old chisels are forged to shape and hardened and tempered at the cutting edge. Although the vast majority of cold chisels are made of steel, a few are manufactured from beryllium copper, for use in special situations where non-sparking tools are required.

Cold chisels are made from carbon tool-steel, which is usually octagonal in cross-section. Tool-steel is used as it can be hardened to form a hard and tough cutting edge.
To make a cold chisel heat the end of the bar of tool steel until it is bright red and hammer to the desired shape.

The cross-section of chisel should be octagonal.

The cutting edge of a chisel should be Hardened and tempered.
A chisel is a tool with a characteristically shaped cutting edge of blade on its end, for carving or cutting a hard material such as wood, stone, or metal by hand, struck with a mallet, or mechanical power.