• PLASTICS -  

Plastic is defined as a material that contains an essential ingredient an organic substance of large molecular weight. It is also defined as polymers of long carbon chains. Carbon atoms are linked in chains and are produced in long-chain molecules.

Compared to metal, plastic has a low melting point, is highly malleable, and can be molded easily into basic or complex forms. That malleability also increases the fabrication and production of parts and pieces.

Properties of Plastic

They are light in weight and are chemically stable.

Easily moulded into different shapes and sizes.

Good insulation and low thermal conductivity.

Good impact resistance and they do not rust.

Good transparency and wear resistance.

Poor dimensional stability and can be easily deformed.

• WOODS - 

Wood is a structural tissue found in the stems and roots of trees and other woody plants. It is an organic material – a natural composite of cellulose fibers that are strong in tension and embedded in a matrix of lignin that resists compression.

The mechanical properties of wood include strength in tension and compression (as measured in axial and transverse directions), shear, cleavage, hardness, static bending, and shock (impact bending and toughness).

• METALS - 

A solid material which is typically hard, shiny, malleable, fusible, and ductile, with good electrical and thermal conductivity (e.g. iron, gold, silver, and aluminium, and alloys such as steel).

Properties of metals

high melting points.

good conductors of electricity.

good conductors of heat.

high density.

malleable.

ductile.

• PROPERTIES  of SOFTWOOD - 

Softwood comes from gymnosperms, which are seed-bearing evergreen trees such as pine, spruce, fir, cedar, juniper, redwood, and yew. As most evergreen trees tend to be less dense than deciduous trees, it is easier to cut them down. They also grow tall and straight, making it easier to cut long straight planks of wood.

A wood will be classified as a softwood if the seeds don't have any type of coating and are instead dropped to the ground and left to the elements.

Durability - Softwoods generally have a shorter service life than hardwoods in external applications as even after treatment they are often less durable and require more care and maintenance over their lifespan.

Strength - The lower density of softwood timber means it's weaker and less durable than hardwood, however there are some 'hard' softwood options with a higher density like Juniper and Yew.

Permeability - Permeability is a function of porosity. Softwoods, which do not have pores are known as non-porous woods. Since soft- woods have no pores, the difference between the earlywood and latewood zones in the growth ring occurs due to effects that the growing season has on the longitudinal tracheids (the dominant cell type in softwoods).

Hardness - Softwoods do not have vessels and therefore have a softer, less pronounced grain than hardwoods.

Toughness - Density: The lower density of softwood timber means it's weaker and less durable, however there are some 'hard' softwood options with a higher density like Juniper and Yew. Longevity: Softwood is less suitable for high traffic areas as it does not wear as well as hardwood over time.

Elasticity - They are flexible, lighter in weight and less dense than most hardwoods.

Workability - Softwood is easier to work with and can be used across a broad range of applications. 

Weight - Softwoods are lighter than hardwoods, making them easier to transport.

• PROPERTIES  of HARDWOOD - 

Hardwood comes from Angiosperms such as maple, oak, and walnut. These trees lose their leaves annually (deciduous or broad-leafed trees). As they grow slowly, hardwood has denser wood fibers (fiber tracheids and libriform fibers).

An interesting fact about hardwood is that some types of hardwood can’t float in water. For example, Black ironwood is perhaps the hardest and heaviest wood that sinks in water.

A wood will be classified as a hardwood if the seeds that the tree produces have a coating. These coatings can either take the shape of a fruit or a shell.

Durability - Hardwoods are naturally more durable as they come from slow-growing, broad-leaved trees. This means the timber has a higher density than softwoods, which gives them enhanced durability and strength.

Strength - Because of their condensed and more complex structure, hardwoods generally offer a superior level of strength and durability. The most common types of hardwoods include Oak, Teak, Sapele, Iroko and Meranti.

Permeability - Permeability is a function of porosity. Flow through hardwoods is much less dependent on pits interconnecting the cells and so drying has less effect on hardwood permeability than on softwoods.

Hardness - Because of their condensed and more complex structure, hardwoods generally offer a superior level of strength and durability. The term hard wood (as opposed to hardwood) is referring to a physical property of the wood itself: hardness. Hardness refers to the ability of the wood to resist indentation.

Toughness - Toughness in wood. Toughness is the resistance of a material to the propagation of cracks or crack-like defects which can ultimately lead to failure. Cracks cause local stress concentrations, the magnitudes of which are dependent on the size and shape of the crack. Toughness is the mechanical property that determines the wood strength when a force acts in a short time interval. Its value is determined in the bending impact test. 

