STAINLESS STEEL HEXAGON COLLAR NUT DIN 6331

Hexagon Collar Nut DIN 6331 — DIN 6331 is a substantially taller nut than a standard hex nut, built around an integral thick collar that gives it two advantages at once: a much larger bearing surface spreading clamp load without needing a separate heavy-duty washer, and greater thread engagement than a standard-height nut of the same diameter thanks to the extra body length. That combination is why it turns up on heavier plant, structural steelwork, and machinery connections where a standard flat-faced nut would concentrate load into too small a contact area, or where the joint is carrying higher clamping forces than a standard nut's thread engagement is really designed for. It's a genuinely different specification from a standard full nut rather than an incremental upgrade — the collar's cylindrical raised section is a distinct design feature, not just a taller version of the same shape, and it's typically used without a separate flat washer since the collar itself performs that enlarged bearing function, though nothing stops one being added where extra surface protection against a soft or coated mating face is wanted. There's no locking feature built in; the collar improves load distribution and bearing area, not resistance to rotation, so where the connection also needs vibration resistance, a separate locking method (nylon insert, spring washer, or mechanical lock) should be added rather than assumed. A2 stainless covers general heavy-engineering indoor use; A4 is worth the extra cost for outdoor structural work, marine plant, or washdown environments, since the larger surface area of the collar means correspondingly more metal exposed to whatever the environment involves. Sizing is driven by the mating bolt or stud's diameter, pitch, and grade exactly as with a standard nut, though because this nut is generally specified for higher-load connections, checking the nut's property class against the bolt's stated grade is particularly worth doing here.

FAQs
Why choose DIN 6331 instead of a standard heavy hexagon nut like DIN 6330?
Both address higher-load connections, but DIN 6331's raised collar specifically increases bearing area for load spreading in one integral part, whereas DIN 6330 is simply a thicker version of the standard hex nut shape without that enlarged bearing surface.

Does the taller body make this nut harder to fit in confined spaces?
Yes, the additional height means more axial clearance is needed above the joint than for a standard nut, so available space should be checked before specifying this nut on a tight assembly.

Should the nut's property class be checked against the bolt on this type?
Yes, more so than with a standard nut, since DIN 6331 is typically specified for higher-load connections; the nut's rated strength should be confirmed as equal to or greater than the bolt's stated grade.

Is this nut suitable for use with a standard flat washer?
It is typically used without a separate washer, as the collar itself performs the enlarged bearing function, though a washer can still be added if additional surface protection is needed.