Home » Full Thread Hex Bolts (DIN 933) - Black Oxide High Tensile Steel (8.8)

Full Thread Hex Bolts (DIN 933) - Black Oxide High Tensile Steel (8.8)

Full Thread Hex Bolts (DIN 933 / GB 5783) — Black Oxide High Tensile Steel Grade 8.8

FULLERKREG DIN 933 / GB 5783 Grade 8.8 full thread hex bolts with black oxide finish combine reliable structural strength with a professional matte black appearance and RoHS-compliant mild corrosion protection. Manufactured from 10B21 or 35K medium carbon steel and finished with hot alkaline blackening (black oxide), these bolts are the preferred choice for automotive, machinery, tooling, and precision equipment applications where a non-reflective black finish is required alongside Grade 8.8 structural performance. The fully threaded shank ensures maximum thread engagement and grip-length flexibility. Compliant with DIN 933, GB 5783, and ISO 4017 standards.

Product Highlights

  • Brand: FULLERKREG
  • Standards: DIN 933 / GB 5783 / ISO 4017
  • Material: 10B21 or 35K Medium Carbon Steel
  • Property Class: Grade 8.8 (per ISO 898-1 / DIN EN ISO 898-1)
  • Thread Type: Full Thread (Fully Threaded Shank)
  • Surface Treatment: Black Oxide (Blackening / 发黑)
  • Coating Thickness: 0.5–1.5 μm (negligible dimensional impact)
  • Head Type: Hexagon (Hex Head)
  • Size Range: M3 – M36
  • Thread: Metric coarse thread per ISO 261 / DIN 13
  • Appearance: Matte black / satin black finish
  • Key Advantage: No hydrogen embrittlement risk — safe for Grade 8.8 without post-baking

Why Choose FULLERKREG DIN 933 Grade 8.8 Black Oxide Hex Bolts?

  • ✅ Grade 8.8 structural strength — Rm ≥ 800 MPa; the global standard structural bolt grade for general industrial and automotive applications
  • ✅ Professional matte black finish — non-reflective appearance ideal for visible fastening in automotive, machinery, and precision equipment
  • ✅ No hydrogen embrittlement risk — hot alkaline blackening process does not introduce hydrogen into the steel, unlike electroplating
  • ✅ Negligible dimensional impact — 0.5–1.5 μm coating; standard nuts fit without modification
  • ✅ RoHS compliant — no hazardous substances; suitable for EU and global markets
  • ✅ Reduced light reflection — matte surface minimises glare in optical, photographic, and precision instrument applications
  • ✅ 10B21 / 35K steel — boron-alloyed or medium carbon steel with excellent cold heading and hardenability characteristics
  • ✅ Full thread design — maximum thread engagement; ideal for through-bolting and variable grip-length applications
  • ✅ Cost-effective — black oxide is one of the most economical surface treatments for steel fasteners
  • ✅ Wholesale & bulk supply — available in large quantities for automotive, machinery, and industrial distributors

Black Oxide Surface Treatment — Properties & Benefits

Property Details
Process Hot alkaline blackening — chemical conversion coating (magnetite Fe₃O₄)
Appearance Matte black / satin black — uniform, non-reflective finish
Layer Thickness 0.5–1.5 μm (negligible dimensional impact)
Corrosion Protection Mild — suitable for indoor and dry environments; oil or wax post-treatment recommended
Salt Spray Resistance (bare) 2–4 hours (bare); significantly improved with oil post-treatment (≥ 24 hours)
RoHS / REACH Compliant — no hazardous substances
Hydrogen Embrittlement Risk None — hot alkaline process does not introduce hydrogen
Thread Tolerance Impact Negligible — standard nuts fit without modification
Temperature Resistance Up to approx. 150°C continuous
Light Reflection Significantly reduced — ideal for optical and precision applications

⚠️ Important: Black oxide provides only mild corrosion protection. For outdoor, wet, or corrosive environments, apply a compatible oil, wax, or additional protective coating after installation. For long-term outdoor protection, consider hot dip galvanised (HDG) or zinc CR3 plated alternatives.

Grade 8.8 Black Oxide vs. Other Grade 8.8 Surface Treatments

Property Grade 8.8 Zinc CR3 Grade 8.8 Black Oxide — This Product Grade 8.8 HDG
Appearance Bright silver Matte black ✅ Matte grey
Coating Thickness 5–12 μm 0.5–1.5 μm ✅ (thinnest) 45–100 μm
Salt Spray Resistance ≥ 72 hours 2–4 hours (bare) ≥ 1,000+ hours
H₂ Embrittlement Risk Low (electroplating) None ✅ None
Thread Fit Standard nuts ✅ Standard nuts ✅ Requires HDG nuts
Dimensional Impact Minimal Negligible ✅ Significant
Light Reflection High (bright) Very low (matte) ✅ Low (matte)
RoHS Compliant ✅ Yes ✅ Yes ✅ Yes
Cost Low Lowest ✅ Higher
Best For General indoor/outdoor Automotive, machinery, optics ✅ Structural outdoor

