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A Quick Start Guide to CNC Machining Metals

In the 21st century, we take metal for granted. Not just steel and aluminum and copper, but titanium and the multitude of steel and copper alloys that make modern life possible. Complex surgical devices and permanent implants in the human body have been made possible by the evolution of sophisticated metals and alloys.

The surprising thing about metals is not how many of them we have today, but how many thousands of years it took for us to move beyond the basics of bronze and iron. For example, the first steel was produced in India in 400 BC, but it was not until the mid-19th century that commercial methods of producing steel were developed, and not until the early 20th century that steel production became a rock of global industry. Today, steel production is a fine art, with many different grades and varieties used for their unique properties in specific applications.

Here at SPM, we are fascinated with all things metal. We work with everything from the bronze and copper of 6000 years ago, to the nitronic alloys of today. To excel in CNC machining, you have to know metal — not in a superficial sense, but deeply and thoroughly. You have to know how it will behave under a variety of circumstances and what properties will produce the desired results.

With that in mind, here is a guide to the most important metals used in CNC machining, their properties, and their applications.

CNC Machining Metals

Copper. One of the first metals discovered around 9000 BC, copper is a strong, formable metal with good conductivity for electricity and heat. It’s also resistant to rust and other corrosive effects. Copper plays an important role in modern society, bringing heat and clean water into our homes and buildings. Copper is used in CNC machining for valves, hydraulic tubing, radiators, cooling systems, and heat exchangers.

Bronze. Bronze is an alloy of copper and tin. We don’t know exactly when it was discovered, but it was being used by the ancient Sumerians as early as 3500 BC. Bronze is a strong, hard metal that is resistant to wear and corrosion. Bronze is used in CNC machining for bearings, bushings, screws, threaded parts, and electrical connectors.

Brass. An alloy of copper and zinc, brass was discovered in about 1400 BC but it is only within the last 1000 years that it has been used for engineering. Brass production became important during the industrial age, especially for parts needed by the wool industry. Today brass is often used for bathroom fixtures and door knobs because it is a poor breeding ground for bacteria. Brass is one of the easiest materials to machine and produces component parts that are durable, cost-efficient, and corrosion-resistant. It is used in CNC machining for bearings, bushings, valves, gears, and hinges.

Iron and Steel. Iron is the king of metals. The discovery and use of iron changed world history. It’s why we divide ancient history into the bronze age and the iron age. Iron was discovered in about 1500 BC and was put into use almost immediately to manufacture weapons and tools. While iron is not used in CNC machining, it’s important because eventually iron would be purified to make steel, a metal alloy which makes the modern world possible.

Steel is an alloy of iron and carbon. It “was produced in bloomery furnaces for thousands of years, but its large-scale, industrial use began only after more efficient production methods were devised in the 17th century…in the mid-19th century…with the invention of the Bessemer process, a new era of mass-produced steel began.” This process was one of many that accelerated the advancement of the industrial age.

Stainless Steel. In the last decades of the 19th century, Andrew Carnegie put U.S. steel on the map, but the most important development for modern machining came in 1919 when Harry Brearley discovered stainless steel — low carbon steel with chromium which makes it corrosion resistant. Stainless steel is used for everything from screws to airplane parts. Stainless steel’s ease of cleaning and strength to weight ratio make it the first choice in many medical applications. Stainless steel and its alloys are used in CNC machining to create components for the aerospace and automotive industries, surgical equipment and medical implants, as well as anything that needs corrosion resistance and strength.

Nitronic 60. A niche metal, nitronic 60 is an anti-galling, wear resistant stainless steel. It provides high performance at both ambient and elevated temperatures making it an effective metal for construction applications. It’s ideal for manufacturing valve stems, fastening systems, chain drive systems, and pump components.

Titanium. Discovered in 1791 AD, titanium is a light-weight, corrosion resistant, high-strength metal that’s used for aerospace, medical, military, and sporting goods applications. It is especially useful for medical implants since it doesn’t cause a negative immune response in humans. Continuous improvement has made titanium easier to machine over the last decade, but it still requires experience, skill, and the right equipment. As the aerospace industry moves more and more from aluminum to titanium, the skill level of the CNC machine shop is going to be an important factor the plane manufacturer’s success.

Aluminum. At one-third the weight of steel, aluminum is the most common metal in the earth’s crust. Aluminum is inexpensive, durable, malleable, and 100% recyclable. After it was discovered in the mid-19th century, it quickly became the metal of choice in the transportation, construction, and defense industries. Aluminum is used in CNC machining to make housings, shafts, worm gears, and medical devices.

As old manufacturing challenges are solved, new ones appear to take their place. In response to these industrial challenges, metallurgists are continually experimenting with new alloys, constantly seeking stronger, lighter weight, less expensive compounds.

Machining metal is our business. We stay at the forefront of equipment, machining techniques, and metals. We would love to talk to you about the perfect material for your next project. Give us a call and ask to speak to one of our engineers about your unique requirements. (847) 647-7111