Critical for identification of commercial timbers
1973 Edition

Scope Summary of IS 4970

This standard provides a diagnostic key aimed at identifying commercial timber species commonly used by purchasing agencies (such as railways and defense), timber traders, and industries.

Highlights:

• Encompasses identification of 60 timber species (original 40 plus 20 added later).
• Focuses on anatomical and general diagnostic traits relevant for species recognition.
• Designed for practical field application in verifying timber supplied.
• Users should possess foundational knowledge of wood anatomy and physical characteristics.
• Supported by an illustrated handbook: Field Identification of Fifty Important Timbers of India (recommended for study).

Diagnostic features included:

• Porosity types (non-porous, ring-porous, pore sizes)
• Prominence of growth rings
• Colour differentiation between sapwood and heartwood
• Hardness and weight classification
• Anatomical features such as radial canals, presence of phloem, ripple marks

Sample classification excerpt:

This code facilitates precise timber species identification crucial for quality control and procurement in commercial usage.

Tools and Equipment as per IS 4970 for Timber Identification

• Punched Cards:

  • Dimensions: 145 x 115 mm
  • Diagnostic traits from Table 1 are indicated by making notches using scissors or clippers (see Fig. 2).
  • Cards display both commercial and botanical names of timbers.

• Identification Procedure:

  • Notch cards according to observed features like pore size, growth rings, colour, hardness, and weight.
  • Feature codes correspond with Table 1 (e.g., pore sizes: non-porous (28), ring-porous (29), etc.).
  • This system enables quick species identification in field conditions.

• Key Features from Table 1 (Sample):

• Required Tools:
  • Scissors or clippers for card notching.
  • Reference handbook: Field Identification of Fifty Important Timbers of India by K.R. Rao & K.B.S. Juneja.

flowchart LR
    A[Timber Sample] --> B[Observe Diagnostic Features]
    B --> C[Match Features on Punched Card]
    C --> D[Notch Corresponding Features]
    D --> E[Identify Timber Species]

Summary: IS 4970 employs a punched card system where specific diagnostic features are notched to assist timber species identification, reinforced by a handbook and simple cutting tools.

Definitions of Diagnostic Features in IS 4970 for Timber Identification

Important Points:

• Clause 3.0: Provides definitions for general and anatomical features used in timber recognition.
• Clause 4.1 and Table 1: Details diagnostic traits for 60 commercial timbers, indicating presence or variability.
• Example (Clause 3.63): Prominent Gum or Resin Streaks — vertical canals appearing as reddish-brown gummy streaks on longitudinal surfaces (e.g., chir, kail, pine).
• Categories of Diagnostic Features:
  • Porosity: Non-porous, ring-porous, pore sizes ranging from very large to very small.
  • Pore Arrangement: solitary, radial multiples, tangential clusters.
  • Growth Rings: distinct or abrupt earlywood to latewood transitions.
  • Colour and Hardness: differentiation of sapwood/heartwood, colour shades, hardness levels.
  • Additional Features: phloem inclusion, ripple marks, resin streaks.

Sample Extract of Diagnostic Features Table:

Usage Recommendations:

• Employ identification cards (145x115 mm) for field use.
• Basic understanding of wood anatomy is necessary.
• Suggested reference: Field Identification of Fifty Important Timbers of India by K. Ramesh Rao & K. B. S. Juneja.

flowchart TD
    A[Start: Timber Sample] --> B{Assess Porosity}
    B -->|Non-Porous| C[Evaluate Pore Size & Arrangement]
    B -->|Ring-Porous| C
    C --> D{Check Growth Rings}
    D --> E[Continue Identification]

Diagnostic Traits for Commercial Timbers under IS 4970

The standard lists diagnostic features for 60 common commercial timber species in Table 1. Species identification is achieved by associating each timber with a combination of numbered anatomical, physical, and visual characteristics.

Key Details:

• Features are numerically coded (e.g., 1, 3, 4, 9) corresponding to traits such as:
  • Pore size and distribution (non-porous, ring-porous)
  • Colour variations (light, yellow, brown, red hues)
  • Hardness levels (soft to very hard)
  • Weight categories (light to very heavy)
  • Presence of anatomical markers like radial canals, included phloem, ripple marks, growth rings
• Some species have multiple identification cards due to feature variability.
• Examples:
  • Aini (Artocarpus hirsutus): Features 1,3,4,9,12,15,20,23,27,30,31,33,37,43,49,50
  • Chir (Pinus roxburghii): Features 1,4,5,9,12,14,19,24,26,28,55,56,61,63

Application:

• Enables field identification by matching observed timber properties.
• Requires familiarity with wood anatomical attributes.
• Recommended study material: Field Identification of Fifty Important Timbers of India by K. Ramesh Rao & K.B.S. Juneja.

Sample Feature Codes from Table 1:

Identification Flow Diagram:

flowchart TD
    A[Start: Timber Sample] --> B[Observe Anatomical Features]
    B --> C[Match Features with Codes]
    C --> D[Identify Timber Species]

Preparation of Identification Cards as per IS 4970

Key Points:

• Punched Card Sets (Clauses 2.6 & 5.1):

  • Cards correspond to diagnostic features of various timbers.
  • Features are marked by making notches on the cards using scissors or clippers (refer Fig. 2).
  • Each card is labeled with both the trade and botanical names of the timber species.

