Home » GB/T 9074.13-1988 Cross Recessed Hexagon Bolt with Indentation, Single Coil Lock Washer and Plain Washer Assemblies - Marine Stainless Steel A4

GB/T 9074.13-1988 Cross Recessed Hexagon Bolt with Indentation, Single Coil Lock Washer and Plain Washer Assemblies - Marine Stainless Steel A4

GB/T 9074.13-1988 Cross Recessed Hexagon Bolt with Indentation, Single Coil Lock Washer and Plain Washer Assemblies — Marine Stainless Steel A4

FULLERKREG supplies GB/T 9074.13-1988 marine-grade A4 (SUS316) SEMS screws — pre-assembled three-piece fastener assemblies combining a cross recessed hexagon bolt, a single coil spring lock washer, and a plain washer into one captive unit. Engineered for demanding environments where superior corrosion resistance is essential: marine, offshore, chemical processing, food-grade, and outdoor infrastructure applications.

What Are GB9074.13 Cross Recessed Hex SEMS Screws?

GB/T 9074.13-1988 defines a three-piece pre-assembled fastener (SEMS) consisting of:

  • GB29.2 — Cross recessed hexagon head bolt (Phillips drive, hex head)
  • GB9074.24 — Plain washer (assembly-grade flat washer)
  • GB9074.26 — Single coil spring lock washer (assembly-grade spring washer)

The three components are permanently captivated onto the bolt shank before thread rolling. After threading, the outer thread diameter exceeds the inner diameter of the plain washer, making the assembly permanently inseparable. This eliminates loose washers on the assembly line and dramatically reduces installation time and error.

Assembly formula: GB9074.13 = GB29.2 + GB9074.24 + GB9074.26

The washer stack order from bolt head outward is: Plain Washer → Spring Lock Washer → Bolt Head (the plain washer sits closest to the workpiece surface).

Benefits of Using GB9074.13 Cross Recessed Hex SEMS Screws

  • ✅ No loose parts — washers are permanently captivated; no risk of dropped or missing washers during assembly
  • ✅ Faster installation — one-piece handling replaces three separate components; ideal for automated and manual assembly lines
  • ✅ Correct washer sequence guaranteed — plain washer always contacts the workpiece; spring washer always contacts the bolt head flange
  • ✅ Vibration resistance — the coil spring lock washer provides reliable anti-loosening performance under dynamic and cyclic loads
  • ✅ Dual drive flexibility — cross recessed (Phillips) drive on a hex head allows both manual screwdriver and power tool / wrench tightening
  • ✅ Superior marine-grade corrosion resistance — A4 (SUS316) stainless steel with 2–3% molybdenum content delivers outstanding resistance to chloride-induced pitting and crevice corrosion in salt-spray and seawater environments
  • ✅ Food & chemical process compatible — SUS316 is widely accepted for food processing equipment and chemical plant hardware
  • ✅ Reduced inventory complexity — one SKU replaces three separate fastener SKUs

Material & Finish

Property Specification
Material A4 Marine Stainless Steel (SUS316 / 316 SS)
Key Alloying Element Molybdenum (Mo) 2.0–3.0% — enhances chloride & pitting resistance
Surface Finish Natural (Bright Passivated)
Property Class A4-70
Tensile Strength ≥ 700 MPa
Yield Strength (0.2% proof) ≥ 450 MPa
Corrosion Resistance Excellent — superior to A2 in chloride, salt-spray, and marine environments
Magnetic Slightly magnetic (work-hardened 316)
RoHS Compliant Yes

A4 vs A2 — Why Choose Marine Grade?

Property A2 (SUS304) A4 (SUS316)
Molybdenum Content None 2.0–3.0%
Chloride Resistance Moderate Superior
Marine / Salt-spray Limited Recommended
Food & Chemical Use General Preferred
Cost Standard Premium

Dimensions of Pre-Assembled Washers in GB9074.13 Hex Head SEMS Screws

Washer dimensions conform to GB9074.24 (plain washer) and GB9074.26 (spring lock washer). All dimensions in millimeters (mm).

