Materials and manufacture

• Permanent - once this type of joint has been constructed, it cannot be reversed without causing damage to the product
• Welding - joining metals by the use of heat, this causes the two main pieces of metal to become molten and using a joining material to mix them before they solidify , forming a permanent strong joint
• Brazing - permanently joining metals such as copper and steel under heat using a rod made form an alloy of copper and zinc
• Soldering - a similar method to brazing but carried out at lower temperatures
• Riveting - using pins that are placed through two metal sheets or plates and then hammered flat to join the two elements together
• Adhesives - joining materials with glues that are generally invisible
• Frame joints - for joining woods e.g. butt joints
• Semi permanent - this type of joint can be disassembled without damaging the materials
• Screws,nuts,bolts,washers - used to hold two or more pieces of materials together in a semi permanent method of joining
• Snap joints - used for joining moulded plastic components
• knock down fittings - joining materials with screws and plastic or wooden corner joints, used in flat pack furnature
• MIG and TIG - can be used to join thin sheets of metal together by adjusting the settings on the main machine unit. MIG and TIG use a gas jet around a filler wire. This prevents the oxidation of the joint, ensuring optimum strength
• Oxy-acetylene - acetylene is burned with oxygen to produce a heat source of ~3500°C, a molten pool of the metal is made before a filler rod of the same material is dipped into the pool and melts, filling the joint
• Electric arc welding - generates enough heat to melt the joint edges by creating an electric current through an arc between the materials being joined and the filler rod. Low voltage, high current produces the arc, the electrode carries the current and is a flux coated filler rod
• Spot and seam - Uses an electric current as a heat source. Spot welding uses a spot to fuse the metals together and is mainly used in the production of car bodies
• Seam welding - passes an electric current through the edges of two sheets of metal as they pass through rollers e.g. food and drinks cans
• Process of soldering:

  1. Materials are cleaned and degreased by the use of flux
  2. Check that the surfaces fit together without gaps and will be held together securely when soldering
  3. A heat source is used to heat the materials around the joint to make sure both pieces are heated evenly. The solder filer rod is rested on the joint as it starts to melt, capillary action will allow solder to run between the joint
  4. Once filled, the joint will be left to cool and harden
• Process of riveting:

  1. The snap head rivet is places into a dolly that is held in the vice
  2. The metal sheets are then placed over the rivet
  3. The rivet set is then placed the rivet and pressed down to ensure that there are no gaps between the sheets
  4. The rivet set is tapped with a ball pein hammer. This closes any gaps and starts to form the rivet joint.
  5. The ball pein hammer is then reversed to form the head of the rivet
  6. the final stage is using a rivet snap to form a similar shaped dome on both sides of the joint
• Synthetic resin glue (cascamite) -

  Joining woods

  strong and water resistant

  Takes a long time to set
• PVA (polyvinyl acetate glue) -

  Joining woods

  strong and water resistant

  Not waterproof
• Compact adhesive -

  Joining different types of materials

  Quick

  Little or no time for repositioning
• Epoxy resin -

  Used to form a rigid bond with unlike materials

  Good water resistance

  Expensive as it needs to be spread over a large area to be permanent
• Density - the amount of mass in an object per unit of space occupied by the matter
• electrical conductivity - the movement of electricity through a piece of material
• Thermal conductivity - the movement of heat through a material
• tensile strength - the ability to withstand tension or pulling force without breaking or stretching
• Compressive strength - the ability to withstand push forces that try to crush or shorten it
• Bending strength - the materials ability to withstand being bent
• Shear force - the force that subjects to sliding action across their surfaces
• torsional force - a force that is applied to a material to try to twist it. Also known as torque
• Elasticity - the ability of the material to flex, bend and be deformed and return to its original shape once the forces are removed
• Plasticity - the ability of a material to permanently change as a result of forces applied to it , without cracking or breaking
• Malleability - the degree to which materials can be deformed in all directions as a compression force caused by impact is applied without breaking or cracking
• Ductility - the ability of a material to be stretched into thin wires without breaking
• Toughness - the ability to withstand sudden shocks or blows
• hardness - the ability to resist indentation
• Scratch tests - used to rank scratch resistance ability of materials
• Durability - the ability of a material to withstand wear and tear over time.
• Brittleness - The tendency of a material to break or shatter when subjected to stress
• Pine -

  Strong

  Cost effective

  Furniture