DEFECTS IN TIMBER

DEFECTS IN TIMBER

IN a timber have a many types of defects.

• Star Shakes 
• Cup shakes or Ring shakes
• Heart shakes
• Bow
• Rind Galls
• Upset
• Knots

Star Shakes

   These are radial splits which are starting from the bark, running in the pales of medullary rays, towards the centre of the tree of shown. These are caused due to rupture of tissues as a result of climatic disturbance such as severs frost or fierce heat of the sun during the growth of the tree.

Cup Shakes

 These are curved splits between annual rings, which separate whole or part of one annual ring from the other, as shown in fig.

These are caused due to excessive bending of a growing tree during a cyclonic weather. 

Heart shakes

These are radial splits running from toward sap wood in the dirtion of the medullary rays as show in fig. This defect is develops in matured trees due to shrinkage of heart wood or if tree is cut and keep unbarked for a long time.

Bow 

 It develops in non-coniferous timber and may develope after felling tree or during conversion and seasoning. Converted timber shrinks, bends in the direction of length as shown fig.

Ring Galls

 These are rarely found in a tree. these are typical curved swelling formed upon the trunk of a tree by successive layer of sap wood. The timber in this part is very weak and not durable see fig.

Upsets

 These are nothing but crippling or bucking of fibers. These are caused by the crushing of fibers when the trunk is felled over a rocy surface. See fig.

 Knots

 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 as dead knot. Timber containing large dead knots are rejected as they are poorer in strength.