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TIMBER.ppt

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TIMBER.ppt

  1. 1.  Wood suitable for building or other engineering works is called timber  When it forms a part of a living tree, it is called standing timber  When the tree has been felled, it is called rough timber  When it has been sawn to various market forms such as beams, battens, planks etc, it is called converted timber
  2. 2. Classification of Trees Trees can be divied into the following groups  Endogenous  Exogenous
  3. 3. ENDOGENOUS:  Trees which grows inward in a longitudinal fibrous mass, such as canes, bamboo, palms etc EXOGENOUS:  Trees which grows outward from the centre in approximate concentric rings across the longitudinal section of the stem. Each ring representing a layer deposited every year. Extensively used in engineering works.
  4. 4. LOCAL TIMBER  Types of Local Timber  Hardwood  Heavy Hardwood  Medium Hardwood  Leightweight harwood  Softwood
  5. 5. Heavy Hardwood Medium Hardwood
  6. 6. Lightweight Hardwood Softwood
  7. 7. Classification of Wood- Based Aspects of Botany, Density, Durability and Strength.
  8. 8. Group Name Density Durability and Strenght Heavy Hardwood Gred A Cengal Balau/ Selayan batu Kekatong Merbau Resak Tembusu 993kg/m3 1027kg/m3 847kg/m3 9.979N/mm2 11.38N/mm2 9.17N/mm2 4.9-11.45N/mm2 8.00N/mm2
  9. 9. Group Name Density Durability and Strenght Medium Hardwood Gred B Kempas Keruing Kapur Tualang 926kg/m3 926kg/m3 791kg/m3 875kg/m3 7.52N/mm2 4.34-9.17N/mm2 6.74N/mm2 8.0N/mm2
  10. 10. Group Name Density Durability and Strenght Lightweight Hardwood Gred C Nyatuh Jelutung Meranti Ramin Sepetir Kayu getah 758kg/m3 707kg/m3 657kg/m3 707kg/m3 2.65N/mm2 3.38N/mm2 5.93N/mm2 4.69N/mm2
  11. 11. Group Name Density Durability and Strenght Softwood Gred D Damar minyak
  12. 12. Standard-Size Wood Production Process No. Name size 1. 2. 3. 4. 5. 6. 7. Timber Column Beam Plank Batten Small Batten Strip board Pieces of wood from the trees or branches that are not sawn. 100 mm x 100 mm - 150 mm x 150 mm Thickness> 100 mm x width> 150 mm Thickness 12 mm - 37 mm x width> 150 mm Thickness 37 mm - 100 mm <150 mm Thickness 20 mm - 37 mm x 25 mm - 75 mm Thickness <20 mm x width <100 mm
  13. 13. MATED OF SAWING TIMBER
  14. 14. Procedure for Drying / Seasoning of Wood  The process of removal of moisture content from wood so as to make it useful for construction and other uses  Wood must be dried up moisture content less than 15% then suitable for use in construction work  The wood drying process is a step that must be done before the wood can be used.
  15. 15. The purpose of drying  increase the strength, durable and with good work.  reduce the likelihood of broken wood, contracting and warping..  prevent the wood from insects and fungi.  weight, cost-effective delivery.  More easy to preserving, painting and polishing.  making it easier to burn, if used as firewood.
  16. 16. Naturally Drying Methods ( Pengeringan secara semulajadi )  The traditional method of seasoning timber was to stack it in air and let the heat of the atmosphere and the natural air movement around the stacked timber removes the moisture. The process has undergone a number of refinements over the years that have made it more efficient and reduced the quantity of wood that was damaged by drying too quickly near the ends in air seasoning.
  17. 17.  The basic principle is to stack the timber so that plenty of air can circulate around each piece. The timber is stacked with wide spaces between each piece horizontally, and with strips of wood between each layer ensuring that there is a vertical separation too.  Air can then circulate around and through the stack, to slowly remove moisture. In some cases, weights can be placed on top of the stacks to prevent warping of the timber as it dries.
