Wastage and addition

Metal is a popular material to use in schools within Design and Technology lessons as it is generally not too expensive in comparison with other materials that are available.

There are many different tools for marking out on metal:

  • scriber - a sharp point to put a fine scratch on the surface of the metal that is being marked
  • steel rule - more accurate than a plastic ruler and often has half millimetres as well as millimetres
  • ball pein hammer - used for tapping a centre punch before drilling a hole
  • centre punch - used to create a drill point before a hole is drilled into metal so that the drill bit does not slip on the surface
  • engineer’s square - used for marking out at 90 degrees to an edge or face
  • marking blue or layout fluid - dye used to coat the surface to be marked, and if it is hard to see the line made with a scriber then it will be easier to scratch a fine line through the blue dye
A man`s hands making markings on a piece of metal with a metal stylus.

Scriber

A hacksaw is normally used to cut metal by hand. If a smaller piece of metal is being cut, then a junior hacksaw can be used. Once the metal is cut close to a marked line, a file can be used to remove material up to the desired line. Files can be bought in different shapes, sizes and cutting grades - a rough-cut file can remove metal faster than a smooth-cut file and should always be used first.

A blue, rectangular hacksaw with a black handle laid on a wooden background.

A junior hacksaw has a smaller blade used for more precise cutting

Once filing has been done and the profile of the metal is at the desired shape, the file marks can be removed with abrasive papers such as emery cloth and silicon carbide paper (often called ‘wet and dry’ paper as it can be used both wet and dry). A buffing machine can be used to polish the metal to achieve a mirror-like finish.

A gloved hand using a buffing machine to polish a car for painting.
A buffing machine

Metal can also be drilled by using a variety of different drill bits, which work by twisting into a piece of metal:

  • twist drills - used to simply drill a hole of fixed diameter into a piece of metal
  • countersink bits - used to profile a hole so that a screw can sit flush with a surface
The three stages in adding a screw to timber, starting with the use of a twist drill followed by a countersink put and then the screw.

Holes

  • countersunk - makes a tapered hole and is used to fit flathead screws
  • counterbored - usually used when the head of a fastener is required to be flush with or below the level of a workpiece surface
A countersunk hole, drilled at a horizontal so a screw would sit on the surface, and a counterbored hole, drilled straight down so that a screw would sit beneath the surface.

A tap is used to cut or form a thread

A close-up of the tapping process to add a thread to a metal component.
Tapping