Selection and Use of Various Types of Medium-Density Fibre Boards - Code of Practice
2004 Edition

Scope Overview: This section outlines the applicable grades and types of MDF materials (Clause 4.2, Table 1), referencing Indian Standards IS 707, IS 12406, and IS 14587. It defines the scope of usage in construction and manufacturing for furniture and interiors.

Reference Standards: Annex A includes a list of related Indian Standards, recommending users consult the most current editions.

Machine Saw Speed Calculation (Clause 9.1.2)

The rpm for circular saw machines is calculated as:

[ \text{rpm} = \frac{\text{Rim Speed} \times 60}{\pi \times \text{Saw Diameter}} ]

where rim speed is in meters per second and saw diameter in meters.

Table 1: Summary of Grades and Types of MDF

Saw Tooth Geometry (Figures 9 & 10)

• Clearance angle: Angle between tooth face and MDF surface
• Sharpness angle: Tooth tip angle enhancing cutting efficiency

flowchart LR
    RS[Rim Speed (m/s)] --> RPM[Calculate rpm]
    SD[Saw Diameter (m)] --> RPM
    RPM --> Formula[rpm = (Rim Speed × 60) / (π × Diameter)]

Refer to IS 15512 Table 1 and Clause 9.1.2 for comprehensive grading and cutting parameters.

Essential References:

• Definitions and related provisions are based on IS 707 (Wood-based panels), IS 12406 (Medium-Density Fibreboards), and IS 14587 (Prelaminated MDF boards).

Grades and Types:

• Detailed in Table 1 (Clause 4.2), describing various MDF grades and types.

Screw Specifications (Clause 7.2):

• Use fully threaded parallel shank screws conforming to IS 7170 (see Fig. 1).
• Cross recessed head screws per IS 7478 are permissible.
• Screw sizes and board thickness compatibility are provided in Table 2.

Table 2: Board Thickness vs. Appropriate Screw Sizes

Fig. 1: Illustration of Fully Threaded Parallel Shank Screw (IS 7170)

flowchart LR
    BT[Board Thickness] --> SS{Select Screw Size}
    SS -->|6 mm| NoS[No Suitable Screw]
    SS -->|8-10 mm| S29[ST 2.9]
    SS -->|12-15 mm| S29S35[ST 2.9, ST 3.5]
    SS -->|18-40 mm| AllScrews[ST 2.9, 3.5, 4.2, 4.8]

Please verify the latest standard editions for updates before application.

Definitions Referenced:

• IS 707 (Wood-based panels)
• IS 12406 (General purpose MDF boards)
• IS 14587 (Prelaminated MDF boards)

Grades and Types According to Clause 4.2 and Table 1

Critical Parameters:

• Environmental Hazard Classes:

  • Class 1: Relative Humidity (RH) ≤ 70%, moisture content ≤ 15%
  • Class 2: RH > 70%, moisture content ≤ 20%

• Thickness and Creep Considerations (Clause 5.2):

  • Painted or thinly laminated MDF may experience up to 50% increase in long-term deflection due to creep.
  • Double-sided decorative laminate reduces creep and deflection.

• Adhesive Usage:

  • Use adhesives compatible with wood substrates.
  • Selection depends on surface treatment, application method, flammability, and pressing conditions.

Summary Diagram: MDF Types and Hazard Classes

graph TD
  MDF[MDF Boards] --> Gen[General Purpose]
  MDF --> Pre[Prelaminated]
  Gen --> G1[Grade I (SBG I) - IS 12406]
  Gen --> G2[Grade II (SBG II) - IS 12406]
  Pre --> P1[Grade I - IS 14587]
  Pre --> P2[Grade II - IS 14587]
  classDef hazard fill:#f9f,stroke:#333,stroke-width:2px;
  H1[Hazard Class 1: RH ≤ 70%, Moisture ≤ 15%]:::hazard
  H2[Hazard Class 2: RH > 70%, Moisture ≤ 20%]:::hazard

Available Grades (Clause 4.2, Table 1):

Grade Selection (Clause 4.3):

• Hazard Class 1: RH ≤ 70%, moisture ≤ 15%
• Hazard Class 2: RH > 70%, moisture ≤ 20%

Prefer Grade I MDF for environments with higher humidity or demanding conditions.

