STAINLESS STEEL SMALL PATTERN HEXAGON NUTS ASME B18.2.2

Small Pattern Hexagon Nuts ASME B18.2.2 — ASME B18.2.2 covers imperial unified-thread hexagon nuts in two series, and the small pattern is the more compact of the two: a smaller across-flats dimension than the heavy series, giving a lighter wrenching profile suited to machine screw and lighter-duty imperial fastener applications rather than high-load structural work. It's the imperial equivalent of a standard metric full nut in terms of role — the everyday, general-purpose nut for UNC or UNF threaded assemblies — and turns up wherever equipment, machinery, or components are built to American thread standards rather than metric, which includes a fair amount of imported plant, legacy equipment, and electrical and instrumentation hardware that historically followed imperial conventions. The critical thing to get right with this nut is confirming the thread system before ordering: ASME B18.2.2 nuts are cut to UNC or UNF pitch, which is not interchangeable with metric threads of a similar-looking nominal size, so a small pattern nut simply will not run onto a metric bolt regardless of how close the dimensions appear. Choosing between small pattern and heavy series comes down to load: small pattern suits lighter assembly and general machine screw work, while heavy series gives more thread engagement and bearing area for higher-strength imperial bolting, so a joint that's marginal on load with a small pattern nut should generally step up to heavy series rather than accepting reduced engagement. It has no locking feature and relies on standard friction and torque like any plain nut, so where vibration resistance matters, a nylon insert version (such as the ASME B18.16.6 thin type) or a separate locking method should be specified. A2 stainless covers general applications; A4 is worth the extra cost for marine or outdoor imperial-threaded equipment. Sizing is governed entirely by the mating bolt's UNC or UNF thread designation and nominal diameter, which must be confirmed before ordering.

FAQs
How can I confirm whether an existing bolt is UNC or UNF before ordering a matching nut?
A thread gauge or pitch gauge is the reliable way to check, since UNC and UNF pitches at the same nominal diameter can look very similar without one; matching by eye risks ordering the wrong pitch.

Should I choose small pattern or heavy series for a general repair job on imperial equipment?
Match whichever series the original nut was, since mixing series changes the across-flats dimension and, more importantly, the load capacity the joint was originally designed around; if the original type isn't known, checking the bolt grade against the small pattern's typical capacity is a reasonable starting point.

Can this nut be used with a metric bolt?
No, ASME B18.2.2 nuts are dimensioned for imperial UNC/UNF threads and are not interchangeable with metric bolts; the thread system must be confirmed before specifying.

Is this nut self-locking?
No, it is a plain nut relying on standard friction and torque, with no built-in locking feature.