Elasticity - Hardwoods are more dense and less elastic. 

Workability - Due to its density, hardwood tends to be a lot harder to work with during construction. 

Weight - Hardwood is heavier and more durable than softwood, which is usually reserved for windows and framing. The weight difference between hardwood and softwood is noticeable. For example, oak weighs between 37 and 56 pounds per cubic foot while a cubic foot of pine weighs between 22 and 35 pounds.

• USES -

Fuel - In the case of burning wood, stored potential energy (in the form of chemical energy) in the log is released due to heating by other excited atoms. Wood pellets and other agglomerated energy products are made from dried sawdust, shavings or wood powder, with the raw material being compressed under high pressure.

Construction - Wood is sustainable, renewable, and generally less energy-intensive to process compared to other construction materials, including concrete and steel. Wood is an available resource that is biodegradable and easy to dispose of.

Sawn Wood - Sawn timber is timber that is cut from logs into different shapes and sizes. Sawn timber is generally cut into varying rectangular widths and lengths, but may also be wedge shaped. Common sawn timber products include solid timber beams and more rectangular timber sections.

Plywood and Veneers - Plywood is a type of manufactured wood panel that's made by gluing veneers together. The layers are glued with the wood grain of the plies at right angles to each other. Veneers are the thin slices of wood that can be peeled off and they're usually less than ⅛ inch thick.

Fibreboards - Fibreboard is an engineered wood wallboard made of wood chips, plant fibres, softwood flakes, sawdust and other recycled materials such as cardboard or paper, all bonded with a synthetic resin under high pressure and heat and then compacted into rigid sheets.

Pulp & Paper - Pulp is made from breaking down the fibrous part of plants, primarily trees or recycled paper, and refers to the main ingredient in the papermaking process. Pulp made from trees (wood fiber) is the most common source of fiber for papermaking and the base for many paper and wood products.

Synthetic Textiles - In the fast-growing next-gen materials market, cellulose fibers extracted from wood, old textiles, and even bacteria are performing akin to cotton, silk, and polyester.

• WHY TIMBER IS SEASONED -

Timber seasoning is the process of reducing moisture content from timber. This can be achieved in a few different ways, with kiln and air seasoning being the most common. If left unseasoned, timber can quickly warp, twist, and break as too much moisture wreaks havoc on the cellular structure.

• ADHESIVES' CURING TIMES AND STRENGTHS -

Curing refers to a chemical reaction that occurs during the application or use of the adhesive. It is the result of two-components reacting or cross-linking, resulting in a physical change from a liquid to a solid. This process is irreversible.

Cure time is the time that determines how long things take to fully cure. A series of chemical reactions occurs during cure time. These chemical reactions allow things to set, harden and develop traits. It may take weeks, months or years. Many factors have an impact on the curing time of a product.

Adhesive strength refers to the ability of an adhesive to stick to a surface and bond two surfaces together. It is measured by assessing the maximum tensile stress needed to detach or unstick the adhesive perpendicular to the substrate.

• THE ADVANTAGES OF WORKING WITH MANUFACTURED BOARDS COMPARED WITH SOLID WOOD - 

Medium Density Fiberboard (MDF) and Plywood are the popular manufactured wood in furniture making. The aesthetic look, workability, screwing and nailing ability, smoothness of the surface, ease to paint, make a manufactured wood a better choice for furniture than any other wood type.

• THE DISADVANTAGES OF WORKING WITH MANUFACTURED BOARDS COMPARED WITH SOLID WOOD - 

Minimal resistance to moisture and humidity: Manufactured wood isn’t made to be resistant to moisture and humidity. There is a high risk of the material soaking up water.

Heavy and sturdy: Manufactured wood can be heavy and sturdy. While that’s not a bad thing, it makes it tricky to handle if you are just one person completing a project.

Veneers showing at the edges: The construction of manufactured wood may leave rough edges. These require more work to remove than natural wood.

Formaldehyde: Manufactured wood is often made with formaldehyde. When cut, the dust from manufactured wood can release carcinogens into the air. It can harm the user if proper precautions are not taken in the cutting process.

• CARBON STEELS -

Also called mild steel, it's commonly used structurally in buildings and bridges, axles, gears, shafts, rails, pipelines and couplings, cars, fridges and washing machines. High carbon steel has a much better tensile strength, used to make cutting tools, blades, punches, dies, springs and high-strength wire.

• CASTING ALLOYS - 

The most typical materials used for metal castings are aluminum, zinc, copper, ductile iron, gray iron, and steel.