Grade 8.8 vs. Other Property Classes

Property Grade 4.8 Grade 8.8 — This Product Grade 10.9 Grade 12.9
Tensile Strength (Rm) min. 420 MPa 800 MPa ✅ 1040 MPa 1220 MPa
Proof Load (Sp) min. 310 MPa 600 MPa ✅ 830 MPa 1100 MPa
Yield Strength (Rp0.2) min. 340 MPa 640 MPa ✅ 940 MPa 1100 MPa
Elongation (A) min. 14% 12% 9% 8%
Hardness (HRC) — 22–32 ✅ 32–39 39–44
Typical Material Low carbon steel 10B21 / 35K ✅ Alloy steel Q&T ML40Cr Q&T

Mechanical Properties — Grade 8.8 (ISO 898-1)

Property Grade 8.8 Value
Property Class 8.8 (per ISO 898-1 / DIN EN ISO 898-1)
Tensile Strength (Rm) min. 800 MPa (116,000 psi)
Proof Load Stress (Sp) min. 600 MPa
Yield Strength (Rp0.2) min. 640 MPa (80% of Rm)
Elongation (A) min. 12%
Reduction of Area (Z) min. 52%
Hardness min. 22 HRC / 250 HV
Hardness max. 32 HRC / 320 HV
Heat Treatment Quenched & Tempered (Q&T) for d > M16; may be non-Q&T for smaller sizes

Material Properties — 10B21 & 35K Steel

Property 10B21 (Boron Steel) 35K (Medium Carbon Steel)
GB/T Standard GB/T 6478 (CHQ Boron Steel) GB/T 699 (Medium Carbon Steel)
Carbon Content (C) 0.18–0.23% 0.32–0.39%
Boron (B) 0.0005–0.003% None
Manganese (Mn) 0.70–1.00% 0.50–0.80%
Hardenability Excellent (boron-enhanced) Good
Cold Heading Excellent Good

Standard Cross-Reference

Standard Region Description
DIN 933 Germany / Europe Hexagon head bolts — full thread (metric)
ISO 4017 International Hexagon head screws — full thread, product grades A and B
GB 5783 China Hexagon head bolts — full thread (equivalent to DIN 933)
ISO 898-1 International Mechanical properties of fasteners — Grade 8.8 definition
ISO 261 / DIN 13 International Metric coarse thread specification

Dimensional Specifications — DIN 933 / ISO 4017 Full Thread Hex Bolts

All dimensions in millimeters (mm). Data per DIN 933 / ISO 4017 standard.

Thread (d) Pitch (mm) s — A/F (mm) e — A/C (mm) k — Head Height (mm) d_w min (mm) Length Range (mm)
M3 0.5 5.5 6.01 2.0 4.6 6 – 30
M4 0.7 7 7.66 2.8 5.9 8 – 40
M5 0.8 8 8.79 3.5 6.9 10 – 50
M6 1.0 10 11.05 4.0 8.9 10 – 80
M8 1.25 13 14.38 5.3 11.6 16 – 100
M10 1.5 17 18.90 6.4 14.6 20 – 120
M12 1.75 19 21.10 7.5 16.6 25 – 150
M14 2.0 22 24.49 8.8 19.6 30 – 150
M16 2.0 24 26.75 10.0 22.5 35 – 200
M20 2.5 30 33.53 12.5 27.7 45 – 200
M24 3.0 36 39.98 15.0 33.3 50 – 200
M30 3.5 46 50.85 18.7 42.8 60 – 200
M36 4.0 55 60.79 22.5 51.1 70 – 200

* Custom sizes and lengths available on request. Contact FULLERKREG for non-standard requirements.

Standard Length Series — Available Bolt Lengths by Size

Thread Standard Lengths Available (mm)
M3 6, 8, 10, 12, 16, 20, 25, 30
M4 8, 10, 12, 16, 20, 25, 30, 35, 40
M5 10, 12, 16, 20, 25, 30, 35, 40, 45, 50
M6 10, 12, 16, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 80
M8 16, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 80, 90, 100
M10 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 80, 90, 100, 110, 120
M12 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 80, 90, 100, 110, 120, 130, 140, 150
M16 35, 40, 45, 50, 55, 60, 65, 70, 80, 90, 100, 110, 120, 130, 140, 150, 160, 180, 200
M20 45, 50, 55, 60, 65, 70, 80, 90, 100, 110, 120, 130, 140, 150, 160, 180, 200
M24 50, 55, 60, 65, 70, 80, 90, 100, 110, 120, 130, 140, 150, 160, 180, 200
M30 60, 70, 80, 90, 100, 110, 120, 130, 140, 150, 160, 180, 200
M36 70, 80, 90, 100, 110, 120, 130, 140, 150, 160, 180, 200

Tightening Torque Reference — Grade 8.8 Black Oxide (Lubricated, μ = 0.12)

Thread Torque (N·m) — 75% Proof Load Clamp Force (kN)
M3 0.9 2.5
M4 2.2 4.8
M5 4.5 7.8
M6 8 10.5
M8 20 20.5
M10 40 33.0
M12 70 48.0
M14 110 65.5
M16 170 87.0
M20 335 136.0
M24 580 195.0
M30 1150 307.0
M36 2000 445.0

* Torque values are for reference only. Actual requirements depend on friction coefficient, lubrication, joint material, and application. Always consult a qualified engineer for safety-critical applications.

