Sharp knife

A knife is a sharp-edged, or pointed instrument that typically consists of a blade and a handle for safely gripping it. The knife is arguably the most useful device in the history of mankind and evidence of its use reaches as far back as two-million years, predating modern humans.

The first known knives were flint or other rock, chipped or ground to an edge, sometimes with a handle. Palaeolithic knives may also have been made from wood, bone or antler, but these materials do not survive in the archaeological record. Advances in smelting and metallurgy have led to blades made of bronze, iron, then steel and more exotic materials. Both materials and designs have changed over time.

Today, knife blades are typically made of steel (metal), but obsidian, glass, titanium, ceramic and plastics are also used. Two recently introduced materials are Stellite and Talonite. There are a large number of alloys used as knife steels, mostly variants of high-carbon and stainless steels. Most knife steel is tempered martensite, which has a fine-grained crystal structure with lattice irregularities that make it hard.