There are hundreds of metal alloys available for CNC milling. Which one is best for your next project depends on many factors including price, machinability, corrosion resistance, strength, weight, and cosmetic appearance.
To help you choose, let’s take a look at how each can benefit your next project.

Aluminum 6061.

This is the most common general-purpose aluminum grade. The main alloying elements are magnesium, silicon and iron. Like all aluminum alloys, it has a good strength-to-weight ratio and is naturally resistant to atmospheric corrosion. Other advantages are that it has good machinability and machinability, can be welded and anodized, and its wide availability means it is economical.
When heat treated to T6 temper, 6061 has a higher yield strength than annealed 6061, although the price is slightly higher. The disadvantage is the lack of corrosion resistance of 6061 when exposed to salt water or other chemicals. It is also not as strong as other aluminum alloys for more demanding applications.
6061 is commonly used in auto parts, bicycle frames, sporting goods, some aircraft components and frames for RC vehicles.

Aluminum 7075.

7075 is a higher grade of aluminum alloyed primarily with zinc. It is one of the strongest aluminum alloys with excellent strength-to-weight properties.
Because of its strength, it has average machinability, which means it tends to spring back to its original shape when cooled. 7075 is also machinable and can be anodized. 7075 is usually hardened to T6. However, it is a good choice for soldering, which should be avoided in most cases. We often use the 7075 T6 to make injection mold tooling. It is also used in high-intensity recreational equipment for mountain climbing, as well as automotive and aerospace frames and other stress components.

Brass

Brass is an alloy of copper and zinc. This is a very soft metal and can usually be machined without lubrication. It’s also highly viable at room temperature, so it often finds applications that don’t require enormous force. There are various types of brass, largely depending on the percentage of zinc. As this percentage increases, the corrosion resistance decreases.
The brass is highly polished and looks a lot like gold. This is why it is commonly found in cosmetic applications. Brass is conductive but non-magnetic, and can be easily recycled.
Brass can be welded, but is most often joined with low-temperature processes such as brazing or welding. Another feature of brass is that it does not catch fire when struck with another metal, so it will find tools used in potentially explosive environments. Interestingly, brass has naturally anti-bacterial and anti-microbial properties, and its use in this regard is still being researched. Brass is common in plumbing fittings, home decorative hardware, zippers, navy hardware, and musical instruments.

Stainless steel 303.

There are many varieties of stainless steel, so called because of the addition of chromium that helps stop oxidation (rust). Since all stainless steels look alike, great care must be taken to test incoming raw materials with modern metrology equipment, such as OES detectors, to confirm the identity of the steel you are using.
In the case of 303, sulfur is also added. This sulfur helps make 303 the easiest stainless steel to machine, but it also tends to reduce its corrosion protection. 303 is not a good choice for cold forming (bending), nor can it be heat treated. The presence of sulfur also means it is not a good candidate for welding. It does have excellent machining properties but must be cared for with speed/feed, cutting tool sharpness commonly used for stainless steel nuts and bolts, fittings, shafts and gears. However, it should not be used with marine-grade accessories.

Stainless steel 304.

This is the most common form of stainless steel found in a variety of consumer and industrial products. Commonly known as 18/8, this refers to an alloy containing 18% chromium and 8% nickel. These two elements also make the material particularly tough and non-magnetic.
304 is easy to handle, but unlike 303, it can be welded. Also more resistant to corrosion in most normal (non-chemical) environments. For a machinist, it should be machined with very sharp cutting tools and not contaminated by other metals. Steel 304 is an excellent choice for kitchen fittings and utensils, tanks and pipes used in industry, construction and automotive trim throughout history.

Stainless steel 316.

The addition of molybdenum makes 316 even more corrosion resistant, so it is often considered a marine grade stainless steel. It’s also tough and easy to solder.
316 is used in construction and marine fittings, for industrial pipes and tanks, automotive trim and kitchen tableware.

Carbon steel 1045.

This is a common mild steel grade, ie, not stainless. It is usually more expensive than stainless steel, but is quite strong and tougher. It is easy to machine and weld, and can be hardened and heat treated for various hardnesses.
1045 steel (European standard, C45) is used in many industrial applications for nuts and bolts, gears, shafts, connecting rods, and other mechanical components that require higher toughness and strength than stainless steel. It is also used in architecture, but is often surface treated to prevent rust if exposed to the environment.

Titanium

Titanium is titanium with high strength, light weight, toughness and corrosion resistance. It can be welded, passivated and anodized for added protection and improved appearance. Titanium does not polish and is especially a poor conductor of electricity, but a good conductor of heat. It is a tough material for machines and special cutters should also be used.
Titanium is generally biocompatible and has a very high melting point. Although more expensive than other metals in commercial form, it is actually very abundant in the Earth’s crust, but more difficult to refine. It finds applications in the most demanding aerospace, military, biomedical and industrial areas where it resists heat corrosive acids.

Did you find what you were looking for?

While these are the most common metal alloys we use for most CNC milling and turning jobs, they can be used for almost any application. We will be happy to work with you to recommend the best solution for quoting referenced CAD files.