Cap & Acorn Nuts
Nuts & Threaded Inserts · 6 specs
Direct Answer
Cap and Acorn nuts (standardized under DIN 1587 and ASME B18.2.2) feature a domed, blind-ended crown that completely encloses the protruding end of a mating screw or threaded rod. They prevent snagging on clothing, protect exposed threads from corrosion and moisture, and provide a finished decorative appearance on consumer goods, bicycles, and furniture.
Source: DIN 1587 / ISO 8673 / ASME B18.2.2 · Last reviewed Aug 28, 2026
Specs
| Standard Specifications | DIN 1587 (High type dome) / DIN 917 (Low profile cap) / ASME B18.2.2 |
| Dome Profile | Hemispherical blind cap permanently enclosing internal tapped threads |
| Safety Function | Eliminates sharp exposed screw threads that cause lacerations or fabric snags |
| Environmental Protection | Seals internal thread engagement from weather, road salt, and industrial grime |
| Common Materials | A2/A4 Stainless steel, solid brass, chrome-plated steel, black oxide steel |
| Primary Applications | Bicycle axle hubs, motorcycle engine covers, outdoor playground structures, furniture |
Safety and Thread Protection in Public Hardware
On outdoor children's playgrounds, fitness equipment, and bicycles, exposed bolt ends present dangerous snag and puncture hazards. DIN 1587 acorn nuts provide smooth, snag-free spherical contours while locking the bolt in place.
Blind Hole Bolt Length Consideration
Because acorn nuts are closed at the top, bolt length must be carefully measured. If the bolt shank is even 1 mm too long, the bolt tip bottom-outs against the inner dome ceiling before the nut's bearing face seats against the workpiece, leaving the joint loose.