Whether you are cutting sheet metal in a factory or in your home workshop, your goal is to separate the sheet or remove a part of the sheet to obtain one or more usable parts. Like most jobs, the method and process you select to cut the metal can mean the difference between success and failure. Personal protective equipment such as gloves and eye protection should always be worn when cutting sheet metal.
Shearing in general means to cut an object by applying shear forces until it fails. In sheet metal cutting, shearing refers to the sheet metal cutting process that cuts the stock in a straight line. Manufacturers use industrial shear machines that may be hydraulic, electric or manual for large shearing jobs. For the home workshop you would more likely use powered hand-held metal shears or tin snips for the shearing process.
Blanking is the process by which a shape or part is cut from a larger piece of stock. The resulting part, called a blank, is usually processed further into its final form. The stock is placed over a blanking die which has an opening that will give the blank its shape. A blanking punch with the same shape as the opening in the die pushes down with force and speed on the stock, forcing the blank to separate from the sheet in the shape of the die. The blanking punch normally gets its force from a hydraulic press.
Punching is the process by which voids of a desired shape and size are cut from the stock. It is identical to blanking except that the part removed is called a slug instead of a blank and it is to be discarded.
Mechanical cutting is similar to cutting paper with scissors. Force is applied by a tool on one side of the stock resting against a tool on the other side. When enough force is applied, the metal will separate. The tools used can be as small as a pair of tin snips or as large as an industrial shear machine.
Water jet cutting uses a high-speed stream of water containing abrasives to cut the metal. A narrow jet of water traveling at 2,000 feet per second can apply as much as 60,000 pounds per square inch (PSI) pressure to the metal. The material struck by this force simply erodes away.
Laser cutting focuses a high-powered laser beam onto the stock and melts or vaporizes the metal. A stream of gas blows away any residue. Similarly, plasma cutting focuses a stream of high-temperature ionized gas, called plasma, to cut the metal. The plasma melts the metal and blows away the molten metal.
You can cut sheet metal at home using a rotary tool fitted with a circular saw or a specially designed drill bit made from very hard carbide steel.