  18. 18. Kiln Drying Methods
  19. 19.  Kiln drying of lumber is perhaps the most effective and economical method available. Drying rates in a kiln can be carefully controlled and defect losses reduced to a minimum. Length of drying time is also greatly reduced and is predictable so that dry lumber inventories can often be reduced. Where staining is a problem, kiln drying is often the only reasonable method that can be used unless chemical dips are employed.
  20. 20. WOOD PRESERVATION Protecting products of timber from deterioration( fungi) decomposition or damage due to pest attacks Wood must have the following characteristics before preservatives are applied to it:  Wood must be well seasoned  Wood must be cut to size before applying preservatives
  21. 21. There are 3 main classeses of preservatives  Oily substances insoluble in water  Water – soluble salts  Salts carried in volatile solvent other than water
  22. 22. Methods of Applying Wood Preservatives Painting & Dipping  Simplest method  Preservatives applied by mean of brush (several times)  Timber can also be immersed in tank full of liquid (preservative)  Penetration should hardly exceed (1/16 inch)  Duration of immersion and temperature of preservative solution ►increased ►to increase penetration
  23. 23. Pressure Process(Full Cell Process)  A higher degree of penetration can be obtained by forcing the preservative into the wood  Timber placed inside a chamber  Air drawn out to create a vacuum  Thus the cells are completely (almost) empty to receive the preservative  Preservative material may be creosote oil or zinc chloride  Preservatives pumped under a pressure of 100 to 200 psi at 120oF  The excess preservative is removed by creating a low vacuum  Timber preserved by this method are used in piles in saltish water, poles, sleeper
  24. 24.  The Empty Cell Process  Similar to the full cell process but no initial vacuum is created  No attempt is made to remove the air from the cells  The preservatives applied under a pressure of 200 psi  The excess preservatives drains away  A deeper penetration of preservatives ►achieved
  25. 25. Wood defects:  Defects in wood can be broadly classified into two categories which are as follows: (A) NATURAL DEFECTS (Knots, Shakes, Cross grain, Compression) (B) OTHER THAN NATURAL DEFECTS ( External Factors )
  26. 26.  Definition of Natural Defects Natural defects are defects that occur within the growing tree and which can infl uence the strength and visual appearance of the surface of the timber. They are sometimes referred to as structural defects. Most structural or natural defects have little effect on the growing tree, but they can degrade the timber cut from it. Not all trees are suitable for structural use and those that are must conform to certainquality checks before it is acceptable for use in the building industry.
  27. 27. Structural defects  Knots.  Shakes.  Waney edge.  Encased bark.  Growth rate.  Resin pockets. There are other defects, which will effect the use and acceptability of timber. These defects are usually the result of incorrect seasoning methods or fungal and insect attack.
  28. 28.  Knots Knots are formed as a result of the tree’s habit of forming branches. All branches are an integral part of the trunk of the tree, and when the tree is cut and converted into timber, the branches are exposed on the faces of the timber. There are two kinds of knots:  Live knots.  Dead knots.
  29. 29.  Live knots Live knots are knots which are bonded into the surrounding wood. They are tightly encased and do not contain any rot or dead wood.  Dead knots Dead knots are knots which separated from the surrounding wood by the bark of the branch which once protected it. They are usually the result of damaged branches which have died and become encased within the trunk over the years. Very often some of these knots become loose in their sockets and are known as ‘loose dead knots’. These types of knots are a potential hazard when machining timber as they often disintegrated and fl y out of the machine, sometimes causing injury to the eyes.
  30. 30.  Shakes Shakes are large cracks (a parting of the wood tissue) in the log caused by uneven stresses being set up, which may increase as the timber dries. Shakes follow the two main directions of weakness in the timber:  Between the growth rings.  Along the line of the rays. Shakes occur in:  The growing tree.  At the time of felling.  During drying or seasoning.
