Timber 4 Flashcards
What are the five main categories of defects in timber?
Defects due to conversion
Defects due to fungi
Defects due to insects
Defects due to natural forces
Defects due to seasoning
What causes chip marks on the surface of timber?
Marks formed by chips on the finished surface or due to parts of a planing machine.
What is a diagonal grain defect, and how is it caused?
Diagonal marks on straight-grained timber due to improper sawing.
What is a torn grain defect?
Small depressions caused by falling tools or other impacts.
What is a wane defect in timber?
Lack of wood on any face or edge of a piece of sawn timber caused due to Presence of the original rounded surface on a manufactured piece of timber.
What is blue stain, and where does it occur in timber?
Blue stain occurs when sapwood is stained bluish in color due to fungal activity.
What happens during sap stain in timber?
Sap loses its color to brown, generally occurring when the moisture content exceeds 25%.
How does wet rot affect timber?
Wet rot occurs under alternating dry and wet conditions, converting timber into a greyish-brown powder.
What conditions lead to dry rot, and what does it do to timber?
Dry rot occurs in damp conditions with improper ventilation, converting timber into a dry powder form.
Converted to dry conditions
Improper sawing
What is white rot, and how is it different from brown rot?
White rot occurs when fungi attack lignin, turning timber into a white mass. In contrast, brown rot removes cellulose and gives timber a brown color.
What is heart rot, and how can it be detected?
Heart rot occurs when heartwood is exposed to atmospheric agents, often where branches break off, and it produces a hollow sound when struck with a hammer.
What defect do beetles cause in timber?
Beetles form pinholes of about 2 mm in size, attack sapwood, and convert timber into fine, flour-like powder.
Where are marine borers found, and how do they affect timber?
Marine borers are found in salty water. They make holes with a diameter of about 25 mm and a length of 60 mm for shelter, causing the timber to lose color and strength, although they do not feed on wood.
What are termites, and how do they damage timber?
Termites, also known as white ants, live in colonies and eat away the core of timber very quickly.
Which types of timber can resist termite attacks?
Teak and sal timber can resist termite attacks.
Ascu treatment
What is Burls (Excrescences)?
Irregular projections caused by shock or injury during the young age of the tree.
What is Callus?
A soft tissue or skin covering the wound of a tree to protect it.
What is Chemical Stain?
Discoloration of timber due to chemical action caused by external agents.
What is Coarse Grain?
A defect caused by rapid growth of the tree, resulting in widened annular rings and reduced strength.
What is Dead Wood?
Timber obtained from dead standing trees, characterized by being lightweight and reddish in color.
What is Foxiness?
A red or yellow tinge in wood caused by poor ventilation, over-maturity, or growth in marshy soil.
What are Knots?
Dark, hard rings formed at the base of branches that have been broken or cut off. They get nourishment result in dark hardening
What is Rind Gall?
Abnormal curved swelling on the tree caused by improper cutting or branch removal.
What are Twisted Fibres (Wandering Hearts)?
Twisted fibers caused by the twisting of young trees due to strong winds.
What is Upset?
Ruptures or injuries in wood fibers caused by compression or crushing.
Due to improper felling of tree
What is Water Stain?
Discoloration in timber caused by contact with water.
What are Wind Cracks?
Cracks caused by the shrinking of the timber’s exterior surfaces due to exposure to fast-blowing winds.
What are Shakes?
Cracks that partly or completely separate timber fibers, categorized as:
Cup shake
Circular cracks formed on annular rings.
Ring shake
Cup shake extending to the entire ring.
Heart shake
Cracks from pith to sapwood. In dn of medullary ray
Star shake
Cracks from bark towards sapwood.
Radial shake
Fine, irregular cracks extending towards the center.
From bark to centre then dn of anular ring and run towards pith
What is Bow?
A curvature defect formed along the length of the timber.
What is Cup?
A curvature defect formed across the transverse dn
What is Case Hardening
A defect where the exposed surface of the timber dries rapidly, causing it to shrink and remain under compression.
What are Checks?
Cracks that separate the wood fibers but do not extend from one end of the timber to the other.
What is Split?
Uneven shrinkage during drying causes the wood to flatten and lose its shape.
What is Collapse?
Uneven shrinkage during drying causes the wood to flatten and lose its shape
What is Honeycombing?
Radial and circular cracks caused by stress during drying, giving the timber a honeycomb-like texture.
What is Radial Shake?
Radial cracks that develop due to seasoning stress.
What is Warp?
A defect where the timber twists or distorts out of its original shape.
What is Twist?
A spirally distorted timber piece along its length.
