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Steel bar that has been cold-drawn through a die after hot rolling. Produces a smooth surface finish and precise dimensional tolerances to BS EN 10278 (typically h9, h10 or h11). More dimensionally accurate than black bar.

Hot rolled steel bar with a characteristic dark mill scale surface. Less dimensionally precise than bright bar but more economical for larger diameters. Tolerances to BS EN 10060. Standard for sections above ~100mm diameter.

ISO tolerance grades for bright bar under BS EN 10278. h9 is the tightest (used for smaller diameters), h11 the widest (larger diameters). All h-tolerances have a zero upper deviation — the bar can only be undersize, never oversize.

Quenched and Tempered. Steel that has been hardened by quenching then tempered to reduce brittleness and achieve specified mechanical properties. The "T" suffix in grade names (e.g. EN24T) denotes this condition as supplied.

A heat treatment process that creates a hard surface layer on low-carbon steel by diffusing carbon into the surface (carburising) and then hardening. Produces 58–64 HRC on the surface with a tough, ductile core. Used for gears and camshafts.

The dimension measured across opposite flat faces of a hexagon bar. This is the spanner size and the number quoted when ordering hex bar. A 25mm A/F hex bar accepts a 25mm spanner directly without any turning required.

The ability of a steel to be hardened throughout its cross-section by quenching. Plain carbon steels (EN8) harden only in thin sections. Alloy steels (EN19, EN24T) harden through much larger sections due to their chromium and molybdenum content.

An EN 10204 material test certificate issued by the manufacturer's authorised inspector, with test results that relate specifically to the material supplied. Required for oil & gas, aerospace, pressure vessel and most ASME/API applications.

The maximum stress a material can withstand before fracture, measured in N/mm² or MPa. A key design parameter for structural and mechanical components. EN8 in the T condition: ~700–850 N/mm². EN24T: ~850–1000 N/mm².

Steel with additions of sulphur (or lead in Pb grades) that break chips into short pieces during machining. EN1A and EN1A Pb produce short chips, allowing higher cutting speeds on automatic lathes. Slightly lower strength than equivalent non-free-cutting grades.

A document issued by the steel mill confirming the chemical composition and mechanical properties of a specific heat (batch) of steel. The basis for EN 10204 certificate types 2.2, 3.1 and 3.2. Referenced by heat number for traceability.

Three hardness measurement scales. HRC (Rockwell C) uses a diamond cone and is used for hard materials. HB (Brinell) uses a ball indenter and suits softer materials and castings. HV (Vickers) uses a pyramid and is accurate across the full range. See conversion table →