UNIT 3 STOCK FORMS Flashcards
Define stock form in material processing
The standard shapes and sizes of which materials are available
What are some key stock forms of timber?
- Regular sections: Planks, PSE (Planed Square Edge), PAR (Planed All Round), rough-sawn
- Mouldings: Used for skirting boards and decorative features
Dowels: Cylindrical wooden rods
Sheets/Boards: Often from manufactured wood
What machine is used to process rough sawn timber into planed timber?
Planer thicknesser, which trims the timber to achieve a smooth and square finish.
What are the characteristics of PAR timber?
Planed on all sides, smooth finish, about 3mm smaller than rough-sawn timber and the most expensive stock form.
What are hardwoods and how are they different from softwoods?
Hardwoods come from deciduous tress (which lose leaves in the winter) and grow slowly (up to 150 years), making them more expensive
List examples of hardwoods and their key properties:
Oak: Tough, durable, resistant to rot, and dense. Contains tannic acid that corrodes steel
Teak: High oil content, resistant to moisture, decay, and insect attack; durable but toxic
Ash: Springy and elastic shock-resistant: often used for sports equipment and tool handles
Beech: Hard, tough, odourless, steam-bendable, used for toys and kitchenware
Mahogany: Beautiful grain, excellent stability often illegal logging issues.
Birch: Fine grain, used for veneers, prone to insect attack.
What defines softwoods and why are they cheaper than hardwoods?
Softwoods grow faster (about 40 years), come from coniferous trees that retain pines year-round and are more affordable.
Name example of softwoods and their uses:
pine: lightweight, straight grain, low-cost, suitable for furniture but prone to dents
Cedar: Resistant to decay and weathering, lightweight but toxic; used for boat building and outdoor panelling
Douglas Fir: Strong, cheap, holds shape well used for large construction
Spruce: Uniform texture, used for housing and aircraft
Larch: Hard, reddish-brown, fades to grey, used for garden furniture and boats
What are manufactured boards and why are they used?
Boards made by binding wood particles, veneers, or fibres with adhesives. They offer consistent quality uniform strength and are cheaper than natural wood
List common types of manufactured boards and their properties:
Plywood: Strong in all directions, layers bonded with waterproof adhesive for marine use
Aeroply: Thin birch veneers for lightweight applications like airplane wings
Flexiply: Curves easily, used for laminated furniture
MDF: Smooth surface, uniform density, good CNC milling
Chipboard: Made from larger wood chips, less predictable quality, often veneered for durability
What are the environmental and durability concerns of manufactured boards?
They use adhesives and resins that are hard to recycle, and there durability can be limited without surface treatments.
What are the advantages of using laminates and veneers?
Laminates make surfaces durable, heat-resistant, and easy to clean. Veneers improve aesthetics by mimicking expensive hardwoods at a lower cost
Where are veneers commonly used?
On manufactured boards like MDF to improve appearance and value
What is melamine formaldehyde, and where is it used?
A resin-based polymer used for protective surfaces in kitchens and furniture
Why are rough sawn timbers used in timber frame housing?
They are cost-effective and do not require a smooth surface for structural process
What is the ethical consideration of using mahogany?
Its endangered status due to illegal logging raises concerns about sustainability and legality
Why cant sheets be made from natural timber?
Natural timber lacks the structural stability and uniformity required for large sheets
