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

IS 12779 - Scope: Key Specifications & Tolerances

1. Flange Width (B) Tolerance (Clause 3.2)

• Applies to flange width measurement as per Fig. 1.

2. Flange Thickness (T) Tolerance (Clause 3.3)

3. Squareness of Cut Section (a) (Clause 3.9)

• Squareness tolerance: 1:6 % of depth or flange width, max 3 mm (see Fig. 6).

4. Rounding Off (General)

• Follow IS 2:1960 rules for rounding numerical values; retain significant figures as per specified values.

This ensures dimensional accuracy for structural steel sections under IS 12779.

IS 12779 - Key References, Tables & Specifications

1. Cutting Tolerances (Clause 5.1)

• Refer to Table 5 for cutting tolerances on hot rolled parallel flange beams and columns.
• Includes limits on:
  • Flanges out of square or parallel (Fig. 2)
  • Web out of center (Fig. 4)
  • Camber and sweep (Fig. 5)
  • Flange width (Clause 3.2, Fig. 1)
  • Squareness of cut section (Fig. 6)

2. Flange Width Tolerance (Clause 3.2)

3. Rounding Off (General Clause)

• Final values must be rounded as per IS 2:1960.
• Retain the same number of significant digits as specified.

4. BIS Contact for Standards

• BIS offices across India handle standardization queries.
• Copyright protected; use symbols and sizes freely for implementation.

Visual Summary of Flange Width Tolerance

graph LR
A[Flange Width, B] --> B{Tolerance}
B -->|All widths| C[± 3 mm]

This standard ensures dimensional accuracy and quality control for structural steel sections.

IS 12779: Dimensional Tolerances for Parallel Flange Sections

Notes:

• These tolerances apply to parallel flange sections (see Fig. 1 in IS 12779).
• Depth (D) and flange width (B) tolerances are absolute.
• Thickness tolerances vary with size to ensure manufacturing accuracy.

flowchart LR
    A[Parallel Flange Section] --> B[Depth (D)]
    A --> C[Flange Width (B)]
    A --> D[Flange Thickness (T)]
    A --> E[Web Thickness (t)]
    B --> F{D ≤ 400?}
    F -- Yes --> G[± 3 mm]
    F -- No --> H[± 4 mm]
    C --> I[± 3 mm]
    D --> J{Flange Width B}
    J --> K[B=100: ±1.0 mm]
    J --> L[100 < B < 250: ±1.5 mm]
    J --> M[B > 250: ±2.0 mm]
    E --> N{Web Thickness t}
    N --> O[1 ≤ t ≤ 6: ±0.7 mm]
    N --> P[t > 6: ±1.0 mm]

IS 12779: Depth Tolerances for Beams/Columns

1. Depth Tolerances (Clause 3.1, Fig. 1)

• For example, for a 500 mm depth, tolerance = ± (500/4) = ±125 mm (check if this large value is practical; usually, it's ±4 mm as per typical practice, verify with code).

2. Web Bow Tolerance (Clause 3.6, Fig. 3)

• Web bow, f:
  • ≤ 400 mm depth: max 1.5 mm

  • 400 mm depth: max 2.0 mm

3. Flange Thickness Tolerances (Clause 3.3, Fig. 1)

4. Squareness of Cut Section (Clause 3.9, Fig. 6)

• Squareness tolerance, a = 1.6% of depth or flange width, max 3 mm.

Summary Diagram (Depth Tolerance)

graph LR
A[Depth D ≤ 400 mm] --> B[Tolerance ± 3 mm]
C[Depth D > 400 mm] --> D[Tolerance ± D/4 mm]

Note: Always cross-check with the latest IS 12779 edition for precise values and interpretations.

IS 12779: Flange Width Tolerances Summary

Flange Width, B (Clause 3.2)

Flange Thickness, T (Clause 3.3)

Flange Out of Square or Parallel (Clause 3.5)

• Flanges must be parallel within 1:5% of flange width (B).
• Individual flange deviation (R or R') from horizontal plane ≤ 2 mm.

Web Thickness, t (Clause 3.4)

Visual Concept: Flange Width Tolerance

graph LR
    A[Flange Width B] -->|±3 mm| B[Tolerance]
    C[Flange Thickness T] -->|Varies with B| D[Tolerance Table]
    E[Flange Parallelism] -->|Within 1:5% B| F[Parallel Flanges]
    G[Web Thickness t] -->|±0.7 or ±1.0 mm| H[Tolerance]

Key:

• Flange width tolerance is fixed ±3 mm.
• Thickness tolerance depends on flange width.
• Parallelism controls flange squareness tightly.

