There are hundreds of metal alloys available for CNC milling and turning. Which one is best for your next project depends on many factors, including price, machinability, corrosion resistance, strength, weight, and aesthetics. To help you choose, here’s a closer look at some we use every day and how they might benefit your next project.

Aluminum 6061

This is the most common general-purpose aluminum grade. The primary 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 include good machinability and workability, the ability to be welded and anodized, and its wide availability means it is economical.

When heat treated to the T6 temper, 6061 has a higher yield strength than annealed 6061, albeit at a slightly higher price. A disadvantage is that 6061 lacks corrosion resistance when exposed to saltwater or other chemicals. It also isn’t as strong as other aluminum alloys for more demanding applications.

6061 is commonly used in automotive parts, bicycle frames, sporting goods, some aircraft components, and frames for RC vehicles.

Aluminum 7075

7075 is a higher grade of aluminum, primarily alloyed with zinc. It is one of the strongest aluminum alloys and has excellent strength-to-weight properties.

Due to its strength, it has average machinability, meaning it tends to spring back to its original shape upon cooling. 7075 is also machinable and can be anodized. 7075 is typically hardened to T6. However, while it is a poor choice for welding, this should be avoided in most cases. We often use 7075 T6 to make injection mold tools. It is also used in high-strength leisure equipment for mountain climbing, as well as automotive and aerospace frames and other pressure-sensitive components.

Brass

Brass is an alloy of copper and zinc. It is a very soft metal and can generally be machined without lubrication. It is also highly workable at room temperature, so it is often found in applications that do not require significant force. There are several varieties of brass, largely depending on the percentage of zinc. As this percentage increases, corrosion resistance decreases.

Brass takes a high polish and looks very similar to gold. This is why it is often found in cosmetic applications. Brass is conductive but non-magnetic and can be easily recycled. Brass can be welded, but is most often joined using low-temperature processes such as brazing or soldering. Another characteristic of brass is that it won’t ignite when struck against another metal, making it suitable for use in potentially explosive environments. Interestingly, brass has natural antibacterial and antimicrobial properties, and its use in this area is still under investigation. Brass is commonly found in plumbing fittings, home decorative hardware, zippers, naval hardware, and musical instruments.

303 Stainless Steel

There are many varieties of stainless steel, so-called because of the addition of chromium, which helps prevent oxidation (rust). Because all stainless steels look similar, great care must be taken to test incoming raw materials with modern metrology equipment, such as OES detectors, to confirm the characteristics 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) and cannot be heat treated. The presence of sulfur also means it is not a good candidate for welding. It does have excellent machinability, but care must be taken with speed/feed and cutting tool sharpness. It is often used for stainless steel nuts and bolts, fittings, shafts, and gears. However, it should not be used for marine-grade fittings.

304 Stainless Steel
This is the most common form of stainless steel found in a variety of consumer and industrial products. Often referred to as 18/8, this refers to the alloying addition of 18% chromium and 8% nickel. These two elements also make the material particularly tough and non-magnetic.

304 is easily processable, but unlike 303, it can be welded. It is also more corrosion-resistant in most normal (non-chemical) environments. For machinists, it should be machined with very sharp cutting tools, free of contamination from other metals. Historically, 304 steel has been an excellent choice for kitchen fittings and cutlery, pots, and pipes used in industry, construction, and automotive interiors.

316 Stainless Steel

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

Carbon Steel 1045
This is a common mild steel grade, i.e., not stainless. It is generally more expensive than stainless steel, but considerably stronger and tougher. It is easy to machine and weld, and can be hardened and heat-treated to 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 if exposed to the environment, it is usually surface-treated to prevent rust.

Titanium
Titanium is a material 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 a particularly poor conductor of electricity, but it is a good heat conductor. It is a tough material for machining, and special cutters should be used.

Titanium is generally biocompatible and has a very high melting point. While 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 fields, where it resists heat and corrosive acids.

If you have future projects requiring CNC machining, please send your drawings to this email address for a quote and evaluation: info1@us.cjcncmachining.com