Chiron 831 MT Twin

$850,000 - $1,250,000 Updated 2025-03-15

Key Specifications

Max Workpiece ⌀

400 mm (15.7 in)

axes

5-axis simultaneous mill-turn

spindle configuration

Twin-spindle with separate turning and milling spindles per station

machining type

Complete machining (mill-turn, dual part simultaneous)

machine design

STAMA heritage, rigid column architecture

machine bed

Cast iron

Overview

The Chiron 831 MT Twin is the dual-spindle variant of the 831 Series mill-turn platform, doubling throughput by machining two identical parts simultaneously while combining 5-axis milling and turning operations in a single setup. Inheriting the STAMA heritage, the 831 MT Twin represents the highest-output complete machining configuration in the Chiron Group mill-turn portfolio, targeting production environments where high volumes of complex, large-diameter parts demand maximum machine utilization.

The twin-spindle design means two identical workpieces are clamped and machined concurrently, with both spindle stations following the same program. Each station handles workpieces up to 400 mm diameter with separate turning and milling spindles optimized for their respective operations. This dual-spindle, dual-operation architecture delivers roughly double the output of the single-spindle 831 MT, with the potential for further gains through the elimination of part handling between stations.

The rigid column architecture with cast-iron bed provides the stiffness required for simultaneous heavy turning and 5-axis milling operations on both spindles. The machine is designed for complete machining — raw material enters and finished parts exit — with all turning, milling, drilling, tapping, and threading operations completed in the machine. The control is Siemens SINUMERIK 840D sl.

New 831 MT Twin machines price between $850,000 and $1,250,000, making them a major capital investment that requires high-volume production to justify. The twin-spindle mill-turn concept directly competes with multi-machine production cells: one 831 MT Twin can replace two single-spindle mill-turn machines while using less floor space, fewer operators, and simplified logistics. Competitors include twin-spindle configurations from DMG Mori (NTX series), Mazak (Integrex Twin), and dedicated production mill-turn systems from Index and Traub. Used 831 MT Twin units from 2016-2022 trade between $450,000 and $850,000.

The 831 MT Twin is exclusively a production machine. Shops running 5,000+ identical complex parts per year with both milling and turning requirements on larger workpieces will find the throughput advantage compelling. For job shops or low-volume work, the single-spindle 831 MT offers the same capability with more flexibility.

Full Specifications

Parameter	Value
Max Workpiece Diameter	400 mm (15.7 in)
Axes	5-axis simultaneous mill-turn
Spindle Configuration	Twin-spindle with separate turning and milling spindles per station
Machining Type	Complete machining (mill-turn, dual part simultaneous)
Machine Design	STAMA heritage, rigid column architecture
Machine Bed	Cast iron
CNC Control	Siemens SINUMERIK 840D sl
Bar Stock	Bar stock and chuck work capable

Specifications sourced from chiron-group.com — verified 2026-03-28

Strengths & Limitations

Strengths

Twin-spindle design doubles mill-turn throughput by machining two identical parts simultaneously
Separate turning and milling spindles per station provide optimized performance without compromise between operations
Complete machining of both parts from raw stock to finished part in one machine eliminates multi-machine part transfer
Replaces two single-spindle mill-turn machines in less total floor space with fewer operators
400 mm workpiece diameter capacity handles large flanges, housings, and structural components at production volume
Rigid column architecture and cast-iron bed deliver stiffness for heavy-duty turning and milling on both spindles

Limitations

Starting price around $850,000 is one of the highest in the Chiron Group lineup, requiring significant production volume for ROI
Both spindles must machine identical parts — zero flexibility for mixed-part production
STAMA brand transition to Chiron Group may create uncertainty about long-term product roadmap and parts continuity
Machine footprint and weight are substantial, requiring dedicated factory space and foundation work
Twin-spindle mill-turn programming is among the most complex CNC programming, demanding specialized expertise

Best For

Aerospace production of landing gear fittings, turbine housings, and structural components at high volume requiring both turning and 5-axis milling Automotive manufacturers producing transmission components, turbocharger housings, and drive system parts at production scale Energy sector companies machining valve bodies and pump components from steel and Inconel at volumes justifying twin-spindle investment Defense contractors producing complex munition components and guidance system housings requiring complete machining at scale Heavy equipment manufacturers running high-volume programs of hydraulic manifolds and structural components up to 400 mm diameter Production environments seeking to replace two single-spindle mill-turn machines with one twin-spindle cell for reduced floor space and labor

Frequently Asked Questions

01 What does a new Chiron 831 MT Twin cost?

New 831 MT Twin machines typically price between $850,000 and $1,250,000 depending on spindle options, tool magazine capacity, automation, and workholding. This is one of Chiron Group's most expensive standard configurations. Used units from 2016-2022 trade between $450,000 and $850,000.

02 How does the 831 MT Twin compare to the single-spindle 831 MT?

The 831 MT Twin machines two identical parts simultaneously, roughly doubling throughput. The single-spindle 831 MT costs $200,000-$300,000 less and offers flexibility to run different parts. Choose the Twin for high-volume production of identical parts; the single-spindle for job shop flexibility or lower-volume programs.

03 Can the twin spindles run different parts?

No. Both spindle stations follow the same program and machine identical parts. For different parts, you need a single-spindle 831 MT. The twin-spindle design is specifically engineered for production runs of identical components.

04 How does the 831 MT Twin compare to two separate 831 MT machines?

One 831 MT Twin costs roughly the same as two single-spindle 831 MTs ($850K-$1.25M vs 2x $650K-$950K) but uses less total floor space, requires fewer operators, and simplifies production logistics. The trade-off is that two separate machines offer flexibility to run different parts simultaneously.

05 What industries use the 831 MT Twin?

Aerospace is the primary market for landing gear and turbine components. Automotive uses it for drive system and transmission parts. Energy and oil/gas sectors use it for valve bodies and flow control components. Any industry running high volumes of identical complex parts requiring both turning and 5-axis milling can benefit.

06 What volume justifies the 831 MT Twin investment?

As a general guideline, shops running 5,000+ identical complex parts per year with combined milling and turning requirements will see clear ROI from the twin-spindle throughput advantage. At lower volumes, the single-spindle 831 MT provides the same capability with more flexibility and lower capital cost.