Methods of measurement and evaluation of defects in timber, Part 2: Converted timber

IS 3364 Part 2 (1976) — Scope & Key Specifications

This part deals with defect evaluation in timber, especially shakes and checks.

Key Tables & Formulas:

1. Defect Values of Shakes (Clause 1.5)

• Defects quantified by length and width of shakes.
• Values (in %) represent affected area or defect severity.
• For multiple shakes, values add up.
• For star shakes, multiply largest shake value by half the number of shakes.
• For cross-section > 0.5 cm², defect values are halved.
• Intermediate values: use next higher measurement.

(Refer Clause 1.5 table for full values)

2. Defect Values for Checks < 2 mm Width (Clause 3.1)

• Defect expressed as % affected area.
• Length of check vs. % affected area on surface.

• For material length > 5 m, multiply values by 5/L (L = length in m

IS 3364 Part 2 - Key Definitions & Defect Values

1. Definitions (Clause 2.0):

   • Definitions from IS 707-1976 apply.
   • Additional definitions relate to defects like shakes and splits in timber.

2. Defect Values for Shakes (Clause 1.5):

   • Shakes are separations in timber fibers; values depend on length and width of shake.
   • Use the table below for defect values (in cm):

• Notes:
  • For multiple shakes, values add up.
  • For star shakes, multiply by half the number of shakes.
  • Values halve for cross sections > 0.5 cm².
  • Use next higher defect size if intermediate.

3. Defect Values for Splits (Clause 3.10, Table 9):
   • Splits measured by length on longitudinal face and depth at end surface.
   • Defect values (cm) depend on both parameters:

IS 3364 Part 2 — Identification & Measurement of Defects

Key Concepts:

• Units of Defects quantify material degradation per defect type.
• Total defect units = sum of all individual defect units.

1. Defect Values for Holes (Clause 3.5, Table 6)

• Notes:
  • Add defect units for multiple hole concentrations.
  • Pin holes excluded.
  • Loose knots treated as unsound knots.

2. Defect Values for Checks < 2 mm Width (Clause 3.1, Table 1)

IS 3364 Part 2: Defect Values & Quantitative Evaluation Summary

1. Units of Defects (Clause 2.3)

• Defect units quantify the degradation of utilizable timber.
• Total defect units = Sum of individual defect units.
• Each defect type has specific units listed in respective tables.

2. Additional Defect Values (Clause 4.2)

• For defects not equivalent to standard ones but reducing timber utility:
  • Add 0 to 10 units to the total defect value for safety.

3. Defect Values for Holes (Clause 3.5, Table 6)

• Defect units increase with hole concentration and size.
• Sum units if holes are concentrated at multiple places.
• Pin holes are excluded.
• Loose knot holes = evaluated as unsound knots.

4. Measurement Tolerance (Clause 5.2)

• Defect units must be evaluated to two decimal places.

flowchart TD
    A[Identify Defects] --> B[Measure Defect Size & Concentration]
    B --> C[Refer to Defect Tables]
    C --> D[Calculate Defect Units]
    D --> E[Sum All Defect Units]
    E --> F[Add 0-10 units if non-equivalent defects present]
    F --> G[Final Quant

IS 3364 Part 2: Tolerances in Measurement and Evaluation of Timber Defects

Key Specifications & Tables:

1. Defect Values for Checks < 2 mm Width (Clause 3.1)

• Defect value depends on length of check (cm) and affected area %.
• For example, a 10 cm check affecting 40% area = 0.04 defect value.
• Values apply for timber length ≤ 5 m; for longer timber, multiply by 5/L (L = length in m).
• Ignore checks < 5 cm or fine checks.

2. Defect Values for Shakes (Clause 1.5)

• Defect depends on length and width of shake.
• Values increase with both parameters.
• For multiple shakes, add values; for star shakes, multiply largest defect by half the number of shakes.
• Values halved if cross-section > 0.5 m².

