Types of Machining Operation

The most widely used engineering materials are metals. They exhibit strength, resistance to both high and low temperatures, and good conductivity of heat and electricity. They can be formed and shaped and joined into a great variety of shapes. Metals become most useful when they are combined with other metals and elements which give them the qualities of strength and toughness. There are many manufacturing methods by which metals and alloys can be made into useful engineering products. Metal shapes can seldom be used without additional machining. Machining means the controlled removal of material by cutting, drilling or shaving of the material off the surface.

There are many kinds of machining operations, each of which is capable of generating a certain part geometry and surface texture.

In turning, a cutting tool with a single cutting edge is used to remove material from a rotating work piece to generate a cylindrical surface.

Drilling is used to create a round hole. It is accomplished by a rotating tool that is typically has two cutting edges. The tool is fed in a direction parallel to its axis of rotation into the work part to form the round hole.

In boring, the tool is used to enlarge an already available hole. It is a fine finishing operation used in the final stages of product manufacture.

Machining.

Machining is a group of operations that change the shape or mechanical properties of a material by the application of special tools and equipment. Machining almost always is a process where a cutting tool removes material to effect the desired change in the work piece.

Cylindrical hole can be produced in a work piece by drilling, milling and electric discharge machining. Special geometrics, such as threads and gears are produced with special tooling and equipment utilizing turning and grinding processes. The process of machining generates heat that must be dissipated before it damages the work piece or equipment. Cooling substances, which also act as lubricants, are often used. One of the most common machining operations is drilling. It is a method of producing a cylindrical hole in a workpiece.

Turning is performed on a lathe. The process involves the removal of material from a workpiece by rotating it against a cutting tool. Sawing is the division of material by using blades, bands or abrasive disks as the cutting tools.

Grinding is the process of removal of material by the cutting action of a solid, rotating, grinding wheel. Grinding is used to machine a wide range of metals, stone and ceramics. Grinding wheels are composed of abrasive grains plus a bonding material. The abrasive most commonly used is aluminium oxide. Coolants are applied to the grinding point to remove the heat generated and fine chips.

Metallurgy

The technology and science of metallic materials. Metallurgy as a branch of engineering is concerned with the production of metals and alloys, their adaptation to use, and their performance in service. As a science, metallurgy is concerned with the chemical reactions involved in the processes by which metals are produced and the chemical, physical, and mechanical behavior of metallic materials.

Metallurgy has played an important role in the history of civilization. Metals were first produced more than 6000 years ago. Because only a few metals, principally gold, silver, copper, and meteoric iron, occur in the uncombined state in nature, and then only in small quantities, primitive metallurgists had to discover ways of extracting metals from their ores.

Fairly large-scale production of some metals was carried out with technical competence in early Near Eastern and Mediterranean civilizations and in the Middle Ages in central and northern Europe. Basic metallurgical skills were also developed in other parts of the world.The winning of metals would have been of little value without the ability to work them. Great craftsmanship in metalworking developed in early times: the objects produced included jewelry, large ornamental and ceremonial objects, tools, and weapons. It may be noted that almost all early materials and techniques that later had important useful applications were discovered and first used in the decorative were discovered and first used in the decorative arts.In the Middle Ages metalworking was in the hands of individual or groups of craft workers. The scale and capabilities of metal working developed with growth of industrial organizations. Today’s metallurgical plants supply metals and alloys to the manufacturing and construction industries in a variety of forms, such as beams, plates, sheets, bars, wire, and castings. Technologies such as communications, nuclear power, and space exploration continue to demand new techniques of metal production and processing.