Reviewed by UsedUltra's senior equipment inspection engineering team. Lead reviewer: Chris (12 years in pre-owned industrial equipment assessment, 1,500+ CNC machines inspected including 200+ surface grinders across Okamoto, Studer, Jung, Chevalier, and other brands).
Core Summary: Okamoto Machine Tool Works is one of Japan's oldest dedicated grinding machine manufacturers, founded in 1926, with its head office established in Tokyo's Ginza district in 1935 and current headquarters in Annaka City, Gunma Prefecture (TSE: 6125.T). First-time used surface grinder buyers choose Okamoto for three reasons: first, accuracy that competes with Swiss brands at 40-60% of the used-market price (PSG series achieves flatness of ±0.001-0.003mm); second, commonly available control systems (touch-panel or Fanuc) with parts and service independent of proprietary brand channels; third, durability — mid-to-high-end models feature hydrostatic guideways with oil-film suspension (<0.001mm accuracy degradation over 15 years), while entry-level V-V guideways are hardened and remain reliable even on 15-20 year old machines. But — you need to know which model fits your workpieces and what to check in a used inspection. This guide builds your selection framework from scratch. Tip: Use UsedUltra's brand filter to browse current Okamoto inventory by equipment type "grinder" and origin JP.
Why First-Time Buyers Get Intimidated by the Grinder Category
First-time used surface grinder buyers — whether you're a small shop owner who just landed a precision parts order or a production supervisor looking to improve mold plate quality — all face the same obstacles:
1. Brand awareness gap. You know Makino, Yasda, HAAS because they make machining centers (VMCs). Grinders are a more vertical category; you may not even know what Japanese grinder brands exist. Faced with Okamoto, Studer (Swiss), Jung (Swiss), Chevalier (Taiwan), KENT (Taiwan), you have no basis to judge who is better.
2. Different precision metrics. With a machining center you care about "positioning accuracy ±0.005mm." Grinder accuracy is measured differently — flatness, surface roughness (Ra/Rz), parallelism — which are blind spots for many machining professionals. You don't know what "0.002mm flatness" means, so you can't tell if a grinder's price is reasonable.
3. Harder to evaluate condition. VMC condition can be assessed by spindle runout, cutting cycles, and listening to sounds. A grinder's core — spindle accuracy, guideway condition, coolant system, wheel balance — requires specialized knowledge and tools to evaluate. Buy the wrong one and repair costs can exceed the machine's value.
4. "Will it grind my parts?" uncertainty. You don't know: "Can this Okamoto 640 handle my 500mm mold plate? Can it hit Ra0.4?" Nobody gives you a clear matching framework.
This article removes all four obstacles.
Okamoto's Technical Positioning & Core Specs
Where Okamoto Sits in the Grinder Market
In the used grinder market, brands fall into three tiers:
| Tier | Brand | Accuracy Level | Used Price Index | Best For |
|---|---|---|---|---|
| Tier 1 | Studer, Jung (Swiss) | Highest | 100 (baseline) | Ultra-precision, medical, aerospace |
| Tier 2 | Okamoto (Japan) | High | 40-60 | Mold & die, precision parts, general precision grinding |
| Tier 3 | Chevalier, KENT, Supertec (Taiwan/China) | Medium-High | 20-35 | General grinding, entry-level, budget-constrained |
Okamoto occupies the "high-value" sweet spot — accuracy sufficient for 95% of surface grinding needs at less than 60% of Swiss brand prices.