Plain Washer Dimensions (GB9074.24)

Thread Size Inner Dia. d₁ (mm) Outer Dia. d₂ (mm) Thickness h (mm)
M4 4.3 9.0 0.8
M5 5.3 10.0 1.0
M6 6.4 12.0 1.6
M8 8.4 16.0 1.6
M10 10.5 20.0 2.0

Spring Lock Washer Dimensions (GB9074.26)

Thread Size Inner Dia. d₁ (mm) Outer Dia. d₂ (mm) Thickness s (mm) Width b (mm)
M4 4.1 7.1 0.9 1.5
M5 5.1 8.7 1.2 1.8
M6 6.1 10.2 1.6 2.0
M8 8.1 13.0 2.0 2.5
M10 10.2 16.2 2.5 3.0

Dimensional Data — GB9074.13 SEMS Screw (A4 Marine Stainless Steel)

All dimensions in millimeters (mm). Bolt head dimensions per GB29.2. Nominal lengths per standard series.

Thread Size Pitch (mm) Head Width Across Flats s (mm) Head Width Across Corners e (mm) Head Height k (mm) Cross Recess Depth (mm) Min. Grip Length (mm) Nominal Length Range L (mm) Est. Unit Weight (g/pc) — M×16
M4 0.7 7 7.66 2.8 1.8 10 10–40 ≈ 1.5
M5 0.8 8 8.79 3.5 2.1 12 10–50 ≈ 2.8
M6 1.0 10 11.05 4.0 2.4 14 12–60 ≈ 4.8
M8 1.25 13 14.38 5.3 3.0 18 16–80 ≈ 10.5
M10 1.5 16 17.77 6.4 3.6 22 20–100 ≈ 19.0

Note: Unit weights are approximate reference values for L=16mm. Actual weight varies with nominal length. Contact FULLERKREG for precise weight data for your specific length requirement.

Product Gallery

Applications

GB9074.13 A4 marine stainless steel SEMS screws are the preferred choice wherever chloride exposure, salt spray, or chemical contact demands superior corrosion resistance:

  • ⚓ Marine & offshore structures — boat fittings, deck hardware, dock equipment, offshore platform enclosures
  • 🌊 Coastal & outdoor infrastructure — street furniture, signage, railing systems, bridge components in salt-air environments
  • 🏭 Chemical & petrochemical processing — equipment panels, pipe flanges, instrument enclosures exposed to corrosive media
  • 🍽️ Food & beverage processing — SUS316 meets hygiene requirements for food-contact equipment and clean-room environments
  • ⚡ Electrical enclosures in harsh environments — outdoor switchgear, waterproof junction boxes, marine control panels
  • 🔬 Pharmaceutical & medical equipment — where non-reactive, cleanable fasteners are required
  • 🔧 General mechanical assembly — wherever pre-assembled washers eliminate loose-part handling on production lines in corrosive environments

Why Choose FULLERKREG GB9074.13 A4 SEMS Screws?

  • 🏭 Direct manufacturer — produced in-house to GB/T 9074.13-1988 standard with full dimensional traceability
  • 📦 Bulk wholesale supply — flexible MOQ, competitive pricing for OEM and MRO procurement
  • 📐 Strict dimensional control — 100% thread gauge inspection; washer captivation verified per standard
  • 📋 Material certification available — mill test reports, SUS316 material certificates, and RoHS compliance documentation on request
  • 🚀 Fast lead times — standard sizes held in stock; custom lengths available with short lead times
  • 🌍 Global export experience — export packaging, ISPM-15 compliant crating, and international logistics support

Standard: GB/T 9074.13-1988 | Material: A4 Marine Stainless Steel (SUS316) | Finish: Bright Passivated | Property Class: A4-70 | Brand: FULLERKREG

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