Demags

Demags are demagnetization devices used to remove residual magnetization from ferromagnetic objects. The term is commonly applied to handheld, bench-top, and industrial units designed to produce controlled, decreasing magnetic fields so that parts or tools lose their remanent magnetism. Removing magnetization can improve measurement accuracy, prevent sticking or attraction of components, and reduce magnetic interference in manufacturing and assembly processes.

Operation and principle

Most demags operate by applying an alternating magnetic field to the object and then gradually reducing the field to zero. As the current through the coil is tapered, the magnetic domains in the material realign in random orientations, leaving the object largely non-magnetic when removed. The process is also known as degaussing in some contexts.

Types

- Hand-held demagnetizers for quick field service or small parts

- Bench-top demagnetizers for workshop use

- Through-hole or through-line demagnetizers used in production lines

- Conveyor or belt-type demagnetizers for large or continuous streams of parts

Applications

- Precision tools and gauging equipment to prevent measurement errors

- Steel tooling, fasteners, and assemblies where magnetism could cause sticking or alignment problems

- Magnetic storage or electronic components that require minimal stray magnetic fields

- Quality control processes that demand repeatable, non-magnetic test specimens

History and notes

Demagnetization techniques emerged in the early 20th century as industry sought to reduce magnetic interference in tooling and accuracy-critical work. Modern demags use electronic control to regulate the strength and duration of exposure, offering portable and integrated solutions for diverse workflows.

See also: degaussing, magnetization, magnet.