Star Micronics SR-20JII Type A/B

$150,000 - $250,000 Updated 2026-03-14

Key Specifications

max machining diameter

20 mm (25/32 in), optional 23 mm (29/32 in)

max headstock stroke

205 mm (8 in)

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 (10 min, 25% ED)

Overview

The Star Micronics SR-20JII is one of the most popular Swiss-type lathes in the world, and for good reason. As Star's standard-class 20mm platform, it delivers the tooling capacity, axis control, and programming sophistication that complex medical, automotive, and electronics components demand—all backed by Star's legendary precision and reliability. Available in Type A and Type B configurations, the SR-20JII covers the 20mm bar capacity sweet spot where the majority of Swiss-type turning work lives.

Both spindles run at 10,000 RPM with matched 2.2 kW continuous power (3.7 kW peak), a significant advantage over competitors that skimp on sub-spindle performance. This matched spindle configuration means back-working operations—drilling, threading, contour turning—run at the same speeds and power as front operations, eliminating the back-end bottleneck that plagues many Swiss lathes. The optional 23mm bar capacity extends reach for shops that occasionally encounter slightly larger parts.

The tooling layout is comprehensive: 6 front turning tools (12mm shank) with a 5-spindle sleeve holder providing both front and rear stations. The Type B adds a Y-axis-controlled 8-tool back-working unit compared to Type A's 4-tool unit, making the Type B the better choice for parts with complex back-end features. The revolving guide bush unit supports long, slender parts, and non-guide bush operation is available for shorter workpieces to reduce bar waste.

Running on the FANUC 32i-B control, the SR-20JII provides multi-path synchronization, high-speed processing, and the interpolation capability needed for complex simultaneous machining operations. At 2,750 kg and a footprint of 2,250 x 1,200 mm, it strikes a balance between capability and shop floor impact. Rapid traverse at 35 m/min on primary axes and 24 m/min on Y2 ensures quick positioning for high-volume production. The 202-liter coolant tank and 4.8 kVA power consumption support sustained production environments.

Full Specifications

Parameter	Value
Max Machining Diameter	20 mm (25/32 in), optional 23 mm (29/32 in)
Max Headstock Stroke	205 mm (8 in)
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 (10 min, 25% ED)
Front Turning Tools	6 tools (12 mm shank)
Sleeve Holder	5-spindle (front 5 / rear 5 tools)
Back Working Unit	Type A: 4 tools / Type B: 8 tools (Y-axis)
Rapid Feed Rate	35 m/min (X1, X2, Z1, Z2), 24 m/min (Y2)
Guide Bushing	Revolving guide bush unit
CNC Control	FANUC 32i-B
Power Consumption	4.8 kVA
Coolant Tank	202 L
Machine Weight	2,750 kg (6,063 lb)
Dimensions	2,250 x 1,200 x 1,700 mm

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 complex bone screws, spinal implants, dental abutments, and multi-feature surgical instruments in the 10-20mm range Automotive Tier 1 suppliers running high-volume production of precision shafts, valve components, and sensor housings requiring complete parts in one cycle Electronics and connector manufacturers producing complex multi-feature pins, housings, and precision terminals Contract shops handling diverse Swiss-type work families and needing a versatile platform with broad tooling capacity Aerospace component manufacturers producing precision fittings, actuator components, and fluid system parts with tight tolerances Shops upgrading from basic SB-series machines and ready for the capability step-up to handle more complex part geometries

Frequently Asked Questions

01 What does a Star Micronics SR-20JII cost?

A new Star SR-20JII runs $150,000-$250,000 depending on Type A vs Type B configuration, tooling packages, bar feeder, and options. The Type B with Y-axis back-working commands the higher end of the range. Used SR-20J series machines in good condition trade for $80,000-$150,000 depending on age and condition. The SR-20JII holds value well due to its popularity.

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

Type A has a 4-tool back-working unit for basic secondary operations. Type B upgrades to an 8-tool back-working unit with Y-axis control, enabling complex off-center drilling, milling, and contouring on the back end of the part. Type B costs more but is essential for parts with complex back-end features. Most shops producing medical and aerospace components choose Type B.

03 How does the SR-20JII compare to the Citizen L20?

Both are premier 20mm Swiss-type lathes with massive installed bases. Star's SR-20JII is known for mechanical precision and reliable construction, while Citizen's L20 features the LFV (low-frequency vibration) chip-breaking technology and Cincom programming. Both are excellent choices—the decision often comes down to regional service availability, existing shop familiarity, and specific tooling configurations.

04 Can the SR-20JII run non-guide bush?

Yes. The SR-20JII supports non-guide bush operation for shorter parts, reducing bar remnant waste from approximately 300mm (guide bush mode) to under 50mm. In non-guide bush mode, the maximum machining diameter remains 20mm and bar stock up to 2.5 times the diameter (maximum 50mm) can be machined. Guide bush and non-guide bush modes can be configured on the same machine.

05 What cycle times can I expect?

Cycle times vary dramatically by part complexity. Simple turned parts (a few diameters, a thread, a cutoff) might run 8-15 seconds. Complex medical screws with multiple diameters, threads, cross-holes, flats, and back-end features typically run 25-60 seconds. The SR-20JII's simultaneous machining capability and 35 m/min rapid traverse help minimize non-cutting time.

06 What maintenance does the SR-20JII require?

Standard maintenance includes daily coolant level and concentration checks, weekly lubrication system inspection, guide bush replacement at scheduled intervals (typically every 2,000-5,000 hours depending on material and operation), and annual spindle bearing inspection. Star provides detailed maintenance schedules in the machine manual. The 32i-B control includes maintenance tracking and alarm functions.