1.2-Performance characteristics of woods Flashcards
What is rough sawn (stock form)
- wood comes driest from seasoning and has rough surfaces producers from initial conversion
- nominal sizes rather than accurate finished sizes and is the cheapest stock form
What is planed square edge (stock form)
- wood has only one edge that is planned accurately- the rest are rough sawn
- planing removes about 3mm from nominal size
What is planed all round (stock form)
- wood has sides and edges that are all planes square, straight and level, leaving a smooth finish
- PAR board 3mm smaller all round than original rough sawn nominal size
- most expensive
Natural wood stock form
- comes from trees and is available only at the maximum width of the tree
- for a wide desktop, wood planks need to be joined together
- planks should be joined with the end grain going in opposite directions
What are manufactured boards
- man made boards produced in large sheets, typically 1220mm x 2440mm
- wide surfaces can be produced from one sheet without the need for joining processes
Mouldings (stock form)
pre made mouldings e.g. skirting boards are readily available in standard lengths up to 4 metres
Characteristics of wood
- natural material, will biodegrade if left in landfill
- wood fibres grow along length of the tree, fibres consist of hollow cells
- it expands and shrinks with changes in humidity
- strong in direction of grain
- converted and seasoned to remove moisture
- seasoned to help prevent defects e.g. twisting
What is air seasoning
- traditional inexpensive method of seasoning
- wood is stacked in shelter outside to protect from rain
- air circulated between planks to remove moisture
- takes up to a year
- wood used for outdoor products
What is kiln seasoning
- expensive but controlled method by controlling temperature and humidity
- wood is stacked onto trolleys
- initially steamy in kiln
- quick process
- wood used for indoor products
Why do we season wood
- gives greater immunity from decay and increased resistance to rot
- increases strength and sability
- helps preservatives to penetrate
- makes wood less corrosive to metals
Why must the toxicity of a wood be considered
the toxicity depends on the species and both wood dust and sap can be a hazard
- different species have different risks and under the COSHH regulations, both hardwood and softwood dusts have workplace exposure limites
- employers should provide PPE and use extraction systems
What are hardwoods
These come from borad leaved (decidious) trees
What are softwoods
these come from a cone bearing (coniferous) tree
Hardwood OAK- properties and uses
- hard, tough, attractive grain, good weather resistence
- contains tannic acid to corrode steel
- boat building, flooring
Hardwood ASH- properties and uses
- tough, attractive open grain pattern
- tool handles, ladders
Hardwood MAHOGANY- properties and uses
- can contain interlocking grain
- rich, dark red colour
- indoor furniture, shop fittings
Hardwood TEAK- properties and uses
- hard, tough, straight grain
- outdoor furniture, laboratory benches
Hardwood BIRCH- properties and uses
- hard, straight closed grained
- furniture, indoor panelling
Hardwood BEECH- properties and uses
- tough, close grained, hard
- chairs, chopping boards
Softwood PINE- properties and uses
- straight grain, knotty
- construction work, roof beams
Softwood SPRUCE- properties and uses
- straight grain, resistant to splitting
- indoor furniture
Softwood DOUGLAS FIR- properties and uses
- straight or slightly wavy grain, stable
- veneers, plywood construction
Softwood LARCH- properties and uses
- hard, tough, attractive grain pattern
- garden furniture, cladding
Softwood CEDAR- properties and uses
- straight grain, can corrode ferrous metals
- exterior cladding, sheds
Manufactured boards PLYWOOD- properties and uses
- thin layers of wood placed and glued at 90 degrees and compressed
- good strength
- structural work, desktops
Manufactured boards MARINE PLYWOOD- properties and uses
- similar construction to plywood but is gap and void free and uses specialist water and boil proof glue
- resistant to fungal attack
- boat dashboards, boat lockers
Manufactured boards AEROPLY- properties and uses
- plywood made from high quality timber such as birch
- lightweight, easy to bend
- gliders, laminated furniture
Manufactured boards FLEXIBLE PLYWOOD- properties and uses
- odd number of layers glued
- bent and glued around a former
- laminated furntiure, curved panels
Manufactured boards CHIPBOARD- properties and uses
- wood chips compressed with a resin
- often veneered or covered with polymer laminate
- flat pack furniture
Manufactured boards MDF- properties and uses
- compressed wood fibres
- two smooth faces
- standard grade or veneered with a layer of timber
- model or mould making such as desks
Veneers- properties and uses
- thin slices of wood less than 3mm thick
- decorative coverings for manufactured boards
MF laminates- properties and uses
- thin sheets of MF polymer, hard, tough
- decorative covering for chipboard for kitchen worktops
MF laminates- properties and uses
- thin sheets of MF polymer, hard, tough
- decorative covering for chipboard for kitchen worktops
