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Wood

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  • 1. WOOD
  • 2. WOOD
  • 3. WOOD • Poor heat-conducting properties  does not remove heat from the hand  warm to the touch • Cold: metals, plastics, stone, concrete • Excellent material for doors, door & window frames, flooring, trim
  • 4. WOOD
  • 5. GROWTH OF TREES • Wood consists of long, narrow, hollow cells called fibers • Cambium: thin growing layer • Sapwood: fibers are active in the life processes of the tree but do not grow • Heartwood: center, consists of dead fibers, shade darker because of resins, gums, minerals • Pith: thin veil of soft tissue in the center, no strength • Bark
  • 6. GROWTH OF TREES • Fibers • Cellulose (70% of the volume) • paper • Lignin (the glue, 25% of the volume) • Age of the tree • Determined by number of rings
  • 7. GROWTH OF TREES • A pack of drinking straws held together w/ rubber bands approximates the fibrous structure of wood • Checks: shrinkage in wood when water inside it evaporates
  • 8. GROWTH OF TREES • Grain: stripes when wood is sawed parallel to the length of the tree
  • 9. GROWTH OF TREES • Slope of grain
  • 10. GROWTH OF TREES Knots in grain
  • 11. LUMBER PRODUCTION • Saw • Edgers • Trim the roughedged wood slabs longitudinally to the desired lumber width & cut of the rounded edges
  • 12. LUMBER PRODUCTION • Saw • Trimmers • Saw the lumber transversely into desired lengths and trim away defective portions
  • 13. LUMBER PRODUCTION
  • 14. LUMBER PRODUCTION • Lumber finishing • Rough lumber • Sawed on all 4 sides • Dressed lumber/surfaced lumber • Planed or surfaced on at least one face • S1S surfaced on 1 side • S1E surfaced on 1 edge • S2S, S2E, S1S2E, S2S1E, S4S • Worked lumber • Dressed and also worked to provide tongue-and-groove or shiplap joints • Seasoning • Process of reducing the moisture until a suitable moisture level is reached
  • 15. LUMBER PRODUCTION
  • 16. LUMBER PRODUCTION • Foot board measure (fbm) • 1 board foot = 1 sq ft x 1 in. thick • Ex. • Calculate the number of board feet in 36 2x4s which are 8 ft long • Board feet = (number of pcs x thickness in inches x width in inches x length in feet) / 12 • Board feet = (36 x 2 x 4 x 8)/12 = 192 bf
  • 17. SEASONING • Green wood • Moisture content • Ways to season • Air: 4 years for hardwoods • Kiln • Subjected to warm, moist air or steams
  • 18. SEASONING
  • 19. STRENGTH • Important stresses & corresponding strengths of wood are divided into 6 types: • Modulus of elasticity (E) • Measure of stiffness or resistance to deflection • Extreme fiber stress in bending (Fb) • The stress (compression at the top, tension at the bottom) that must be resisted in a beam undergoing bending • Tension parallel to grain (Ft) • Stress induced by pulling apart in a longitudinal direction • Compression parallel to grain (Fc) • Stress induced by pressing together longitudinally • Compression perpendicular to grain • Stress induced by pressing together in a transverse direction • Horizontal shear (Fv) • Stress induced by the tendency for upper fibers to slide over lower fibers as a beam bends
  • 20. LUMBER CLASSIFICATION • Grading • Lumber • Term including all finished or semifinished wood shaped with parallel longitudinal surfaces • Boards • Pieces 1 ½ in. or less in thickness and 2 in. or more in width • Dimension lumber • Pieces at least 2 in. thick and less than 5 in. thick and 2 in. or more wide • Timbers • Pieces 5 in. or more in thickness and width
  • 21. LUMBER CLASSIFICATION • Factory and shop lumber • Pieces to be used in making sash, doors, jambs, sills and other millwork items • Yard lumber • Used structurally and includes most of that used in construction • Divided according to size and shape into boards,dimension lumber and timbers • Boards: roofs, floors, siding, paneling and trim • Dimension lumber: joists, studs, rafters • Timbers: infrequently used as part of a structure • Shoring earthwork or mine tunnels, bracing for concrete forms
  • 22. LUMBER CLASSIFICATION
  • 23. LUMBER CLASSIFICATION • Stress-graded • Each piece is assigned to a grade depending on its strength • Characteristics • Natural marks resulting in tree’s growth or from seasoning, and manufacturing inspections resulting from sawing, planing, or other manufacturing operations
  • 24. LUMBER CLASSIFICATION • Stress-graded • Each piece is assigned to a grade depending on its strength • Characteristics • Natural marks resulting in tree’s growth or from seasoning, and manufacturing inspections resulting from sawing, planing, or other manufacturing operations
  • 25. DETERIORATION OF WOOD
  • 26. DETERIORATION OF WOOD • 4 major enemies of wood: • Insect, marine borers, fungi, fire • Insects • Termites • Provide physical barrier or a chemical barrier to keep them from reaching the wood • Physical barrier: concrete or steel supports that provide a space between the ground and the wood • Chemical barrier: saturating the soil adjacent to the structure with poison • Marine borers • • • • Mollusks & crustaceans Docks Creosote oil or creosote-coal tar solution Encasement of the wood within concrete • Fungi • Rotten wood • Chemicals
  • 27. PRESERVATION OF WOOD • Treating with poison so that fungi and insects do not consume it • Typical treated wood products: • Dimension lumber, heavy timbers, round stock, plywood, specialty items • Finishes • • • • • • • Paint Enamel Varnish Sealer Semi-transparent stain Opaque stain Polyurethane varnish