Machining

Machining is an occupation or hobby that involves using a power-driven machine tool, such as a lathe or drill, to shape metal. Machining is a part of the manufacture of almost all metal products. Some plastic parts are machined. A person who specializes in machining is called a machinist.

Machining operations

Most machining operations can be divided into those that remove metal from an item, and those that form metal in an item.

Often an unfinished workpiece will need to have some parts removed or scraped away in order to create a finished product. For example, a lathe is a machine tool that generates circular sections by rotating a metal workpiece, so that a cutting tool can peel metal off, creating a smooth, round surface. A drill or punch press can be used to remove metal in the shape of a 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.

Metal can be formed into a desired shape much more easily than materials such as wood or stone, especially when the metal is heated. A machinist may use a forging machine to hammer or mold a hot metal workpiece into a desired shape. Dies or molds may be used if the metal is soft enough, or under high pressures. A press is used to flatten a piece of metal into a desired shape.

Advanced machining operations might use electrical discharge, elecro-chemical erosion, or laser 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 as a hobby

Machining can be a hobby in itself, or it can be useful in pursuing other hobbies. For instance plenty of car restorers would have good 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 project's, techniques, and theory.

Machining hobbyists will often own a variety of machine tools, and may find the following accessories useful as well.

• Vices to hold the work on the table. These are a precision vice with flat jaws to hold the job without marking it. They are much lower in profile than bench vices used for hand work.
• Dividing head. These are used for machining features that repeat around a circular job repeatedly such as gear teeth or flats. The better ones are based on a worm gear and permit a very wide range of divisions to be performed.
• Rotary table. A form of dividing head that has a vertical axis. Very useful on Vertical mills for setting out holes around acircle or machining partly circular shapes.
• Propane/butane torches. These cannot perform welding, but are useful for braxing, silver soldering, and hardening items.

Many hobbyists discover that the maintaining, repairing, collecting, and building of machine tools and tooling becomes a significant and satisfying focus of their hobby. A large collection of information on numerous home shop-sized machine tools, the Machine Tool Archive (http://lathes.co.uk/), is located at http://lathes.co.uk/fr:usinage