Aluminum machining: mastery of nuances and precision of parts
What you must remember :
- Aluminium can withstand cutting speeds 3 to 5 times higher than steel : a key asset for high-volume production productivity.
- The choice of shade is crucial : 2024 and 7075 for high resistance (aeronautics, defense); 6061 and 6082 for the versatile compromise; 5052 for corrosive environments.
- The 2xxx (2024) and 7xxx (7075) grades anodize poorly and do not weld : they are reserved for mechanical assemblies with surface protection.
- The shape of the supply (round, hexagon, square, billet) directly determines the geometry of the piece Anticipating this choice reduces machining costs.
- Lubrication and chip management are the two critical parameters Neglecting them degrades the surface condition and prematurely wears out the tools.
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Aluminium is today one of the most machined materials in industrial machining. Lightweight, conductive, anodizable, available in a wide range of grades with very different properties, it meets the requirements of the most varied sectors: aeronautics, automotive, medical, electronics, general industry.
At Jacquemoux Décolletage, we produce machined aluminum parts (round, hexagonal, square, and complex shapes) in both large and small production runs. This article provides a technical overview of the main aluminum grades used in machining, from their mechanical properties to their machining constraints, to help you make the right material choice.
Why choose aluminium for machining?
Aluminium possesses a set of properties that make it a material of choice for machining industrial mechanical parts:
- Lightness: density of approximately 2,7 kg/dm³, almost three times less than steel, with an excellent strength-to-weight ratio on high-strength grades.
- High machinability: Most aluminum alloys are easy to cut, allowing for high cutting speeds and a good surface finish. In large-scale production, this increase in production rate is significant.
- Corrosion resistance: The natural oxide layer protects the surface. This property can be enhanced by anodizing, depending on the shade.
- Versatility of supply methods: Round bars, hexagonal bars, square bars, flat bars, tubes, aluminum comes in a wide variety of profiles, suitable for standard round parts as well as hexagonal or complex parts.
The main grades of aluminum used in screw machining
2xxx Series: Aluminum-copper alloys for demanding machining
The 2xxx series alloys have copper as their main alloying element. They offer high mechanical strength (up to 470 MPa in tensile strength for 2024 in the T3 condition), but their corrosion resistance is more limited than that of the 5xxx or 6xxx series due to the presence of copper. They generally require a protective coating or anodizing.
The most common types of aluminum used in machining are:
- 2024: A benchmark grade in aeronautics due to its high strength and good fatigue resistance. It tends to deform during machining due to residual stresses. Careful planning of the machining process is essential.
- 2011 (shade of décolletage): Specifically designed for high-volume, rapid production. Short, consistent chips, excellent productivity. It has gradually replaced the 2030 and 2007 for environmental reasons (presence of lead and bismuth).
Good to know: 2xxx grades are not recommended for welding (risk of hot cracking) and do not anodize well due to their copper content. They are suitable for machined parts with mechanical assembly.
5xxx Series: Aluminum-magnesium alloys, the anti-corrosion choice
The 5xxx series, the most common representative of which in bar turning is 5052, is characterized by excellent corrosion resistance and very good weldability. However, its machinability is less favorable than that of the 2xxx or 6xxx series: 5052 exhibits higher elasticity and produces larger chips, which can lead to increased tool wear and reduced accuracy in high-speed bar turning.
5052 stainless steel is preferred for parts exposed to humid or corrosive environments, and for assemblies requiring welding. For high-volume machining with tight tolerances, the 6xxx or 2xxx series are generally more suitable.
6xxx Series: Aluminum-magnesium-silicon alloys, the universal choice
The 6xxx series alloys are the most versatile. 6061 and 6082 are easy to machine, weld well, anodize perfectly, and are corrosion resistant. They are the economical and reliable choice for the majority of mechanical parts in the aerospace and automotive industries.
- 6061: Excellent compromise between machinability, weldability, and strength. It allows for high-speed machining, tight tolerances, and fine surface finishes. Tensile strength of approximately 310 MPa in the T6 condition. Widely used in automotive, aerospace, and general engineering.
