Star Micronics SR-20R IV Type A/B

$200,000 - $350,000 Updated 2026-03-14

Key Specifications

Max Spindle

10,000 min-1

Tool Capacity

41 tools

Spindle Power

2.2kw (continuous) / 3.7kw (10 min/25% ED)

Max Turn Length

205mm (8in)

max machining diameter

20 mm (25/32 in)

max headstock stroke standard

205 mm (8 in)

Overview

The Star Micronics SR-20R IV is the premium variant of Star's 20mm Swiss-type platform, designed for the most demanding applications where maximum tooling capacity, axis control, and machining flexibility are non-negotiable. With a 27-position tool station accommodating up to 41 tools and advanced features like B-axis controlled power-driven tooling, the SR-20R IV represents the pinnacle of what a 20mm sliding headstock lathe can deliver. It is Star's answer to the most complex medical implants, aerospace fittings, and precision components that push the boundaries of single-setup production.

The main and sub spindles both run at 10,000 RPM, with the main spindle delivering 2.2 kW continuous (3.7 kW peak) and the sub spindle matching at 2.2 kW continuous (3.7 kW peak) with built-in motor drive. The headstock provides 205mm stroke in standard configuration and 160mm with the revolving magic guide bush unit. The B-axis controlled power-driven tool unit—available as an option—adds angular interpolation capability for machining angled features, compound holes, and complex contours that would otherwise require secondary operations.

The tooling layout is extraordinary for a 20mm Swiss lathe: 5 front tools (12mm) plus rear 2 tools on the gang-type stations, with 3 cross milling tools and the B-axis unit. The 27-position tool station means the SR-20R IV can accommodate the tools for multiple part families simultaneously, reducing setup time when transitioning between jobs. Star's revolving guide bush unit with dedicated drive and air purge system provides clean, precise bar support for long slender parts.

The SR-20R IV is available in Type A (FANUC 31i-B control) and Type B (FANUC 31i-B5 control with enhanced features). Both variants include Star's Motion Control System for optimized axis coordination and the C-axis control on main and sub spindles. At 2,600 kg and a footprint of 2,334 x 1,200 mm, the machine is only slightly larger than the SR-20JII while delivering substantially more capability. This is the machine for shops where part complexity drives the equipment decision.

Full Specifications

Parameter	Value
Max Machining Diameter	20 mm (25/32 in)
Max Headstock Stroke Standard	205 mm (8 in)
Max Headstock Stroke Rmgb	160 mm
Main Spindle Speed	10,000 RPM
Main Spindle Power	2.2 kW continuous / 3.7 kW (10 min, 25% ED)
Sub Spindle Speed	10,000 RPM
Sub Spindle Power	2.2 kW continuous / 3.7 kW (built-in motor drive)
Tool Stations	27-position (up to 41 tools)
Front Tools	5 tools (12 mm) + 2 rear tools
Cross Milling Tools	3 tools
B Axis	Available (power-driven tool unit)
Guide Bushing	Revolving guide bush with air purge
C Axis	Main and sub spindle
Control Type A	FANUC 31i-B
Control Type B	FANUC 31i-B5
Star Motion Control	Yes
Machine Weight	2,600kg
Dimensions	2,334 x 1,200 x 1,700 mm
Max Turning Diameter	ø20mm (25/32in)
Max Turning Length	205mm (8in)
Bar Capacity	ø50mm (1-31/32in)
Turret Stations	27-position
Tool Capacity	41 tools
Max Spindle Speed	10,000 min-1
Spindle Motor Power	2.2kw (continuous) / 3.7kw (10 min/25% ED)
Coolant Capacity	170ℓ
Floor Space	2,334 x 1,200 x 1,700mm
Electrical	4.7KVA
Cnc Control	Fanuc 31i-B (Type A) / Fanuc 31i-B5 (Type B)
Rapid Traverse X	35m/min-1
Rapid Traverse Y	35m/min-1 (Y1), 15m/min-1 (Y2)
Rapid Traverse Z	35m/min-1

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

Strengths & Limitations

Strengths

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Limitations

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Best For

Medical device manufacturers producing the most complex spinal implants, dental prosthetic components, and multi-feature surgical instruments requiring complete single-setup production Aerospace manufacturers producing precision hydraulic fittings, actuator components, and fluid system parts with angled holes and compound features Contract shops handling high-mix work requiring multiple part families to be set up simultaneously, minimizing changeover time Automotive R&D and prototype shops producing complex precision components with features that would otherwise require lathe-plus-mill workflows Defense manufacturers producing complex precision components with tight tolerances and multi-axis features Shops where eliminating secondary operations on complex parts provides enough cycle time and labor savings to justify the premium investment

Frequently Asked Questions

01 What does a Star Micronics SR-20R IV cost?

A new Star SR-20R IV runs $200,000-$350,000 depending on Type A vs B configuration, B-axis option, tooling packages, and bar feeder. The Type B with FANUC 31i-B5 and B-axis commands the upper end. Used SR-20R series machines are less common than SR-20J models but trade for $120,000-$200,000 when available.

02 What is the difference between Type A and Type B?

Type A uses the FANUC 31i-B control while Type B uses the enhanced FANUC 31i-B5 with additional processing power, more memory, and enhanced motion control features. Type B is recommended for the most complex programs, particularly when using B-axis interpolation. Most new purchases are Type B unless budget is the primary constraint.

03 How does the SR-20R IV compare to the SR-20JII?

The SR-20R IV offers substantially more tooling capacity (41 tools vs approximately 19), B-axis capability, 31i-B/B5 control (vs 32i-B), and Star Motion Control System. The SR-20JII is the right choice for standard-complexity Swiss parts; the SR-20R IV is for shops where every part requires maximum tool positions and feature complexity.

04 What is the B-axis and when do I need it?

The B-axis provides controlled angular rotation of the power-driven tool spindle, enabling machining of angled holes, tapered features, and compound surfaces that cannot be produced with standard X/Y/Z/C axis movements alone. You need it when parts have features at angles other than 0 or 90 degrees to the part centerline—common in medical implants, aerospace fittings, and precision hydraulic components.

05 Can I run multiple part families without setup changes?

Yes, this is one of the SR-20R IV's key advantages. With 41 tool positions, you can load tooling for 2-3 different part numbers simultaneously and switch between them with a program change rather than a physical setup change. This dramatically reduces changeover time for high-mix, low-to-medium volume production environments.

06 What is the Star Motion Control System?

Star Motion Control System is Star's proprietary software that optimizes axis movements during machining. It coordinates acceleration, deceleration, and interpolation across multiple axes to minimize vibration, reduce cycle time, and improve surface finish. The system is particularly effective during complex simultaneous operations where multiple axes are moving at once.