UNIT 1-2 different

UNIT 1-2 different

1. TOOLS

   • The first tools made by humans
     • the most primitive tools didn´t have handles. They were held directly in the hand and were chosen for their shape and size created through natural erosion. The first stone tools had sipe carved edges. Tools such as hammers axes and spearheads originated from them. It took many years of development to arrive at utensils similar to knives.
     • used ability for abstract thought inspired them to use sticks and stone to make their actions more effective
   • Mechain tools
     • the term `machine tool´ is used to refer to complex tools, whose energy source does not come from hand movements or the human body in general. Usually applied to heavy machinery, such as large or large mechanical presses
     • Machines may be controlled using buttons, levers or wheels. Nevertheless, more sophisticated models may be automatic. This is the case of a Computer Numerical Control Machine that uses a computer to control the machine
   • there are many types of tools that they have many functions from magnifying the force applied by our hands to protecting them from direct contact with dangerous elements and products. Tools may be defined as objects defined to carry out mechanical work and tasks

2. WOOD

   • Wood is the fibrous material that trees are made of. It is made up of two main substance: cellulose (a natural fibre that forms the walls of plant cells) and lignin ( which holds the cellulose together, making the tree hard and rigid)
   • Types of wood
     • NON-RESINOUS: This kind of wood mainly comes from trees that have little resin and a fibrous texture. It often comes from deciduous trees and comes in a wide range of colours, hardness and tones. Many varieties withstand bad weather well, which makes them suitable for garden furniture
     • RESINOUS: this kind of wood usually comes from evergreen trees, which produce resin, have white or light-coloured wood and are, in general, quite soft. It is common in cold areas in both hemispheres and is usually easy to work with. It is the only type of wood that can be laminated

3. PROPERTIES OF WOOD

   • There are many different types of wood as there are trees. This means that there is a wide variety to choose from.
     • HARDNESS: is a resistance against being pierced or scratched by another object. In comparison to other materials, wood is soft and easy to scratch,although there are different degrees of hardness
     • THERMAL AND ELECTRICAL INSULATION: Wood is a good barrier against the flow of heat and electricity.
     • FLEXIBILITY: is the ability to be deformed in the direction of the fibres without breaking. Wood is flexible in comparison to other materials, although some types of wood are more flexible than others
     • DENSITY: is the radio of mass to volume of the material. In general, wood is not dense and it has a resistance: weight ratio that makes it very good for building with
     • HYGROSCOPICITY: is the ability to absorb or release moisture
     • SPLITABILITY: refers to how easily it easily it splits in the longitudinal direction of the fibres.
     • TOUGHNESS: it is very resistant to breaking when hit by something
     • SOUND CONDUCTIVITY: wood conducts sound very well, owing to its low density and high elasticity.

4. FORMS OF WOOD

   • NATURAL WOOD: can be sawn into different shapes to obtain pieces used to build objects. Some of the most commercial shapes or uses include
     • Strips, mouldings or profiles, boards and planks, beams, panels and sheets or veneers
   • PREFABRICATED WOOD: sometimes, we need wooden panels that, because of their size, are difficult to obtain from natural pieces. There are different ways to overcome this problem, such as turning the trunks into thin sheets or chips and using them to make artificial boards