Citizen Miyano BNJ-42

$200,000 - $280,000 Updated 2025-03-15

Key Specifications

Max Turn Length

100 mm (3.94 in)

max bar capacity

42 mm (1.65 in)

max turning diameter

200 mm (7.87 in) chuck work

main spindle speed

6,000 RPM

sub spindle speed

6,000 RPM

live tool speed

6,000 RPM

Overview

The Citizen Miyano BNJ-42 is a twin-turret, twin-spindle fixed-headstock CNC lathe engineered for high-production machining of complex parts up to 42mm in diameter. The dual turret configuration is the BNJ's defining advantage over the single-turret BNE-42—it enables simultaneous front and back operations, dramatically reducing cycle times on parts that require both turning and secondary features.

The BNJ-42 features a main spindle and sub-spindle both reaching 6,000 RPM, with the upper turret serving the main spindle and the lower turret dedicated to the sub-spindle. This arrangement means the machine can be turning on the main spindle while simultaneously drilling on the sub-spindle, effectively cutting cycle time in half on many parts. Both turrets accommodate live tooling, and Y-axis capability enables off-centerline features on both spindles.

Citizen's Miyano thermal stability technology is critical on a twin-turret machine where two cutting processes generate heat simultaneously. The thermally symmetric cast iron construction and strategic coolant management maintain dimensional accuracy even under sustained dual-cutting conditions. The rigid box-way slides provide the vibration damping needed for excellent surface finishes across both turrets working concurrently.

The BNJ-42 is built for production environments where cycle time directly impacts profitability. Automotive, medical, and hydraulic component manufacturers who produce large volumes of complex small parts see the most dramatic return on investment—the ability to overlap operations can reduce per-part cycle times by 30-50% compared to single-turret machines. The Mitsubishi M80W control with dual-path programming handles the complex synchronization required.

While the twin-turret configuration demands more programming expertise and setup time than a single-turret machine, the per-part productivity gains compound quickly in medium-to-high volume applications. The BNJ-42 represents the performance ceiling of Citizen's 42mm fixed-headstock platform.

Full Specifications

Parameter	Value
Max Bar Capacity	42 mm (1.65 in)
Max Turning Diameter	200 mm (7.87 in) chuck work
Max Turning Length	100 mm (3.94 in)
Main Spindle Speed	6,000 RPM
Sub Spindle Speed	6,000 RPM
Live Tool Speed	6,000 RPM
Spindle Motor	7.5 kW (10 hp)
Number Of Axes	8 (X1, Z1, Y1, X2, Z2, Y2 + C1, C2)
Turret Positions	24 (12 upper + 12 lower)
Rapid Traverse X	20 m/min
Rapid Traverse Z	24 m/min
Machine Weight	5,300 kg
CNC Control	Mitsubishi M80W dual-path (Citizen Miyano)
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
Floor Space	2,840×1,560mm(Without Chip Conveyor)
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.)
Machine Height	1,700mm
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

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Limitations

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Best For

High-volume automotive production of complex turned parts requiring both front and back machining operations Medical device manufacturers producing implants, surgical instruments, and precision components where cycle time matters Hydraulic component producers running large quantities of valve bodies and fittings with features on both ends Shops where per-part cycle time directly impacts competitiveness and the 30-50% time savings justifies the investment Contract manufacturers with established high-volume programs that run continuously on dedicated machines Production environments already familiar with multi-turret programming looking to upgrade their 42mm turning capability

Frequently Asked Questions

01 What does a Citizen Miyano BNJ-42 cost?

A new Citizen Miyano BNJ-42 typically costs between $200,000 and $280,000 depending on tooling configuration, Y-axis options, and automation accessories. The twin-turret configuration adds approximately $60,000-$80,000 over a comparable BNE-42 single-turret model. Used BNJ-42 machines are relatively rare on the secondary market due to high production demand.

02 How much cycle time does the twin turret save?

On parts that have significant back-working operations (facing, drilling, tapping on the sub-spindle side), the BNJ-42 can reduce cycle times by 30-50% by overlapping front and back operations. The actual savings depend on the specific part geometry—simple parts with minimal back-work see less benefit than complex parts with extensive front and back operations.

03 Is the BNJ-42 harder to program than the BNE-42?

Yes, significantly. The dual-path Mitsubishi M80W control requires synchronized programming of both turrets, including collision avoidance logic. Most shops use offline CAM software with simulation (like Esprit or GibbsCAM) to program and verify BNJ programs before running them on the machine.

04 Can the BNJ-42 run with only one turret active?

Yes, the BNJ-42 can operate in single-turret mode, using only the upper turret like a standard BNE-42. This is useful during setup, prototyping, or when running simpler parts that don't benefit from simultaneous operations.

05 What is the difference between the BNJ-42 and BNJ-51?

The BNJ-51 increases bar capacity from 42mm to 51mm and adds more spindle power to handle the larger diameter, but with a lower maximum spindle speed. Choose the BNJ-42 for smaller parts where higher RPM and faster cycles matter; choose the BNJ-51 when part diameters regularly exceed 42mm.