  31. 31. There are two main types of shakes.  Heart or star shake.  Ring or cup shake.  Heart shake Wood tissue separates due to uneven stress forming a crack.  Star shake This occurs where several shakes radiate from the centre region.  Ring or cup shake This type of shake follows the line of the growth ring. The split occurs between two growthring and is the result of uncontrolled seasoning.
  32. 32.  External Factors Types of external defects: (a) Warping: The distortion in converted timber caused departure from its original plane usually during seasoning period is called warping. Warping can be culping, bowing, twist, string. (b) Check, Split and Shakes: These are the examples of separation or ruptures of the wood along the grain. These three forms differ in whether the crack is confined to the interior of the wood or extends to the surface. (c) Stain: Fungi causing stain in wood, when it feeds only on food materials stored in the sapwood. In this case, fungi do not attack the heart wood which normally does not contain food material within the cell. Stain defect does not affect strength properties of wood. For example: Ceratocystis.
  33. 33. (d) Decay: This is observed due to wood destroying or wood rotting fungus of wood. These fungi nourish cell wall material and break down the cell structure and enzymatic activities. Decay fungi attack both sapwood and heartwood. This defect reduces the strength properties of wood. (e) Insects: Insects borers and termites together constitute one of the most destructive biological agencies causing defects in timber. Some insects infest standing trees others infest felled logs before conversion or converted timber. The damage is visible in the form of tunnels and wood dust packed galleries in timber.
  34. 34. Wood defects:  Knots ( buku )  Slope of grain ( ira serong )  Wane (ira menurun )  Shake (rekah)  Splits and cracks ( terbelah dan retak )  Insect attact  Decay ( reput )
  35. 35. Wood production  Plywood  Particle board  Fiber board - softboard - MDF - hardboard
  36. 36. Wood finishing Wood finishing refers to the process of embellishment and protecting the surface of a wooden material.
  37. 37. Types And use Of Wood Finishing  Wax – a finish that is commonly used as the final layer for a smooth, flat and shiny.  Shellac - is the most commonly finishers used on wood. Shellac is a natural resin produced from insect called lac bug excrement.  Lacquer – consisting of resin types ( nitro-cellulose ) its is transparent, quick dry , lacquer is dissolved with thinner.  Paint – Liquid paint binder containing materials and natural immune and smooth.
  38. 38. Types of Solvents And Its Use  Turpentine – to dissolve the paint and cleaning  Spirit – as a solvent to dissolve shellac  Thinner – to dissolve the paint  Kerosene – to dissolve lacquer
  39. 39. Wood Joints  What is a joint? A joint is the juncture of two pieces of wood that are connected together. The connection may be made by fasteners, like screws or nails, by glue, by interlocking parts, or by any combination of these. A joint may stand on its own, or may be reinforced by hardware, glue blocks, dowels, biscuits or other methods.
  40. 40.  Names of joints As with most things, a joint may have more than one name. People in different trades often use different names for the same joint. People from different places sometimes have different names for the same joint. The names used here are common to cabinet and furniture makers.
  41. 41.  Strength of joints  In evaluating the strength of a joint you should consider the following: 1. If the joint is secured by mechanical fasteners, a joint that positions the fasteners so that the main force on them is a shearing force will be stronger. 2. If the joint is secured by glue, a joint with more gluing surface will be stronger, as long as increasing the gluing surface doesn't decrease the size of the members too much. 3. A locking joint is one that interlocks mechanically, so that separating the members in at least one direction requires actually breaking one of the members. Locking joints are generally stronger than non-locking joints.
  42. 42.  Butt Joints  Mortise and Tenon Joints  Dado Joints  Rabbet joints  Dovetail Joints  Splice Joints  Edge Joints  Other Joints  Lap Joints  Miter Joints
  43. 43. Butt joints
  44. 44. Lap or halved joints
  45. 45. Tee half joint
  46. 46. Mitre joints
  47. 47. Rebate joints
  48. 48. Stopped rebate joint
  49. 49. Tongue and groove joints
  50. 50. Tenon and mortise joints
  51. 51. Dovetail joints

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