Home » GB/T 9074.13-1988 Cross Recessed Hexagon Bolt with Indentation, Single Coil Lock Washer and Plain Washer Assemblies - Steel 4.8 - Zinc Cr3

GB/T 9074.13-1988 Cross Recessed Hexagon Bolt with Indentation, Single Coil Lock Washer and Plain Washer Assemblies - Steel 4.8 - Zinc Cr3

GB/T 9074.13-1988 Cross Recessed Hexagon Bolt with Indentation, Single Coil Lock Washer and Plain Washer Assemblies — Low Carbon Steel 4.8, Zinc Cr3

FULLERKREG supplies GB/T 9074.13-1988 low carbon steel class 4.8 SEMS screws with trivalent zinc (Zinc Cr3) plating — 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. The economical class 4.8 grade with RoHS-compliant Zinc Cr3 coating is the standard choice for light-duty assembly, sheet metal, electrical enclosures, and general-purpose industrial applications where moderate clamping force and environmental compliance are required.

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
  • ✅ Cost-effective class 4.8 — low carbon steel provides adequate strength for light-to-medium duty joints at the most competitive price point; ideal for high-volume, cost-sensitive applications
  • ✅ Vibration resistance — the coil spring lock washer provides reliable anti-loosening performance under moderate dynamic loads
  • ✅ Dual drive flexibility — cross recessed (Phillips) drive on a hex head allows both manual screwdriver and power tool / wrench tightening
  • ✅ RoHS-compliant Zinc Cr3 finish — trivalent chromium zinc plating replaces hexavalent Cr6+ coating; meets EU ELV, RoHS, and REACH directives; silver-grey appearance with good corrosion resistance
  • ✅ Reduced inventory complexity — one SKU replaces three separate fastener SKUs

Material & Finish

Property Specification
Material Low Carbon Steel (A3 / Q235)
Surface Finish Zinc Cr3 (Trivalent Chromium Zinc Plating)
Plating Appearance Silver-grey
Plating Thickness Typically 5–8 µm
Salt Spray Resistance ≥ 72 hours (white rust per ISO 9227)
Property Class 4.8
Tensile Strength ≥ 420 MPa
Yield Strength (0.2% proof) ≥ 340 MPa
RoHS / ELV Compliant Yes — Cr3 (trivalent), no hexavalent chromium (Cr6+)
REACH Compliant Yes

Class 4.8 vs Class 8.8 — Choosing the Right Grade

Property Class 4.8 Class 8.8
Material Low Carbon Steel Medium Carbon Steel (Q&T)
Tensile Strength ≥ 420 MPa ≥ 800 MPa
Yield Strength ≥ 340 MPa ≥ 640 MPa
Typical Use Light-duty, sheet metal, enclosures Structural, machinery, automotive
Cost Most economical Higher
Heat Treatment None required Quenched & tempered

Zinc Cr3 vs Traditional Zinc Plating

Property Zinc Yellow (Cr6+) Zinc Cr3 (Trivalent)
Chromate Type Hexavalent Cr6+ Trivalent Cr3+
RoHS Compliant No Yes
EU ELV / REACH Restricted Compliant
Appearance Yellow / iridescent Silver-grey
Corrosion Resistance Good Good (≥ 72 h salt spray)
Automotive / Electronics Use Phased out Standard requirement

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 (Low Carbon Steel 4.8, Zinc Cr3)

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) — @L16
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 low carbon steel 4.8 Zinc Cr3 SEMS screws are the standard choice for high-volume, cost-sensitive assembly where moderate strength and RoHS compliance are required:

  • ⚡ Electrical enclosures & control panels — securing panel covers, cable trays, DIN rail brackets, and junction box lids; the most common application for class 4.8 SEMS
  • 🖥️ Consumer electronics & appliances — chassis assembly, sheet metal housings, white goods; RoHS-compliant Zinc Cr3 finish meets regulatory requirements
  • 🏭 Light industrial machinery — guards, covers, access panels, and non-structural brackets where high clamping force is not required
  • 🚗 Automotive interior & trim — non-structural interior panels, trim clips, and bracket assemblies requiring ELV-compliant plating
  • 🛠️ HVAC & sheet metal fabrication — ductwork flanges, access door hinges, equipment mounting on thin sheet metal
  • 🔧 General-purpose assembly — wherever pre-assembled washers eliminate loose-part handling and cost efficiency is the primary driver

Why Choose FULLERKREG GB9074.13 Steel 4.8 Zinc Cr3 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; class 4.8 offers the best value per piece
  • 📐 Strict dimensional control — 100% thread gauge inspection; washer captivation verified per standard
  • 📋 Compliance documentation available — material test reports, RoHS certificates, and REACH declarations 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: Low Carbon Steel (A3 / Q235) | Finish: Zinc Cr3 (Trivalent Zinc) | Property Class: 4.8 | Brand: FULLERKREG

Sorry, this collection is empty.
Continue shopping