Application Scenarios

  • 🚗 Automotive & motorsport — engine bay assembly, suspension components, and chassis fastening where a black finish matches vehicle aesthetics
  • 🔧 Machinery & industrial equipment — machine frames, equipment enclosures, and general OEM assembly requiring a professional black appearance
  • 🎭 Optical & photographic equipment — camera rigs, telescope mounts, and optical instruments where non-reflective fasteners are essential
  • 🛠️ Tooling & jig fixtures — precision fixtures, jigs, and tooling where minimal dimensional impact of the coating is critical
  • 🎮 Consumer electronics & AV equipment — speaker enclosures, rack-mount equipment, and AV installations requiring black hardware
  • 🏗️ Architectural & interior design — visible fastening in furniture, fixtures, and interior metalwork where black aesthetics are desired
  • 🤖 Robotics & automation — robot frames and automation equipment where black finish reduces visual clutter
  • 🏭 General manufacturing — cost-effective black fastening for indoor production equipment and assembly lines

Product Gallery

FULLERKREG DIN 933 Grade 8.8 Black Oxide Full Thread Hex Bolts — actual product photos:

[Product Photo 1] [Product Photo 2] [Product Photo 3] [Product Photo 4]

Ordering & Packaging Information

  • Packaging: Bulk carton / polybag per size and length; custom labeling available for OEM and distributor orders
  • MOQ: Contact FULLERKREG sales for wholesale minimum order quantities
  • Lead Time: Standard stock sizes ship promptly; large-volume orders subject to production schedule
  • Certifications: Material test reports (MTR) and ISO 898-1 Grade 8.8 compliance certificates available on request
  • Custom Requirements: Non-standard sizes, lengths, and thread forms available — contact us

Frequently Asked Questions

Q: What is black oxide and how does it protect steel?
A: Black oxide (blackening) is a hot alkaline chemical conversion coating that converts the surface iron into magnetite (Fe₃O₄), creating a thin (0.5–1.5 μm) black layer. It provides mild corrosion inhibition by reducing the surface area exposed to moisture and oxygen. For enhanced protection, apply oil or wax after installation. The primary benefits are the matte black appearance and negligible dimensional impact.

Q: Why is black oxide preferred over electroplating for steel bolts?
A: Black oxide does not introduce hydrogen into the steel during processing, eliminating the risk of hydrogen embrittlement. Electroplating processes (zinc, nickel) can introduce hydrogen, which is a concern for high-strength steels. For Grade 8.8 bolts, hydrogen embrittlement risk is low (below the ~1000 MPa threshold), but black oxide remains the preferred choice for applications requiring zero embrittlement risk and negligible dimensional change.

Q: Is black oxide suitable for outdoor use?
A: Black oxide alone provides minimal outdoor corrosion protection (2–4 hours salt spray bare). For outdoor applications, apply a compatible oil or wax after installation to extend service life. For prolonged outdoor exposure, FULLERKREG recommends zinc CR3 plated or hot dip galvanised Grade 8.8 bolts for significantly better corrosion protection.

Q: Do black oxide bolts require special nuts?
A: No. The extremely thin black oxide coating (0.5–1.5 μm) has negligible impact on thread dimensions. Standard DIN 934 / ISO 4032 Grade 8 hex nuts fit without modification — a key advantage over hot dip galvanised bolts which require specially oversized HDG nuts.

Q: What is the difference between Grade 8.8 and Grade 12.9 black oxide bolts?
A: Both use black oxide surface treatment, but differ significantly in strength and material. Grade 8.8 (10B21/35K) has Rm ≥ 800 MPa and is used for general structural and industrial applications. Grade 12.9 (ML40Cr) has Rm ≥ 1220 MPa — 53% stronger — and is used for extreme-load automotive, tooling, and high-stress applications. Choose Grade 8.8 for standard structural use; Grade 12.9 for maximum strength requirements.

Q: What nuts are compatible with Grade 8.8 bolts?
A: Use ISO 4032 / DIN 934 Grade 8 hex nuts for Grade 8.8 bolts. Using lower-grade nuts (e.g., Grade 4 or 6) risks thread stripping before the bolt reaches its proof load. FULLERKREG supplies the complete range of compatible Grade 8 nuts and washers.

Q: Can I get material test reports (MTR)?
A: Yes. FULLERKREG provides material test reports and ISO 898-1 Grade 8.8 compliance certificates upon request for wholesale and OEM orders.

FULLERKREG — Precision Fasteners to ISO/DIN/GB Standards. All technical data is provided for reference. Always verify fastener selection and torque requirements with a qualified engineer for structural and safety-critical applications.

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