Cold heading is the industrial process used to cold-form different screw heads onto screws. The process uses rams, bolsters, punches, and dies to force the metal into the desired shape while it is still cold. The process uses a tremendous amount of pressure, but the benefit of the process is that the metal does not weaken like it can during a hot-forming process. The addition of computer-controlled part forming and heading machines make the number of cold headed part designs nearly endless, but there are a few basic shapes that most factories use, including:
Hexagonal heads: Hexagonal heads are used with ratchets and many other tools for screwing different objects together. The heads have a flat, hexagonal shape that is easy to grip. This form of head does not easily strip, and can come in a huge variety of sizes and thicknesses.
Square heads: Square heads are much like hexagonal heads, but often the machine will press a screwdriver shaped dent into the center of the head so that a standard screwdriver can fix the screw in place. Some pieces, such as rivets, have a flat head.
Round heads: Round heads can be completely smooth, or have a groove in the top to fit a screwdriver into the slot. Smooth heads are often used for rivets and nuts and often come in larger sizes. Smaller round heads are more likely to have screw dents in the center of the head.
Radial slots: Radial slots have a flat head that tapers at an angle toward the screw body. These screws are ideal for attaching a screw that becomes nearly undetectable after use.
Collars: A collar on a screw can act as a spacer between two different objects or it can prevent the screw from entering a material all the way. The collar has a piece of screw on both sides of the protruding collar.