The standard outlines the classification, allowable imperfections, sizing, and evaluation techniques for non-coniferous timber logs primarily intended for conversion into sawn wood. It provides grading guidelines based on defect thresholds and explains methods for measuring log dimensions and identifying common defects such as knots, splits, and decay. This specification is vital for producers, traders, and end-users to maintain consistency and quality in non-coniferous logs throughout India.
Overview
The standard outlines the classification, allowable imperfections, sizing, and evaluation techniques for non-coniferous timber logs primarily intended for conversion into sawn wood. It provides grading guidelines based on defect thresholds and explains methods for measuring log dimensions and identifying common defects such as knots, splits, and decay. This specification is vital for producers, traders, and end-users to maintain consistency and quality in non-coniferous logs throughout India.
Audience
Contents
Structure
This section defines the applicability of the standard, emphasizing that buyers may specify particular options during ordering as per Clauses 7.1 and 8.6.3. It highlights key clauses governing selection flexibility, measurement protocols, and normative references to other relevant standards. Rounding rules for test results follow IS 2:1960, ensuring consistency. Details on the technical committee and amendments are provided in Annex C, with BIS contact points listed for support.
IS 7308 incorporates references to other Indian Standards essential for compliance, including specifications for logs used in plywood, matches, sliced veneers, and artificial limbs. Users must consult the latest editions of these documents. The section also reiterates the application of IS 2:1960 for rounding numerical values and notes BIS copyright and reproduction policies.
Key definitions are drawn from IS 707 concerning seasoned timber and IS 1150 for timber species nomenclature, with Annexes A and B listing species covered. The standard describes the method for adjusting permissible defect values for logs differing from the 2.5 m reference length, ensuring proportional defect limits relative to log size.
Non-coniferous logs are grouped into three grades based on cumulative permissible defects: Grade I (highest quality), Grade II (moderate quality), and Grade III (lowest quality with more defects permitted). The classification supports suitability for conversion into sawn timber, with defect limits quantified according to Clause 8. The section also cross-references related IS standards for specific log types.
This clause enables purchasers to select options tailored to their needs at the time of order. It specifies that final test and analysis results must be rounded following IS 2:1960 rules, maintaining the prescribed significant figures. Definitions from IS 707 support this standard, and compliance is verified using the final rounded values.
Minimum dimensions for logs are established as 2.5 meters in length and a mean girth of 100 cm. Measurement guidance includes rounding lengths down to the nearest 0.05 meters and calculating volume using the quarter-girth formula. References to other IS standards for logs intended for various applications are also provided.
This section details the measurement of log length as the shortest distance between ends and girth as the mean circumference, with instructions to trim buttresses and knots flush and ensure ends are cut perpendicular to the log axis. Volume estimation techniques are described, including formulas relevant to cylindrical logs.
Permissible defects are quantified per 2.5 m log segments, with maximum allowable deviations and defect units defined for each grade. The standard mandates evaluation of defects such as knots, shakes, splits, and rot according to IS 3364 (Part 1). For logs with lengths other than 2.5 m, permissible defect units are adjusted proportionally.
Volume calculation employs the quarter-girth formula, utilizing the measured length and girth (converted to meters). Length measurement is rounded down appropriately, and volume results are expressed to three decimal places. Minimum dimension requirements ensure the accuracy of volume estimations.
Logs are subject to limits on twist (maximum 10° slope) and must have their ends coated at least 150 mm in length according to IS 1141 to prevent moisture loss. Debarked logs require immediate prophylactic treatment post-inspection per IS 401 to protect against fungal and insect damage.
Each log must be clearly marked with species abbreviation, supplier's code and year, dimensions, and grade symbol (Square for Grade I, Triangle for Grade II, Circle for Grade III). Optionally, the BIS Standard Mark may be applied to certify compliance. Numerical rounding follows IS 2:1960.
Annex C lists members of the technical committee responsible for the standard's development, representing manufacturers, users, government, and academia. The section reiterates purchaser options and rounding rules, and provides BIS headquarters and regional office contact information.
Frequently Asked
The permissible defect units per 2.5-meter log segment vary by grade: Grade I permits up to 3 units, Grade II allows up to 6, and Grade III permits up to 9 units. Additionally, only a certain percentage of logs with permissible defects are allowed—10% for Grade I, 20% for Grade II, and 30% for Grade III. Logs must be free from serious defects like hollow heart, insect attack, and decay, ensuring suitability for sawn timber production.
For irregularly shaped logs, length is measured as the shortest distance between the two ends and rounded down to the nearest 0.05 meters. Girth is measured at three points—near each end and at mid-length—avoiding bark or protrusions. The mean girth is calculated by averaging these three measurements, expressed in centimeters rounded down to the nearest whole number. Volume is then calculated using the quarter-girth formula.
Defects such as shakes, knots, splits, and decay are acceptable within specified limits and are quantified using a "unit of defect" system according to IS 3364 (Part 1). For example, shakes up to 250 mm in length are allowed. Each defect's severity is assigned numeric values, enabling cumulative assessment to determine log grading.
Post-inspection, logs must have their ends coated for at least 150 mm following IS 1141 to prevent moisture loss and cracking. Additionally, all debarked logs require immediate prophylactic treatment as per IS 401, which involves applying preservatives to protect against fungal decay and insect infestation, ensuring the logs' durability prior to processing.
Checks are surface cracks typically less than 50 mm long and 2 mm wide, often ignored if not frequent. Larger checks exceeding 200 mm in length and 2 mm in width are classified as shakes. Shakes are internal separations along the grain permitted up to 250 mm in length. Splits are more extensive separations penetrating through the wood section. Defect limits are set per 2.5 m log length, varying by grade.
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