Thickness Selection (Clause 5.2):

• MDF with thin laminates or paint may show up to 50% increased creep deflection.
• Double-sided decorative laminates mitigate creep and initial deflection.

Adhesive Guidelines:

• Use adhesives suitable for wood substrates.
• Selection based on surface conditions, application technique, flammability, and pressing parameters.

Grade Selection Summary Table

flowchart LR
  RH[Environment RH] -->|≤ 70%| HC1[Hazard Class 1]
  RH -->|> 70%| HC2[Hazard Class 2]
  HC1 --> G1[Use Grade I or II MDF]
  HC2 --> G2[Use Grade I MDF]

Grade I MDF is recommended for humid or challenging environments to ensure durability and minimize creep.

Thickness Calculation Formula (Clause 5.1):

For a simply supported shelf, the required thickness ( t ) is given by:

[ t = \sqrt[5]{\frac{32 \times E \times b \times d^5}{W \times L^3 \times 9.81}} ]

Where:

• ( t ): Thickness of shelf (mm)
• ( E ): Modulus of elasticity (N/mm²)
• ( b ): Shelf width (mm)
• ( d ): Allowable center deflection (mm)
• ( W ): Total uniformly distributed load (kg)
• ( L ): Span length between supports (mm)

Thickness Selection Notes (Clause 5.2):

• Painted or thinly laminated MDF may experience up to 50% additional deflection due to creep.
• Double-sided decorative laminates reduce creep effects and initial deflection.
• Grade and thickness should be chosen based on hazard class and environmental humidity.

Table 2: Board Thickness vs Screw Size (Clause 7.2)

Grades and Types Summary (Clause 4.2)

In summary, calculate thickness using the formula considering load and span, and select grade and thickness according to environmental hazard classifications.

Adhesive Guidance and Bonding Procedures (IS 15512)

Adhesive Selection:

• Use adhesives compatible with wood-based substrates.
• Consider surface properties of MDF and bonding materials.
• Application methods include hand application, glue rollers, or spraying.
• Take into account flammability and pressing conditions (ambient or elevated temperatures).

Environmental Hazard Classes:

• Class 1: Relative Humidity ≤ 70%, MDF moisture content ≤ 15%
• Class 2: Relative Humidity > 70%, MDF moisture content ≤ 20%

Bonding Specifications

Screws for Bonded MDF (Clause 7.2)

• Screw length formula: Board thickness + 1.5 × surface thickness
• Drill pilot holes before screwing as per Table 3:

• Maintain minimum screw distances: 75 mm from edges and 25 mm from faces.
• Avoid screwing into MDF edges thinner than 12 mm.

flowchart TD
    SP[Surface Preparation] --> PU[Apply 2 coats polyurethane primer]
    PU --> AD[Apply PVAC Adhesive]
    AD --> LP[Lamination with 2-3 kg/cm² pressure]
    LP --> DR[Dry for 4-6 hours]
    DR --> EP[Edge protection using nails or tapes]

This ensures strong, durable bonding with optimal adhesive application and curing.

IS 15512: Hardware and Fastening Recommendations for MDF Panels

Screw and Nail Selection (Clause 7.2, Table 2)

• Use fully threaded parallel shank screws complying with IS 7170.
• Cross recessed head screws per IS 7478 are preferred.

Screw Length Calculation (Clause 1.5b)

[ \text{Screw length} = \text{Board thickness} + 1.5 \times \text{Surface thickness} ]

Pilot Hole Specifications (Clause 7.2c, Table 3)

• Always drill pilot holes before screwing.
• Avoid screwing into edges of MDF boards thinner than 12 mm.

