STAINLESS STEEL HEXAGON HEAD BOLTS ISO 4014

Hexagon Head Bolts ISO 4014 — ISO 4014 is the harmonised international standard for the part-threaded hexagon bolt that used to be specified almost exclusively under its German equivalent, DIN 931, and it describes the same essential design: a hexagon head, a length of thread sized proportionally to the bolt's nominal length, and a plain shank filling the remainder, intended to bear cleanly within a clearance hole rather than rely on a thread crest for positioning or shear resistance. That plain shank is what earns this bolt its place in through-bolted structural connections, machinery frames, plant assemblies, and any joint fitted with a nut on the far side and subject to transverse as well as tensile load — the unbroken cross-section resists shear and positions the joint more precisely than a fully threaded fastener could. Grade guidance follows the pattern common to most structural stainless fixings: A2 is well suited to indoor and general external use in temperate, low-salinity conditions, while A4 is the sounder choice for coastal structures, marine environments, washdown-cleaned plant, or any joint that would be costly or disruptive to inspect and replace later — the modest cost premium is easily justified against the alternative. As the current international reference, ISO 4014 sets thread length according to the bolt's nominal length by a defined formula, meaning shorter bolts carry proportionally more thread and longer bolts retain more plain shank, alongside head dimensions and tolerance class that keep bolts from different manufacturers interchangeable. Choosing the right bolt starts with grip length — the full clamped thickness, washers included — so the plain shank spans the joint while enough thread remains proud to seat the nut and develop clamp load properly; diameter should be sized to the calculated load and the clearance holes already present in the structure. Where the joint sits in a tapped hole rather than taking a nut, the fully threaded ISO 4017 set screw is the more efficient specification.

FAQs
Are ISO 4014 and DIN 931 bolts interchangeable?
Yes in almost all practical situations — geometry and tolerance classes are closely aligned, so a bolt to either designation will suit the same nut, washer, and clearance hole without adjustment.

How do I check the exact thread length for a specific bolt size?
Thread length follows the standard's defined proportional formula relative to nominal bolt length, so the exact figure for a given size and length combination should be checked against the ISO 4014 dimension table rather than assumed from a similar-looking bolt.

What washer type pairs well with an ISO 4014 bolt?
A standard flat washer under the nut is common practice to spread bearing load and protect the surface, with a larger-diameter washer sometimes specified where the clearance hole is oversized or the mating material is soft or thin.

Should I specify a nut to a matching ISO standard?
It's good practice to pair an ISO 4014 bolt with an ISO-designated nut, such as ISO 4032, since thread tolerances are harmonised across the ISO metric fastener family, reducing the risk of a tight or loose fit compared with mixing standards arbitrarily.