Citizen Miyano BNE-51S6

The Citizen Miyano BNE-51S6 is the large-bar BNE without a Y axis. Its main spindle (SP1) machines bar up to 51 mm dia. in a 6" hydraulic chuck, while the second spindle (SP2) keeps the 42 mm dia. capacity and 5" chuck of the smaller models. Two 12-station turrets, HD1 and HD2, serve the pair.

The bigger bore costs speed. SP1 tops out at 5,000 rpm here, against 6,000 rpm on the Miyano BNE-42S6, while the SP1 motor stays at 15/11 kW. On 51 mm stock that speed is rarely the constraint, but on small diameters cut from the same machine it will be. SP2 also runs to 5,000 rpm, on a 5.5/3.7 kW motor.

The mismatch between the spindles shapes what you can make. A part turned from 51 mm bar can only be picked up by SP2 on a section of 42 mm dia. or less, so the back-end grip has to be planned into the design: a turned-down shank, a neck, or a smaller end feature. Parts that stay at full bar diameter right to the cut-off are better suited to a machine with equal spindles.

Without a Y row in the table, revolving tools (up to 12+12) work on centre: cross drilling, face drilling and tapping. HD1 has 175 mm of X1 and 380 mm of Z1 stroke, HD2 145 mm of X2 and 175 mm of Z2, and the back spindle travels 450 mm. The machine weighs 7,800 kg, against 7,600 kg for the Miyano BNE-42S6, on the same 2,690×2,160 mm footprint and 1,925 mm height.