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TIMBER

TIMBER. 1. TIMBER: The wood which is suitable or fit for engineering construction or engineering purpose is called timber. 2. WOOD: The organic matter obtained from trees is called wood. LUMBER: The sawed wood meant for construction in the form of boards is called lumber.

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TIMBER

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  1. TIMBER 1

  2. TIMBER: The wood which is suitable or fit for engineering construction or engineering purpose is called timber. 2

  3. WOOD: The organic matter obtained from trees is called wood.

  4. LUMBER: The sawed wood meant for construction in the form of boards is called lumber.

  5. Structure of a Tree

  6. TYPES OF TREES:Trees are classified into two groups depending upon growth pattern.(1) Endogenous trees:The trees which grow inwards in longitudinal fibrous mass are called endogenous trees.

  7. (2) Exogenous tress : The trees which grow in out wards across horizontal section of stem are called exogenous trees. These trees are only fit for engineering construction. Exogenous trees are again subdivided in to two types.

  8. Conifers or Evergreen: • They give soft wood. • They have pointed leaves. Examples: • Deodar • Pine • Chir • Kail,etc

  9. Deciduous: • These have hard wood. • These have broad leaves. Examples: • Teak • Sal • Shisham, etc.

  10. Hardwood Trees

  11. Softwood Trees Developed by:Nadeem Asghar

  12. SEASONING OF TIMBER:As fresh timber which is obtained from trees contains about 30 to 40 % sap or moisture. This sap is very harmful for the life of a timber. Therefore, it is necessary to remove that sap by applying some special methods. All those methods which are used for removing the sap from timber are collectively termed as seasoning of timber.

  13. Advantages of seasoned timber: • It has reduced weight, • It is strong and durable, • It has resistance to decay or rot, • It takes high polish, • It is easier to work, • Its life is more.

  14. Types of Timber Seasoning: The main types of timber seasoning are as under. • Natural Seasoning, • Artificial Seasoning, (a) Kiln Seasoning, (b) Chemical Seasoning, (c) Electric Seasoning, (3) Water Seasoning,

  15. (1) Natural Seasoning: In the air seasoning or natural seasoning or natural drying, seasoning of timber, timber is dried by direct action of air, wind and sun. In this method, the timber logs are arranged one over the other, keeping some space or distance between them for air circulation of fresh air. Generally this type of seasoning requires few months to over a year, this is very slow process.

  16. (2) ARTIFICIAL SEASONING (a) Kiln Seasoning, (b) Chemical Seasoning, (c) Electric Seasoning, Developed by:G.S.Solangi

  17. (a) Kiln Seasoning: In kiln seasoning timber is placed in a chamber with some special heating arrangement. In this process one thing should be kept in mind that heating system should be under control, other wise timber will be crack or wrap. The time required for this seasoning is 3 to 12 days. This is quick process.

  18. Kiln Seasoning

  19. (b)Chemical Seasoning: In chemical seasoning carbon dioxide, ammonium carbonate or urea are used as agents for seasoning, those are applied in dry state, the inter surface of timber dries first than outer side. This ensures uniform seasoning. The time required for this seasoning is 30 to 40 days.

  20. (c) Electric Seasoning: In this method electric current is passed through the timber logs. The time required for this seasoning is 05 to 08 hours.

  21. Electric Seasoning Developed by:G.S.Solangi

  22. (3) Water Seasoning: In water seasoning, timber logs are kept immersed whole in the flowing water. The sap present in timber is washed away. After that logs are taken out from water and are kept in open air, so water present in timber would be dried by air. The time required for this type of seasoning is 2 to 4 weeks.

  23. USES OF TIMEBR: Timber is used in: 1.Building construction, 2.Construction of house posts, 3.Construction of beams, 4.Construction of rafters, 5.Construction of bridges, 6.Construction of piles, poles and railway sleepers, Continued--------

  24. For furniture making, • For light packing cases, • For high packing cases (for machinery and similar stores), • For manufacturing of agricultural implements, • For making toys, etc, • For manufacturing of veneers and ply woods.

  25. VENEER: Thin sheet of uniform thickness of wood is called veneer. • PLYWOOD: Veneers used for making plywood are known as plies and ply wood is made by gluing together plies in odd numbers. Gluing is done under pressure.

  26. DEFECTS IN TIMBER: Most common defects in timber are: • Heart Shakes • Star Shakes • Cup Shakes • Radial Shakes • Rind Galls • Wind Cracks • Knots • Dead Wood

  27. (1) Heart Shakes: These are splits occurring in the centre of the tree and running from the pith (inner most part) to wards the sap wood from the medullary (vascular tissues) rays. In some timbers, these splits are hardly visible and in some timbers these are quite permanent. Heart shakes are caused due to shrinkage of interior parts due to age. A heart shake straight across the trunk is not a serious defect.

  28. Heart Shakes

  29. Medullary Rays: These are thin horizontal veins radiating from the pith to wards the bark. These carry sap from outer side to inner side.

  30. (2) Star Shakes: These are splits which radiate from the centre of the timber or from the bark (outer side), running in the planes of medullary rays. These occur due to severe frost or scorching heat of the sun.

  31. (3) Cup Shakes: These are curved splits which separate the whole or part of one annual ring from an other. These are caused due to the unequal growth of the timber.

  32. Cup Shakes

  33. (4) Radial Shakes: These are similar to the star shakes and occur in felled timber when exposed to the sun during seasoning. Radial shakes are generally irregular, fine and numerous. In this many splits are appeared.

  34. Radial Shakes

  35. Radial Shakes

  36. (5) Rind Galls: These are typical enlarged swellings and occur due to branches cut-off.

  37. Rind Galls

  38. Rind Galls

  39. (6) Wind Cracks: These are shakes or splits on the sides of a bark of timber due to shrinkage of exterior surface exposed to atmospheric influence.

  40. Wind Cracks

  41. (7) Knots: These are the roots of the small branches of the tree. These are not harmful.

  42. Knots

  43. (8) Dead Wood: It is the deficient in strength and weight and is the result of trees being felled after maturity.

  44. Dead Wood

  45. DETERIORATION OF TIMBER (OR) DECAY OF TIMBER:

  46. DETERIORATION OF TIMBER (OR) DECAY OF TIMBER: There are so many agencies which may cause decay of timber. But there are three main harmful agencies which cause timber decay.

  47. (1) Decay or Rot: Decay or rot of timber is the result of the activity of various bacterias and fungi, which utilize various portions of timber as food; they require both oxygen and excess moisture. Hence timber having moisture content below 25 % will not rot easily.

  48. (2) Insects: There are so many insects which attack the wood, out of them termites (white ants) are the main insects which are very dangerous for timber. Termites of one class live under ground and eat wood and forms tubes or tunnels inside it.

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