teak logs

IS 4895 - Scope & Key Specifications

• Scope: Covers definitions and measurements related to logs as per IS 707-1976.
• Measurement Unit: Curvature deviations are measured per 2.5 m length from the butt end of the log.

Curvature Deviation Table (Clause 4.1.1)

• Rounding Off (Clause 0.5): Final test/analysis values must be rounded as per IS 2-1960, retaining the same significant figures as the specified values.

This ensures standardized measurement and evaluation of log curvature for quality control.

IS 4895: Definitions & Key Specifications

• Clause 2.0: Definitions align with IS 707-1976 for timber and wood-based materials.

• Clause 2.8 - Units of Defect:

  • Represents quantitative degradation due to defects in timber.
  • Helps in assessing quality and grading.

• Clause 4.1.1 - Curvature Measurement:
  For every 2.5 m length from the butt end of a log, curvature deviation is measured as:

• Clause 6.2 - Measurements:
  Specifies standard procedures for measuring dimensions and defects, ensuring consistency.

Summary:

• Use units of defect to quantify timber quality loss.
• Measure curvature every 2.5 m with deviation limits as above.
• Refer to IS 707 for detailed timber definitions.

flowchart LR
    A[Log Length 2.5 m] --> B{Measure Deviation}
    B -->|≤ 50 mm| C[Curvature 0.02]
    B -->|50-75 mm| D[Curvature 0.05]
    B -->|75-100 mm| E[Curvature 0.08]
    B -->|100-125 mm| F[Curvature 0.12]
    B -->|125-150 mm| G[Curvature 0.16]

This ensures uniform grading and quality control per IS 4895.

IS 4895: General Requirements - Key Points

1. Units of Defect (Clause 2.8)

• Unit of defect quantifies the approximate degradation caused by each defect in timber.
• It helps in assessing quality by assigning numerical values to defects.

2. Rounding Off (Clause 0.5)

• Final test or analysis results are rounded as per IS 2-1960.
• Retain the same number of significant figures as specified.

3. Curvature Measurement (Clause 4.1.1)

• Curvature is measured for every 2.5 m length from the butt end.
• Defect units based on deviation:

Summary Diagram: Defect Unit Assignment by Curvature

graph LR
A[Deviation ≤ 50 mm] -->|0.02| B[Unit of Defect]
C[50 < Deviation ≤ 75 mm] -->|0.05| B
D[75 < Deviation ≤ 100 mm] -->|0.08| B
E[100 < Deviation ≤ 125 mm] -->|0.12| B
F[125 < Deviation ≤ 150 mm] -->|0.16| B

Use these units to quantify timber quality and ensure compliance with IS 4895 standards.

IS 4895: Permissible Defects in Logs and Their Evaluation

Key Formulas:

• Permissible number of defects in logs > 2.5 m length:

[ \text{Permissible defects} = 2.5 \times P \times L ]

Where:

• (L) = Length of log in meters
• (P) = Permissible defect value for 2.5 m length

Grade-wise Permissible Defects:

Important Specifications:

• No plugging or covering of visible defects is allowed (Clause 3.3).
• Grading is based on estimated sawn out-turn considering:
  • General wood quality
  • Probable loss due to visible defects under normal conversion methods
• Maximum permissible defects do not guarantee qualification for that grade.

flowchart TD
    A[Log Length (L)] --> B[Calculate Permissible Defects: 2.5 × P × L]
    B --> C{Defect Units in Log}
    C -->|≤ Grade 1 Max (2.5)| D[Grade 1]
    C -->|> 2.5 and ≤ Grade 2 Max (5)| E[Grade 2]
    C -->|> 5| F[Reject or Lower Grade]

This ensures quality control without masking defects.

IS 4895: Grading of Logs - Key Points

Grading Criteria (Clause 2.5)

• Grade 1: Max 2.5 units of defects per log.
• Grade 2: Max 5 units of defects per log.
• (Units of defects refer to a quantified measure based on visible defects affecting sawn out-turn.)

Branding Specifications (Clause 7.1)

Each log must be branded on both ends with:

• Supplier's ID (abbreviated initials)
• Length and mid-girth of the log
• Grade mark:
  • Grade 1: Square
  • Grade 2: Triangle
  • Grade 3: Circle

Notes

• Grading depends on wood quality and visible defect losses.
• Based on FAO Asia-Pacific Regional Grading Rules for Teak Logs.
• Maximum permissible defects ensure expected sawn out-turn quality.

Summary Table

This grading helps estimate sawn timber yield and quality for conversion.

IS 4895: Dimensions and Measurements Key Points

1. Minimum Dimensions of Logs (Clause 6.1)

• The standard specifies minimum dimensions for logs but exact values depend on application and species (refer to full IS 4895 Table).

2. Permissible Number of Defects (Clause 2.5)

• For logs > 2.5 m length:

  [ \text{Permissible defects} = 2.5 \times P \times L ]

  • L = length of log (m)
  • P = permissible defect value per 2.5 m length

3. Curvature Limits (Clause 4.1.1, Table 4.1)

• Curvature is measured per 2.5 m length from the butt end.

Summary:

• Use 2.5 m as base length for measurements.
• Defects allowed scale linearly with length.
• Curvature limits increase with deviation size, controlling log straightness.

flowchart LR
    A[Log length L > 2.5m] --> B[Calculate permissible defects: 2.5 x P x L]
    A --> C[Measure curvature per 2.5 m segment]
    C --> D{Deviation (mm)}
    D -->|<=50| E[Curvature ≤ 0.02]
    D -->|50-75| F[Curvature ≤ 0.05]
    D -->|75-100| G[Curvature ≤ 0.08]
    D -->|100-125| H[Curvature ≤ 0.12]
    D -->|125-150| I[Curvature ≤ 0.16]

For detailed dimensional tables, refer to IS 4895 full document Clause 6.1.

IS 4895: Marking and Certification - Key Points

1. Marking of Logs (Clause 7.1)

Each log must be legibly and indelibly branded on both ends with:

• Supplier's ID: Abbreviated initials
• Length and mid-girth of the log
• Grade identification:
  • Grade 1: Square
  • Grade 2: Triangle
  • Grade 3: Circle

2. ISI Certification Mark (Clause 7.1.1)

• Logs may carry the ISI Certification Mark.
• ISI Mark assures compliance with Indian Standards under ISI supervision.
• Use of ISI mark is governed by the Indian Standards Institution (Certification Marks) Act.
• Continuous quality checks by ISI ensure conformity.

3. End Coating (Clause 8.1)

• After inspection, coat log ends at least 150 mm deep with coatings recommended in IS:1141-1973 (Code of Practice for Seasoning of Timber).

4. Rounding Off (Clause 0.5)

• Test results must be rounded per IS:2-1960, retaining the same significant figures as specified values.

Summary Table for Marking Symbols

Visual Summary

flowchart LR
    A[Log End Marking] --> B[Supplier's ID]
    A --> C[Length & Mid-Girth]
    A --> D[Grade Symbol]
    D --> D1[Grade 1: Square]
    D --> D2[Grade 2: Triangle]
    D --> D3[Grade 3: Circle]
    A --> E[ISI Certification Mark (optional)]
    A --> F[End Coating ≥ 150 mm (IS:1141)]

For detailed licensing and ISI mark use, contact Indian Standards Institution regional offices as listed in IS 4895.