Tornos Sigma 7

$150,000 - $250,000 Updated 2026-03-16

Key Specifications

Accuracy

±0.001 mm (±0.00004 in)

max bar capacity

7 mm (0.276 in)

min bar capacity

0.5 mm (0.020 in)

max machining length

60 mm (2.36 in)

main spindle speed

Up to 20,000 RPM

back spindle

Yes

Overview

The Tornos Sigma 7 is an ultra-precision CNC Swiss-type automatic lathe engineered for parts at the extreme small end of the Swiss turning spectrum—bar stock from 1mm to 7mm in diameter. Developed to address the most demanding micro-precision applications in the watchmaking, medical micro-device, and micro-electromechanical sectors, the Sigma 7 represents Tornos' application of its 150-year Swiss screw machine heritage to the most geometrically demanding and dimensionally tight parts that Swiss-type machines produce. At 7mm maximum, the Sigma 7 is purpose-built for work that most 20mm Swiss machines compromise when operating at their small-diameter limits.

The Sigma 7's machine structure is designed from the ground up for thermal stability and micro-scale precision. The spindle arrangement uses precision angular contact bearings rated for the 20,000+ RPM speeds required to maintain appropriate cutting speeds at 1–3mm diameters. At 2mm diameter in titanium, 20,000 RPM produces a surface speed of approximately 125 m/min—adequate for clean cutting, but demanding on spindle thermal management. The Sigma 7's thermal compensation and spindle cooling systems are engineered to maintain spindle position accuracy over extended production runs at high speed.

The guide bushing system on the Sigma 7 uses ultra-precision collet-type bushings with clearances measured in microns for the smallest bar diameters. Maintaining concentricity between the spindle centerline and guide bushing bore at these scales is the primary determinant of turned diameter accuracy and surface finish. Tornos' precision in guide bushing bore-to-spindle alignment on the Sigma 7 delivers the sub-micron cylindricity that watchmaking and micro-implant applications demand.

For watch movement manufacturers producing escapement wheels, balance staffs, pallet fork arbors, and cannon pinions; for micro-medical device producers making guidewire components, neurovascular implant shafts, and cochlear implant contacts; and for MEMS and micro-electromechanical parts producers, the Sigma 7 provides a level of precision, surface quality, and dimensional consistency that cannot be achieved on machines designed for larger diameter ranges. It is the most specialized and high-precision Swiss-type platform in the Tornos lineup.

Full Specifications

Parameter	Value
Max Bar Capacity	7 mm (0.276 in)
Min Bar Capacity	0.5 mm (0.020 in)
Max Machining Length	60 mm (2.36 in)
Main Spindle Speed	Up to 20,000 RPM
Back Spindle	Yes
Back Spindle Speed	Up to 20,000 RPM
Number Of Axes	Up to 11-axis simultaneous
Driven Tools	Yes, front and back
Guide Bushing	Yes, ultra-precision Swiss-type
Tool Positions	Up to 26
Positioning Accuracy	±0.001 mm (±0.00004 in)
CNC Control	Tornos TB-DECO / Fanuc
Machine Dimensions	Approx. 1,400 x 1,000 x 1,600 mm
Machine Weight	Approx. 1,200 kg (2,646 lbs)

Specifications sourced from tornos.com — verified 2026-03-28

Strengths & Limitations

Strengths

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Limitations

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Best For

Swiss watchmaking and movement component manufacturers producing escapement parts, balance staffs, and cannon pinions requiring sub-micron dimensional consistency Micro-medical device manufacturers producing neurovascular guidewire components, cochlear implant contacts, and micro-implant shafts in titanium and cobalt-chrome alloys MEMS and micro-electromechanical parts producers requiring the highest achievable precision in micro-turned shafts, pivots, and bearing seats Aerospace gyroscope and inertial navigation component manufacturers where dimensional accuracy at sub-5mm diameters is mission-critical

Frequently Asked Questions

01 What is the smallest bar diameter the Tornos Sigma 7 can machine?

The Tornos Sigma 7 is designed to handle bar stock down to approximately 0.5mm in diameter, making it capable of producing components at scales that few CNC turning platforms can approach. Workholding and guide bushing selection at these diameters requires specialist Tornos application engineering support.

02 How does the Sigma 7 compare to the Deco 10?

The Sigma 7 is engineered for the 0.5–7mm range with ultra-high spindle speeds and micro-precision structural design. The Deco 10 covers 1–10mm with broader capability suitable for more varied micro-part families. For watchmaking-grade precision at the smallest diameters, the Sigma 7 is the appropriate platform. For more diverse micro-Swiss production up to 10mm, the Deco 10 is more versatile.

03 What industries use the Tornos Sigma 7?

The primary markets for the Sigma 7 are Swiss watchmaking (escapement and movement components), micro-medical devices (neurovascular, cochlear, ophthalmic implants), aerospace micro-components (gyroscopes, inertial measurement), and micro-electromechanical systems manufacturing. All share a requirement for precision at diameters under 7mm that standard Swiss machines cannot reliably achieve.

04 Does the Sigma 7 include a back spindle?

Yes, the Sigma 7 includes a back spindle for secondary operations on the cut-off end of the part. Back spindle operation on the Sigma 7 is scaled for micro-work, with the same high-speed spindle capability and driven tool support as the main spindle—enabling complete part machining in a single setup.

05 What is the price of a Tornos Sigma 7?

New Tornos Sigma 7 machines typically range from $150,000 to $250,000 depending on axis configuration, driven tool count, and optional equipment. The Sigma 7's specialized precision and limited production volumes mean it commands a premium over more common 20mm Swiss platforms. Used examples are infrequently available given the specialized nature of the machine.