Product Summary

Longze Heavy-Duty U-Bolts are precision-engineered for critical structural applications in the automotive and power utility industries. Manufactured in Yongnian, China, our U-bolts provide superior

clamping force for heavy-duty truck leaf springs and high-voltage transmission tower cross-arms.

• ✔ Dual Industry Standard: Fully compliant with ASTM A394 (Tower Bolts) and SAE J429 (Automotive Grade).

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• ✔ Fatigue Resistance: Cold-formed threads and quenched-and-tempered steel ensure durability under constant vibration.

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• ✔ Maximum Protection: Available with Hot Dip Galvanized (HDG) coatings exceeding 86μm for long-term outdoor exposure.

• Standards: ASTM A394, SAE J429, DIN 3570, ASME B18.31.5.

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• Material Grade: Class 8.8, 10.9 | Grade 5, Grade 8 | ASTM A394 Type 0/1.

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• Diameter Range: M10 – M36 | 3/8" – 1-1/2".

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• Surface Finish: Hot Dip Galvanized, Black Oxide, Zinc Plated, Dacromet.

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Mechanical Properties & Tensile Strength

• Matching the strength grade to the specific stress requirements of truck chassis and steel towers.

• Property Class / Grade	Tensile Strength	Yield Strength	Hardness (Rockwell)	Typical Application
  Grade 8 (SAE J429)	150 ksi	120 ksi	33 – 39 HRC	Truck Leaf Springs
  Class 10.9 (Metric)	1040 MPa	940 MPa	32 – 39 HRC	Heavy Machinery Mounts
  ASTM A394 Type 1	120 ksi	92 ksi	25 – 34 HRC	Transmission Towers
  Class 8.8 (Metric)	800 MPa	640 MPa	22 – 32 HRC	General Structural Utility

U-Bolt Dimensional Configuration

• Precise bending radius and thread length for secure fitment on axles and tower angles.

• Thread Size	Inside Width (C)	Inside Height (B)	Thread Length (T)	Fitment Pipe/Axle
  M16 (5/8")	76 mm	150 mm	75 mm	3" Truck Axle
  M20 (3/4")	102 mm	200 mm	100 mm	4" Chassis Rail
  M24 (1")	127 mm	250 mm	120 mm	5" Tower Cross-arm
  M30 (1-1/8")	152 mm	300 mm	150 mm	6" Heavy Structural

Coating Selection for Extreme Environments 

• Ensuring 30+ years of service life in corrosive outdoor and industrial conditions.

• Surface Treatment	Coating Thickness	Salt Spray Test	Môi trường
  Hot Dip Galvanized (HDG)	≥ 86 μm	1000+ Hours	Coastal Towers / Salted Roads
  Dacromet / Geomet	8 – 12 μm	500 - 1000 Hours	Automotive Underbody
  Zinc Plated	5 – 8 μm	72 - 96 Hours	Indoor / Dry Storage
  Black Oxide (Oiled)	N/A	24 - 48 Hours	Lubricated Engine Parts

Avoid Pitfalls:

• Bending Stress Cracks: We prevent micro-cracks at the U-bend radius by utilizing temperature-controlled induction bending for high-tensile Grade 8 and 10.9 materials.

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• Hydrogen Embrittlement: All high-strength U-bolts (Grade 8+) undergo a mandatory 8-hour de-embrittlement baking process after plating to ensure zero brittle failure on the road or the tower.

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• Thread Tolerance: We maintain strict 2A/6G thread tolerances to ensure nuts can be easily installed by hand but stay locked under extreme vibration.

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Perfect Fit Assembly:

• Chassis Alignment: Our U-bolts feature precision leg spacing to ensure they drop into factory-drilled truck chassis or tower plates without forcing.

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• Matched Hardware: Every U-bolt is available as a kit with Heavy Hex Deep Nuts Và Hardened Flat Washers to ensure the clamping force is evenly distributed.

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Quality Control & Logistics:

• ISO 9001 Certified: 5-step QC including magnetic particle inspection (MPI) and full-scale tensile testing.

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• Sea-Worthy Packaging: Double-strapped reinforced cartons on Fumigation-Free Pallets to prevent movement of heavy steel during maritime transit.

• Q: Can you produce custom-sized U-bolts from a drawing? A: Yes, our Yongnian facility can manufacture custom round, square, or semi-round U-bolts based on your specific technical drawings.

• Q: Do you provide MTC (Mill Test Certificates)? A: Yes, full traceability and MTCs including chemical analysis and mechanical testing are provided for every export batch.

• Email:eric@lzfastener.com  What'sApp:+86 15350500528 WeChat:+86 18830006928 or 15350500528