1.2-Performance characteristics of woods Flashcards
1
Q
What is rough sawn (stock form)
A
- 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
2
Q
What is planed square edge (stock form)
A
- wood has only one edge that is planned accurately- the rest are rough sawn
- planing removes about 3mm from nominal size
3
Q
What is planed all round (stock form)
A
- 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
4
Q
Natural wood stock form
A
- 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
5
Q
What are manufactured boards
A
- 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
6
Q
Mouldings (stock form)
A
pre made mouldings e.g. skirting boards are readily available in standard lengths up to 4 metres
7
Q
Characteristics of wood
A
- 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
8
Q
What is air seasoning
A
- 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
9
Q
What is kiln seasoning
A
- 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
10
Q
Why do we season wood
A
- gives greater immunity from decay and increased resistance to rot
- increases strength and sability
- helps preservatives to penetrate
- makes wood less corrosive to metals
11
Q
Why must the toxicity of a wood be considered
A
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
12
Q
What are hardwoods
A
These come from borad leaved (decidious) trees
13
Q
What are softwoods
A
these come from a cone bearing (coniferous) tree
14
Q
Hardwood OAK- properties and uses
A
- hard, tough, attractive grain, good weather resistence
- contains tannic acid to corrode steel
- boat building, flooring
15
Q
Hardwood ASH- properties and uses
A
- tough, attractive open grain pattern
- tool handles, ladders