PSG-CA1 Series Core Specifications
The CA1 series is Okamoto's most common used grinder line. Specifications for the popular models:
| Parameter | PSG-64CA1 (Best Seller) | PSG-84CA1 | PSG-104CA1 |
|---|---|---|---|
| Magnetic Chuck Size | 600 × 400 mm | 800 × 400 mm | 1,000 × 400 mm |
| Worktable Size | 605 × 400 mm | 805 × 400 mm | 1,016 × 400 mm |
| Max Grinding Length | 600 mm | 800 mm | 1,000 mm |
| Max Grinding Width | 400 mm | 400 mm | 400 mm |
| Guideway Type | V-V | V-V | V-V |
| Control | Touch-panel + Self-diagnostic | Touch-panel + Self-diagnostic | Touch-panel + Self-diagnostic |
| Auto Wheel Dressing | ✅ Standard | ✅ Standard | ✅ Standard |
| Spindle Type | Ultra-precision angular contact ball bearing | Ultra-precision angular contact ball bearing | Ultra-precision angular contact ball bearing |
| Spindle Motor Power | 5.5 kW | 5.5 kW | 5.5 kW |
| Wheel Spec (OD × Thickness × Bore) | 350 × 35 × 127 mm | 350 × 35 × 127 mm | 350 × 35 × 127 mm |
| Max Workpiece Load (incl. accessories) | 1,000-1,500 kg | 1,000-1,500 kg | 1,000-1,500 kg |
| Net Machine Weight | 4,500 kg | 5,500 kg | 7,000 kg |
| Floor Space (L × W × H) | 3,710 × 3,150 × 2,200 mm | 3,940 × 3,150 × 2,200 mm | 4,440 × 3,150 × 2,200 mm |
| Typical Used Year | 2010-2019 | 2010-2019 | 2010-2019 |
| Typical Used Price | $15,000-35,000 | $20,000-45,000 | $25,000-55,000 |
Selection Rule: Chuck Size Determines Your Range
Your largest workpiece dictates your model choice. Simple rule:
Workpiece length/width + 50-100mm clearance on each side ≤ Chuck size
Check your actual parts:
| Your Largest Part | Recommended Model | Why |
|---|---|---|
| Up to 400 × 300 mm | PSG-64CA1 ⭐ Best Pick | Covers most mold plates and parts; largest used inventory |
| Up to 600 × 300 mm | PSG-84CA1 | Longer parts |
| Up to 800 × 300 mm | PSG-104CA1 | Long parts, width-limited |
For first-time buyers, PSG-64CA1 (600×400mm chuck) is the safest choice. It covers most mold plate and precision part sizes, has the largest used-market inventory, best parts availability, and best resale liquidity.
Surface Grinder vs VMC Milling — Why Not Just "Grind" on Your Machining Center?
A question many first-time buyers don't fully think through:
"I have a VMC. Why not just use a grinding tool in the spindle and grind on the machining center?"
The answer lies in the physics of material removal:
| Dimension | VMC Milling | Surface Grinding |
|---|---|---|
| Material removal method | Rotating cutter + chip removal | High-speed wheel + abrasive grain cutting |
| Achievable surface roughness | Ra 0.8-3.2μm | Ra 0.1-0.8μm |
| Achievable flatness | ±0.01-0.02mm | ±0.001-0.005mm |
| Suitable material hardness | Typically HRC 50 and below | HRC 30-68 (including hardened steel) |
| Heat effect | High cutting heat, workpiece distortion | Excellent cooling, minimal thermal effect |
| Efficiency (batch flat surfaces) | Low (layer-by-layer) | High (reciprocating grinding) |
Simply put: if you need Ra 0.4 surface finish or you're machining hardened steel (mold steel HRC 50+), milling cannot deliver — you must use a grinder.
This is why Okamoto and similar grinder brands are irreplaceable in mold and precision parts manufacturing. Your injection mold plates, stamping die sets, and precision part faces can only achieve their final accuracy on a grinder.
Okamoto's Technical Moat: Three Layers of Precision Assurance
Layer 1: Guideway Technology — The Core of Accuracy Life
Okamoto's guideway strategy varies by model tier:
- PSG-CA1 Series (Entry to Mid-Range): V-V Guideways. Guideway surfaces are induction-hardened (HRC 45+) with precision-scraped sliding surfaces. While not wear-free like hydrostatic ways, they significantly outlast linear ball guide rails. Under normal maintenance, accuracy degradation over 15,000 hours is typically <0.005mm.
