HSC - Woodwork Flashcards
Timber Structure - Cross section
- Bark/epidermis
- Cambium layer
- Phloem/Xylem
- Sapwood
- Growth ring
- Medullary rays
- Latewood
- Early-wood
- Heartwood
- Pith
Properties and Characteristics - Timber
- figure – grain direction – texture – colour – strength – durability – weight – hardness – weathering
Photosynthesis
The process by which plants use sunlight, water, and carbon dioxide to create oxygen and energy in the form of sugar
Timber industry terms
1) Grade
2) Sizes
- timber boards
- Manufactured boards
Timber Defects
– splits – checks – warping – shakes – bowing – knots – twists and winds
Planning
-- sketches – working drawings – materials lists – calculations – costing
Preparation of Timber
– dressing
– thicknessing
– face
– edge
Widening Joints
– dowelled butt – tongue and groove – rebate – groove and feather – biscuit
Framing Joints
– mitre – halving joints – dowelled – box pin – mortise and tenon joints – bridle joints
Carcase Joints
– rebate
– scribed
– dovetail
– housing
Construction Techniques
– sawing – drilling – edge treatments – nailing and screwing – sanding – scraping – turning – carving – inlaying – marquetry – veneering – parquetry and intarsia – laminating – bending – routing
Assembly of components
– test, fit and check joints
– dry cramp
– use of cramps
– testing for square and flatness
Finishing
– preparation – staining – filling – oils – finishes (oil and water-based) – shellac – french polish – spray finishes
– environmental issues associated with finishing
– industrial processes
Timber recovery and conversion
– sawing: live, quarter, back – flitches and burls – stability – seasoning: air, kiln – equilibrium moisture content (EMC)
Timber Selection considerations
– plantation timbers – exotic timbers – recycling/reusing timbers – ‘green’ timbers – economical usage/waste minimisation – environmental issues/pollution – sustainability – WHS issues
Manufactured boards
– construction and manufacture, veneers, plywood, particle board, fibre boards, block and lamiboards – glues – environmental/WHS issues
Hardware and Fitting
– screws – nails – nuts – bolts – knockdown fittings – hinges – handles – knobs – staples/staple guns – drawer runners – table clips – latches – catches – shelf hangers
Other materials used in timber projects
– glass – metal – polymers – upholstery materials – composite materials
Adhesives
– PVA – epoxy resin – hot melt – urea-formaldehyde – resorcinol – contact
Bark/Epidermis
Outside protective layer
Phloem and xylem
PHLOEM = vascular tissue in charge of transport and distribution of the organic nutrients.
XYLEM = vascular tissue in plants which conducts water and dissolved nutrients upwards from the root and also helps to form the woody element in the stem.
Cambium Layer
Layer of actively dividing cells between xylem (wood) and phloem (bast) tissues that is responsible for the secondary growth of stems and roots (secondary growth occurs after the first season and results in increase in thickness).
Medullary rays
cellular structures found in some species of wood perpendicular to growth rings. horizontal cells for food storage and conducting it radially. from the pith to out zones
Sapwood
soft outer layers of recently formed wood between the heartwood and the bark, containing the functioning vascular tissue.
Growth Rings
a cross section of the stem of a woody plant, the increment of wood added during a single growth period.
Latewood
wood that is formed late in a tree’s growing season and which forms the darker part of the annual ring of growth.
Early-wood
the light-coloured wood made by a tree in the spring that shows up in the yearly growth ring.
Heartwood
central wood in a branch or stem characterised by being composed of dead cells, more resistant to decay, generally darker and harder than the outer sapwood
Pith
Pith, or medulla, is a soft tissue in the stems of vascular plants. Conducts food materials horizontally in the trunk of a tree
Figure
The pattern in timber caused by variations in colour, grain and texture
Splits
separation of the wood through the piece to the opposite surface or to an adjoining surface due to the tearing apart of the wood cells.
Checks
Checks are a separation of the wood normally occurring across or through the rings of annual growth and usually as a result of seasoning.
Warping
deviation from flatness in timber as a result of stresses and uneven shrinkage.
bow: a warp along the length of the face of the wood
crook: a warp along the length of the edge of the wood
kink: a localised crook, often due to a knot
cup: a warp across the width of the face, in which the
edges are higher or lower than the center of the wood
twist or wind: a distortion in which the two ends do not lie
on the same plane. Winding sticks assist in viewing
this defect.