Recommended Screw Placement (Clause 7.2d)

• Minimum distance from edge: 75 mm
• Minimum distance from face: 25 mm

For Repetitive Fixings (Clause 7.2e)

• Use plastic or metal sleeves to prevent damage from repeated screw removal.

Avoid

• Hammering screws into MDF
• Excessive tightening of screws

Summary Diagram: Hardware Fixing Procedure

graph TD
  A[Select Hardware Type] --> B{Is it a hinge?}
  B -- Yes --> C[Use Surface Mounted Hinges (e.g., spring, flap)]
  B -- No --> D[Use Recommended Screws or Nails]
  D --> E[Drill Pilot Holes as per Table 3]
  E --> F[Fix Screws with Correct Length]
  F --> G{Is Repeated Fixing Required?}
  G -- Yes --> H[Use Plastic/Metal Sleeves]
  G -- No --> I[Fix Directly]
  I --> J[Avoid Hammering and Over-tightening]

Ensures durability, proper fastening, and aesthetic appeal.

Guidelines for Handling and Storage of MDF (IS 15512)

Nailing Parameters (Clause 1.40):

• Maximum nail shank diameter: 1.40 mm
• Minimum distance from surface corners/edges: 25 mm
• Minimum distance from edges (board edges): 75 mm
• Minimum spacing between nails: 150 mm

Storage Recommendations (Clause 8):

• Store MDF boards horizontally on dry, firm bearers.
• Use polyethylene sheets or equivalent on damp floors to prevent moisture absorption.
• Bearer spacing:
  • For boards ≥ 15 mm thickness: maximum 800 mm center-to-center with at least 3 bearers.
  • For thinner boards: bearer spacing should not exceed 50 times the board thickness.
• Bearers in each stacked layer must be vertically aligned with those below.
• Maximum overhang of boards during stacking should not exceed 100 mm.
• Maintain relative humidity around 50% to keep MDF moisture content between 7-9%.
• Wrap pallets with plastic sheets if exposed to extreme moisture or dryness.
• Use scrap boards at least 18 mm thick as top and bottom covers during storage.

Bearer Spacing Table

Visual Flowchart for Stacking

flowchart TB
    A[Place MDF Sheets Horizontally] --> B[Position Dry Bearers ≤ 800 mm Apart]
    B --> C[Align Bearers Vertically in Each Layer]
    C --> D[Ensure Maximum Overhang ≤ 100 mm]
    D --> E[Cover Top and Bottom with ≥ 18 mm Thick Boards]
    E --> F[Maintain Storage RH Around 50%]

These practices protect MDF panels from deformation, moisture ingress, and damage during storage and handling.

Guidelines for Fabrication and Handling of MDF (IS 15512)

1. Nailing MDF (Clause 1.40)

• Maximum nail shank diameter: 1.40 mm.
• Maintain minimum distances:
  • Surface edges: ≥ 25 mm
  • Board edges: ≥ 75 mm
• Nail spacing should be ≥ 150 mm.

2. Storage and Handling (Clause 8)

• Store boards horizontally on dry bearers spaced:
  • ≤ 800 mm center-to-center for boards ≥ 15 mm thick (minimum 3 bearers).
  • 50 times the board thickness for thinner boards.
• Bearers must be vertically aligned in stacked layers.
• Maximum overhang of boards during stacking: 100 mm.
• Maintain relative humidity of about 50% to keep moisture content between 7-9%.
• Use polyethylene wrapping if exposure to dampness or dryness is anticipated.
• Utilize 18 mm thick scrap boards as top and bottom covers.