Metal casting methods

Semi-permanent molds - Semi-permanent mold is a casting process - producing Aluminum alloy castings - using re-usable metal molds and sand cores to form internal passages within the casting. Molds are typically arranged in two halves - the sand cores being put into place before the two halves are placed together.

• ZINC -

Zinc is a chemical element with the symbol Zn and atomic number 30. Zinc is a slightly brittle metal at room temperature and has a shiny-greyish appearance when oxidation is removed. It is the first element in group 12 of the periodic table.

Most zinc is used to galvanise other metals, such as iron, to prevent rusting. Galvanised steel is used for car bodies, street lamp posts, safety barriers and suspension bridges.

Large quantities of zinc are used to produce die-castings, which are important in the automobile, electrical and hardware industries. Zinc is also used in alloys such as brass, nickel silver and aluminium solder.

Zinc oxide is widely used in the manufacture of very many products such as paints, rubber, cosmetics, pharmaceuticals, plastics, inks, soaps, batteries, textiles and electrical equipment. Zinc sulfide is used in making luminous paints, fluorescent lights and x-ray screens.

• LEAD - 

Lead is a chemical element with the symbol Pb and atomic number 82. It is a heavy metal that is denser than most common materials. Lead is soft and malleable, and also has a relatively low melting point. When freshly cut, lead is a shiny gray with a hint of blue. It tarnishes to a dull gray color when exposed to air.

Lead is still widely used for car batteries, pigments, ammunition, cable sheathing, weights for lifting, weight belts for diving, lead crystal glass, radiation protection and in some solders. It is often used to store corrosive liquids.

• TIN -

Tin is a chemical element with the symbol Sn and atomic number 50. Tin is a silvery-coloured metal. Tin is soft enough to be cut with little force and a bar of tin can be bent by hand with little effort.

It is a soft, silvery white metal with a bluish tinge, known to the ancients in bronze, an alloy with copper. Tin is widely used for plating steel cans used as food containers, in metals used for bearings, and in solder. 

• WORK HARDENING -

Work hardening, in metallurgy, increase in hardness of a metal induced, deliberately or accidentally, by hammering, rolling, drawing, or other physical processes. Although the first few deformations imposed on metal by such treatment weaken it, its strength is increased by continued deformations.

 The Stages of Work Hardening after Diehl, stage I/Easy Glide, stage II/Athermal Work Hardening and stage III/Dynamic Recovery.

An example of desirable work hardening is that which occurs in metalworking processes that intentionally induce plastic deformation to exact a shape change. These processes are known as cold working or cold forming processes.

• ANNEALING OF ALL METALS -

Annealing steel or any other metal involves heating it to a specific temperature and allowing it to cool at a specified rate. Doing so removes impurities in the grain, increasing the metal's ductility and reducing its hardness.

While steel and alloy steel annealing is common, other metals can also benefit from the process, such as aluminium, brass, and copper.

What are the 3 types of annealing? Included in the list are: Complete Annealing. Isothermal Annealing. Incomplete Annealing.

During the annealing process, the metal is heated to a specific temperature where recrystallization can occur. At this stage, any defects caused by deformation of the metal are repaired. The metal is held at that temperature for a fixed period, then cooled down to room temperature.

• CASE HARDENING OF MILD STEEL -

Case-hardening involves packing the low-carbon iron within a substance high in carbon, then heating this pack to encourage carbon migration into the surface of the iron. This forms a thin surface layer of higher carbon steel, with the carbon content gradually decreasing deeper from the surface.

What is case hardening of steel?

Case hardening is a material processing method that is used to increase the hardness of the outer surface of a metal. Case hardening results in a very thin layer of metal that is notably harder than the larger volume of metal underneath of the hardened layer.

• HARDENING AND TEMPERING TOOL STEEL [HCS] -

Hardening and tempering of engineering steels is performed to provide components with mechanical properties suitable for their intended service. Steels are heated to their appropriate hardening temperature {usually between 800-900°C), held at temperature, then "quenched" (rapidly cooled), often in oil or water.

What is the difference between hardening and tempering of tool steel?

The maximum hardness of a steel grade, which is obtained by hardening, gives the material a low toughness. Tempering reduces the hardness in the material and increases the toughness. Through tempering you can adapt materials properties (hardness/toughness ratio) to a specified application.

What is hardening and tempering?

A treatment in which a part is subjected to two complete hardening operations, or first an annealing process followed by a hardening process. Tempering. Tempering is a low temperature heat treatment process normally performed after a hardening process in order to reach a desired hardness/toughness ratio.