Nachi’s Solid Carbide Drill Portfolio
Nachi-Fujikoshi Corporation, a Japanese industrial manufacturer with roots in bearing and robotics production, has developed a respected line of cutting tools including solid carbide drills for precision hole-making operations. Among their drill offerings, the SGESS and SGS series represent two distinct approaches to solid carbide drilling, each optimized for different production requirements. Understanding the technical differences between these series is crucial for engineers selecting drill tools for automotive, aerospace, and hydraulic component manufacturing.
Fundamentals of Solid Carbide Drilling
Solid carbide drills offer significant advantages over indexable insert drills in applications requiring tight hole tolerances (IT7-IT8), superior surface finish (Ra 1.6-3.2 um on bore walls), and high length-to-diameter ratios (3xD to 12xD). The monolithic carbide construction eliminates the mechanical interfaces inherent in indexable drills, resulting in better concentricity, lower runout (typically below 0.005 mm), and higher rigidity that enables faster feed rates and deeper drilling without deflection.
Modern solid carbide drills feature internal coolant channels that deliver high-pressure cutting fluid directly to the cutting edges, improving chip evacuation and extending tool life by 300-500% compared to external coolant delivery. Both the SGESS and SGS series incorporate this through-coolant design as standard.
Nachi SGESS Series — Premium Performance
The SGESS (Super General Endmill Solid Super) series represents Nachi’s premium solid carbide drill line, incorporating the company’s most advanced substrate, coating, and geometry technologies.
SGESS Substrate Technology
SGESS drills use Nachi’s proprietary ultra-fine grain carbide substrate with a grain size of 0.4-0.6 micrometers and 8-10% cobalt content. This substrate achieves a hardness of 93.5 HRA and a transverse rupture strength above 4,200 MPa — a combination that allows the drill to maintain edge sharpness while resisting chipping under the cyclic impact loads present in drilling. The ultra-fine grain structure also enables Nachi to grind sharper cutting edge radii (below 5 micrometers) without micro-fracturing, which is essential for achieving low cutting forces in hard-to-machine materials.
SGESS Coating
SGESS drills feature Nachi’s SG coating, a multi-layer PVD coating consisting of alternating titanium aluminum nitride (TiAlN) and aluminum chromium nitride (AlCrN) layers. The total coating thickness is 3-4 micrometers, providing excellent wear resistance (coating hardness above 3,500 HV) while maintaining the sharp cutting edge geometry. The AlCrN layers contribute oxidation resistance up to 1,100 degrees Celsius, allowing the drill to operate effectively in dry or minimum quantity lubrication (MQL) conditions where cutting zone temperatures can exceed 800 degrees Celsius.
SGESS Geometry
The SGESS cutting geometry features a modified S-shaped thinning (cross-point) that reduces thrust force by 20-30% compared to standard point geometries. This thrust force reduction is particularly important when drilling deep holes (5xD and above) where high axial forces can cause drill deflection, poor hole straightness, and premature tool breakage. The SGESS flute profile uses a variable helix angle that increases from 30 degrees at the tip to 40 degrees at the shank, optimizing chip evacuation at different depths within the hole.
SGESS drills are available in 3xD, 5xD, 8xD, and 12xD length-to-diameter ratios, covering diameters from 3.0 mm to 20.0 mm. The 12xD variant incorporates Nachi’s proprietary vibration-damping flute geometry that suppresses chatter during deep hole drilling, maintaining hole straightness within 0.05 mm per 100 mm of depth.
Nachi SGS Series — Reliable Standard
The SGS (Super General Solid) series occupies the standard-performance position in Nachi’s drill lineup, offering proven technology at a more accessible price point than the SGESS series.
SGS Substrate and Coating
SGS drills use a fine-grain carbide substrate with a grain size of 0.8-1.2 micrometers and 10-12% cobalt content. The slightly larger grain size and higher cobalt content provide excellent toughness (transverse rupture strength above 3,600 MPa) at a moderate hardness of 92.5 HRA. This substrate-coating balance prioritizes fracture resistance over maximum wear resistance, making SGS drills forgiving in less-than-ideal machining conditions such as worn machine spindles or inadequate workholding.