- CA-iQ Series / ACC Series (Mid to High-End): Hydrostatic Guideways. The table rides on an oil film (0.01-0.03mm thickness) with no metal-to-metal contact. This eliminates friction wear entirely. Accuracy degradation: <0.001mm over 15 years. On the used market, a hydrostatic-guideway Okamoto commands a 30-50% premium and is considered a "blue-chip" buy.
Layer 2: Grinding Spindle — Precision Output Core
Okamoto uses ultra-precision angular contact ball bearings (P4/SP grade or higher). Post-assembly runout at the wheel flange is held to under 0.003mm.
Common spindle configurations:
| Spindle Type | Series | Characteristics |
|---|---|---|
| Standard Grinding Spindle | PSG-CA1 | General grinding, 4,000-6,000 rpm |
| High-Rigidity Spindle | CA-iQ | Heavy / deep-cut grinding |
| High-Speed Spindle (opt.) | Selected models | 8,000+ rpm, suitable for CBN wheels |
Layer 3: Coolant & Wheel Dressing — Stability Assurance
Okamoto's coolant system and automatic dressing design are good news for used buyers:
- Coolant system is simple, easy to maintain, and not brand-sensitive
- Automatic wheel dressing is standard — critical because it means the auto-compensation mechanism for wheel wear is still operational
- Optional TWIN-BIX fine-bubble generator and other cooling upgrades available
Industry Case Studies
Case 1: Mold Shop Replaces Outsource Grinding with Okamoto PSG-64CA
| Item | Details |
|---|---|
| Background | Small mold shop in Dongguan, 6-person team, producing stamping dies and injection mold plates |
| Problem | ~1,500 mold plates requiring surface grinding monthly. Outsourced to a shop 3km away at ¥35-55/piece, average 4-day delivery delay. During peak season, the outsource shop would simply reject orders |
| Solution | Purchased Okamoto PSG-64CA (2015, 5,200h, supplier provided inspection report showing good guideway condition and 0.002mm spindle runout) via UsedUltra. Total investment including freight and installation ~$40,000 |
| 15-Month Results | Grinding cost dropped from ¥42/piece outsourced to ¥12/piece in-house (including wheel, coolant, power, labor). Monthly savings ~$6,400. Equipment payback: 6.2 months. Flatness improved from 0.007mm outsourced to 0.003mm in-house. No longer constrained by outsource delivery. Mold delivery lead time reduced 35% |
Validation: The PSG-64CA's 600×400mm chuck covered 95% of this shop's mold plate sizes. Production manager's feedback: "If I'd known a grinder would make this much difference, I'd have bought it in year one."
Case 2: Precision Parts Shop Expands Grinding Capacity
| Item | Details |
|---|---|
| Background | Precision parts manufacturer in Suzhou with 8 CNC machining centers and 2 lathes |
| Problem | Grinding operations fully outsourced at ¥25-40/piece, monthly outsource cost ~$8,000-11,000. Worst issue: process waiting time for grinding became the production bottleneck |
| Solution | Purchased Okamoto PSG-104CA1 (2016, 8,200h, asking $42,000) with electromagnetic chuck and wheel dressing unit |
| Results | Grinding throughput increased 3x (from 80 parts/day outsourced to 250+ in-house). Surface roughness stabilized from outsourced Ra0.6 to Ra0.2-0.3 in-house |
Long-Tail FAQ Section
Q: How does Okamoto compare to Swiss brands like Studer, and which should a first-time buyer choose?
A: Swiss brands (Studer, Jung) hold an edge at the very top of the precision spectrum, but Okamoto is usually the more practical choice for first-time buyers:
- Accuracy difference: The gap in published accuracy is small (Okamoto flatness ±0.002mm vs Studer ±0.001mm). Most users cannot feel this difference in 95% of applications. However, Swiss brands do have an edge in thermal stability over 8-hour continuous runs.
- Massive price gap: Same-year, same-spec used Swiss grinders cost 2-3x Okamoto's price. For a first-time buyer who doesn't yet have the team to maintain an ultra-precision Swiss machine, Okamoto is a more rational starting point.
