DIN931 Hexagon Head Bolts

DIN 931 Hexagon Head Bolts feature a six-sided head and a partially threaded shank, leaving a defined plain section between the head and the threaded portion. This configuration allows the unthreaded section to pass through the clamped components while the threaded section engages with the nut, providing a controlled grip length for many mechanical joints.

The partially threaded design can be particularly useful when the joint requires a clear bearing section or a specific clamping thickness. The external hexagon head provides straightforward access for a wrench or socket, while the available thread length can be selected according to the thickness of the components and the required nut engagement. We supply DIN 931 bolts in carbon steel, alloy steel, and stainless steel, with common steel property classes including 8.8, 10.9, and 12.9, and stainless-steel grades such as A2-70, A2-80, A4-70, and A4-80. Different materials, finishes, and dimensions can be selected according to the mechanical load, corrosion exposure, and service environment. Compared with a fully threaded DIN 933 bolt, DIN 931 is generally considered when the joint benefits from a defined unthreaded shank. The correct choice therefore depends not only on bolt diameter and length, but also on how the fastener interacts with the components being clamped.

Specification:

DIN 931 bolts can be specified according to the nominal diameter, overall length, thread length, material, property class, thread tolerance, and surface finish. The partially threaded configuration is particularly important when the length of the unthreaded shank needs to match the grip thickness of the joint.

For carbon and alloy steel, we supply common property classes including 8.8, 10.9, and 12.9. These grades are selected according to the required tensile strength, proof load, and joint loading conditions, with mechanical property requirements based on ISO 898-1. Stainless-steel options include A2-70, A2-80, A4-70, and A4-80, with the appropriate grade selected according to the required combination of strength and corrosion resistance under ISO 3506-1.

Thread & Shank Configuration

The main dimensional difference from a fully threaded DIN 933 bolt is the presence of a plain shank between the head and threaded section. The specified thread length should provide sufficient nut engagement while the unthreaded portion provides the required grip section through the joined components. The external thread follows the ISO metric thread system, normally using a 6g external thread tolerance unless another tolerance or fit is specified. Thread pitch, major diameter, head dimensions, shank length, and overall length are controlled according to the applicable product standard and customer drawing.