Mitsui Seiki Horizontal Machining Centers

Mitsui Seiki HS5A

$700,000 - $1,100,000 Updated 2026-03-16

Key Specifications

X Travel

800 mm (31.5 in)

Y Travel

700 mm (27.6 in)

Z Travel

850 mm (33.5 in)

Spindle Taper

No. 50 (standard) / No. 40 (option)

Tool Capacity

50 (standard) / 100 (optional)

Rapid Traverse

40 m/min (1,575 ipm) all axes

Overview

The Mitsui Seiki HS5A is a 500 mm pallet precision horizontal machining center that occupies the middle ground in Mitsui Seiki's horizontal line — larger than the HV4A's 400 mm pallet and smaller than the HS6A's 630 mm platform, while sharing the same Kiyohara factory DNA of box way construction, Meehanite cast iron, and laser-calibrated accuracy. For precision shops working medium-format prismatic parts in aerospace, defense, and precision hydraulics, the HS5A delivers the accuracy of the HS6A in a footprint that fits a wider range of facility layouts.

The HS5A achieves ±0.001 mm full-stroke positioning accuracy with ±0.0005 mm repeatability, confirmed by laser interferometry on every machine. Linear scale feedback on all axes provides full-closed-loop control. The 500 mm pallet handles workpieces up to 800 mm diameter and 1,000 mm height, accommodating engine housing components, gearbox cases, hydraulic manifolds, and structural brackets typical of the aerospace and defense supply chain.

X/Y/Z travels are 800 x 700 x 850 mm. The spindle is available as a 10,000 RPM, 26 kW (35 hp) No. 50 taper unit for heavy material removal in titanium, Inconel, and hardened steel, or a 12,000 RPM, 22 kW (30 hp) No. 40 taper spindle for general precision work. Oil-cooled spindle and ballscrew thermal compensation maintain dimensional stability across production shifts. A 50-tool ATC and 2-station APC are standard.

Compared to standard 500 mm pallet HMCs from Okuma (MB-5000H), Mazak (HCN-5000), and Makino (a51nx), the HS5A commands a significant price premium but offers a guaranteed accuracy specification that none of these machines match out of the box. It is specified by buyers who know the cost of a scrapped aerospace part.

Full Specifications

Parameter	Value
Pallet Size	500 mm (19.7 in)
X-Axis Travel	800 mm (31.5 in)
Y-Axis Travel	700 mm (27.6 in)
Z-Axis Travel	850 mm (33.5 in)
Max Workpiece Diameter	800 mm (31.5 in)
Max Workpiece Height	1,000 mm (39.4 in)
Max Workpiece Weight	1,000 kg (2,205 lb)
Spindle Taper	No. 50 (standard) / No. 40 (option)
Spindle Speed	10,000 RPM (No. 50) / 12,000 RPM (No. 40)
Spindle Motor Power	26 kW (35 hp) / 22 kW (30 hp) continuous
Rapid Traverse Rate	40 m/min (1,575 ipm) all axes
Feed Rate	1–20,000 mm/min
Positioning Accuracy	±0.001 mm (±0.00004 in) full stroke
Repeatability	±0.0005 mm (±0.00002 in)
Rotary Table Resolution	0.001°
Feedback	Full-closed loop, linear scales all axes
Thermal Compensation	Spindle oil cooling, ballscrew cooling, ambient temperature compensation
Tool Capacity	50 (standard) / 100 (optional)
Tool Change Time	3.8 sec (chip-to-chip)
Pallet Changer	2-station APC (standard)
Pallet Change Time	16 sec
Way Type	Box ways, induction hardened and precision ground, all axes
Base Material	Meehanite cast iron, stress-relieved
CNC Control	FANUC 31i-B5
Machine Weight	18,000 kg (39,683 lb)
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X Axis	33.5"
Y Axis	27.5"
Z Axis	21.65"
Power	20 hp
Rpm	4,500 RPM
Atc	180
Taper	CAT #50
Pallet W	24.8"
Pallet L	24.8"
Axis	4
Brand	MITSUI SEIKI
Model	HS5A
Id	427493
Type	Horizontal Machining Centers
Year	1994
Location	United States
Stock	28884
First Name	Last Name
Will You Need Financing	YesNo
Yes	No
Will You Need Freight Service	YesNo