3. Adhesives and Bonding (Clause 9)

• Use adhesives suitable for wood substrates, considering surface, application method, flammability, and pressing conditions.
• Hazard Classes:
  • Class 1: RH ≤ 70%, moisture ≤ 15%
  • Class 2: RH > 70%, moisture ≤ 20%

4. Profiling MDF (Clause 9.2)

• Employ tungsten carbide cutting tools.
• Maintain cutter speed at or above 3600 rpm.
• Cutter angles:
  • Cutting angle between 10° and 20°.
  • Clearance angle between 20° and 22°.
• Round off sharp edges after profiling.

Bearer Spacing Table

Diagram: Stacking and Bearer Alignment

graph LR
A[Bottom Bearer] --> B[First MDF Layer]
B --> C[Second Bearer Layer (Vertically Aligned)]
C --> D[Second MDF Layer]

These procedures ensure MDF panels are processed and stored maintaining dimensional stability and surface quality.

Surface Finishing Requirements (Clause 10) - IS 15512

• The objective is to achieve desired aesthetics, durability, and color schemes.
• Common finishing methods include laminating, veneering, painting, polishing, and waxing, especially on visible surfaces.
• Surfaces not exposed to view must be sealed with polyurethane primer, paint, or polish, including edges.
• Follow recommendations on the number of coats provided by panel manufacturers.
• Decorative veneers require additional polishing or waxing for enhanced appearance.

Application of Finishing Coats (Clause 10.2.2)

• Refer to IS 2338 Parts 1 & 2 for comprehensive finishing procedures for wood and wood-based materials.
• Also consult IS 14587 for specifications on prelaminated MDF boards.

Surface Finishing Process Flow

flowchart TD
    A[Fabricate MDF Panel] --> B[Surface Preparation]
    B --> C{Type of Surface}
    C -->|Exposed| D[Apply 2 or More Coats: Paint/Polish]
    C -->|Unexposed| E[Apply Primer and Balance Coat]
    D --> F[Polish or Wax (if veneer)]
    E --> F
    F --> G[Final Inspection and Quality Assurance]

Adhering to these finishing guidelines ensures long-lasting, attractive surfaces on MDF products.

Key Indian Standards Referenced in IS 15512:

• IS 707: Plywood
• IS 12406: Medium-Density Fibreboard for General Use
• IS 14587: Specifications for Prelaminated MDF Boards
• IS 7170: Fully Threaded Parallel Shank Screws
• IS 7478: Cross Recessed Head Screws

Screw Size Selection Table (Table 2)

Fig. 1: Fully Threaded Parallel Shank Screw (IS 7170)

This annex serves as a reference guide to ensure all components and fasteners conform to recognized standards for safety and performance.

Composition of the Committee for IS 15512 Development

• The Wood and Other Lignocellulosic Products Sectional Committee (CED 20) is responsible for the standard's creation.
• Membership includes representatives from:
  • Indian Plywood Industries Research and Training Institute, Bangalore (Chair: Dr. C. N. Pandey)
  • All India Agro-Board Association, Pune
  • Building Materials & Technology Promotion Council, New Delhi
  • Central Building Research Institute, Roorkee
  • Directorate General of Quality Assurance (Ministry of Defence), Kanpur
  • Federation of Indian Plywood & Panel Industry, New Delhi
  • Various plywood manufacturers and research bodies across India

Supporting Specifications and Tables

• Finishing coat application (Clause 10.2.2): Two coats on exposed surfaces, balance coat on unexposed.
• Screw selection (Clause 7.2) summarized:

• Screws must be fully threaded parallel shank types per IS 7170, with cross recessed heads per IS 7478.

Committee Structure Diagram

graph TD
A[Wood & Lignocellulosic Products Committee] --> B[Chair: Dr. C.N. Pandey]
A --> C[Research Institutes]
A --> D[Government Agencies]
A --> E[Industry Representatives]
C --> F[IPIRTI, Bangalore]
C --> G[Forest Research Institute]
D --> H[Ministry of Defence]
D --> I[Central Public Works Department]
E --> J[Plywood Manufacturers]
E --> K[Coir Board]

This committee ensures comprehensive expertise and multi-sector collaboration for standard formulation.