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Grading

Sorting Criteria. Structural grade. Appearance grade. Grading. Sorting of products into groups with similar characteristics and properties. Specify product by calling up a specific grade. Appearance Grading. Criterion for sort is appearance of timber surface.

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Grading

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  1. Sorting Criteria Structural grade Appearance grade Grading Sorting of products into groups with similar characteristics and properties Specify product by calling up a specific grade

  2. Appearance Grading Criterion for sort is appearance of timber surface • Classification of timber used for • furniture • joinery and architectural trim • decorative building products • Grading rules • knot size & frequency (location unimportant) • splits, cracks, checks (size and frequency) • colour, grain uniformity • utility - want, wane, cup, bow, spring, twist • Feature grade • makes a feature of natural characteristics eg knots

  3. AS 2858 Swd AS 2082 Hwd AS 4063 Structural Grading Methods • Structural grading is based on correlation between strength and a grading parameter • Visual stress grading - presence or absence of natural characteristics • Machine stress grading - stiffness on flat (minor axis MoE) • Proof grading - ability to take a proof load. Each piece passed through machine, bending applied at about characteristic strength level. Broken pieces fail - unbroken ones pass • Quality control - verification of grade properties by testing

  4. Stress Grade Deflection Timber Stress Grades • Structurally graded products need to be assigned properties for designers to use • limited number of grade descriptions • most versatile for sawn timber is F-grade system High Stress grade = High strength and stiffness

  5. Grade Markings • Structurally graded timbers carry a stamp or paint marking to signify the stress grade • Other relevant information may also be shown including: • Method of grading • The standard used for grading • Mill producer • Seasoned or unseasoned • Species

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