Since most products are made up of numerous components, the metalworking industry is vitally concerned with methods of joining parts.

Nuts, bolts, and directly threaded members are widely used. Threading and tapping can be done on special equipment or on converted and specially tooled standard machine tools. In addition to the processes of riveting, welding, brazing, soldering, and mechanical joining, industrial adhesives have come into the metalworking industry. These synthetic materials have been widely used to join nonmetals to metallic parts and are also used to join metals to each other. Temperature limitations, which hampered rapid growth of such techniques, have been constantly expanded.

A micrometer is a screw gauge instrument that uses a very accurately machined screw to measure distances to a high degree of precision. The micrometer caliper, the most common of these instruments, is used to measure the dimensions of small machine parts. The part to be measured is placed between two jaws, one fixed and one movable. The movable jaw moves forward as a screw is turned. American micrometers often advance at 0.025 inch per turn. Scales readable to 0.0001 inch show how many turns and fractions of a turn the screw has advanced. A variant of this type of micrometer measures inside dimensions, such as the diameter of a hole. In addition, some types of depth gauges work on the same principle as the micrometer.

The filar micrometer is used to measure distances through an optical instrument, such as a telescope or microscope. In this case a micrometer arrangement is used to measure the distance traveled by a hairline across the field of the instrument. By moving the hair

A chisel is a cutting tool with the blade at one end, driven with a thrusting action by hand or hammer. Chisels differ widely in shape and purpose. The cold chisel is used for cutting unheated metal and stone; it is formed of highly tempered steel, and is driven by a hammer. Carpenters’ chisels are driven by hand or by blows from a mallet.

The process of producing metallic coatings on metal by the action of an electric current is termed electroplating. The purpose of coating is usually to improve the appearance (such as cadmium on steel and silver or gold on copper), but plating is also used to improve hardness, resistance to corrosion and bearing properties.

Steel is electroplated with tin for food cans, and tableware is often plated with silver.

Most electroplating is done in special baths containing a compound of the metal to be deposited; the baths are usually either cyanide or sulphate. The object to be plated is first thoroughly cleaned; then an electrical current is passed through the bath, this causing the dissolved metal salts to form as a plate metal layer on the surface of the object. The thickness of the coating is determined by the time in the plating bath and the current density used. More than 30 metals can be electrodeposited, but only about half that number are used commercially.

The commonly plated metals are copper, nickel, chromium, tin, cadmium, zinc, silver and gold. Silver articles that have been electroplated usually bear the initials EPNS (Electroplated Nickel Silver) to distinguish them from real silver.