3. Defect Values for Holes (Clause 3.5)

• Depends on hole concentration per 100 cm³ and largest hole diameter.
• Values add if holes are in multiple concentrations.
• Pin holes excluded; knot holes treated as unsound knots.

Additional Notes:

• For defects not equivalent but reducing utility, add 0-10 to total defect for safety (Clause 4.2).
• For intermediate values, always take the next higher measurement.
• Defect values are additive

IS 3364 Part 2 - Influence of Defects on Timber Properties

Key Points from Clause 6.1.15:

• Sap Stain (Blue Stain):
  • Does not affect strength but spoils appearance.
  • Indicates susceptibility to wood rot fungi if untreated.
  • Can be ignored if timber is preservative treated.

General Notes on Defects (Clause 2.1):

• Defects reduce technical quality, strength, and commercial value.
• Defects are classified by kind and evaluated quantitatively by size.
• Quantitative evaluation aids in grading and pricing.

Typical Influence of Defects on Strength:

Formula for Strength Reduction (Generalized):

[ f_{effective} = f_{base} \times (1 - k_d) ] Where:

• (f_{effective}) = strength after defect influence
• (f_{base}) = base strength without defects
• (k_d) = defect factor (depends on defect size/type, typically 0 to 0.3)

Summary Table for Defect Evaluation (Indicative)

flowchart TD
    A[Timber with Defects] --> B{Type of Defect}
    B --> C[Knots]
    B --> D[Checks & Splits]
    B --> E[Decay]
    B --> F[Sap Stain

Application of Defect Values in Grading (IS 3364 Part 2)

• Concept: Defect values quantify the reduction in utility of timber due to defects. The sum of defect units gives total degrade.

• Key Notes:

  • Defect evaluation is partly subjective; inspectors' judgment is crucial.
  • Defects not equivalent but reducing utility may add 0-10 units for safety (Clause 4.2).

• Defect Units for Spiral Grain (Clause 3.2, Table 2):

• Usage: Sum units of all defects to estimate total degrade; use as guidance for grading and pricing.

flowchart LR
    A[Timber Sample] --> B[Identify Defects]
    B --> C[Assign Defect Units from Tables]
    C --> D[Sum Defect Units]
    D --> E{Add Safety Units?}
    E -- Yes --> F[Add 0-10 Units]
    E -- No --> G[Total Defect Units]
    F --> G
    G --> H[Determine Grade & Utility]

This approach balances quantitative defect values with inspector expertise per IS 3364 Part 2.

Rounding Off and Reporting of Results (IS 3364 Part 2)

• Rounding Rule (Clause 0.8):
  Final test or analysis values must be rounded according to IS:2-1960.

  • Retain the same number of significant figures as in the specified standard value.

• Defect Units Precision (Clause 5.2):
  Defect units must be evaluated correct to two decimal places.

• Estimating Units (Clause 5.3):
  If exact values are unavailable in Tables 1–9, estimate proportionally following the table's pattern.

  • In doubt, select the next higher value.

Key Table: Defect Values for Checks < 2 mm Width (Clause 3.1)

Notes:

• Checks < 5

IS 3364 Part 2 (1976) — Annexures & Tables Key Points

1. General Estimation (Clause 5.3)

• If values are not in Tables 1-9, estimate proportionately following the table's pattern.
• In doubt, choose the next higher value for safety.

2. Influence of Defects on Timber (Clause 6.1.15)

• Sap Stain: Does not reduce strength but affects appearance.
• Preservative-treated timber: sap stain can be ignored.

3. Defect Values of Shakes (Clause 1.5)

• Shake dimensions (length and width) affect defect values.
• Values are additive for multiple shakes.
• For star shakes, use largest shake value × half the number of shakes.
• For cross-section > 0.5 cm², halve the defect values.
• Use next higher measurement for intermediate values.

(Refer to IS 3364 Part 2 for full table)

4. SI Units Used

• Force: Newton (N) = 1 kg·m