Citizen Miyano BNJ-51
Key Specifications
max bar capacity sp1
max bar capacity sp2
main spindle speed
main spindle power
sub spindle speed
sub spindle power
Overview
The Citizen Miyano BNJ-51 is the larger twin-turret, twin-spindle fixed-headstock CNC lathe in the BNJ lineup, handling bar stock up to 51 mm diameter. It combines dual-turret simultaneous machining with the expanded working envelope needed for medium-sized industrial components that exceed the 42 mm capacity of the BNJ-42 series.
The main spindle (SP1) reaches 5,000 RPM with 15/11 kW (20/15 hp), while the sub-spindle (SP2) matches at 5,000 RPM with 7.5/5.5 kW (10/7.5 hp). Both spindles accept 51 mm bar stock for full-diameter capability on both ends. The upper turret (HD1) has 12 stations with live tools at 6,000 RPM, and the lower turret (HD2) has 8 stations with live tools at 3,000 RPM, providing 20 total tool positions.
Axis travels mirror the BNJ-42SY configuration with 165 mm on X1, 246 mm on Z1, 85 mm on X2, and 590 mm on Z2. Maximum machining length scales up with the larger bar diameter. The 590 mm Z2 travel provides generous clearance for part transfer and extended backworking operations on the larger workpiece sizes. The Mitsubishi M80W dual-path control manages independent turret synchronization.
At 5,300 kg with a floor space of 2,840 x 1,560 mm, the BNJ-51 maintains the same footprint as the BNJ-42 while offering the larger bar capacity. The additional torque from the 15/11 kW spindle is essential for maintaining productive cutting parameters in steel and stainless steel at the 51 mm bar size.
The BNJ-51 is the machine of choice for production shops that have outgrown the 42 mm BNJ capacity but want to maintain twin-turret cycle time advantages. Automotive transmission components, hydraulic manifold blocks, large coupling nuts, and industrial fitting bodies that exceed 42 mm diameter are the core applications where the BNJ-51's combination of capacity, speed, and precision delivers maximum return on investment.
Full Specifications
| Parameter | Value |
|---|---|
| Max Bar Capacity Sp1 | 51 mm (2.0 in) |
| Max Bar Capacity Sp2 | 51 mm (2.0 in) |
| Main Spindle Speed | 5,000 RPM |
| Main Spindle Power | 15/11 kW (20/15 hp) |
| Sub Spindle Speed | 5,000 RPM |
| Sub Spindle Power | 7.5/5.5 kW (10/7.5 hp) |
| Upper Turret Stations | 12 |
| Lower Turret Stations | 8 |
| Upper Turret Live Tool Speed | 6,000 RPM |
| Lower Turret Live Tool Speed | 3,000 RPM |
| Max Drilling Hd1 | 13 mm |
| Max Drilling Hd2 | 10 mm |
| Travel X1 | 165 mm (6.50 in) |
| Travel Z1 | 246 mm (9.69 in) |
| Travel X2 | 85 mm (3.35 in) |
| Travel Z2 | 590 mm (23.23 in) |
| Machine Weight | 5,300 kg |
| Floor Space | 2,840×1,560mm(Without Chip Conveyor) |
| Machine Height | 1,700 mm |
| CNC Control | Mitsubishi M80W dual-path |
| Items | BNJ-42S6 |
| Machining Capacity | Standard Turning Length |
| Standard Machining Diameter | SP1/SP2 |
| Spindle | Spindle Speed Range |
| Sp2 | JPN, H-S16, DIN171E |
| Type Of Collet Chuck | SP1 |
| Type Of Power Chuck | SP1/SP2 |
| Turret | Type of Turret |
| Hd2 | M10×1.0 |
| Revolving Tools | Maximum Number of Revolving Tools |
| Spindle Speed Range | HD1 |
| Maximum Drilling Diameter | HD1 |
| Maximum Tapping Diameter | HD1 |
| Slide Stroke | Turret Slide Stroke |
| Z1 Axis | 246mm |
| Spindle Slide Stroke | X2 axis |
| Z2 Axis | 590mm |
| Motors | Spindle Motor |
| Sp2 Cs | 7.5/5.5kw(15min./Cont.) |
| Machine Dimensions | Machine Height |
| Sliding Headstock Type | A20 |
| Bar Work | BNC42 |
| Turning Machine | BNA42CY |
| High Precision Turning Machines | BNA42SY |
| Multi Station Machining Cell | MC20 III |
| Standard Turning Length Sp1 Sp2 | 100mm |
