Wood Flashcards
Rough sawn
Wood comes direct from seasoning and has rough surfaces produced during initial conversion
Rough-sawn wood will have nominal sizes rather than accurately finished sizes
Cheapest stock form
Planed square edge (PSE)
Wood has only one edge that is planed accurately, the rest are rough sawn
Planing removed roughly 3mm from the original nominal size
Planed all round (PAR)
Wood has sides and edges that are all planed square, straight and level
Smooth finish and ready to use
PAR board is 3mm smaller in every dimension than original rough sawn nominal size
Most expensive stock form to buy
Natural wood - width and joining
Comes from trees and is only available at a limited width due to the diameter of the tree trunk
To produce wider products natural wood planks must be joined together
Planks should be joined with the end grain going in opposite directions to minimise distortion
Manufactured boards standard sizes and width
Man-made produced in large sheets, typically 1220mm X 2440mm
Wide surfaces can be produced from one sheet without the need for joining
Mouldings
Pre-made mouldings such as skirting boards or wooden trims are readily available in standard lengths up to approx. 4m
Wood properties
Wood fibres grow along the length of the tree - consist of hollow cells (tracheids) supported by lignin resin
Expands and contracts with changes in humidity
Strong in along the grain, weaker across the grain
Converted (sawn into useful pieces) and then seasoned
Seasoning
Used to remove excess moisture (80-90%)
Helps prevent defects:
Warping Twisting Cracks Cupping Bowing
Trees should be felled in winter when they have less sap hence contain the least moisture - reduces seasoning time
Seasoning gives:
Greater immunity to decay and rot
Increased strength and stability
Helps preservatives to penetrate
Makes wood less corrosive to metals
Air seasoning
Traditional and inexpensive
Wood is stacked in a shelter outside - protected from the rain
Air circulates between the planks to remove excess moisture
A slow process - takes up to one year
Wood is used for outdoor products
Kiln seasoning
Expensive - uses controlled temperature and humidity
Wood is stacked on trolleys
Initially steamy in kiln then becomes hotter and drier
Quick process - a few weeks
Wood used for indoor products
Toxicity
Depends on the wood species, different species carry different risks - e.g. Respiratory infection, carcinogenic
Both wood dust and sap can be a hazard
Control of substances hazardous to health (COSHH) regulations 2002 - hardwood and softwood dusts have workplace exposure limits (WEL’s) of 5mg per cubic metre
Employers should provide PPE, extraction and ventilation systems
Oak
Hardwood
Hard Tough Durable Good insect and fungal resistance Attractive grain Good weather resistance Tannic acid - corrodes steel screws and fixings
Used for:
Furniture Flooring Boat building Cladding Joinery
Ash
Hardwood
Tough
Attractive open grain pattern - more flexible
Used for:
Tool handles
Ladders
Sports goods
Laminating
Mahogany
Hardwood
Can contain interlocking grain - more difficult to work, but it is generally easy to work with
Stable and durable
Rich, dark red colour
Uses:
Indoor furniture
Shop fittings and cabinets
Veneers - for manufactured boards
Teak
Hardwood
Hard
Tough
Straight grain
Natural oils - resists moisture, acids and alkalis
Uses:
Outdoor furniture
Lab benches
Traditional boat decks
Birch
Hardwood
Hard
Straight close grained
Resists warping
Uses:
Furniture
Indoor panelling
Veneers - for plywood
Beech
Harwood
Tough Close grained Hard Steamed - White Un-steamed - pink Has few knots Easy to work with Durable
Uses:
Chairs Chopping boards Tools - e.g. Mallets Steam bent laminated furniture Turned bowls
Pine (European redwood)
Softwood
Straight grain
Knotty
Can contain resinous knots
Uses:
Construction work
Roof beams
Timber frame construction
Interior joinery
Spruce
Softwood
Straight grain
Resistant to splitting and stable
Easy to work with
Used for indoor furniture
Douglas fir
Softwood
Straight/slightly wavy grain
Few knots
Stable
Good resistance to corrosion
Uses:
Veneers
Plywood construction
Joinery and construction work
Larch
Softwood
Hard Tough Attractive grain pattern - fades to silver on exposure Stable Good chemical resistance
Uses:
Garden furniture
Cladding
Decking
Fencing
Cedar
Softwood
Straight grain Acidic nature - corrodes ferrous metals Low density Good sound damping Good rot and insect resistance
Uses:
Exterior cladding Sheds Greenhouses Beehives Interior panelling
Plywood
Thin layers of wood placed and glued at 90 degrees to one another and compressed to form a board
Good strength in all directions
Always an odd number of layers
No grain weakness
Uses:
Structural work
Desktops
Indoor furniture
Floorboards
Marine plywood
Similar construction to plywood
Uses special water and boil proof glue (WBP) - provides moisture resistance
Higher quality marine ply - resistant to fungal attack
Uses:
Boat dashboards
Boat lockers
Boat panelling
Aeroply
Made from high-quality timber e.g. Birch
Available in very thin sheets
Lightweight
Easy to bend around a support frame
Uses:
Gliders
Laminated furniture
Jewellery items
Flexible plywood
Two outer layers are made from open-grained timber - allows the sheet to flex
Bent and glued around a former to achieve a solid shape
Used for laminated furniture and curved panels
Chipboard
Wood chips compressed with a resin - e.g. Urea formaldehyde
Uses:
Often veneered or covered with polymer laminate
Kitchen worktops and units
Shelving
Flat pack furniture
MDF
Compressed wood fibres - sometimes urea formaldehyde is added
Two smooth faces
Available in standard grade or veneered
Uses:
Model or mould making
Furniture - bookcases, cabinets and desks
Hardwood examples
Oak
Ash
Mahogany
Teak
Birch
Beech
Softwood examples
Pine
Spruce
Douglas fir
Larch
Cedar
Manufactured boards examples
Plywood
Marine plywood
Aeroply
Flexible plywood
Chipboard
MDF
Melamine formaldehyde laminates
Laminated with thin sheets of MF polymer
Hard
Tough
Chemical resistant
Decorative coverings for chipboard for kitchen worktops etc