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

Strengths & Limitations

Strengths

±0.001 mm guaranteed positioning accuracy with laser calibration certificate — the same specification as the larger HS6A at a slightly lower price point
Box way construction across all axes provides superior vibration damping for difficult aerospace and defense alloys
500 mm pallet is the most common HMC pallet size — broad tombstone, fixture, and automation ecosystem compatibility
Full thermal compensation system ensures accuracy holds across multi-shift production without manual recalibration
50–100 tool capacity accommodates complex multi-operation aerospace and defense part families on a single setup
10,000 RPM No. 50 taper spindle delivers high torque for heavy Ti-6Al-4V and Inconel material removal rates

Limitations

Price premium of $300–600K over mainstream 500mm HMCs requires a clear business case based on accuracy requirements
40 m/min rapids are conservative versus linear-guide competitors — not the choice for high-speed aluminum aerospace production
Lead times of 6–12 months are typical; Mitsui Seiki's Kiyohara factory does not maintain large finished-goods inventory
Box way maintenance (way lubrication, periodic scraping inspection) requires more effort than linear guide machines
Dealer support network is concentrated in the United States and Japan — European and Asian buyers may face longer service response times

Best For

Aerospace Tier 1 and Tier 2 suppliers machining titanium structural components, engine cases, and hydraulic manifolds to AS9100 tolerances Defense primes and subcontractors producing precision housings, mounts, and structural brackets where dimensional certification is required Precision hydraulics and fluid power manufacturers producing manifold blocks with tight bore-to-bore positional accuracy Medical device contract manufacturers producing large implant fixtures and surgical instrument components Job shops specializing in low-volume, high-complexity precision work where accuracy certification is a competitive requirement

Frequently Asked Questions

01 How does the HS5A compare to the HS6A?

The HS5A and HS6A share the same accuracy specifications (±0.001 mm positioning, ±0.0005 mm repeatability) and the same thermal compensation architecture. The HS6A has a 630 mm pallet, larger X/Y/Z travels (900 x 850 x 950 mm vs 800 x 700 x 850 mm), and higher maximum workpiece weight (1,500 kg vs 1,000 kg). Choose the HS5A for medium-format aerospace and defense parts; the HS6A for larger structural components and molds.

02 Is a No. 40 or No. 50 taper spindle better for aerospace work on the HS5A?

The answer depends on material. For titanium (Ti-6Al-4V), Inconel, and hardened steels where maximum torque is needed, the No. 50 taper at 10,000 RPM is the right choice — it allows larger diameter tools and heavier cuts. For aluminum aerospace structures, stainless, and general precision work where surface finish and speed are balanced, the No. 40 taper at 12,000 RPM is preferable. Mitsui Seiki can configure either spindle; discuss application requirements with your distributor before ordering.

03 What automation options are available for the HS5A?

The HS5A's standard 2-station APC expands to multi-pallet storages of 4, 8, and 16 pallets for lights-out operation. Robot loading through the door is also supported. The 500 mm pallet size is compatible with many third-party tombstone and modular fixture suppliers, giving broad tooling flexibility for complex part families.

04 What is the typical ROI argument for specifying the HS5A over an Okuma MB-5000H?

The Okuma MB-5000H is an excellent production HMC priced $200–400K less than the HS5A. The ROI case for the Mitsui Seiki turns on scrap and rework costs for tight-tolerance parts. If one rejected aerospace part costs $10,000–$50,000 in rework or replacement, a machine that eliminates positional uncertainty pays for its premium quickly. The HS5A is specified when customers cannot tolerate unmeasured thermal drift or unverified positioning.