Different types of defects That appears in Timber
Defects in timber are normally caused by changing climatic conditions. Some important defects and diseases are :
- Star Shakes: These are radial splits which are starting from the bark, running in the planes of medullary rays, towards the center of the tree. These are caused due to rupture of tissues as a result of climatic disturbance such as severe frost or fierce heat of the sun during the growth of the tree.
2. Heart shakes: These are radial splits running from pith towards sap wood in the direction of the medullary rays. This defect is develops in matured trees due to shrinkage of heart wood or if tree is cut and kept unbarked for a long time.
3. Cup shakes or Ring shakes: These are curved splits between annual rings, which separate whole or part of one annual ring from the other. These are caused due to excessive bending of a growing tree during a cyclonic weather.
4. Bow: It develops in non-coniferous timber and may develops after felling tree or during conversion and seasoning. Converted timber shrinks, bends in the direction of length.
5. Upsets: These are nothing but crippling or buckling of fibres. These are caused by the crushing of fibres when the trunk is felled over a rocky surface.
6. Rind Galls: These are rarely found in a tree. These are typical curved swellings formed upon the trunk of a tree by successive layers of sap wood. The timber in this part is very weak and not durable.
7. Knot: These are dark and hard pieces which are the part of branch incorporated in the body of a tree. These are the sources of weakness in a timber. When knot is intact with surrounding wood, free from any defect, it is called live knot. When it is not held firmly it is called as dead knot. Timbers containing large dead knots are rejected as they are poorer in strength.
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