tárcsa

Tárcsa is a Hungarian term for a flat, circular disc, typically with a central mounting hole. The form and function vary widely, which is why the word appears in several different technical contexts. In everyday language it can simply mean any round, flat disk or plate used as a component.

In mechanical engineering, 'tárcsa' most commonly refers to brake discs (fék tárcsa) and clutch discs used in transmissions. Brake discs are designed to withstand repeated heating from friction with pads; materials include grey cast iron, steel, and, in high-performance applications, composite or ceramic matrices. They are usually mounted on axles and cooled by ventilation or drilled/vented designs to manage heat and wear. Clutch discs transfer torque between input and output shafts via friction materials, and they must balance friction, heat resistance, and dimensional stability.

In information technology and data storage, the term can denote the disks or platters inside storage devices. Hard-disk drives use multiple circular platters with magnetic surfaces, mounted on a spindle. Optical discs (CD, DVD, Blu-ray) are also flat circular media, though in common language they are typically called lemez rather than tárcsa; nonetheless the concept of a circular data carrier is the same.

In measuring instruments and timepieces, tárcsa can mean the dial or face of a gauge or clock—its markings or numerals indicate units, angles, or time.

Sizes and materials vary by application. Diameters can range from a few millimeters to over 400 millimeters; thicknesses are from fractions of a millimeter (thin optical discs) to several millimeters (engineered brake discs). Central holes accommodate mounting axles or spindles, and surface finishes or coatings optimize wear, heat resistance, or optical properties.