DIN 960 Fine Thread Partial Thread Hex Bolt Selection Guide

Standard Overview

The DIN 960 standard has been officially withdrawn by the German Institute for Standardization (DIN), and its technical content has been superseded by ISO 8765. In actual purchasing, DIN 960 is still widely used as a product name, but the latest design documents should preferentially reference ISO 8765.

The main differences between ISO 8765 and DIN 960 are the widths across flats (wrench sizes) for M10, M12, M14, and M22:

Verify wrench sizes and tooling when substituting. DIN 960 specifies fine thread partially threaded hex head bolts, covering metric fine thread sizes from M8×1 to M64.

Key Technical Features

Engineering Advantages of Fine Thread

The core characteristic of DIN 960 is its metric fine thread. Per Würth product documentation, fine thread offers the following engineering advantages over coarse thread:

1. Stronger self-locking ability: Fine thread has a smaller thread lead angle (lower rise), providing more self-locking power than standard coarse thread and effectively reducing loosening risk under vibration.

2. Higher tightening torque: Fine thread allows higher tightening torque to be applied, while the bolt's larger stress diameter delivers higher reliability.

3. More precise adjustment: The smaller pitch means less axial displacement per turn, making it suitable for connections requiring precision adjustment.

4. Better sealing performance: The tighter thread form provides better sealing at the mating surface than coarse thread.

Partial Thread (Shank) Design

Unlike the fully threaded DIN 961, DIN 960 retains an unthreaded shank between the head and the threaded section. Russian fastener documentation notes that the shank (a smooth neck with an undiminished cross-section) improves the bolt's resistance to transverse loads. When the connection carries shear load, the full cross-section of the shank provides higher shear strength rather than the thread root carrying the shear force.

Property Grades and Materials

DIN 960 covers a complete range from general strength to ultra-high strength:

Grade 10.9 is the most common high-strength grade, made from medium-carbon alloy steel that is quenched and tempered, achieving tensile strength of 1040 N/mm². Grade 8.8 is used for general structures and machinery connections, made from medium-carbon steel with quench and temper treatment.

Thread Length Specifications

The thread length (b) of DIN 960 depends on the bolt's overall length (L) and thread diameter (d). Per FABORY product documentation and German standard fastener catalogs:

Common Size Dimensions

Per German fastener catalog DIN 960 dimensional data:

Surface Finish Options

Critical warning: FABORY and Würth product documentation both explicitly state that electroplated zinc on Grade 10.9 high-strength bolts carries hydrogen embrittlement risk (Warning: electroplating of these products may cause hydrogen embrittlement). Berner's technical documentation further explains: for fasteners with tensile strength above 1000 N/mm² (such as Grades 10.9 and 12.9) and parts with hardness above 390 HV, electroplated zinc coating can cause metal hydride degradation (hydrogen embrittlement) risk.

For Grade 10.9 high-strength bolts, zinc-nickel plating is the safer corrosion protection option. Würth documentation shows zinc-nickel plating provides 720-hour salt spray protection, a significant improvement over the 96 hours of yellow zinc plating.

Application Areas

Automotive Industry

DIN 960 fine thread bolts are widely used for fastening automotive chassis, suspension systems, and critical engine components. The self-locking performance of fine thread provides reliable anti-loosening under continuous vibration, with Grade 10.9 bolts used at connection points carrying high dynamic loads. Russian fastener documentation explicitly notes that DIN 960 bolts are particularly used in the automotive industry for fastening critical components such as suspension and engines.

Precision Machinery and Instruments

The precise adjustment capability of fine thread makes DIN 960 bolts suitable for precision machinery and instrument assembly. The small axial displacement per turn allows fine clearance adjustment and preload control.

Heavy Machinery and Engineering Structures

Grade 10.9 DIN 960 bolts are used in heavy machinery, cranes, and bridges where connection reliability requirements are extremely high. The partial thread design ensures the shank sits at the shear plane for optimal shear performance. Dinmark product documentation notes that DIN 960 bolts are suitable for structural connections subjected to dynamic loads, such as engines, gearboxes, and other mechanisms.

Hydraulic and Pneumatic Systems

The sealing performance of fine thread makes DIN 960 bolts suitable for hydraulic cylinders, pneumatic components, and piping system connections, reducing leakage risk.

Energy and Power Facilities

In wind turbine, steam turbine, and other energy equipment fastening, DIN 960 fine thread bolts with Grade 10.9 strength provide long-term stable preload.

Selection Guide

Summary

DIN 960 specifies metric fine thread partially threaded hex head bolts, and its core value lies in the self-locking performance and precision adjustment capability of fine thread, combined with the shear bearing and locating functions of the shank. The standard has been superseded by ISO 8765, with M10/M12/M14/M22 differing in width across flats. Property grades cover 5.6 through 10.9, with Grade 10.9 using quenched and tempered alloy steel at 1040 N/mm² tensile strength. Among surface finishes, zinc-nickel plating provides 720-hour salt spray protection and a hydrogen-embrittlement-free corrosion solution for high-strength bolts, while electroplated zinc is not recommended for Grade 10.9 and above. DIN 960 bolts are widely used in automotive chassis, precision machinery, heavy equipment, and hydraulic systems, making them the precision connection solution in the metric fine thread high-strength fastener system.