Special nuts: cap nuts, slotted round nuts, castle nuts, round nuts

Special nuts are nuts that differ from the ISO 4032 hex nut in shape, material, dimensions or function. The cap nut (not to be confused with the domed cap nut to DIN 1587, a standard part with a low domed cap) closes off the end of the thread with a cap and protects it against damage, contamination and corrosion, or seals against media; in the high design it is forged and fully load-bearing. Slotted round nuts to DIN 981 and round nuts with face holes secure rolling bearings and shafts, castle nuts to DIN 935 are locked with a split pin, collar nuts distribute the surface pressure, and square nuts sit in pockets and profiles. In addition, there are nuts for reduced-shank bolts to DIN 2510, heavy hex nuts to ASTM A194 and nuts with special internal threads.

Where special nuts are needed

Pumps and valves with cap nuts to prevent media leakage, gearboxes and bearing assemblies with slotted round nuts, rail vehicles with locked castle nuts, pressure equipment with nuts for reduced-shank bolts, shipbuilding and offshore with stainless or coated special designs.

How RS Randack manufactures them

Nuts are forged and hot-pierced or turned from solid, hexagons are milled on a special-purpose machine, and internal threads are cut or turned, typically up to M80, also as fine threads; special shapes are turned up to 300 mm in diameter. Quenching and tempering by qualified partners, proof load test and hardness in our own laboratory, property classes 5 to 12 to ISO 898-2 and grades to ASTM A194, materials from Q&T steel and stainless steel to nickel-based alloys. Nuts for bolts from the same order come with a joint certificate and are matched to each other before coating.

What you should specify

Drawing or standard, thread with pitch and tolerance class, height, width across flats or diameter, property class or material, function such as sealing or locking, coating, certificate type, quantity.