DIN 931 Hex Head Bolt

About DIN 931 Hex Head Bolt

The Stainless Steel DIN 931 Hex Head Bolt is a highly durable, precision-engineered industrial fastener with a hexagonal head and a partially threaded shank. It complies with the widely recognized German DIN 931 industrial standard (dimensionally similar to ISO 4014). Because it is partially threaded, it leaves a smooth, unthreaded section (shank) directly below the head, providing exceptional shear strength and perfect alignment in high-load structural assemblies.

Key Features & Design

• Partial Threading (With Shank): Features a plain, smooth portion on the shaft that maximizes resistance to lateral forces and shear stress.

• Hexagonal Drive: Six-sided head style permits maximum torque application using standard spanners, wrenches, or ratchet socket systems.

• Industrial Threading: Precision-machined metric coarse threads (6g thread tolerance class) guarantee an optimal fit with compatible nuts or pre-tapped holes.

• Corrosion Protection: Built from high-quality stainless steel, removing the need for extra anti-rust coatings and preventing rust bleeding in exposed areas.

Material Grades & Specifications

Stainless Steel DIN 931 bolts are typically categorized under specifications like DIN 267 Part 11 and are available in two primary material variants:

• A2 Stainless Steel (Grade 304): The most versatile economic grade. Known colloquially as 18/8 stainless (18% Chromium, 8% Nickel). It delivers excellent rust protection under standard outdoor atmospheric and moisture-heavy conditions.

• A4 Stainless Steel (Grade 316): A premium, acid-proof, austenitic grade. Formulated with molybdenum, it stands up to severe marine, chemical, saline, and industrial environments.

• Property Class: Most commonly supplied in Class 70 (e.g., A2-70, A4-70), meaning cold working provides a high minimum tensile strength of 700 MPa.

Standard Technical Parameters

• Size Range: Produced in standard diameters ranging from M3 to M64.

• Standard Thread Formula: The minimum length of the threaded section varies by bolt size, typically following a rigid metric baseline:
• Lengths up to 125 mm: (2 Diameter) + 6 mm
• Lengths 125 mm to 200 mm: (2 Diameter) + 12 mm
• Lengths over 200 mm: (2 Diameter) + 25 mm

Target Applications & Industries

These heavy-duty fasteners are heavily relied upon across the following professional fields:

• Heavy Infrastructure: Securing structural steel bridge components, building frame joints, and wind turbine bases.

• Marine Engineering: Dock construction, shipbuilding, boat frames, and seaside machinery assemblies where salt corrosion is a threat.

• Mechanical & Automotive: High-vibration installations including engine mounts, water pumps, plant maintenance frames, and heavy factory cranes.

• Process Industries: Used for industrial pipe flanges, mining platforms, chemical processing facilities, and sanitary food-grade equipment due to hygienic, non-magnetic attributes.