Acorn (Cap) Nuts

Acorn nuts, also called cap nuts, have a domed closed end that covers the bolt threads — providing a finished appearance and protecting against sharp thread ends. They're used where bolt ends are exposed and either safety or aesthetics matters: furniture, railings, machinery guards, and decorative assemblies. We stock acorn nuts in steel, brass, and stainless.

Why Acorn Nuts

The closed dome hides the bolt's cut threads, giving a clean, finished look and preventing injury or snagging on exposed sharp ends. It also keeps moisture and debris off the thread tip. This combination of safety and appearance makes them popular on visible, hand-contacted assemblies.

High-Crown vs. Low-Crown

High-crown acorn nuts have a tall dome that fully covers longer bolt projections — the decorative standard. Low-crown have a shallower dome for shorter projections and tighter clearance. Choose by how far the bolt extends past the nut; the dome must clear the thread end.

Materials and Finishes

Steel with chrome or zinc plating: economical and durable. Brass: decorative, corrosion-resistant, common on visible fixtures. 18-8 stainless: corrosion resistance and a bright finish for outdoor and marine use.

Dimensional Standards

Acorn nuts follow DIN 1587 (metric high-crown) and ASME cap nut standards (inch), sized by thread.

Selecting the Right Acorn Nut

Match thread size and pitch to the bolt, and confirm the bolt projection fits within the dome — too long and the bolt bottoms out before the nut seats. Choose high-crown for longer projections, low-crown for tight clearance. Select material and finish for appearance and environment.

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