Sumitomo 16GC256 Pcbn Turning Insert BN350 55 Degree Diamond

Product Description

The SUMITOMO 16GC256 is a Polycrystalline Cubic Boron Nitride (PCBN) turning insert engineered for hard material machining on CNC lathes and turning centers. Manufactured to ANSI code NUDNMA431 and ISO code NU-DNMA150404, this insert features a 55-degree diamond shape, negative rake geometry, and an uncoated BN350 PCBN grade. With a 0.5-inch inscribed circle and a 0.0156-inch corner radius, it is designed for precision single-edge cutting on hardened steels, cast irons, and other hard workpiece materials. CNC machinists and tool-and-die professionals specify this insert for finishing and semi-finishing operations where tight tolerances are required.

This insert is suited for hard turning applications in both production and job-shop environments. It is commonly used on horizontal and vertical turning centers handling workpiece materials classified under ISO material group H, which includes hardened steels and hard cast irons. The NUDNMA431 style and N clearance code make it appropriate for profiling and straight turning passes where a rigid, negative-rake setup is preferred. One cutting edge is available per insert.

Key Features

• PCBN insert material (Polycrystalline Cubic Boron Nitride) for hard material cutting
• BN350 manufacturer grade — uncoated, suited for high-heat hard turning
• 55-degree diamond insert shape with negative rake for stable cutting geometry
• 0.5-inch inscribed circle and 0.1875-inch insert thickness for rigid tool engagement
• Single cutting edge with 0.0156-inch corner radius for precise finish passes
• Held by clamp and pin method; conforms to ANSI and ISO 13399 standards

Compatibility

Designed as an OEM-style replacement or direct-specification PCBN turning insert for toolholders accepting DNMA-style inserts with a 0.2030-inch hole diameter and clamp-and-pin holding. Confirm holder compatibility against ANSI code NUDNMA431 or ISO code NU-DNMA150404 before ordering.

Installation Notes

Installation should be performed by a qualified CNC machinist or toolroom technician with the machine powered off and locked out per facility LOTO procedures. Seat the insert fully in the pocket and torque the clamp according to the toolholder manufacturer specifications before engaging the spindle. Handle PCBN inserts with care — edge chipping from improper seating or side loading during installation will reduce cutting life. Verify workpiece material hardness and cutting parameters against the BN350 grade application range before first cut.