This ensures dimensional accuracy and fit in structural steel members.

IS 12779: Flange Thickness Tolerances

1. Flange Thickness, T (Clause 3.3)

2. Flange Width, B (Clause 3.2)

• Tolerance on flange width for all widths: ± 3 mm

3. Web Thickness, t (Clause 3.4)

4. Flange Out of Square or Parallel (Clause 3.5)

• Flanges must be parallel within 1:5% of flange width (B)
• Individual flange deviation (R or R') from horizontal ≤ 2 mm

Summary Diagram (Flange Thickness Tolerance)

graph TD
    A[Flange Width, B] -->|B=100| B1[Tolerance ±1.0 mm]
    A -->|100 < B < 250| B2[Tolerance ±1.5 mm]
    A -->|B ≥ 250| B3[Tolerance ±2.0 mm]

Note: These tolerances ensure proper fit and structural integrity of steel flanges per IS 12779.

IS 12779: Web Thickness Tolerances

1. Web Thickness, t (Clause 3.4)

2. Flange Thickness, T (Clause 3.3)

3. Web Bow, f (Clause 3.6)

• For depth ≤ 400 mm: max bow = 1.5 mm
• For depth > 400 mm: max bow = 2.0 mm

4. Off-Centre of Web, e (Clause 3.7)

Visual Summary (Fig. 1 - Web Thickness & Flange Thickness)

graph LR
A[Web Thickness, t] -->|1 ≤ t ≤ 6| B[± 0.7 mm]
A -->|t > 6| C[± 1.0 mm]

D[Flange Width, B] -->|B = 100| E[± 1.0 mm]
D -->|100 < B < 250| F[± 1.5 mm]
D -->|B ≥ 250| G[± 2.0 mm]

Note: These tolerances ensure structural integrity and fit during fabrication and erection. Always verify with the latest IS 12779 edition.

IS 12779 - Flange Out of Square or Parallel (Clause 3.5)

• Flange Parallelism Tolerance:
  [ (R + R') \leq 1.5% \times B ]
  Where:

  • (R, R') = deviation of individual flange from horizontal plane
  • (B) = flange width

• Individual Flange Out of Horizontal Plane:
  [ R \leq 2 \text{ mm}, \quad R' \leq 2 \text{ mm} ]

Flange Width and Thickness Tolerances

Summary Diagram (Flange Out of Square)

graph LR
A[Flange] --> B[Horizontal Plane]
subgraph Flange Deviations
  R[Deviation R ≤ 2 mm]
  R'[Deviation R' ≤ 2 mm]
end
B --> R
B --> R'
Note[Total deviation (R + R') ≤ 1.5% of B]

Key Points:

• Flanges must be parallel within 1.5% of flange width (B).
• Individual flange tilt limited to 2 mm max.
• Flange width and thickness tolerances ensure dimensional accuracy.

Use these for quality control and fabrication checks as per IS 12779.

IS 12779: Off Centre of Web (Clause 3.7)

Key Specification:

• Tolerance on off-centre of web, e, depends on the depth of section, D:

(Refer Fig. 4 in IS 12779 for illustration)

Related Tolerances:

• Web Thickness, t (Clause 3.4):

• Web Bow, f (Clause 3.6):

• Squareness of Cut Section, a (Clause 3.9):

  Squareness tolerance = min(1/6% of depth or flange width, 3 mm)

Summary:

• Off-centre web tolerance controls the web alignment within ±2.5 mm for sections up to 300 mm depth, and ±3.5 mm for deeper sections.
• These tolerances ensure proper fitment and structural performance.

graph LR
A[Depth of Section, D] -->|≤ 300 mm| B[Off-centre Tolerance ±2.5 mm]
A -->|> 300 mm| C[Off-centre Tolerance ±3.5 mm]
D[Web Thickness, t] -->|≤ 6 mm| E[Tolerance ±0.7 mm]
D -->|> 6 mm| F[Tolerance ±1.0 mm]
G[Web Bow, f] -->|≤ 400 mm| H[Max 1.5 mm]
G -->|> 400 mm| I[Max 2.0 mm]
J[Squareness, a] --> K[Max 3 mm or 1/6% depth/flange width]

This concise overview

IS 12779: Camber and Sweep Limits (Clauses 3.8 & 3.9)

