Rolling and cutting tolerances for hot rolled parallel flange beam and column sections
1989 Edition

The scope of IS 12779 covers the prescribed tolerances for dimensions of hot rolled steel parallel flange beams and columns as detailed in IS 12778. Flange width tolerance is fixed at ±3 mm for all sizes, with flange thickness varying by width category. Squareness of cut sections must not exceed 1.6% of depth or flange width, capped at 3 mm. Rounding of values follows IS 2:1960. These criteria ensure dimensional precision in structural steel profiles.

IS 12779 references IS 12778 for dimensional specifications and IS 2:1960 for numerical rounding conventions. Cutting tolerances include flange squareness, web centering, camber, and sweep limits. Flange width tolerance remains ±3 mm across all sizes. BIS offices handle standardization queries and usage permissions.

Detailed tolerances for depth, flange width, flange thickness, and web thickness are tabulated. Depth tolerance is ±3 mm for sections up to 400 mm deep and ±4 mm beyond. Flange thickness tolerances increase with flange width, while web thickness tolerances depend on thickness range. These ensure manufacturing accuracy and interchangeability.

Depth deviations allowed are ±3 mm for depths ≤400 mm and ±4 mm for greater depths. Web bow limits are set at 1.5 mm for shallower sections and 2.0 mm for deeper ones. Squareness of cuts is limited to 1.6% of depth or flange width, maximum 3 mm.

Flange width is permitted a uniform tolerance of ±3 mm regardless of size. Thickness tolerances vary by flange width category: ±1.0 mm for 100 mm, ±1.5 mm for 100–250 mm, and ±2.0 mm for widths exceeding 250 mm. Flanges must remain parallel within 1.5% of flange width, with individual flange deviation capped at 2 mm.

Thickness tolerances for flanges depend on flange width categories: ±1.0 mm for 100 mm widths, ±1.5 mm for intermediate widths, and ±2.0 mm for widths above 250 mm. These tolerances ensure proper fit and structural performance.

Web thickness tolerances are ±0.7 mm for thicknesses between 1 and 6 mm, and ±1.0 mm for greater thicknesses. Allowed web bow is 1.5 mm for sections ≤400 mm depth, increasing to 2.0 mm for deeper sections. Off-centre web positioning tolerance is ±2.5 mm for depths up to 300 mm and ±3.5 mm beyond.

Flanges must be parallel within 1.5% of flange width, and individual flange deviation from horizontal must not exceed 2 mm. These requirements maintain dimensional accuracy crucial for fabrication and assembly.

Tolerance for web offset from centreline depends on section depth: ±2.5 mm for depths ≤300 mm and ±3.5 mm for deeper sections. This ensures correct web alignment for structural integrity.

Allowed camber and sweep are limited to 0.15% of member length for depths up to 400 mm, and 0.10% for sections exceeding 400 mm depth. These limits control curvature and lateral deviation during rolling.

Cut sections must have a squareness deviation not exceeding 1.6% of the depth or flange width, with an absolute maximum of 3 mm, ensuring cuts are perpendicular for proper fitment.

Individual section mass may vary by ±4% from the specified value per IS 12778, whereas lots of sections are allowed a ±3% variation. These tolerances aid in quality control during manufacturing and procurement.

Cutting tolerances require squareness within 1.6% of depth or flange width, capped at 3 mm deviation. Flange thickness tolerances and mass tolerances are maintained as per earlier clauses to guarantee dimensional accuracy.