Hello friends in this article I am going to say you about “Describe the different type of defect of timber”. So, to get full knowledge read carefully one by one.
The different type of defect of timber are given below.
- Natural Defects
- Artificial Defects
1) Natural defect:- This group includes all those defect that are developed on a tree during it’s growth. Their development, therefore, can not be generally controlled by man. Most common natural defects are knots, shakes, Rind galls, Cross grain etc.
Further Natural defects are divided into following types:-
a) Shakes- The main reason of shakes are, shrinkage of aging of tree, Due to movement cause by wind action in the growing tree and freezing the sap in the cells.
Shakes is further subdiveded into following types:-
- Heart shakes.
- Star shakes.
- Cup shakes.
b) Knots- A knots marks the position of growth of a branch on tree. Knots show great variation in their size, shape and stage of development. They make the workability of timber quite difficult. Some types are as; live knots, Dead knots,
Encased knots, Edge knots, Face knot.
Further Knots are subdevided into following types:-
- live knots.
- Dead knots.
- Edge knots.
- Face knots.
c) Rind galls – over growth of timber of some part of tree may result in same typical defects. Rind galls are quite common. It’s high thickness, enlarged wood cover developed over and injured part of the tree.
d) Cross grain:- Fibers of a wood in normal tree are usually parallel to the axis growth. This structure is called straight grain. In some cases, however, these Fibers are not straight they make angle or slope with the axis of tree. This structure is called Cross grain. Compressive and tensile strength are related with it.
2) Artificial defects:- Such defects are developed in the timber after it’s feeling and conversion to different sizes.
The different types of Attificial defects are given below:-
a) Warps:- It is defined as deformation in the original plane surface of a board cut from the timber. This is also attributed to unequal shrinkage. It is most commonly developed in those boards that are cut from Green or unseasoned timber.
b) Bow: It is a curvature of the board developed in a longitudinal direction.
c) Cupping: It is distribution developed transversely length of board remain unaffected but the width suffers distortion.
d) Twisting: It is complex type of distortion in which one end of the board is so much distorted that is comes to lie a over a part of the other edge.
e) Checks- These are cracks developing longitudinally in the logs after their feeling. These cracks are after cutting across the annual ring of the log. When log of wood remains exposed to atmosphere only one side, the upper side will lose more moisture then the underside. The develop of such crack could be avoided by changing the position of the timber log at regular intervals. This will insure uniform shrinkage which will not allow the checks to developed.
So friends I hope this article on different types of defects in timber remains helpful for you.