Saws and timber Flashcards
What is sawing for?
For cutting waste materials off quickly
Why use the right saw
Safety, accuracy and efficiency
Tenon saws
- straight lines
- stiffened back bone
- wood
- teeth pointing forward
Coping saw
- curve lines in thin wood/plastic
* sprung steel frame
Hacksaws
- straight lines in metal
- Junior for smaller jobs
- teeth pointing forward
Kerf
Size of the hole which the saw cuts
Green timber
- 70% moisture
- just felled
- used to because when timber dries it can become tough and difficult to work
- E.g. oak framed buildings, boats
PBS , PAR
PBS- planed timber on both sides
PAR- Planed all the way round
Conversion
- Makes timber marketable
- branches removed
- Home grown timber as Bark left on to retain moisture
- imported timber has Bark Removed so bugs don’t come into our country
Seasoning
Why? seasoning removes unwanted sap and moisture from timber
- this increases resistance to rot/decay, strengthens and makes it less corrosive.
Two types of seasoning
Natural air dried and artificial kiln dried
- natural takes almost a year and depends on the weather conditions, cheap, boards to separate wood, only reduce moisture content to that of the air, uneconomical for large quantities.
- artificially dried is quicker and controlled, timber is stacked on trolleys and wheeled out then steam is fed, the pressure is reduced, Dean is extracted and Pete is gradually raised. Controlled moisture content, only takes one to 2 weeks, kills insects and eggs, less space required and more efficient
Hardwood
• Expensive, tough, heavy, hard to work
• for furniture, toys
e.g. oak, Teak, beech, mahogany
Softwood
• Cheaper, lightweight, knot-free
• for furniture, frame work
e.g. pine, cedar, redwood
Guillotine
Cut material using force
Crosscut saw
Cut wood perpendicular to grain
