timber defects. knots a hard cross grain mass of wood that is formed in the trunk of a tree where a...
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Timber Defects
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KnotsA hard cross grain mass of wood that is formed in the trunk of a tree where a branch grows.
Knots spoil the appearance and reduce the strength properties of wood. It also raises the seasoning defects and makes difficulties during wood working.
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Gum Pockets
Cracks in the timber which contain gum.
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Shakes
• A Shake is a partial or complete separation between the adjoining layers.
• Maybe caused by growing stresses in the tree or by the impact of the tree with the ground during felling
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Cup Sahkes
• Separation of wood fibres around the growth rings
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Heart Shake
• A split which extends from the pith
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Felling Shake
• Are fractures across the grain in which the fibres are broken transversely or are crushed by compression.
• Various causes are suggested, such as felling across obstructions, and failure inside the growing tree caused by
high winds.
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Cupping
• A concave curvature across the face of a board.• Curvature is usually away from the centre of the tree.
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Spring
• Curvature along the edge of the board.
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Bow
• Curvature along the wide face of the board in the direction of the length.
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Twist
• A spiral distortion along the length of a board.• Also known as wind.
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Wane
• Edges or corners of sections of timber that encroach into the area of the bark.
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Splits & Checks
• A split is a longitudinal crack which extends through the board, usually on the end
• A check is a longitudinal crack that does not extend all the way through the board.