1. Camber and Sweep Limits (Clause 3.8):

• For beam/column depth ≤ 400 mm:
  [ \text{Max Camber/Sweep} = 0.15% \times \text{Length} ]

• For beam/column depth > 400 mm:
  [ \text{Max Camber/Sweep} = 0.10% \times \text{Length} ]

2. Squareness of Cut Section (Clause 3.9):

• Squareness tolerance:
  [ \leq \frac{1}{6}% \times \text{Depth or Flange Width} \quad \text{(whichever is relevant)} ]
• Maximum allowed: 3 mm

Summary Table for Camber/Sweep Limits

Additional Tolerances for Reference

flowchart LR
    A[Beam/Column Length] --> B{Depth ≤ 400 mm?}
    B -- Yes --> C[Camber/Sweep ≤ 0.15% of Length]
    B -- No --> D[Camber/Sweep ≤ 0.10% of Length]
    E[Cut Section] --> F[Squareness ≤ 1/6% of Depth or Flange Width, max 3 mm]

Note: Always verify camber/sweep during fabrication to ensure structural integrity and fitment.

IS 12779 - Squareness of Cut Section

Key Specification (Clause 3.9):

• Squareness tolerance of cut section shall be within:
  • 1:6% of depth or flange width of beam/column section, whichever is less
  • Subject to a maximum deviation of 3 mm

Interpretation:

• If d = depth or flange width,

  [ \text{Maximum allowed squareness deviation} = \min \left( \frac{d}{6%}, 3 \text{ mm} \right) ]

• This ensures the cut face is nearly perpendicular to the web or flange, critical for proper fitment and welding.

Reference Figure:

• Fig. 6 in IS 12779 illustrates the squareness tolerance visually (not shown here).

Additional Notes:

• Squareness is crucial to avoid misalignment during assembly.
• The tolerance is tighter for smaller sections due to the 1:6% ratio.
• Maximum 3 mm limit prevents excessive deviation in large sections.

Summary Table:

flowchart LR
    A[Cut Section] --> B{Measure depth or flange width (d)}
    B --> C[Calculate 1:6% of d]
    C --> D[Compare with 3 mm]
    D --> E[Allowable Squareness = Min(C, 3 mm)]
    E --> F[Check cut face perpendicularity]

This ensures quality and fitment in hot rolled parallel flange beams and columns.

IS 12779: Mass Tolerances & Related Specifications

1. Mass Tolerances (Clause 4.1)

• Individual section mass tolerance: ±4% of specified mass (per IS 12778:1989)
• Lot mass tolerance: ±3% of specified mass

2. Squareness of Cut Section (Clause 3.9)

• Squareness tolerance = 1.6% of depth or flange width, max 3 mm

3. Flange Thickness Tolerances (Clause 3.3)

4. Web Thickness Tolerances (Clause 3.4)

flowchart TD
    A[Specified Mass] --> B{Individual Section}
    B -->|±4%| C[Mass Tolerance]
    A --> D{Lot}
    D -->|±3%| E[Mass Tolerance]
    F[Section Dimensions] --> G[Flange Width B]
    G -->|≤100 mm| H[±1.0 mm]
    G -->|100 < B < 250| I[±1.5 mm]
    G -->|≥250 mm| J[±2.0 mm]
    F --> K[Web Thickness t]
    K -->|≤6 mm| L[±0.7 mm]
    K -->|>6 mm| M[±1.0 mm]

Summary: Mass tolerances ensure quality control with ±4% for sections and ±3% for lots. Dimensional tolerances on flange and web thickness maintain structural integrity per IS 12779.

IS 12779: Cutting Tolerances Summary

1. Squareness of Cut Section (Clause 3.9)

• Squareness tolerance = 1.6% of depth or flange width, whichever applies.
• Maximum deviation = 3 mm.
• Ensures perpendicular cuts on beams/columns.

2. Flange Thickness Tolerance (Clause 3.3)

3. Mass Tolerance (Clause 4.1)

• Individual section mass tolerance: ±4% of specified mass (IS 12778:1989).
• Lot mass tolerance: ±3% of specified mass.

Visual: Squareness Tolerance Concept

graph TD
A[Beam/Column Section] --> B[Depth or Flange Width]
B --> C[Calculate 1.6% of dimension]
C --> D[Check cut squareness deviation]
D -->|Deviation ≤ 3 mm| E[Acceptable Cut]
D -->|Deviation > 3 mm| F[Reject Cut]

This ensures dimensional accuracy and quality in hot rolled parallel flange beams and columns.