Shakes
Shakes are cracks in timber. Arising in cut timber they generally cause a reduction in strength. When found in a log they can result in a significant amount of waste, when a log is converted to lumber. Apart from heart shakes, often found in trees felled past their best, shakes in a log have no effect on the strength of shake free lumber obtained therefrom.
Knots
Knots are visible imperfections in wood grain that are circular and darker than the surrounding area.
Plywoods
A type of strong thin wooden board consisting of two or more layers glued and pressed together with the direction of the grain alternating.
High strength and stability.
High resistance to impact.
Resistance to water, chemicals, fire, and heat.
Flexibility in shape, size and thickness makes it fit for every requirement.
No shrinking, swelling and wrapping.
Durable.
Cost-effectiveness.
used in applications such as car-case construction, doors, panels, linings, shelves, cupboard backs, drawer bottoms.
Medium Density Fibreboards (MDF)
It is a dry-processed fibreboard manufactured from wood fibres, as opposed to veneers or particles, and is denser than plywood and particleboard. MDF has an even density throughout and is smooth on both sides.
MDF is primarily used for internal use applications
- poor moisture resistance
Particle boards
Engineered wood product manufactured from wood chips
- made from thinning and trimmings from pine plantations and whole trees
Production Process
plantation, logs and thinning to mill, billet cut, billets flaked, flakes milled to size, flakes dried, flakes sprayed with glue, mattress formed, mattresses pressed, sheets sanded and trimmed.
- Chemically treated for mould and termites/borers
- Very little expansion/contraction
- Expands in rain and disintegrates. Nail and screws cause chipping
5 by-products of timber
Building Boards = particle board, hardboard, soft board, medium density fibreboard
Sawdust = can be used in fuel, insulation, packing, stuffing. Up to 20% is made into sawdust from aloy
Paper pulp = wood is cut into chips, ground and pulped in water and chemicals to bind fibres. Then compressed
Chemicals = Creosote, methanol etc. produced by distillation process.
Plastics = Source of cellulose from which plastic materials may be viewed.
Cross Grain
When the direction of fibres is not parallel to a face of edge
Interlocked Grain
When the angle of fibres changes or reverses in alternate layers
Timber Grading
when timber is categorised according to suitability for particular end uses. determined by number, size, type and position of knots, gum veins etc.
graded by standards association of Australia
Sawing
Live (or slab sawing) = log is sawn about halfway through on the opening face and then turned once to the opposite face for sawing until the log is finished.
- easiest and quickest sawing method
- every piece must be edged
- lower quality logs
Quarter = Where the annular growth rings intersect the face of the board at 60 to 90 degrees. Each log is sawed at a radial angle into four quarters
- Less effected by warping
- more expensive than live sawing
Back = The sawing is done at right angles to the medullary rays and tangential to the annular rings. Due to the cutting of the medullary rays, the sections cut become weaker
- high quality timber
- most common in Australia
flitches and burls
Burls = tree growth in which the grain has grown in a deformed manner
Flitches
equilibrium moisture content
The point at which wood stops absorbing or releasing moisture into the surrounding air
Aspects of Forest Management
1) thinning = remove every 2nd tree as they grow
2) pruning = selectively removing parts of a plant
3) fire protection = remove potential fire fuel
Reforestation
The replenishment of depleted forests and woodlands. This process often occurs after deforestation. Can happen through silviculture of dropping seeds.
Silviculture Processs
Clear felling = felling the whole of the useable crop at the one time. Area is often cleared and trees replanted or natural growth can occur
Selection = Felting just the largest or specific trees as they mature, leaving smaller ones to develop.
Grouping = The process of not removing single trees but whole groups of trees. Up to 1 hectare
Australian Hardwood and Softwood
Jarrah - hardwood
- High resistance to weather, rot, termites and even marine borers
- fire resistant
- It can be used in wharf and bridge construction, railway sleepers, cross arms, poles and piles.
Hoop Pine - Softwood
- Grain is usually straight to interlocked, with a fine to medium uniform texture. Moderate natural luster.
- Rated as non-durable to perishable; poor insect resistance. Also susceptible to fungal staining.
Difference between Hardwood and Softwood
hardwood comes from deciduous tree’s which lose their leaves annually. Softwood comes from conifer, which usually remains evergreen
