The development team at Princes Risborough-based Sumitomo Electric Hardmetal Ltd (www.sumitomotool.com) has released the AC6000M series of turning inserts for stainless-steel materials.

Three complementary chip-breaker styles (NEF, NEG and NEM) cover the roughing, semi-finishing and finish-machining of ferritic high-chrome, martensitic, austenitic and two-phase austenitic/ferritic materials, as well as precipitation-hardening stainless steels.

The range comprises AC6020M, AC6030M and AC6040M inserts and can be used at cutting speeds up to 250m/min. AC6020M is recommended for the high-speed turning of stainless steels and light interrupted cutting cycles.

This is due to the toughness of the substrate and the use of the company’s Absotech Platinum CVD coating — a boride-based titanium compound multi-layer coating featuring high surface smoothness coupled with low stress, says Sumitomo, adding that the stable cutting edge linked to good coating adhesion creates a high resistance to chipping.

AC6030M has the same Absotech Platinum coating but can undertake a wider range of applications, making it suitable for more-general stainless-steel turning tasks. These can involve continuous, light interrupted or heavier interrupted cycles; and when compared with more-conventional grades, AC6030M resists the onset of flank wear, says the company.

For particularly demanding applications, such as heavy interrupted turning, the improved fracture-resistance of the proprietary carbide substrate used in the AC6040M grade, coupled with the newly developed Absotech Bronze TiALSiN multi-layer PVD coating, gives higher resistance to heat oxidation. The high level of coating adhesion also ensures greater resistance to ‘peeling’ at speeds up to 150m/min.

With regard to the three new chip-breakers, NEF is designed to reduce chip curling under finish-cutting conditions, especially when low depths of cut are involved.

There is a sharp 20deg rake angle that helps to reduce wear, while the inclusion of grooves on the rake face lowers heat generation and further assists chip flow.

The NEG chip-breaker incorporates a ‘special’ 30deg top rake with 0.9mm land to aid chip management under cut and reduce the onset of wear, while several smooth bumps on the insert surface prevent crater wear.

NEM, which is designed for rough turning, has a large-radius rake face designed to evacuate chips at feed rates between 0.2 and 0.6mm/rev and at depths of cut up to 6mm. This chip-breaker also reduces wear attributed to cratering, while maintaining edge strength.