Product Summary

Longze Fine Pitch Hex Head Bolts are precision-engineered according to DIN 960 (partially threaded) and DIN 961 (fully threaded) standards, widely used in automotive engines, hydraulic systems, and high-

precision machinery. Featuring a fine thread pitch, these Longze Fine Pitch Hex Head Bolts provide superior adjustment precision, higher vibration resistance, and greater tensile strength compared to standard coarse

threads, making them ideal for critical stress-bearing joints.

• ✔ Enhanced Vibration Resistance: The smaller helix angle of Fine Pitch Hex Head Bolts prevents self-loosening under constant dynamic loads.

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• ✔ Superior Tensile Strength: Due to the larger minor diameter, these bolts offer a higher cross-sectional area, increasing their load-bearing capacity.

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• ✔ Precise Torque Control: Allows for finer tension adjustments, which is essential for cylinder heads and high-pressure fluid connections.

Key Features of Fine Pitch Hex Head Bolts

• Self-Locking Performance – The shallower thread angle provides a natural locking effect, reducing the need for additional locking washers.

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• High-Strength Grades – Available in Grade 8.8, 10.9, and 12.9 alloy steels to meet extreme industrial safety standards.

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• Leak-Proof Reliability – Ideal for thin-walled components and pressurized systems where tight thread engagement is mandatory.

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• Dual Thread Options – Fully compliant with ISO 8676 (Full Thread) and ISO 8765 (Partial Thread) specifications.

Technical Specifications

• Standards: DIN 960 / DIN 961 / ISO 8765 / ISO 8676 / ASME B18.2.1

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• Metric Size Range: M8 to M64 (Fine Pitch)

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• Inch Size Range: 1/4" to 2" (UNF / UNEF / UNS Fine Series)

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• Property Class: Grade 8.8, 10.9, 12.9 / Grade 5, Grade 8 / Stainless Steel A2 to A4

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• Thread Type: Metric Fine Pitch / UNF (Unified National Fine) / UNEF (Extra Fine)

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• Finish: Zinc Plated / HDG / Dacromet / Geomet / Plain (Oiled)

• Material & Mechanical Properties

• Material	Grade (Metric / Inch)	Tensile Strength	Yield Strength	Hardness
  Alloy Steel	8.8 / Grade 5	$\ge 800$ MPa	$\ge 640$ MPa	22 to 32 HRC
  Alloy Steel	10.9 / Grade 8	$\ge 1040$ MPa	$\ge 940$ MPa	32 to 39 HRC
  Alloy Steel	12.9 / Grade 9	$\ge 1220$ MPa	$\ge 1100$ MPa	39 to 44 HRC
  Edelstahl	SS304/316 / B8/B8M	$\ge 700$ MPa	$\ge 450$ MPa	140 to 200 HV

• Dimensions & Global Size Conversion
• Technical Standard: Longze specializes in high-precision fine-pitch fasteners manufactured to DIN 960 (Partially Threaded) and DIN 961 (Fully Threaded) standards. Fine threads provide higher tension adjustment accuracy and superior resistance to loosening in high-vibration automotive and aerospace applications.

• American Size (UNF - Fine)	Nearest Metric Size (Fine)	Metric Diameter x Pitch	Decimal Equiv. (mm/inch)	Hex Key/Wrench Size (s)
  1/4" - 28	M6 x 0.75	6.0 mm x 0.75 mm	6.35 mm / 0.250"	10.0 mm / 7/16"
  5/16" - 24	M8 x 1.0	8.0 mm x 1.0 mm	7.94 mm / 0.312"	13.0 mm / 1/2"
  3/8" - 24	M10 x 1.0	10.0 mm x 1.0 mm	9.53 mm / 0.375"	17.0 (16) mm / 9/16"
  3/8" - 24	M10 x 1.25	10.0 mm x 1.25 mm	9.53 mm / 0.375"	17.0 (16) mm / 9/16"
  7/16" - 20	M11 x 1.0	11.0 mm x 1.0 mm	11.11 mm / 0.437"	18.0 mm / 5/8"
  1/2" - 20	M12 x 1.25	12.0 mm x 1.25 mm	12.70 mm / 0.500"	19.0 (18) mm / 3/4"
  1/2" - 20	M12 x 1.5	12.0 mm x 1.5 mm	12.70 mm / 0.500"	19.0 (18) mm / 3/4"
  5/8" - 18	M16 x 1.5	16.0 mm x 1.5 mm	15.88 mm / 0.625"	24.0 mm / 15/16"
  3/4" - 16	M20 x 1.5	20.0 mm x 1.5 mm	19.05 mm / 0.750"	30.0 mm / 1-1/8"

• Surface Treatment

• Coating	Process	Salt Spray	Anwendung
  Zinc Plated	Electroplating	72 to 144h	General Mechanical
  Hot-Dip Galvanized	Molten Zinc	500 to 800h	Outdoor Infrastructure
  Dacromet	Zinc-Flake	1000+h	Automotive Engines
  Phosphated	Chemical	<24h	Internal Oiled Parts