by a mixture of cutting conditions such as the depth of cut, feed rate, rake angle, lead angle, and the insert's nose radius. Therefore, after selecting the right insert and chip breaker for your workpiece material, you need to ensure that you can set the right feed rate to produce the desired type of chips. A feed rate that is too low will result in very long windy chips while a very high feed rate will cause the chips to break too quickly and can lead to chip hammering and early tool edge failure.

Similarly, lead angles influence the chip flow, length, and thickness. Large lead angles require high cutting forces and they produce wider and shorter chips. So they may be used for roughing applications. On the other hand, small lead angles require low cutting forces and produce soft, smooth chips with less chip curling and they are more suitable for medium or finishing applications. The lead angle determines the shape of the tool insert. So you should select the most appropriate shape for your workpiece and application. Square, rectangular and round shaped inserts perform better during roughing while triangular and diamond shaped inserts are more appropriate for finishing operations.

Conclusion

Continuous cost pressures force manufacturers of gray cast iron brake disks to look for cost-cutting solutions, and polycrystalline cbn turning inserts deliver high productivity and long tool life. pcbn inserts offer high metal removal rates, faster machine setup, quicker cycle times, and greater flexibility, it is recommened preferred machining method for hardened steels and reduce the machining cost per part in finish turning.

Despite these advantages, hard turning has sometimes had issues with poor chip control causing surface scratching and bird-nest formations. SWIFT solved these problems by integrating special chipbreaking geometries, giving customers total control of their hard machining.

Inserts with chipbreaker provides a chipbreaking solution for applications requiring more toughness, improves surface quality to reduce scrap rates. And pcbn inserts require less machine stops due to swarf issues to improve machine availability, less bird-nest formation to reduce clean up time.

Those are some of the most important criteria to consider when you are selecting polycrystalline cbn turning inserts with chip breaker for your machining operations. After you have selected the best insert for your workpiece material and application, you should carefully adjust all necessary cutting data to produce the desired shape of chips.

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