Machining

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A lathe is a common tool used in machining.

Machining may refer to a occupation or a hobby. For further information on the occupation see machinist.

Machining may also refer to a collection of material-working processes that involves using a power-driven machine tools, such as a lathe, milling machine, or drill, to shape metal by removing excess material. Machining is a part of the manufacture of almost all metal products. It is not uncommon for other materials to be machined. For example, some plastic parts are machined. A person who specializes in machining is called a machinist.

A room, building, or company where machining is done is called a machine shop.

[edit] Machining operations

In the strictest sense machining operations are known as chip cutting operations. That is that metal is removed, cut away, from a material in the form of small chips. These chips are analogous to the sawdust produced by operations cutting wood with a saw or drill.

There are other operations that may be performed on metals and plastics that are related to the production of finished work but are not machining. Operations such as forging, forming, and welding do not qualify as machining since there is no chip-producing cutting of material to achieve a final form.

An unfinished workpiece requiring machining will need to have some material cut away to create a finished product. A finished product would be a workpiece that meets the specifications set out for that workpiece by engineering drawings or blueprints. For example, a workpiece may be required to have a specific outside diameter. A lathe is a machine tool that can be used to create that diameter by rotating a metal workpiece, so that a cutting tool can cut metal away, creating a smooth, round surface matching the required diameter and surface finish. A drill can be used to remove metal in the shape of a cylindrical hole. Other tools that may be used for various types of metal removal are milling machines, saws, and grinding tools. Many of these same techniques are used in woodworking.

More recent, advanced machining techniques include electrical discharge machining (EDM), electro-chemical erosion, laser, or water jet cutting to shape metal workpieces.

As a commercial venture, machining is generally performed in a machine shop, which consists of one or more workrooms containing major machine tools. Although a machine shop can be a stand alone operation, many businesses maintain internal machine shops which support specialized needs of the business.

Machining requires attention to many details for a workpiece to meet the specifications set out in the engineering drawings or blueprints. Beside the obvious problems related to correct dimensions, there is the problem of achieving the correct finish or surface smoothness on the workpiece. The inferior finish found on the machined surface of a workpiece may be caused by incorrect clamping, dull tool, or inappropriate presentation of a tool. Frequently, this poor surface finish, known as chatter, is evident by an undulating or irregular finish, and the appearance of waves on the machined surfaces of the workpiece.

[edit] Machining as a hobby

Machining can be a hobby in itself, or it can be useful in pursuing other hobbies. For instance, more serious car restorers have home workshops with a range of machine tools. There are also individuals who start building up a home workshop with the idea of eventually building some project, such as maybe a miniature steam locomotive, but get sidetracked into building the machine tools themselves and their accessories. The home machine shop thus may end up being a satisfying hobby in itself. There are in fact at least four magazines that cater to this side of the hobby, Home Shop Machinist and Machinist's Workshop in the USA, and Model Engineer and Model Engineer's Workshop in the United Kingdom. Machinist's Workshop and Model Engineer's Workshop tend to be very project-oriented, while the other two tend to present a mix of projects, techniques, and theory.