A die is a tool or mold used to shape metal, plastic, paper, or other materials. Dies stamp, forge, cast, draw or extrude these materials into many products including wrenches, wire, bowls, cutting tools, and coins. Dies are widely used to mass-produce products at low cost. Many dies are made of tool steel, a steel that contains a high percentage of carbon. Tool steel can be made very hard by treating it with heat, and it can be ground into very precise shapes. Some dies are made either entirely or partly of rubber or plastic. Stamping dies are sometimes made of tungsten carbide, an extremely hard material that can stamp out many parts without being sharpened or repaired.
Stamping dies have two basic parts, an upper and a lower half, between which the material to be stamped is placed. The upper half often has a punch and the lower half a hole or indentation into which the punch forces the material.
Some stamping dies punch through sheets of material and cut out fully formed parts. Other stamping dies bend and form the material without cutting it. Another kind of stamping die, called an embossing or coining die, is used to make coins, medals, jewelry, and other things that have raised writing or designs on them. Both sides of the material can be embossed in a single stamping operation if patterns are cut in both parts of the die. To emboss a coin, for example, a metal disk is placed on the lower half of the die and enclosed in a metal ring so it will not spread when it is stamped. One half of the die has the "head" pattern of the coin, and the other half has the "tail" pattern. When the blank is stamped between the two halves of the die, it is embossed on both sides at once.
Forging dies are used to squeeze slugs of hot metal into shape. In drop-forging, the slug is pounded into shape by the repeated hammering of the upper half of the die.
Casting dies are metal molds into which molten material is forced under pressure. The material hardens in the shape of the mold and is then removed.
Drawing and Extrusion Dies
Drawing and extrusion dies contain holes through which cold or hot metal is either squeezed or pulled. The shape and size of the hole determines the shape and size of the resulting product.