Defects in Timber

Defects in Timber

The most common natural Defects in Timber are knots, shakes, cross-grain, crookedness, rind galls, burr, and curl.

(a) Burls ⟹ is a tree boom wherein the grain has grown in a deformed manner. It is typically discovered withinside the shape of a rounded outgrowth on a tree trunk or department this is packed with small knots. A burl outcomes from a tree present process a few shapes of stress. It can be because of an injury, virus, or fungus.

(b) Callus⟹ it indicates soft tissues or skin which covers the wound of trees.

(c) Chemical stain ⟹ Discolored due to chemical action on trees.

(d) Coarse grain ⟹ Trees grow rapidly hence, annual rings are widened and hence timber possesses less strength.

(e) Deadwood ⟹  Timber received from useless status bushes

(f) Druxiness ⟹ White decay spots of fungi.

(g) Foxiness ⟹ This disorder in timber is indicated through purple or yellow tinge in timber or reddish-brown stains or spots spherical the pith of tree discoloring the timber. it is brought on both because of bad air flow throughout garage or through timber.

(h) Knots ⟹ These are the bases of branches or limbs which might be damaged or reduce off from the tree. The element from which the department is eliminated gets nourishment from the stem for a quite lengthy time. And it in the end effects withinside the formation of darkish difficult jewelry which might be referred to as knots. As continuity of wooden fibers is damaged with the aid of using knots, they shape a supply of weakness.

CLASSIFICATION OF (Defects in Timber) KNOTS BASED ON SIZES :

  • PIN KNOT:-diameter up to 6.50mm
  • SMALL KNOT:-diameter up to 6.5 and 20mm
  • MEDIUM KNOT:-diameter between 20 and 40mm
  • LARGE KNOT:-diameter greater than 40mm.

CLASSIFICATION OF KNOTS ON BASIS OF FORM AND QUALITY:

  • DEAD KNOT:-knot which is separated from the body of the wood.it is not safe to use wood with such a knot for engineering purposes.
  • DECAYED KNOT:-popularly known as unsound knot and form by the action of fungi on wood.
  • LIVE KNOT:-it is very well constant in timber and can not separate out from the frame of timber.it’s far unfastened 
  • LOOSE KNOT:-it is the preliminary stage of the dead knot.
  • ROUND KNOT: The cross-segment of this form of knot is both spherical or oval.

(i) Rind Galls ⟹ the rind means bark and gall indicates abnormal growth, hence peculiarly curved swelling found on the body of the tree is known as rind gall. They broaden at factors from in which branches are improperly reduced off or removed, they may be not often located in a tree and the wooden on this element may be very vulnerable and now no longer durable.

(j) Shakes ⟹ These are cracks which partially or absolutely separate is frequently discovered in older bushes that develop in moist areas. These are both radial or tangential shakes-

  • Star shakes: – radial splits in wooden originating from bark and narrowing toward pith are referred to as famous person shakes. These spilled has a tendency to open increasingly more because of the wooden seasoned.
  • Heart shakes: – generally it occurs in mature trees. More frequent in hardwoods than in conifers. They are because of shrinkage of the indoors a part of the tree that is drawing near maturity.
  • Frost shakes: – starts offevolved at the out of doors wherein moisture from rain or different way has penetrated and freezes, inflicting harm to the timber at the inside.
  • Cup shakes: –  resulting from the rupture of tissue in a round direction.
  • The ring shakes –  consequences from the pulling aside of or extra growth rings.

(k) Twisted fibers or Wandering Hearts ⟹ they are caused by twisting of young trees by fast blowing wind in one direction.

(l) Upsets ⟹ Indicate timber fibers which might be injured through crushing or compression.

(m) Excrescences ⟹ are formed when the tree has received a certain shock or injury so that the growth of the tree completely upset and irregular projections appear on the body of timber.

Defect Due to Conversion (Defects occurs during converting timber to commercial form)

  • Chip mark ⟹ or sign placed by a chip on the finished surface of the timer.
  • Diagonal grain ⟹ Due to improper sawing of timer  Torn Grain ⟹ Due to falling of tool, the impression is formed.
  • Wane ⟹ Presence of original rounded surface on the manufactured piece of timber.

DEFLECTION OF TIMBER:-

  • When beam supporting brittle coverings like AC sheets, earthenware, slates, gypsum, etc. then maximum deflection should not be more than span/360. Otherwise, the deflection of span/ 240 is allowed.
  • In the case of cantilever deflection should not exceed clear span/180.

Application of timber obtained from different trees:-

  • BABUL: – used for bodies of bullock cart, tool handles agricultural instruments, etc.
  • BENTEAK: – furniture construction works, building construction, and boat construction, etc.
  • MULBERRY: – used for sports goods, baskets, hockey sticks tennis rackets, cricket bats, etc.
  • BIJASAL: – every day constructing production, cartwheel, furnishings, etc.
  • SHISHAM OR SISSOO:- since it is strong durable and tough and takes fine polish hence is used for high-class furniture, plywood’s, bridge poles, sports goods, railway carriages, etc.
  • TEAK WOOD: – high quality and durable furniture, shipbuilding, railway carriage, well curbs, piles, house construction, etc.
  • SANDALWOOD: – used for agricultural implements, wheels, mallets, boxes, fancy goods.
  • DEODAR:- it provides softwood and is used for making cheap and rough furniture, railway sleepers, packing boxes, structural work, etc.

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