Machinable Metals

Steels that contain specified amounts of alloying elements — other than carbon and the commonly accepted amounts of manganese, copper, silicon, sulfur, and phosphorus are known as alloy steels. Alloying elements are added to change mechanical or physical properties.

Aluminum comes in many different shapes and grades. The type of aluminum grade you choose ultimately depends on how you intend to use the metal. Your intended use allows you to rank the characteristics of each grade from most important to least important. This will help you narrow down the list of suitable grades. For example, for machinabilitiy and streangth are important to your project, it may make sense to choose Alloy 2011, as this aluminum grade may be machined at high speeds with relatively heavy feeds. Its corrosion resistance is good with excellent hardness and strength.

Brass is a metal made of copper and zinc, having a muted yellow color, somewhat similar to gold. Brass parts are easy to machine, look great and benefit from the unique properties of this special metal. Parts made from brass can leverage density and attractive appearance as in many decorative parts. Brass parts often get by without a surface finish, saving on cost and delivery time.

When it comes to machining bronze components, it’s all about knowing what speeds and feeds to use, and what type of tooling is required. Many of these variables depend on the machinability of the material. With a wide variety of bronze alloys to choose from it is critical to understand the application. Alloys such as C954 or C955 can be quenched and tempered to reach even higher strengths when necessary. Resistance to seawater corrosion is extremely high in nickel aluminum bronzes such as C955. Due to its resistance to corrosion, erosion, and cavitation, it is widely used for propellers and other marine hardware.

Carbon steel is commonly used across many industries. It is affordable while still providing excellent mechanical properties. Carbon steel is typically composed of 0.05% to about 2.0% carbon measured by weight, along with iron and trace amounts of other elements. There are many types of carbon steel that can be easily machined, but there are also many that may prove to be difficult. Grades of lower carbon steel such as C1010 and C1018 have good machinability. Alternatively, carbon steel with higher amounts of carbon such as C1141 and C1144 can also be machined without difficulty due to the sulfur that is added to their chemical composition.

Cast iron is typically much easier to machine than steel. The graphite structure in cast iron breaks away more easily, and in a more uniform manner. Harder irons, such as white iron, are much more difficult to machine due to their brittleness. Depending on the final application, cast parts may need to be machined to achieve specific tolerances, or to create a desired finish.

Copper alloys exhibit good to excellent corrosion resistance and high thermal conductivity and very high electrical conductivity. Applications include architectural uses, coinage, condenser/heat exchangers, plumbing, radiator cores, musical instruments, locks, fasteners, hinges, ammunition components, and electrical connectors.

Nickel alloys are used primarily in applications involving electrical properties or requiring good corrosion resistance or high strength and oxidation resistance at high temperatures.

Tool steel is a term used for a variety of high-hardness, abrasion resistant steels. Specific tool applications are dies (stamping or extrusion), cutting, mold making, or impact applications like hammers (personal or industrial). It is also a common material used to make knives.

Stainless steel is often thought of as a singular material, but in fact there are approximately 150 separate and distinct compositions. Each one formulated to serve a specific application and/or manufacturing requirements. For example, Type 304, one of the most frequent used stainless steel compositions having application in a broad range of products from cookware to chemical plant equipment.