| Standard Machining Diameter Sp1 Sp2 | 51mm Dia./42mm Dia. |
| Spindle Speed Range Sp1 | 50 - 5,000min-1 |
| Spindle Speed Range Sp2 | 50 - 5,000min-1 |
| Type Of Collet Chuck Sp1 | H-S22, DIN177E |
| Type Of Collet Chuck Sp2 | JPN, H-S16, DIN171E |
| Type Of Power Chuck Sp1 Sp2 | 6"/5" Hollow |
| Type Of Turret Hd1 | 12st. |
| Type Of Turret Hd2 | 8st. |
| Maximum Number Of Revolving Tools Hd1 | Max.12 |
| Maximum Number Of Revolving Tools Hd2 | Max.4 |
| Spindle Speed Range Hd1 | 6,000min-1 |
| Maximum Drilling Diameterhd1 | 13mm Dia. |
| Maximum Drilling Diameterhd2 | 10mm Dia. |
| Maximum Tapping Diameter Hd1 | M12×1.75 |
| Maximum Tapping Diameter Hd2 | M10×1.0 |
| Turret Slide Stroke X1 Axis | 165mm |
| Turret Slide Stroke Z1 Axis | 246mm |
| Spindle Slide Stroke X2 Axis | 85mm |
| Spindle Slide Stroke Z2 Axis | 590mm |
| Spindle Motor Sp1 Cs | 15/11kw(15min./Cont.) |
| Spindle Motor Sp2 Cs | 7.5/5.5kw(15min./Cont.) |
| Spindle Speed Range Hd2 | 3,000min-1 |
| Maximum Drilling Diameter Hd1 | 13mm Dia. |
| Turret Slide Stroke Y Axis | ±40mm |
| Maximum Drilling Diameter Hd2 | 10mm Dia. |
| Inquiries | Feel free to get in touch with us by phone or online if you have any questions or need advice about any of our products or services. |
Specifications sourced from cmj.citizen.co.jp — verified 2026-03-28
Strengths & Limitations
Strengths
- Full 51 mm bar capacity on both spindles enables complete front-and-back machining of medium-sized components that exceed the 42 mm BNJ capacity
- True dual-turret independence with 12+8 stations provides simultaneous machining on both spindles for 30-50% cycle time reduction on balanced parts
- 15/11 kW main spindle delivers the torque needed for aggressive roughing in steel and stainless at the full 51 mm bar diameter
- Same compact 2,840 x 1,560 mm footprint as the BNJ-42, maximizing capacity without additional floor space requirements
- 590 mm Z2 travel handles extended backworking operations and part transfer for the larger 51 mm workpieces
- 6,000 RPM upper turret live tools handle cross-drilling, tapping, and milling operations on the main spindle side
Limitations
- 5,000 RPM maximum spindle speed is lower than the 6,000 RPM on the BNJ-42, limiting surface speeds on smaller-diameter features
- 3,000 RPM lower turret live tool speed limits backworking milling performance to lighter operations
- No Y-axis on the base BNJ-51 model limits milling to on-center operations only
- Complex dual-path programming requires experienced multi-turret programmers and offline simulation software
Best For
Frequently Asked Questions
01
New BNJ-51 machines typically range from $250,000 to $350,000 depending on tooling configuration, automation options, and Y-axis specification. The premium over a single-turret BNE-51 is approximately $80,000-$100,000 for the second turret and associated axes.
02
The BNJ-51 increases bar capacity from 42 mm to 51 mm on both spindles but with a lower maximum spindle speed of 5,000 RPM versus 6,000 RPM. Choose the BNJ-42 for smaller parts where higher RPM and faster cycles matter; choose the BNJ-51 when part diameters regularly exceed 42 mm.
03
The base BNJ-51 does not include Y-axis. The BNJ-51SY adds Y-axis travel of +/-40 mm on the upper turret for off-center milling capability at additional cost. Choose the base model for turning-focused work; choose the SY for parts requiring flats, keyways, or off-center features.
04
The BNJ-51 is compatible with 51 mm (2-inch) class bar feeders including the LNS Quick Load Servo 80, Edge FMB Turbo 5-65, and Iemca Master 80. Magazine-style feeders are preferred for production runs.
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