The coating on SGS drills is a standard TiAlN PVD layer with a thickness of 2-3 micrometers and hardness of approximately 3,000 HV. While less advanced than the SGESS multi-layer coating, the SGS TiAlN provides adequate protection for drilling carbon steels, low-alloy steels, and cast irons at moderate cutting speeds.
SGS Geometry
SGS drills feature a conventional 140-degree point angle with standard chisel edge thinning. The flute geometry uses a constant helix angle of 35 degrees along the entire flute length. While this design generates slightly higher thrust forces than the SGESS variable helix, it provides excellent chip control and predictable wear patterns in standard drilling operations up to 5xD depth.
SGS drills are available in 3xD and 5xD configurations with diameters from 3.0 mm to 16.0 mm, covering the majority of general-purpose drilling requirements in production machining.
Performance Comparison
Tool Life on Steel
In drilling C45 carbon steel at 100 m/min cutting speed and 0.15 mm/rev feed rate, 10 mm diameter SGESS 5xD drills achieve 800-1,200 holes before reaching the recommended flank wear limit of 0.2 mm. Under identical conditions, SGS drills produce 500-700 holes — approximately 40-50% fewer. The SGESS advantage becomes more pronounced at higher cutting speeds (120-150 m/min) where the superior coating maintains its protective effect.
Hole Quality
SGESS drills consistently produce holes with diameter tolerances within H7 (approximately +0.015 mm for 10 mm diameter) and bore surface roughness of Ra 1.6-2.0 um. SGS drills achieve H8 tolerance (+0.022 mm) with Ra 2.5-3.2 um surface roughness. For applications requiring tight positional tolerances (true position below 0.05 mm), the SGESS series’ lower thrust force and better concentricity provide a clear advantage.
Stainless Steel and Difficult Materials
When drilling austenitic stainless steel (304, 316L), the SGESS series significantly outperforms SGS due to its sharper cutting edges and oxidation-resistant coating. SGESS drills maintain productivity at cutting speeds of 40-60 m/min on 316L, while SGS tools experience rapid built-up edge formation and require speed reductions to 30-40 m/min to achieve acceptable tool life.
Selection Guidelines
- Deep holes (above 5xD) in any material: Use SGESS for its reduced thrust force and vibration-damping geometry.
- Tight tolerance holes (H7 or better): SGESS is the only choice — its lower runout and sharper edges produce the dimensional accuracy required.
- Stainless steel and superalloys: SGESS with its advanced coating and fine-grain substrate.
- Standard depth holes (3xD to 5xD) in carbon steel: SGS offers excellent value with adequate performance for most production requirements.
- Low-rigidity setups or older machines: SGS provides more forgiving performance due to its tougher substrate.
- High-volume automated production: SGESS justifies its premium through longer tool life and reduced unplanned tool changes.
Competitive Context
Nachi’s SGESS and SGS drills compete with Sandvik’s CoroDrill 860 series, Guhring’s TiAlN-coated series, and OSG’s ADO and EX drills. Nachi differentiates through competitive pricing (typically 20-35% below European equivalents) and strong technical support in Asian manufacturing markets. The SGESS series matches Guhring’s premium offerings in hole quality and tool life on most steel and stainless applications, while the SGS series provides a cost-effective alternative for general-purpose drilling where extreme performance is not required.
Conclusion
Nachi’s dual-series approach to solid carbide drilling — SGESS for premium performance and SGS for reliable standard drilling — gives manufacturing engineers the flexibility to match tool investment with application requirements. The SGESS series justifies its higher cost through superior substrate technology, advanced multi-layer coatings, and optimized geometry that delivers longer tool life, tighter tolerances, and better performance in difficult-to-machine materials. The SGS series, meanwhile, provides dependable performance for the vast majority of standard drilling applications at a price point that supports cost-effective production operations.
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