dome

A dome is the convex metal component of a press stud or snap fastener, typically made from nickel-plated brass or stainless steel. It sits on top of the socket (the concave receiving piece) and is forced down to interlock and hold two pieces of fabric, leather, or thin material together. The dome is loaded with spring tension; when pressed, its curved profile compresses and seats into the socket with an audible or tactile snap, then springs back slightly to maintain closure.

Domes vary in diameter from 6 mm to 16 mm for most apparel and light industrial use, with 10 mm being common for jackets and bags. The crown height (the depth of the curve) affects both the force required to snap and the holding strength once closed. A shallower dome requires less pressure but provides lighter grip; a deeper profile demands more force but resists accidental separation better. Domes are typically 0.8 to 1.2 mm thick depending on the alloy and intended load.

The dome is installed by setting it into a die on a press, with the garment layers sandwiched below. A hardened punch strikes the center of the dome, deforming the post underneath and anchoring it to the material. Poor installation shows as a dome that rocks or spins freely, indicating the post did not properly compress. Corrosion can seize the dome to the socket, especially in salt or high-humidity environments; stainless steel domes resist this better than nickel plate but cost more.

The term 'dome' refers to the visible domed or hemispherical shape of the cap. In North America it is often called a snap fastener or press stud interchangeably; in British usage, press stud is more precise (the dome being one half, the socket the other). Manufacturers specify fasteners by dome diameter and material, and by the socket or stud pattern to ensure compatible pairs.