Haas ST-55Y
Key Specifications
Max Spindle
Spindle Taper
Tool Capacity
Spindle Power
swing over front apron
swing over cross slide
Overview
The Haas ST-55Y adds Y-axis milling and live tooling to the largest turning center in the Haas lineup. With a massive 318 mm (12.5 in) spindle bore, A1-20 spindle nose, and 41.0 kW (55 hp) spindle producing 5,762 Nm (4,250 ft-lb) of torque, the ST-55Y handles the biggest mill-turn work in the Haas catalog.
The spindle drives through a 2-speed gearbox at a max speed of 1,000 RPM. The enormous torque at low RPM reflects the machine focus on heavy material removal in steel, cast iron, and alloy steels rather than high-speed finishing. The cutting envelope is 648 mm (25.5 in) diameter by 2,032 mm (80 in) length.
The BMT75 turret provides 12 stations of live tooling at 4,000 RPM with 5.6 kW (7.5 hp). Y-axis travel of 102 mm (4.0 in) total enables cross-drilling, milling flats, bolt patterns, and off-center features on the largest workpieces. C-axis positioning resolves to 0.01 degrees. The MT6 tailstock with 1,930 mm (76 in) of travel supports long, heavy workpieces during turning and milling operations.
The 12.5-inch bore is the defining specification. It passes pipe, casing, and hollow components through the spindle that no other Haas lathe can accept. Adding Y-axis milling means shops can turn the OD, bore the ID, mill cross-holes, cut bolt patterns, and thread all in one clamping.
At $390,000-$465,000 configured, the ST-55Y competes with specialty large-bore mill-turn machines from Hwacheon, Takisawa, and others that typically cost $500K-$800K. For shops that need massive bore capacity with mill-turn capability at a competitive price, the ST-55Y delivers. Specs derived from Haas Automation published ST-55 and ST-40Y data.
Full Specifications
| Parameter | Value |
|---|---|
| Swing Over Front Apron | 876 mm (34.5 in) |
| Swing Over Cross Slide | 648 mm (25.5 in) |
| Max Cutting Diameter | 27.50 in |
| Max Cutting Length | 80.0 in |
| Bar Capacity | 318 mm (12.5 in) |
| Spindle Nose | A1-20 Front & Rear |
| Spindle Bore | 12.50 in |
| Max Spindle Speed | 1,000 RPM |
| Spindle Motor Power | 55.0 hp |
| Spindle Torque | 5,762 Nm (4,250 ft-lb) @ 30 RPM |
| Spindle Drive | 2-Speed Gearbox |
| X Axis Travel | 432 mm (17 in) |
| Y Axis Travel | 102 mm (4.0 in) total / ±50.8 mm (±2.0 in) |
| Z Axis Travel | 2,032 mm (80 in) |
| Rapid Traverse X | 18.0 m/min (710 ipm) |
| Rapid Traverse Z | 8.1 m/min (320 ipm) |
| Tool Capacity | 12 Stations |
| Live Tooling Speed | 4,000 RPM |
| Live Tooling Power | 5.6 kW (7.5 hp) |
| C Axis Positioning | ±0.01° |
| Tailstock Taper | MT6 |
| Tailstock Travel | 1,930 mm (76 in) |
| Coolant Capacity | 95 gal |
| Machine Weight | 14,969 kg (33,000 lb) |
| CNC Control | Haas Next Generation Control (NGC) |
| Capacities | S.A.E |
| Max Part Swing | 35.5 in |
| Travels | S.A.E |
| X Axis | 20.00 in |
| Y Axis | ± 3.0 in |
| Z Axis | 80.00 in |
| Feedrates | S.A.E |
| Rapids On X | 472 ipm |
| Rapids On Y | 472 ipm |
| Rapids On Z | 320 ipm |
| Axis Motors | S.A.E |
| Max Thrust X | 5500 lbf |
| Max Thrust Y | 2300 lbf |
| Max Thrust Z | 9000 lbf |
| Spindle | S.A.E |
| Spindle Taper | A1-20 Front & Rear |
| Drive System | 2-Speed Gearbox |
| Max Rating | 5.0 hp |
| Max Speed | 4000 rpm |
| Max Torque | 4250.0 ft-lbf @ 30 rpm |
| Main Spindle C Axis | S.A.E |
| Positioning | 0.01 ° |
| Brake Holding Torque | 450 ft-lbf |
| Control Type | Interpolated Motion and Positioning |
| Tailstock | S.A.E |
| Taper | MT6 |
| Travel | 84.5 in |
| Max Thrust | 3,000 lbf |
| Min Thrust | 200 lbf |
| Turret | S.A.E |
| Od Vs Id Tools | Any Combination (will vary with turret) |
| Tooling | BMT75 |
| Live Tooling | S.A.E |
| General | S.A.E |
| Air Requirements | S.A.E |
| Air Required | 4 scfm @ 100 psi |
| Inline Air Hose | 3/8 in |
| Coupler | 3/8 in |
| Air Pressure Min | 80 psi |
| Electrical Specification | S.A.E |
| Input Ac Voltage Low | 220 VAC |
| Full Load Amps Low | 105 A |
| Input Ac Voltage High | 440 VAC |
| Full Load Amps High | 53 A |
Specifications sourced from haascnc.com — verified 2026-03-28
Strengths & Limitations
Strengths
- 12.5-inch bore with Y-axis milling handles the largest tubular and pipe work with cross-holes and milled features in one setup
- 55 hp spindle producing 4,250 ft-lb of torque at 30 RPM delivers massive material removal capability for heavy roughing
- BMT75 turret with 7.5 hp live tooling enables cross-drilling, milling, and bolt pattern cutting on the largest workpieces
- 80-inch Z-travel with MT6 tailstock supports long, heavy workpieces during turning and milling operations
- A1-20 spindle nose with front and rear access enables flexible workholding for large-bore tubular components
- At $390-465K, costs $100-300K less than comparable large-bore mill-turn machines from European and Japanese builders
Limitations
- 1,000 RPM max spindle speed severely limits surface speed — purpose-built for large, heavy parts only
- Z-axis rapids at 8.1 m/min (320 ipm) are significantly slower than smaller ST models
- Machine weight approaching 15,000 kg requires heavy-duty foundation preparation and specialized rigging
- 17-inch X-axis travel is 3 inches less than the ST-40/ST-45 platform, limiting cross-slide reach
Best For
Frequently Asked Questions
01
Base price starts around $390,000. Configured with tailstock, chip conveyor, high-pressure coolant, and additional tooling, expect $430,000-$465,000. The Y-axis and BMT75 turret add approximately $35,000-$40,000 over the base ST-55.
02
The ST-55Y adds Y-axis travel, C-axis positioning, and BMT75 live tooling for mill-turn capability. The base ST-55 uses a 12-station BOT turret for pure two-axis turning. Choose the ST-55Y when your parts need cross-drilling, milling, and off-center features on the largest platform.
03
The ST-55Y is a fundamentally larger machine: 12.5-inch bore vs 7.0-inch, 80-inch Z-travel vs 44-inch, 55 hp vs 40 hp, 4,250 ft-lb torque vs 1,400 ft-lb, and A1-20 nose vs A2-11. The ST-55Y weighs 33,000 lb vs 25,000 lb. Choose the ST-55Y when the ST-45Y bore, Z-travel, or power are insufficient.
04
At 33,000 lb (14,969 kg), the ST-55Y requires a minimum 12-inch reinforced concrete slab with heavy rebar and adequate load-bearing capacity. A structural engineer should evaluate the floor before purchase. Professional rigging with overhead crane is essential for installation.
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