Okuma GP-GA25W
Key Specifications
X Travel
Z Travel
max grinding diameter
distance between centers
grinding wheel size
wheel speed max
Overview
The Okuma GP-GA25W is a mid-range CNC cylindrical grinder that steps up from the GA15W with a larger 250 mm (9.8 in) maximum grinding diameter and 650 mm (25.6 in) distance between centers. It sits in the sweet spot of Okuma's GA-W grinding lineup, handling the medium-diameter shafts, spindles, and precision components that make up the bulk of work in automotive, aerospace, and general manufacturing grinding departments.
The grinding wheel is 455 x 75 mm (17.9 x 3.0 in) with a maximum peripheral speed of 45 m/s (8,858 sfm). The wider 75 mm wheel face compared to the GA15W's 50 mm allows wider plunge grinding zones and higher material removal rates on larger-diameter workpieces. The wheel spindle uses hydrodynamic bearings for vibration-free grinding, and the table traverse is driven by precision ball screws with linear glass scales.
The X-axis (infeed) travel is 250 mm (9.84 in) with a minimum feed increment of 0.0001 mm (0.000004 in). The Z-axis (traverse) travel is 675 mm (26.57 in). Rapid traverse rates are 10 m/min (394 ipm) on X and 15 m/min (591 ipm) on Z. The headstock provides workpiece rotation from 10 to 500 RPM with an MT5 center, supporting heavier workpieces than the GA15W's MT4.
The machine includes Okuma's automatic wheel dressing system with diamond dresser, gap elimination for reduced air grinding time, and in-process gauging capability. The OSP-P300G control handles multi-step grinding sequences and stores programs for repeat jobs. The table swivels +/- 6 degrees for taper grinding applications.
Machine weight is approximately 5,500 kg (12,125 lb). Floor space runs approximately 3,600 x 2,400 mm (142 x 94 in). New pricing typically ranges from $180,000-$260,000. The GP-GA25W competes with Studer S31, Kellenberger Vita, and Toyoda GE4Pi-II for medium-diameter precision cylindrical grinding.
Full Specifications
| Parameter | Value |
|---|---|
| Max Grinding Diameter | 250 mm (9.8 in) |
| Distance Between Centers | 400 or 650 |
| Grinding Wheel Size | 455 x 75 mm (17.9 x 3.0 in) |
| Wheel Speed Max | 45 m/s (8,858 sfm) |
| X-Axis Travel | 250 mm (9.84 in) |
| Z-Axis Travel | 675 mm (26.57 in) |
| Min Feed Increment | 0.0001 mm (0.000004 in) |
| Rapid Traverse X | 10 m/min (394 ipm) |
| Rapid Traverse Z | 15 m/min (591 ipm) |
| Workhead Speed | 10 - 500 RPM |
| Workhead Center | MT5 |
| Swivel Angle | +/- 6° |
| Machine Weight | 5,500 kg (12,125 lb) |
| Floor Space | 3,600 x 2,400 mm (142 x 94 in) |
| CNC Control | Okuma OSP-P300G |
| Max Grinding Dia | Ø200 |
| Grinding Wheel Odxid | Ø508 × Ø203 |
| Max Grinding Wheel Width | 150 |
| Rapid Traversex | 30 |
| Rapid Traversez | 20 |
| Wheel Spindle Motor | 7.5 [15] |
| Okuma Global Repair Center | Charlotte, North Carolina |
| Inches | Metric |
Specifications sourced from okuma.com — verified 2026-03-28
Strengths & Limitations
Strengths
- 250 mm grinding diameter and 650 mm between centers handle the medium-shaft work that represents the majority of production cylindrical grinding in automotive and aerospace
- 75 mm wide grinding wheel enables wider plunge zones and higher material removal rates compared to the GA15W's 50 mm wheel, reducing cycle times on production parts
- 0.0001 mm minimum feed increment provides the fine infeed control needed for finishing passes on tight-tolerance bearing journals and precision shafts
- Hydrodynamic wheel spindle bearings deliver vibration-free operation for surface finishes below Ra 0.2 micrometers on hardened steel components
- MT5 headstock center supports heavier workpieces than the GA15W's MT4, matching the machine's larger grinding capacity
- Gap elimination and in-process gauging reduce cycle time and eliminate post-process measurement on production runs
Limitations
- 650 mm between centers may still be limiting for longer shafts; shops grinding motor armatures or long spindles should consider the GA26W or larger
- Single wheelhead limits multi-diameter grinding flexibility; complex parts requiring both OD and ID grinding need either repositioning or a dedicated ID grinder
- OSP-P300G control has a learning curve for operators familiar with Fanuc or Siemens grinding controls used by European grinder manufacturers
- 45 m/s wheel speed is standard but not high-speed; shops pushing CBN productivity limits may want faster wheel speeds
- No integrated ID grinding spindle; shops needing combined OD/ID capability should look at universal grinders
Best For
Frequently Asked Questions
01
New pricing runs $180,000-$260,000 depending on options including in-process gauging, automatic wheel balancing, filtration upgrades, and loading automation. This positions it competitively against European grinders like the Studer S31, which typically prices higher for comparable specifications.
02
The GA25W offers 250 mm vs 150 mm grinding diameter, 650 mm vs 500 mm between centers, a wider 75 mm grinding wheel vs 50 mm, and MT5 vs MT4 headstock center. It handles medium-diameter work that the GA15W can't reach. The GA15W is the better choice for shops primarily grinding small-diameter precision parts where its compact size is an advantage.
03
Yes. The machine is designed for grinding hardened steel (55-65 HRC) using conventional aluminum oxide or CBN wheels. The hydrodynamic wheel spindle bearings and fine infeed resolution produce excellent surface finish on hardened components. CBN wheels are recommended for production grinding of hardened steel due to longer wheel life and better finish consistency.
04
Both are proven CNC cylindrical grinders in the medium-diameter class. The Studer S31 offers a wider range of wheelhead configurations including angular and turret options. The Okuma counters with competitive pricing and OSP control integration for existing Okuma shops. The Studer typically achieves slightly better documented roundness and surface finish specifications, reflecting its pure grinding heritage.
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