Citizen Miyano BNJ-51

The Citizen Miyano BNJ-51 is the larger twin-turret, twin-spindle fixed-headstock CNC lathe in Citizen's BNJ lineup, handling bar stock up to 51mm in diameter. It combines the simultaneous dual-turret productivity of the BNJ platform with the expanded working envelope needed for medium-sized industrial components that exceed the 42mm capacity of the BNJ-42.

Both turrets operate independently with live tooling and Y-axis capability, enabling the BNJ-51 to machine complex features on both ends of a part simultaneously. The main spindle reaches 5,000 RPM with an 11 kW motor—the additional torque at the 51mm bar size is essential for maintaining productive cutting parameters in steel and stainless steel. The sub-spindle matches at 5,000 RPM for balanced back-working performance.

The BNJ-51's thermal management is especially critical given the higher cutting forces and heat generation at the 51mm bar diameter with two turrets cutting simultaneously. Citizen's thermally symmetric design and strategic coolant placement ensure dimensional stability across extended production runs. The box-way construction on all axes provides the vibration damping needed to maintain surface finish quality during aggressive dual-cutting operations.

The dual-path Mitsubishi M80W control manages the complex synchronization between four independent axes groups. Programming dual-turret operations requires careful planning for tool interference avoidance and optimal cycle overlap, but the productivity rewards are substantial—30-50% cycle time reductions are typical on parts with significant back-working requirements.

The BNJ-51 is the machine of choice for production shops that have outgrown the 42mm BNJ capacity but want to maintain the cycle time advantages of twin-turret operation. Automotive transmission components, hydraulic manifold blocks, large coupling nuts, and industrial fitting bodies are typical applications where the BNJ-51's combination of capacity, speed, and precision delivers the best value.