A cold chisel is a tool that can cut through "cold," i.e. unheated, metal. This is in comparison to other blacksmith tools that are typically used only after the metal has been heated. Sometimes these chisels are also called "coal chisels." These chisels are strong and heavy because they are usually made of tempered steel, which is hard enough to bite through most other metals.
Some cold chisels are made of copper in order to ensure that they will not produce sparks. In most cases, however, the chisel is forged from steel and then flame-tempered until its head takes on a hard, browned appearance. This gives it roughly the same cutting ability as a metal saw or cutting machine.
In most cases, a cold chisel will not be the right choice if a refined surface is desired. They are intended to perform many of the same functions as cutting machines but are typically less accurate and harder to use. This tool may come in handy if a cutting machine is either unavailable or out of service, or in special circumstances where the machine can't do the job properly.
Unlike a woodworking chisel, a cold chisel tends to be darker in color and may not have a handle. Technically there are four main types of cold chisel: those that are equipped with a diamond-shaped point for making sharp cuts or punching holes; those that have a cross-cut head for making slots or grooves; those that have a rounded blade for making indentations; and those that have a flat, wide cutting head. The most common type of this chisel is the flat chisel.
The flat cold chisel can be used as a substitute for a masonry chisel where necessary, due to its heavy shaft and sharp blade. It is able to split bricks and stone almost as easily as metal. Cold chisels don't make very precise cuts, so they are best suited to jobs where a rough edge is acceptable. For this reason, they are often used to split larger metal sheets into pieces or to chip away excess. Weak or pre-formed metal objects, like pipes, are not usually good candidates for cold chisel cutting.
These chisels come in a wide range of sizes. Some are small, designed to be used for delicate work, while others are extremely large, heavy chisels that have to be struck with a large sledgehammer or mallet. The operator should hold the chisel perpendicular to the metal surface he or she wishes to split.