The IS 1708 Parts 1-18 (1986) delineate uniform procedures for assessing small, clear timber samples to identify their physical and mechanical attributes. This extensive guideline addresses tests such as specific gravity, bending strength under static and impact loads, compressive and tensile strength aligned and perpendicular to the grain, hardness, nail and screw withdrawal resistance, brittleness, and torsional strength, making it invaluable for engineers, researchers, and quality assurance personnel working with timber.
Overview
The IS 1708 Parts 1-18 (1986) delineate uniform procedures for assessing small, clear timber samples to identify their physical and mechanical attributes. This extensive guideline addresses tests such as specific gravity, bending strength under static and impact loads, compressive and tensile strength aligned and perpendicular to the grain, hardness, nail and screw withdrawal resistance, brittleness, and torsional strength, making it invaluable for engineers, researchers, and quality assurance personnel working with timber.
Audience
Contents
Structure
Frequently Asked
Per IS 1708, test specimens must be free from defects with grain slope not exceeding 1:20 relative to longitudinal edges. Specimens are prepared in two standard cross-sections: 5 x 5 cm or 2 x 2 cm, with lengths varying by test type (e.g., 6 cm to 100 cm for 5 x 5 cm). When 5 x 5 cm pieces are unavailable, multiple 2 x 2 cm sticks may be glued to achieve a minimum 4 x 4 cm cross-section with aligned grain. For shear tests, specimens are notched at one end to promote failure along radial or tangential surfaces. Ends must be cut perpendicular to length, ensuring uniformity and reproducibility.
According to IS 1708 Part 2, specific gravity is calculated by dividing the specimen's weight (W1) by its volume (V1) at the test condition. To adjust for moisture content (m%), the value is multiplied by 100/(100 + m) to obtain the standard specific gravity for green specimens. Oven-dry specific gravity is computed by dividing the oven-dry weight (W0) by the oven-dry volume (V0). These calculations provide consistent density measurements accounting for moisture variations.
For static bending tests, IS 1708 specifies that the testing machine's movable head advances at controlled rates depending on specimen size, commonly 2.5 mm/min for 5 x 5 x 75 cm samples and 1.0 mm/min for 2 x 2 x 30 cm specimens. Alternative rates such as 3 mm/min or 0.6 mm/min may be applied depending on the test part. Impact bending tests utilize controlled impact energy via drop weights or pendulum devices rather than displacement rates, focusing on velocity and energy delivered.
IS 1708 Parts 15 and 16 describe nail and screw holding power as the maximum load required to extract these fasteners from timber samples. Nails used are typically 50 mm long with 2.5 mm shank diameter, bright galvanized with diamond points and plain heads. The test involves securely gripping the timber specimen and applying a tensile load to pull out the fastener, measuring maximum pull-out loads on radial, tangential, and end grain surfaces. The average of radial and tangential results defines the side holding power. Tests are performed on green wood immediately and after drying, as well as on dry timber at 12% moisture.
IS 1708 recommends cutting specimens close to failure points immediately after mechanical testing and preventing moisture loss by wiping dry and sealing ends with hot paraffin. Specimens should be air-conditioned at ambient temperature with periodic weighing and measurement until uniform moisture content near 12% is attained. Moisture content is calculated using the difference between specimen weight at testing and oven-dry weight, ensuring consistent moisture conditions critical for reliable mechanical property assessment.
Ask AI about any clause, requirement, or provision in IS 1708 PART 1 18. Get instant, clause-cited responses powered by our indexed library.
Free tier includes 150 queries (50 AI + 100 Reference) · No credit card required