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IS 9576:1980 is the Indian Standard (BIS) for guide for mill sawing of timber. This standard serves as a guide for the mill sawing of timber, outlining principles for the efficient and economical conversion of logs into lumber. It covers different sawing patterns like plain and quarter sawing, considerations for log characteristics, guidance on saw blades, and essential safety precautions for sawmill operations.
! Quarter sawing produces more dimensionally stable timber with better grain appearance but results in more wastage compared to plain sawing.
! Always inspect logs for embedded foreign objects like nails, stones, or metal before sawing to prevent severe damage to the saw blade and ensure operator safety.
! Proper maintenance, sharpening, and tensioning of saw blades are critical for achieving dimensional accuracy, good surface finish, and maximizing timber yield.
Specifies dimensional tolerances for sawn softwood, which relates to the 'allowances' section of IS 9576.
EN 1313-2:2000CEN (European Committee for Standardization)
MediumCurrent
Round and sawn timber - Permitted deviations and preferred sizes - Part 2: Hardwood sawn timber
Defines dimensional tolerances and preferred sizes for hardwood, aligning with the IS code's guidance on calculating sawing allowances.
NHLA Rules BookNHLA (National Hardwood Lumber Association), USA
HighCurrent
Rules for the Measurement and Inspection of Hardwood and Cypress
Provides grading rules that are the primary driver for sawing patterns and decisions for North American hardwoods to maximize value.
ISO 24294:2013ISO (International Organization for Standardization)
LowCurrent
Wood — Sawn timber — Appearance grading of hardwoods
Defines terminology for sawing patterns (e.g., flat sawn, quarter sawn) which is a core topic of IS 9576.
Key Differences
≠IS 9576 is a prescriptive 'guide' on the sawing process, whereas modern standards like ISO 3179 or EN 1313-2 focus on the final product's dimensional tolerances, leaving the process to the manufacturer.
≠The Indian standard is general for timbers found in India, while international standards are often specific to species groups (e.g., European hardwoods, North American hardwoods, conifers).
≠IS 9576 provides a methodology for calculating sawing allowances for shrinkage and planing. In contrast, standards like ISO 3179 specify fixed permissible deviation limits for given dimensions and moisture content.
≠IS 9576 includes guidance on saw characteristics like kerf and tooth shape, which is now considered equipment-specific and is generally absent from international product standards for sawn timber.
Key Similarities
≈Both the IS code and international standards/practices (e.g., defined in ISO 24294) recognize fundamental sawing patterns like plain sawing (flat-sawn) and quarter sawing and their effect on grain and stability.
≈The principle of 'oversizing' timber during initial sawing to account for shrinkage during drying and material loss from planing is a fundamental concept shared by IS 9576 and implied in the tolerance systems of international standards.
≈The ultimate objective in both IS 9576 and practices guided by international standards (like NHLA rules) is to maximize the yield and/or value of usable timber from a log by selecting an appropriate sawing method.
≈The importance of preparing the log before sawing (e.g., cleaning, debarking) is mentioned in the IS code and is a universally accepted best practice in sawmilling globally to ensure quality and protect equipment.
Parameter Comparison
Parameter
IS Value
International
Source
Quarter Sawing Definition (Angle of growth rings to face)
Not less than 45°, preferably near 90°.
60° to 90° (Quarter sawn); 30° to 60° (Rift sawn).
ISO 24294:2013
Plain Sawing Definition (Angle of growth rings to face)
Less than 45°.
Less than 30° (Flat sawn).
ISO 24294:2013
Allowance for Saw Kerf
Generally 3 to 6 mm, depending on saw type.
Not specified in product standards; modern thin-kerf bandsaws are typically 1.5-2.5 mm.
General Sawmilling Practice
Planing Allowance (per face)
1.5 mm for thickness up to 50 mm; 3.0 mm for thickness over 50 mm.
Not standardized; general practice is similar (e.g., 1.5 - 3.0 mm), but left to manufacturer's process control.
General Sawmilling Practice
Dimensional Tolerance (Sawn Thickness/Width)
Provides a formula to calculate required green size, not a final tolerance.
For dimensions up to 100 mm: ±1 mm (at 20% moisture content).
ISO 3179:2013
Preferred Thicknesses (Hardwood)
Refers to other IS codes (e.g., IS 1331); does not list them directly.
What are the main methods of sawing timber covered in this guide?+
The primary methods are plain sawing (or flat sawing), quarter sawing, and rift sawing, each yielding different grain patterns and board characteristics (Clause 4).
Why is quarter sawing often preferred for high-quality furniture and flooring?+
It produces boards that are more dimensionally stable, less prone to warping and cupping, and feature an attractive vertical grain pattern (Clause 4.3).
What is 'saw kerf' and why is it important?+
Kerf is the width of material removed by the saw blade during a cut. Minimizing kerf by using thinner, well-maintained blades increases the overall yield of usable timber from a log (Clause 6).
What safety measure is emphasized before sawing a log?+
The log must be thoroughly inspected and cleaned of any dirt, grit, or foreign objects like metal to prevent blade damage and potential injury to the operator (Clause 7).