Woods Flashcards
What is a common use for mouldings made from wood?
Skirting boards or wooden trims
These mouldings are readily available in standard lengths.
What is one reason why manufactured boards are preferred over solid wood?
They are generally less affected by temperature and humidity
This stability makes them suitable for various applications.
What are the qualities of spruce wood ?
-hard
- good strength to weight ratio
- not very durable
- very knotty
What type of wood is used to manufacture musical instruments and why?
Spruce wood , as it has a good resonance producing a pleasant sound
What are the qualities of Douglas fir wood ?
- high quality wood
- harder than regular soft woods
- durable
- resistant to rot and insect attacks
What are the uses of Douglas fir wood ?
- doors
- flooring
- windows
What are the qualities of redwood ?
- rich colour (making it popular )
- durable
- strong
- weather and insect resistant
What are the uses of redwood ?
- decking
- outdoor furniture
- fences
What are the qualities of cedar wood ?
- high oil content (making it resistant to decay to moisture, weathering , insect attack )
- straight grain (less chance of warping )
-less inconsistency (knots ) - good sound damping
- low density making it lightweight
What are the uses of cedar ?
- exterior cladding
- sheds
- interior panelling
What are the qualities of pine wood ?
- inexpensive
- strong
- straight grain
- very knotty (tends to fall out posing challenges whilst manufacturing
Uses of pine wood ?
Low cost furniture and fencing as well as construction
What are the qualities of larch wood ?
- tough
- durable
- resistant to rot as a result of its high resign content
Which soft wood has a high resign content ?
Larch wood
Which softwood has a high oil content ?
Cedar
What are the different soft woods ?
Cedar / spruce / Pine / Larch / redwood / Douglas fir
In which direction would the would tend to split in ?
Working across the grain would result in the wood splitting.
What does planning the wood along the grain keep the wood from doing ?
Splitting / tearing
How is the pattern in the grain created ?
Every season the tree would produce a new ring
Do knots affect the performance ?
It tends to weaken the wood and it sometimes may fall out producing a hole.
What is the wood structure like ?
Wood fibres are made from hollow straw like cells which are held in lignin. These make the wood strong along its length
What are the straw like cells within the wood called ?
Tracheid
What is the function of tracheid within the structure of the wood ?
Carry water and nutrients to and from the roots to the leaves
What is a pro of using manufactured boards instead of natural woods in terms of surface defects ?
Manufactured boards are uniform in their surface finish whereas natural woods are much less predictable
What are the possible surface defects that natural wood may consist of ?
- knots (may fall out as the wood shrinks
- machining can produce marks on the timber from saw mills
- woods can be damaged by insect attack and rot
What do surface defects of the wood affect ?
Surface defects such as knots can affect the stability of the wood
Once the timber is felled what process must it go through ?
Seasoning
Why must timber be seasoned once felled ?
To prevent distortions such as twisting / cupping/warping/ bowling and split
Wood acts as a sponge and absorbs moisture and swells when placed in damp conditions. What is the technical name given for this ?
Hygroscopic
What are the different ways that wood can be seasoned ?
Air dried / kiln dried
What process do air dried wood go through ?
Planks are stored under cover and left to dry naturally
What process do kiln dried wood go through ?
Steam is used to artificially dry the timber and speed up the drying process
What process do kiln dried wood go through ?
Steam is used to artificially dry the timber and speed up the drying process
What happens to the wood in exposure to different levels of moisture as well as the seasons in any given environment?
The wood tend to swell and shrink
Where does most shrinkage occur ?
It occurs around the year rings
What is the percentage of radial shrinkage ?
2-8%
What are the working properties of seasoned woods ?
- stronger and much more stable
- less likely to decay and rot
- it is less likely to corrode metals
- absorbs preservatives more readily
What are the different ways that the working properties and aesthetic of the wood be enhanced?
- combing woods with resins to produce a composite material
- adding a preservative / finish or coating to prevent decay
- adding laminates to improve the properties of the surface
How can cheaper materials be made to look much more expensive by changing the colour to improve aesthetics ?
- pigments can be applied to the surface of the wood
How do preservatives work in improving the resistance to decay ?
- preservatives often contain copper which has anti microbial properties, which reduces the chance of a fungal attack
What are the new methods to guard against decay ?
Using biopolymers or natural acid compounds to impregnate wood cells to hair against decay
What are non- destructive tests that can detect faults within the material without causing any physical damage?
-ultrasonic testing
- X-ray testing
What is the ability of a malleable wood ?
Malleability is the ability of a material to be moulded without breaking.
The flexibility can be tested by measuring how far a thin piece will bend before it snaps
What would a tensile testing machine show ?
- the stretching force applied
- distance travelled
- yield point (where elastic deformation become regular )
- ultimate elastic limit (the most the material would stretch )
- breaking point (point at which the material snaps )
What are the two standard industry tests for toughness ?
Charpy and izod test
What is a measure of the toughness of a material ?
The distance the pendulum travels after breaking the test piece that had a 2mm deep notch
What does a tensile testing machine do ?
The tensile testing machine clamps a piece at each end and pulls the material apart until it breaks
What test measures the ability of wood to resist scratches or dents ?
