Timber 3 Flashcards
What are the four main stages in the processing of timber?
Felling of trees, Seasoning of timber, Conversion of timber, and Preservation of timber.
When should trees be felled?
Trees should be felled when they are just mature or very near to maturity.
What happens if trees are felled too early?
There will be an excess of sapwood.
What happens if trees are felled too late?
The heartwood may decay.
What is the ideal age for felling good trees?
50 to 100 years.
What are the seasons for felling trees in different areas?
For hilly areas: Mid-summer.
For plain areas: Mid-winter.
What is seasoning of timber?
Seasoning is the process of reducing the moisture content in freshly cut timber.
Why is seasoning of timber important?
It increases the durability of timber.
What is the fibre saturation point?
It is the point where cell cavities no longer contain free moisture after seasoning.
What are the two main methods of seasoning timber?
Natural seasoning and Artificial seasoning.
How is natural seasoning carried out?
Timber pieces are stacked on platforms 300 mm above ground level with spacers for proper air circulation.
What is the moisture content achieved by natural seasoning?
Moisture content can be reduced to 10–20%.
Also known as air seasoning
How long does natural seasoning take?
2 to 4 years.
What are the various methods of artificial seasoning?
Boiling, Chemical seasoning, Electrical seasoning, Kiln seasoning, and Water seasoning.
What are the advantages and disadvantages of the boiling method?
Advantages: Quick method, reduces shrinkage.
Disadvantages: Reduces strength and elasticity.
Boiling method
Timber immersed in water boiled for 3-4 hours and then dried slowly under shed
What is chemical seasoning also known as?
Salt seasoning
Timber immersed in solution of suitable salt, taken out and seasoned ordinary way
Which seasoning method uses high-frequency alternating current?
Electrical seasoning.
Rapid method
What is the purpose of kiln seasoning?
To dry timber in an airtight chamber or oven.
2 types of kiln
Stationery kilns and Progressive kilns
Stationery kiln/
Compartment kiln - Carried out in a single compartment
What is the process of conversion of timber?
Cutting and sawing timber into suitable sections to minimize wastage.
What is the allowance made for shrinkage during conversion?
3–6 mm.
What percentage of wastage is typical for round and square logs?
Round logs: 40%.
Square logs: 30%.
What are the different types of sawing methods?
Ordinary sawing, Quarter sawing, Tangential sawing, and Radial sawing.