- 6082: The strongest grade in the 6xxx series, with a tensile strength of up to 340 MPa in the T6 condition. Widely used in Europe, it has gradually replaced 6061 in many structural applications. It offers good machinability in the T5 and T6 conditions, with the recommendation to use chip breakers to improve chip formation.
Good to know: Alloy 6061 is a good compromise in terms of machining/welding/strength, but alloy 6082 is preferable when structural strength is a priority.
7xxx Series: Aluminum-zinc alloys, maximum strength
The 7xxx series, and in particular 7075, represents the pinnacle of high-strength aluminum. With a tensile strength of up to 572 MPa in the T6 condition, comparable to some mild steels, it is the strongest aluminum alloy currently available.
Its machinability index is approximately 70% compared to free-cutting brass. High-speed machining with abundant coolant is recommended to prevent work hardening. However, 7075 has significant limitations: very poor weldability (risk of cracking), reduced stress corrosion cracking resistance, and the almost systematic need for surface treatment (anodizing, coating).
Its applications are mainly in the aerospace, defense, motor racing and high-performance sports equipment sectors, i.e. anywhere mechanical strength takes precedence over weldability or chemical resistance.
Supply methods and part geometries
One of the advantages of aluminum machining is the diversity of bar shapes available, which opens up a very wide range of finished part geometries:
- Round bars: the most common form, suitable for all shades and the majority of parts of revolution (axles, rings, screws, fittings…).
- Hexagonal bars: enable the production of hexagonal heads, screws and inserts without additional milling operation, reducing cycle time.
- Square bars and flat surfaces: suitable for rectangular geometry parts or square aluminium parts machined on CNC lathes with rework.
- Plots (large sections): for complex large section aluminium parts, prototypes and medium series requiring several operations.
This diversity of input forms, combined with a varied machine park, allows Jacquemoux Décolletage to easily produce complex aluminum parts.
Key parameters of aluminum machining in bar turning
Aluminium is generally easier to machine, but it has its own technical constraints that must be mastered:
- High cutting speed: Aluminium can withstand very high cutting speeds (often 3 to 5 times higher than those of steel). In large-scale production, this translates into short cycle times and competitive unit costs.
- Chip management: Certain grades (6082, 5052) tend to produce long chips that can wrap around the tool. The use of suitable chip breakers and appropriate tool geometry are essential.
- Essential lubrication : to prevent the aluminum from sticking to the cutting edges (adhesion phenomenon). Abundant watering improves the surface finish and extends tool life.
- Residual stresses (grades 2xxx and 7xxx): 2024 and 7075 steels can deform after machining if internal stresses are not anticipated. Defining the machining range and the sequence of operations is critical to ensuring dimensional stability.
- Post-machining surface treatments: Anodizing, shot blasting, painting… Some grades anodize better than others. For example, 6061 and 7075 anodize well, while 2024, on the other hand, anodizes poorly due to its copper content and requires a suitable protective coating. This should be considered when choosing the grade.
Jacquemoux's expertise in aluminum machining
High-precision aluminum machining requires simultaneous mastery of the alloys, machining parameters, and constraints related to surface treatments and final tolerances. At Jacquemoux Décolletage, we support our clients at every stage:
- A word of caution beforehand: We guide you towards the grade best suited to your use: mechanical strength, corrosion resistance, suitability for anodizing, welding constraints, to optimize both the performance of the part and manufacturing productivity.
- Diversity of geometries: Round, hexagonal, square, complex multi-axis parts, our machine park processes all forms of aluminum supply available on the market.
- Production of small and large series: from prototype to industrial series, with the same rigor of dimensional control and material traceability.
Aluminum machining covers a very wide range of grades, geometries, and industrial applications. From aerospace-grade 2024 to structural 6082, and including high-strength 7075, each alloy has its own rules and potential. Mastering these materials also means anticipating machining constraints, residual deformations, and surface treatment requirements.
Do you have a project involving machined aluminum parts?
From defining the grade to delivering your finished parts, the Jacquemoux Décolletage technical team studies your specifications and offers you a solution adapted to your dimensional requirements, volumes and time constraints.
