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How to Machine Aluminum-A Comprehensive Guide

Table of Contents

Aluminum is a versatile material that is used in a wide variety of applications. It is one of the easiest metals to machine today, so it can be processed quickly and efficiently. But machining aluminum involves many complementary nuances, so machining aluminum can also be challenging.

In this comprehensive guide, the types of aluminum and their properties, tools for machining aluminum, the best strategies for machining aluminum, and other common problems and solutions are described in detail. We trust that after reading this article, you will have a better understanding of aluminum machining.

aluminum machining
aluminum machining

Effective Sequence for Machining Aluminum

To improve the process, I would go in this order:

  1. Setting parameters such as stepover/stepdown, feed rate, RPM, and toolpath.
  2. Select a cutting tool geometry suitable for aluminum and the type of operation (roughing, finishing, etc) such as helix angle, carbide grade, and number of flutes.
  3. Consider the cutter coatings and finish.
  4. Utilize coolant.
aluminum blocks for milling
aluminum blocks for milling

Why Can Aluminum Be Challenging?

Aluminum is one of the most widely used metals in the world and is highly versatile and cost-effective. However, aluminum can also be challenging to machine due to its unique properties. Mainly manifested in the following three points.

– Aluminum is challenging to machine due to its unique properties, a lightweight yet surprisingly strong metal with high thermal conductivity and low melting point. Additionally, aluminum is highly resistant to corrosion and oxidation, which can lead to inaccurate and inconsistent machining.

– Aluminum produces strong burrs or chips when cutting. This burr or chip can make it difficult to achieve a smooth finish that meets the necessary specifications. Additionally, burrs or chips can cause the aluminum to break or crack while being machined, resulting in costly repairs or replacements.

– Aluminum has low shear strength, making it difficult to cut accurately. Aluminum’s low shear strength can also make it difficult to achieve a consistent finish when machining large parts. Additionally, aluminum is a soft metal that can be easily damaged or deformed when machined.

end mill for aluminum
end mill for aluminum

Common Types of Aluminum

Aluminum is a versatile material used in various products, from beverage cans to aircraft parts. The type and grade of aluminum used depend on the application and desired results. Some common aluminum types are listed below along with some notes on machinability.

 1. Aluminum alloy – Aluminum alloy is an aluminum-like metal that contains other metal components and is commonly used to manufacture parts and structures with high strength, corrosion resistance, and high thermal stability. They can be machined using various machining techniques such as cutting, extrusion, drawing, and stamping, among others.

 2. Aluminum Mineral – Aluminum mineral is a low-cost alloy often used to make lightweight parts and structures. They can adopt machining techniques such as cutting, drawing, stamping, welding, etc.

 3. Aluminum mass – Aluminum mass is a high-quality alloy that is often used in the manufacture of high-performance components such as machine tools, auto parts, etc. They can employ machining techniques such as milling, turning, drilling, cutting, etc.

 4. Aluminum Powder – Aluminum powder is a reliable aluminum alloy that is often used to make complex structures and parts. They can employ machining techniques such as spark machines, milling, turning, cutting, etc.

Among them, the grade of aluminum can be divided into:

1000 series (represents pure aluminum, containing not less than 99% aluminum)
2000 series (mainly copper alloy)
3000 series (mainly manganese)
4000 series (mainly based on silicon)
5000 series (mainly magnesium)
6000 series (mainly magnesium and silicon)
7000 series (mainly zinc)

Common Types of Aluminum
Common Types of Aluminum

CNC tools for machining aluminum


Flutes is not a musical instrument, but a sharp groove positioned with the cutting tool. Best endmills for aluminum are usually available in 2 or 3 flute styles. But it is not that the more slots, the better. With more than 3 slots, aluminum can’t effectively evacuate debris at high speeds.


      • 2 flutes can further reduce clogging due to metal shavings. When cutting forces are low and chip clearance is critical to the process, 2-flute is the first choice for traditional machining of aluminum and is better suited for ramping and plunging operations.

     • 3 flutes are the best choice for solid carbide end mills for aluminum. 3 flutes provide a balance of tool strength and chip clearance.

      •4+ Flute: Designed to run at faster feed rates but due to having more flutes it causes issues with chip removal.


Helix Angles

The helix angle of the tool generally refers to the angle of attack of the tool, which is an angle in radians, indicating the angle of attack of the tool, and is a fixed and immutable value. Higher helix angles remove chips from the part faster and provide a better surface finish, but there is a commensurate increase in friction and heat during cutting.