- Maintenance cost: Okamoto uses standard Fanuc or touch-panel controls that any electrician can service. Swiss brands use proprietary control systems — when something breaks, you're limited to the manufacturer or a small pool of specialized repair shops, with costs and lead times an order of magnitude higher.
- Bottom line: Unless your work requires Ra0.05 or your customer specifies Swiss brand, Okamoto is the smarter choice for a first purchase.
Q: What's the difference between Okamoto PSG-64CA1 and PSG-64CA-iQ?
A: The core difference is guideway technology and control precision:
- PSG-64CA1 (Standard): V-V guideways + touch-panel control + auto wheel dressing. Used price $15,000-35,000. Handles 80%+ of surface grinding needs (mold plates, general parts, stamping dies). Guideways are durable; under normal maintenance, accuracy holds for 10-15 years.
- PSG-64CA-iQ (Premium): Hydrostatic guideways (oil-film) + more precise control + higher grinding efficiency. Used price 30-50% above CA1. If your parts require sub-micron flatness consistency over long runs, or you're planning high-volume production, the iQ's wear-free hydrostatic ways justify the premium.
Recommendation: First-time buyers should start with CA1. Once you have a clearer picture of your grinding process and volume, upgrading to iQ is straightforward. CA1 has excellent used-market liquidity.
Q: What's the reasonable price range for a used Okamoto grinder?
A: Based on UsedUltra's 2026 inventory data:
| Model | Year Range | Hours Range | Price Range |
|---|---|---|---|
| PSG-64CA1 | 2010-2019 | 2,000-12,000h | $15,000-35,000 |
| PSG-84CA1 | 2010-2018 | 4,000-15,000h | $20,000-45,000 |
| PSG-104CA1 | 2010-2019 | 5,000-15,000h | $25,000-55,000 |
| ACC-84GX (high-precision) | 2012-2020 | 3,000-12,000h | $40,000-100,000 |
Key price factors:
- Hours: ~3-4% depreciation per 1,000h (vs category median)
- Included accessories: electromagnetic chuck ($1,000-3,000), wheel dresser ($500-2,000), coolant filtration ($1,000-3,000)
- Year: pre-2015 machines depreciate faster
- Guideway type: hydrostatic (iQ/ACC series) commands 30-50% premium
Q: Does the previous owner type affect my used Okamoto buying decision?
A: Yes. Machines from different backgrounds vary significantly in condition:
- Mold shop machines (most recommended): Typically run under high-precision requirements with experienced operators and good maintenance. The risk is with machines being replaced due to wear — carefully assess wear before buying.
- Job shop / outsource grinder machines (moderately recommended): High utilization (possibly 2-3 shifts), but maintenance is usually scheduled. Higher hours with complete records can still be a good buy.
- School / training institution machines (caution): Low hours and low utilization, but non-standard operation may have caused localized guideway damage. Don't assume "low hours = good condition."
- Bankruptcy / liquidation machines (careful): Priced low but often neglected for long periods. No maintenance records, possibly idle for years. Only consider if you can inspect in person or have a thorough inspection report.
Q: How easy is it to get Okamoto parts and service in China?
A: Generally good, with a few realities to understand:
- Fanuc controls — no worries: Most CNC Okamoto models use Fanuc controls. Fanuc's service network covers all major industrial cities in China. Spare parts and service for the control system are not an issue.
- Mechanical parts — standard parts are easy: Spindle bearings (NSK/SNFA), seals, belts, and filters are standard industrial components available from local bearing/seal suppliers. No need to import.
- Dedicated parts — may need import: Hydrostatic guideway components (pumps, proportional valves on iQ/ACC series) are Okamoto-specific and may need import from Japan. Before buying a hydrostatic model, confirm the supplier can support ongoing oil system parts supply.
- Who to call for service: Major cities (Shanghai, Suzhou, Dongguan, Shenzhen) have individual technicians and small companies specializing in Okamoto grinder repair. Before purchasing, ask locally: "Can you service a Japanese Okamoto grinder?" Get a confirmed yes before buying.