Star Micronics ST-20

Est. $200,000 - $330,000 Specs verified 2026-10-03 · ellisontechnologies.com Updated 2026-10-03

Image: starcnc.com, Star Micronics

Key Specifications

Max Spindle

10,000 rpm

Tool Capacity

Max. 3 tools/station

Rapid Traverse

30 m/min (for X1, X2, X3, Z1, Z2, Z3 axes)

Spindle Power

3.7 kW (continuous) / 5.5 kW (10min/60%ED)

Max Turn Length

350mm (13-25/32in)

max machining diameter

20 mm (25/32 in)

How much does the Star Micronics ST-20 cost?

Estimated price range

Est.$200,000 - $330,000

Our best estimate for a swiss-type lathe in this class — not a quote from Star Micronics. Configuration moves it a long way.

Overview

The Star Micronics ST-20 is a Swiss-type lathe built around three turrets: 8 stations at the front, 8 at the rear and 8 for back working. It takes Ø20 mm (25/32 in) bar, turns at 10,000 rpm on both spindles and has a 350 mm (13-25/32 in) maximum turning length.

Each station can hold up to 3 tools, with the front turret row giving 12/16 mm shanks, so the tool count is far higher than the station count suggests. The rapid row names X1, X2, X3, Z1, Z2 and Z3 at 30 m/min: three independent tool slides. With three slides, cuts can overlap, for example two turrets on the main spindle while the third works a part held in the sub-spindle. How much overlap a part allows decides whether this layout earns its place.

The two spindles are matched. Main and sub are each rated 3.7 kW continuous and 5.5 kW at the 10min/60%ED rating, each reaches 10,000 rpm, and the C-axis row covers both. With equal power on the sub-spindle, the back of the part need not be treated as light finishing work.

Headstock stroke is 350 mm in standard form and 317 mm in the RMGB version, an abbreviation the table does not expand. Control is a FANUC 31i-B5. At 4,850 kg and 2,988 × 1,720 × 1,845 mm the ST-20 is a large machine for its bar size; the ST-38, which takes Ø38 mm (1-1/2 in) bar at 7,000 rpm, weighs 6,250 kg.

Full Specifications

Parameter	Value
Max Machining Diameter	20 mm (25/32 in)
Max Headstock Stroke Standard	350 mm
Max Headstock Stroke Rmgb	317 mm
Sub Spindle Speed	10,000 rpm
Sub Spindle Power	3.7 kW (continuous) / 5.5 kW (10min./60%ED)
Front Turret	8 stations (max 3 tools per station, 12/16 mm shank)
Rear Turret	8 stations
Back Turret	8 stations
C Axis	Main and sub spindle
CNC Control	FANUC 31i-B5
Machine Weight	4,850 kg
Max Turning Diameter	ø20mm (25/32in)
Max Turning Length	350mm (13-25/32in)
Max Spindle Speed	10,000 rpm
Spindle Motor Power	3.7 kW (continuous) / 5.5 kW (10min/60%ED)
Turret Stations	8 stations (front), 8 stations (rear), 8 stations (back working)
Tool Capacity	Max. 3 tools/station
CNC Control	Fanuc 31i-B5
Headstock Stroke	350 mm (13-25/32 in
Turning Tools	3 tools/station
Bar Capacity	Ø20 mm (25/32 in)
Rapid Traverse Rate	30 m/min (for X1, X2, X3, Z1, Z2, Z3 axes)
Floor Space Required	2,988 × 1,720 × 1,845 mm

Specifications sourced from ellisontechnologies.com (authorised dealer / distributor, not the manufacturer's own site) — verified 2026-10-03

Strengths & Limitations

Strengths

Three turrets: 8 stations front, 8 rear and 8 for back working
Up to 3 tools per station, with 12/16 mm shanks listed for the front turret
Sub-spindle matches the main spindle at 10,000 rpm and 3.7 kW continuous / 5.5 kW (10min./60%ED)
C-axis on both main and sub spindle
350 mm (13-25/32 in) maximum turning length on Ø20 mm (25/32 in) bar
30 m/min rapids on X1, X2, X3, Z1, Z2 and Z3

Limitations

The rapid traverse row names only X and Z axes; no Y axis is listed in the table
Headstock stroke drops from 350 mm to 317 mm in the RMGB version
4,850 kg and a 2,988 × 1,720 × 1,845 mm footprint for a Ø20 mm (25/32 in) machine
Bar capacity is Ø20 mm (25/32 in) with no larger option listed; the ST-38 takes Ø38 mm (1-1/2 in)

Best For

Complex Ø20 mm (25/32 in) parts that need a large tool complement in one cycle Overlapping operations on three tool slides to shorten cycles Parts with heavy back-end work, using the 5.5 kW (10min./60%ED) sub-spindle Long slender parts up to 350 mm (13-25/32 in)

Frequently Asked Questions

01 How many tools can the ST-20 hold?

The table lists three turrets of 8 stations each: front, rear and back working. Each station takes a maximum of 3 tools, and the front turret row gives the shank size as 12/16 mm. The table does not state a total tool count or how many stations can be driven.

02 Is the sub-spindle as powerful as the main spindle?

Yes. Both are listed at 10,000 rpm with 3.7 kW continuous and 5.5 kW at the 10min/60%ED rating, and the C-axis row covers main and sub spindle. Back-end operations can be planned with the same cutting data as front-end ones.

03 What is the headstock stroke of the ST-20?

350 mm (13-25/32 in) as standard. A second row gives 317 mm for the RMGB version; the table does not spell out the abbreviation. Maximum turning length is listed as 350mm (13-25/32in).

04 How does the ST-20 differ from the ST-38?

Bar size, speed and weight. The ST-20 takes Ø20 mm (25/32 in) bar at 10,000 rpm and weighs 4,850 kg. The ST-38 takes Ø38 mm (1-1/2 in) bar at 7,000 rpm with 7.5 kW continuous and weighs 6,250 kg. The ST-38 is listed with 10 stations and a maximum of 2 tools per station (16mm); the ST-20 with 8 stations per turret and up to 3.

05 Which control and axes does the ST-20 have?

Control is a FANUC 31i-B5. The rapid traverse row lists X1, X2, X3, Z1, Z2 and Z3 at 30 m/min, and C-axis is listed for main and sub spindle. No Y axis appears in the table, so check the specification if off-centre milling is needed.