spacer

A spacer is a generic term for a component that creates a defined gap between two parts of an assembly. Spacers are used to set distance, improve alignment, simplify assembly, or isolate components. They occur in mechanical engineering, electronics, plumbing, and construction, and include cylindrical spacers, flat shims, and standoffs. Spacers can be threaded or non-threaded, and may be used with bolts, nuts, or screws to achieve a precise depth.

Common forms and materials: Cylindrical spacers with through-holes or threaded holes; flat washers or shims; shoulder spacers that position a part while providing bearing surface. Materials include metal (steel, stainless steel, aluminum, brass), plastics (Nylon, acetal), and composites. Tolerances and finishes vary depending on load, corrosion resistance, and thermal expansion. Some spacers are used with inner bushings or bearings.

Applications span automotive assemblies, machinery, electronics and PC assemblies (motherboard standoffs are spacers), and cabinetry or construction where panels must be separated by a precise gap. In electrical contexts, insulating spacers provide creepage distance and prevent short circuits; plastic spacers are common where electrical isolation is required.

In design and user interfaces, the term spacer refers to an element used to create whitespace and control layout. In web design, margins, padding, or dedicated spacer elements (or gap properties in flexbox or grid) achieve consistent separation between components.

Selection considerations include required thickness or depth, inner and outer diameters, thread type and pitch, material strength, environmental exposure, and compatibility with mounting hardware. Proper torque, clearance, and seating are important to avoid distortion or loosening.