Nachi SGESS vs SGS: Solid Carbide Drill Selection for Production Machining
Nachi-Fujikoshi Corporation, a major Japanese cutting tool and robotics manufacturer, offers two high-performance solid carbide drill series that dominate production holemaking: the SGESS (Super Golden-EZ Drill Short) and the SGS (Super Golden Drill Short) series. While both feature Nachi’s advanced SG coating technology, their geometries and application ranges differ significantly. Understanding these differences is critical for optimizing cycle times, hole quality, and tool cost per part.
Nachi SG Coating Technology
Nachi’s SG (Super Golden) coating is a multi-layer TiAlN-based PVD coating applied at approximately 450°C. The coating achieves a surface hardness of 3,400 HV and an oxidation onset temperature of 900°C. The latest generation, SG coating, features a nano-layered structure with individual layer thicknesses of 3-8 nm, totaling 2-4 µm of coating thickness. This nano-structure provides both hardness and toughness — the alternating layers deflect crack propagation while maintaining wear resistance.
SGESS Series: Internal Coolant, Short Length
The SGESS series represents Nachi’s premium through-coolant drill line for 3xD and 5xD drilling depths. Key features include:
- Double-margin design: Two lands per flute provide superior hole straightness and stability, especially at high penetration rates
- Optimized point geometry: 140° point angle with a proprietary S-shaped thinning reduces thrust force by 15-20% compared to conventional split points
- Curved flute profile: Promotes chip curling and evacuation even in deep, stringy-chip materials
- Internal coolant channels: Helical coolant holes deliver fluid directly to the cutting edges for high-pressure chip flushing
| Specification | SGESS-3D (3xD) | SGESS-5D (5xD) |
|---|---|---|
| Diameter range | 3.0-20.0 mm | 3.0-16.0 mm |
| Drilling depth | 3 x diameter | 5 x diameter |
| Flute count | 2 | 2 |
| Point angle | 140° | 140° |
| Coating | SG (TiAlN nano-layer) | SG (TiAlN nano-layer) |
| Coolant | Internal (helical) | Internal (helical) |
| Substrate | Ultra-fine grain WC (0.5 µm) | Ultra-fine grain WC (0.5 µm) |
| Substrate hardness | 92.5 HRA | 92.5 HRA |
SGS Series: External Coolant, Short Length
The SGS series uses external coolant delivery and is designed for shallower drilling applications where through-coolant is not available or not necessary. The geometry differs from SGESS in several important ways:
- Single-margin design: One land per flute reduces friction and cutting torque, beneficial on machines with lower spindle power
- Standard 118° point angle: With cross-thinning for self-centering, suitable for a wider range of entry surface conditions
- Conventional flute profile: Straight flutes optimized for chip evacuation at 2-3xD depths
- No internal coolant: External flood or mist cooling; cost-effective for less demanding applications
| Specification | SGS-2D | SGS-3D |
|---|---|---|
| Diameter range | 1.0-20.0 mm | 3.0-16.0 mm |
| Drilling depth | 2 x diameter | 3 x diameter |
| Flute count | 2 | 2 |
| Point angle | 118° | 118° |
| Coating | SG (TiAlN nano-layer) | SG (TiAlN nano-layer) |
| Coolant | External | External |
| Substrate | Ultra-fine grain WC (0.5 µm) | Ultra-fine grain WC (0.5 µm) |
| Substrate hardness | 92.5 HRA | 92.5 HRA |
SGESS vs SGS: Detailed Comparison
| Parameter | SGESS (Internal Coolant) | SGS (External Coolant) |
|---|---|---|
| Hole depth capability | Up to 5xD (deeper with pecking) | Up to 3xD |
| Hole straightness | Excellent (±0.02mm at 5xD) | Good (±0.05mm at 3xD) |
| Hole diameter tolerance | H7-H8 achievable | H8-H9 typical |
| Surface finish (Ra) | 1.6-3.2 µm | 3.2-6.3 µm |
| Maximum cutting speed (steel) | 120-180 m/min | 80-140 m/min |
| Feed rate (steel) | 0.10-0.25 mm/rev | 0.08-0.20 mm/rev |
| Chip evacuation | Excellent (high-pressure internal) | Moderate (flood dependent) |
| Minimum machine requirement | 20+ bar coolant pressure | Standard flood coolant |
| Tool cost | 30-50% higher | Lower |
| Cost per hole (deep) | Lower (longer life, fewer breaks) | Higher (shorter life, risk of break) |
Material-Specific Performance
| Workpiece Material | Grade/Hardness | Recommended Drill | Vc (m/min) | f (mm/rev) |
|---|---|---|---|---|
| Low carbon steel | S15C / 1015, 120 HB | SGESS-3D | 140-180 | 0.15-0.25 |
| Medium carbon steel | S45C / 1045, 200 HB | SGESS-3D | 120-160 | 0.12-0.20 |
| Alloy steel | SCM440 / 4140, 280 HB | SGESS-3D | 100-140 | 0.10-0.18 |
| Stainless steel | SUS304 / 304SS, 200 HB | SGESS-3D | 60-100 | 0.08-0.15 |
| Cast iron | FC250 / GG25, 200 HB | SGS-3D or SGESS | 120-200 | 0.15-0.30 |
| Aluminum alloy | A6061-T6, 95 HB | SGS-2D | 150-300 | 0.15-0.30 |
| Heat-resistant alloy | Inconel 718, 400 HB | SGESS-3D (peck cycle) | 20-40 | 0.05-0.10 |
Decision Matrix
| Application Scenario | Recommended Series | Reason |
|---|---|---|
| Deep holes (>3xD) in steel | SGESS-5D | Internal coolant prevents chip packing |
| High-volume automotive production | SGESS-3D | Maximum cycle time, best hole quality |
| Shallow holes (≤2xD) on CNC lathe | SGS-2D | External coolant sufficient, lower cost |
| Stainless steel cross-holes | SGESS-3D | Internal coolant flushes chips from cross-drilling |
| Low-production job shop | SGS-3D | Versatile, lower investment |
| Titanium or HRSA drilling | SGESS-3D (with peck) | Essential cooling and chip clearance |
Competitor Comparison
| Nachi | OSG | Sandvik | Guhring | Kennametal |
|---|---|---|---|---|
| SGESS-3D | ADO-3D | CoroDrill 860-GM | Series 5515 | B033A |
| SGESS-5D | ADO-5D | CoroDrill 860-GM 5xD | Series 5515 5xD | B033A 5xD |
| SGS-3D | EX-GDX | CoroDrill 460 | Series 5513 | B012A |
Key Takeaways
- SGESS with internal coolant is mandatory for holes deeper than 3xD in steel and stainless steel
- The 140° point angle of SGESS reduces thrust force and improves centering accuracy compared to the 118° SGS point
- Internal coolant pressure of at least 20 bar is required for SGESS to achieve its rated performance
- SGS external-coolant drills offer excellent value for shallow holes on machines without high-pressure coolant
- For titanium and HRSA drilling, SGESS with peck cycles provides the chip evacuation and cooling that prevent catastrophic tool failure
- Both series use Nachi’s ultra-fine grain substrate at 92.5 HRA, providing the base toughness needed for interrupted drilling entry
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