The janka hardness test
What does the janka hardness test consist of ?
The test measure the average force needed 11.28 mm steel ball halfway into a piece of wood
Other than the janka hardness test what tests can be used to measure the hardness of a wood ?
Vickers , Brunel and Rockwell hardness test
What does a worm drive do ?
It pulls the clamps apart at a constant rate and the load and distance travelled is plotted
Where might non destructive testing be used ?
- cruise ships (as they are very expensive)
How do ultrasonic testings work ?
They detect internal defects via sound waves.
Sound waves are pulsed into the material and the intensity of the recorded sound is recorded.
What are pros of using ultrasonic testing ?
- suitable for any material
- highly accurate
- quick and portable
How do X-ray testings work ?
X-ray beams are passed through a material and project an image onto a screen. This can detect damage and splits inside the wood providing information about the properties of the timber
What test is used to test the thermal conductivity?
The guarded hot plate method
What is the guarded hot plate method
The test sandwiches a material test piece between two temperature controlled plates. One of the plates is kept hot and the other cold , the test measures the time taken for the test material to reach a constant temperature
What is the combination of natural wooden planks with glues to create large laminated curved beams for structural use called ?
Glulam
What type of joints are used to join smaller planks into longer lengths before multiple pieces are glued and clamped ?
Finger joints
What are the pros of having an engineered floor board with plywood or mdf with a polymer laminate ?
-strong and stable product
- wipe clean hard
Durable surface
What are the environmental benefits of using composite laminate flooring ?
-sustainable due to scrap materials being used to produce the boards ..
What is the bridge featuring a series of exposed structural beams ?
Wooden bridges , sneak , Netherlands
What material was used in the manufacture of the wooden bridges , sneek , Netherlands ?
Accoya - a modified timber made from sustainably sourced softwoods enhanced with a preservation treatment ( with a low carbon foot print /50% less than concrete emissions )
What are the properties of plywood ?
Regular plywood and marine plywood both are strong in every direction and can’t split along the grain
What are the properties of marine plywood ?
Water resistant hardwood layers are used and each layer is thinner than those used in standard plywood
What is used to ensure the marine plywood can withstand wet conditions?
A resin (a waterproof adhesive ) bonds the defect free layers together
What makes plywood so strong ?
- layered structure
- even stress distribution
What are two flexible plywoods ?
Aeroply and flexibly
What is aeroply made from and developed to form around ?
- several birch veneers
- aeroply was developed to form around frameworks to make aeroplane wings
How is mdf manufactured ?
Made from fine wood dust particles that have been bonded with resin under pressure
Why would mdf be a better option over chip board ?
- mdf has a smooth finish and a uniform density making it ideal for cnc milling ,whereas chipboard is less predictable
What are standardised components ?
-hinges
- brackets
-screws
- nails
- nuts and bolts
- riverts
What are knock down fittings ?
They are temporary joints - usually used for cheap flat pack furniture
Types of knock down fittings -
- scan fitting (a cylinder with a screw thread that gets inserted )
- can locks (disks and peg -hidden in the surface )
-single and two piece blocks (hold things at right angles )
-dowels (inserted into holes )
Advantages of knock down fittings ?
-easily assembled
- no technical knowledge is required
-can be disassembled and reassembled
-spare parts are readily available
- manufactured in large numbers so it’s is relatively cheap
What are the different stock forms of timbers ?
- roughsawn
- planed square edge (pse)
-planed all round (par )
What machine is used to trim rough sawn timer to par and pse timbers ?
Planer thicknessers
What is rough sawn timber used for ?
Commonly used for construction as they act as support and is built on top of so don’t require any finishing
How much material gets planned from each surface ?
Around 3mm is planned from each surface
What are mouldings ?
They are machined profiles made for functional and aesthetic purposes
What are the uses of mouldings ?
Architraves , skirting boards , frames , beading , balusters , spinsters
What are the properties of oak wood ?
Tough , durable , strong , finishes well , resistant to moisture when exposed to rot
However it contains tannic acid which corroded steel
Properties of mahogany?
- Easy to work with
- durable
- excellent stability
Properties of beech ?
- doesn’t dent easily
- can be steambent
- hard
- tough
- resistant to abrasion
- close grain making it hygienic
- odourless
Uses of beech wood ?
Children’s toys / kitchen products
Properties of ash wood ?
-Shock resistant
-open pores providing elasticity
Properties of teak wood ?
- high oil content making it weather resistant
- close grain (doesn’t warp as much )
- hard
-heavy and resistant to alkali and acids
Properties of birch wood ?
- Light wood
- elastic and tough
What are examples of hardwoods ?
- beech
- birch
- mahogany
- oak
- teak
- ash
What is rough sawn wood?
Wood that comes directly from seasoning and has rough surfaces produced by initial conversion. Roughan would will have nominal sizes rather than having accurate finishes and is the cheapest stock form to buy.
What is planed square edge?
Wood that has only one edge that is planed accurately
What direction must plant of wood be joined in to minimise distortion?
They must be jointed with the engineering travelling in different directions
What are the limits of wood esposure ?
Coshh regulations state both hardwood and softwood dusts have work place exposure limits to 5 mg per cubic metre