• Diagnostic Feature Listings (Clause 4.1):

  • Table 1 enumerates features for 60 commercial timber species.
  • Bracketed features indicate variable occurrence; thus, some species have multiple cards.

• Usage Method (Clause 6.1):

  • Cards function as a key by sequentially matching notched features to timber characteristics (Clauses 6.1.1 to 6.1.7).

Conceptual Workflow:

Visual Flowchart:

flowchart TD
    A[Start: Timber Identification] --> B[Select Cards from Set]
    B --> C[Notch Diagnostic Features]
    C --> D[Label Cards with Names]
    D --> E[Use Cards to Identify Timber]
    E --> F{Features Match?}
    F -- Yes --> G[Timber Identified]
    F -- No --> B

Note: Detailed diagnostic features per timber are provided in Table 1 of IS 4970.

Using the Identification Key in IS 4970

This standard offers a structured key for classifying commercial timbers based on their diagnostic anatomical and physical traits.

Important Notes:

• Prerequisite Knowledge: Users should have a basic understanding of wood anatomy and physical properties.
• Diagnostic Traits Considered: Pore size/type, growth ring characteristics, colour, hardness, weight, and anatomical details such as radial canals, phloem inclusions, and pore patterns.
• Sequential Identification: The key adopts a decision tree methodology, starting from broad categories like pore type (non-porous or ring-porous) and increasingly distinguishing species-specific traits.
• Physical Reference Tools: Punched cards (145 x 115 mm) are provided to simplify field identification.
• Recommended Literature: The handbook "Field Identification of Fifty Important Timbers of India" is advised for comprehensive understanding.

Example Feature Table (Simplified):

Identification Flowchart:

graph TD
A[Start: Observe Timber Sample] --> B{Determine Pore Type}
B -->|Non-porous| C{Evaluate Pore Size}
B -->|Ring-porous| D{Assess Growth Rings}
C --> E[Check Colour]
D --> E
E --> F[Assess Hardness]
F --> G[Determine Weight]
G --> H[Identify Timber Species]

Summary: Identification proceeds by sequentially analyzing timber features like pore attributes, colour, hardness, and weight, consulting the punched card system or tabulated data to isolate the species. Studying the recommended handbook enhances accuracy.

Examination Notes for Timber Samples According to IS 4970

1. Diagnostic Features (Clause 4.1 & Table 1):

• Tabulates characteristics for 60 common commercial timber species.
• Features in brackets highlight occasional or partial presence.
• Characteristics include:
  • Porosity types (non-porous, ring-porous)
  • Pore sizes (very large to scanty)
  • Prominence of growth rings
  • Colour variations (light, yellow, brown, red, others)
  • Hardness levels (soft to very hard)
  • Weight categories (light to moderately heavy)
  • Anatomical traits such as radial canals, included phloem, ripple marks.

2. Preparation of Identification Cards (Clause 5.1):

• Cards measuring 145 x 115 mm are notched to represent diagnostic features.
• Each timber species is associated with one or more cards indicating its feature set.
• Cards bear trade and botanical names.

3. Usage Approach (Clause 6.1.2):

• Identify a unique feature in the unknown timber.
• Insert a needle through the corresponding hole in the card bundle.
• Shake the bundle; cards with that feature notched fall out, reducing candidate species.

Feature Summary Table:

Visual Diagram of Identification Process:

flowchart TD
    A[Inspect Timber Sample] --> B[Determine Distinctive Feature]
    B --> C[Insert Needle into Card Pack Hole]
    C --> D[Shake Card Pack]
    D --> E[Cards Matching Feature Eject]
    E --> F[Identify Timber Species]

Additional References:

• Field Identification of Fifty Important Timbers of India by K.R. Rao & K.B.S. Juneja
• Resources from Forest Research Institute and affiliated colleges, Dehra

While IS 4970 mainly focuses on the identification of commercial timbers and does not provide direct design formulas or usage precautions, general timber engineering principles and related IS codes suggest the following guidelines:

General Precautions and Constraints:

• Moisture Control: Maintain timber moisture content typically between 12-15% to avoid shrinkage, swelling, or fungal decay.
• Accurate Species Identification: Utilize IS 4970 to confirm species to ensure mechanical property expectations are met.
• Avoid Defects: Exclude timber exhibiting knots, splits, rot, or decay as these compromise strength.
• Load Considerations: Account for timber’s anisotropic behavior when designing for bending, shear, and compression, referencing IS 883 and IS 1734.
• Durability Measures: Protect timber from termites, fungal attack, and weathering via treatments or design detailing.
• Fire Safety: Recognize timber’s combustibility; apply fire retardants or protective coverings as needed.

Common Design Calculations (from IS 883 / IS 1734):

• Bending Stress (( \sigma_b )): [ \sigma_b = \frac{M}{Z} ] where (M) is bending moment and (Z) is section modulus.

• Shear Stress (( \tau )): [ \tau = \frac{V}{A} ] where (V) is shear force and (A) is cross-sectional area.

Typical Timber Property Ranges:

flowchart LR
    A[Select Timber] --> B[Confirm Species via IS 4970]
    B --> C[Control Moisture Content]
    C --> D[Inspect for Defects]
    D --> E[Perform Structural Design (IS 883)]
    E --> F[Apply Protection Measures]
    F --> G[Installation and Maintenance]

Note: For detailed mechanical design, refer to IS 883 and IS 1734.