                       35° Helix: For roughing, keeps the tool cool.
                       40° Helix: Versatile
                       45° Helix: For finishing

Helix angle
Helix angle

Drill bit

For small spot cutting on aluminum

Face milling cutter

For flat-section machining


A reamer is used to enlarge an existing hole in aluminum and the CNC machine must be set to a lower feed rate and a faster spindle speed.

Tips for using tools

If a worker wants to do a good job, he must first sharpen his tools.

Surface treatment of tools

-Tools Polishing: Tools lose their sharpness the longer they are used. Be sure to clean out the cutting grooves regularly to keep a good tool smooth.

-Coated: In general, uncoated tools are best. But in order to improve the part process, we sometimes have to do this.

Common coatings

  • Aluminum Oxide: This is a coating on steel and cannot be used on aluminum.
  • Zirconia: Recommended. This is a good coating for aluminum to help with chip flow and reduce friction.
  • Titanium Boron: Available. But it has a low affinity for aluminum and may slip off during use.


Cutting Fluid

Never dry-milled aluminum, it’s a dangerous thing to do. When the cutter jams from molten aluminum that builds up around the edges, it can cause an explosion. Cutting fluid is added to the aluminum cutting process, it is the “oil” in CNC machining, which increases the precision of the cutting tool and improves the finish.


Feeds and Speeds

When it comes to feeds and cutting speed for aluminum, many people use 1000 SFM to calculate their RPM, but that’s not going any faster than everyone else. In general, 1000-1500 SFM is a normal rpm for cutting aluminum to run a spindle. However, advanced harmonic testing techniques can allow you to reach up to 3 times that speed.

When it comes to the feed rate, many tend to be conservative. If you’re feeding a 1/2″ endmill at 0.003″ per tooth, you’re just wasting time. To take full advantage of production, you should aim for at least 1% of the cutter diameter per tooth; in this case, .005″ per tooth or .010” per revolution. With a stable setup and short tool, you might even be able to double that.

The only exception to this is when you’re working with small tools, such as 1/8″ or less. In these cases, chip clearance may become an issue, which means that you’ll need to slow down for thinner chips.


Best Strategies for Aluminum Machining

Novices who process aluminum often encounter some difficulties. Here are some tips and experiences for CNC machining aluminum, which can help you better machine aluminum.

– Add appropriate coolant.
Aluminum is more thermally conductive and dissipates high heat during processing. Proper coolant flow keeps chips away from the work zone and keeps cutting surfaces properly lubricated.

– Needs a lot of horsepowers.
When machining aluminum, since it is a metal, a major amount of power is necessary. If the power needed for the cut is not met by your machine, it will lead to issues like chatter and deflection. In such cases, it is advisable to use horsepower “derating” in feed and speed calculations, particularly when using lightweight, smaller machines for aluminum milling.

– Clean up chips in time.
Aluminum’s high ductility results in long, unbroken chips that quickly build up around the tool. This can lead to tool breakage, leading-edge buildup (more stickiness issues), and heat buildup (smudged surfaces)。 The process of cleaning chips should be added to the actual processing to reduce the heat accumulation in the cutting area.

It is also necessary to maintain the cleanliness of the coolant, replace the coolant in time, and install a filter at the return port of the coolant on the workbench to filter out impurities and keep the coolant clean. Add soap blocks and detergents to the coolant to increase its ability to remove chips.

milled aluminum
milled aluminum

Some Common Questions and Solutions to Issues

1. How do I get an excellent surface finish on aluminum?

A common problem encountered during aluminum machining is vibration-induced chatter. Chatter can introduce poor surface finish and dimensional errors.
On the one hand, it is necessary to reduce flutter during processing, and on the other hand, it is necessary to use other iron sheets or chip removal belts to directly transport the aluminum chips discharged from the machine to the aluminum chip groove, so as to reduce the aluminum chips falling to the ground and the contact between the aluminum chips and the air, Reduce the oxidation of aluminum chips.

2.Why does aluminum turn brown when milled?

 Aluminum turns brown when milled because aluminum is easily oxidized at high temperatures, and the oxidized aluminum turns into a gray or brown substance, also known as aluminum oxide. You should make sure the metal is not exposed to additional moisture.

Summary of Machining Aluminum

Aluminum is malleable, lightweight, thermally and electrically conductive, and has excellent strength properties. Cannot be machined like stainless steel or any other hard material. I believe that after reading this article, you will have a general understanding of aluminum processing.

Finally, if you have a deeper exploration of aluminum processing or need to machine aluminum, you can contact us and share your ideas

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