Aluminum is probably the most widely machined material in the world after steel. Lightweight, easy to machine, corrosion-resistant — it checks nearly every box. However, “machining aluminum” actually encompasses very different situations, depending on the chosen grade, and certain pitfalls arise repeatedly, even among experienced teams.

Why Aluminum Dominates So Many Industries

Aluminum’s strength-to-weight ratio makes it a material of choice wherever weight reduction matters: aerospace, automotive, electronics, medical equipment. It lends itself well to high cutting speeds, wears tools less than steels do, and delivers excellent surface finishes straight off the machine — an advantage exploited in both production runs and custom parts alike.

The Most Common Grades in Machining

6061 — the all-rounder

The most widely used grade in precision machining. A good balance of mechanical strength, corrosion resistance, weldability, and machinability. Used for housings, flanges, structural brackets, and general parts with no extreme requirements.

7075 — the high-strength option

Significantly stronger mechanically than 6061 (comparable to some mild steels), but less corrosion-resistant and not weldable using common processes. It is the reference grade in aerospace and motorsport, where the strength-to-weight ratio is critical — a context detailed in our article on precision machining for the aerospace and aviation industry.

2024 — fatigue resistance and stiffness

Excellent fatigue performance, historically used in aircraft structures subject to cyclic loads (fuselages, spars). Less corrosion-resistant than 6061 and generally requires cladding or a protective treatment.

5052 — formability and marine-grade corrosion resistance

Good corrosion resistance in marine environments, excellent formability, but more modest mechanical strength. Often chosen for sheet-metal parts and components exposed to moisture.

3003 — the economical choice

Low mechanical strength but excellent corrosion resistance and reduced cost. Used for non-structural components, tanks, and parts where weight and price take priority over mechanical performance.

Common Pitfalls in Aluminum Machining

Thermal distortion and dimensional accuracy

Aluminum has high thermal conductivity and a significant coefficient of expansion. A part that heats up during machining can distort slightly, throwing off measurements taken “while hot.” This is a particularly critical factor on tight-tolerance parts — an issue similar to one encountered in laser cutting of thermally conductive metals.

Burrs and sharp edges

Aluminum tends to form burrs rather than break cleanly, especially at tool exit edges. A deburring operation — manual or automated — is almost always necessary, and its cost should be anticipated as early as the design stage, as discussed in our article on calculating the price of a machined part.

Holding thin-walled parts

Aluminum alloys are often used precisely for lightweight parts with thin walls. These geometries are prone to vibration and distortion under clamping or cutting pressure, which calls for carefully considered fixturing and operation-sequencing strategies — an area where 5-axis machining often provides an advantage by reducing the number of setups and part-handling steps.

Built-up edge (adhesion) on the tool

At unsuitable cutting speeds, aluminum can stick to the tool’s cutting edges, degrading surface finish and precision. A well-chosen tool geometry, coating, and lubrication generally solves this problem — an example of a parameter invisible on a technical drawing but one that directly affects the final result.

Aluminum or Steel: How to Decide

The choice between aluminum and steel isn’t just about weight. Steel remains the better option when stiffness, wear resistance, or high-temperature performance take priority — common cases in the defense sector or for certain structural automotive parts. Aluminum wins out when weight reduction, corrosion resistance without treatment, and ease of machining are the priorities.

Common Finishing Treatments

Anodizing remains the most common surface treatment for aluminum: it improves corrosion and wear resistance and allows for aesthetic coloring. Other treatments — passivation, specific coatings — address particular functional needs. These post-machining operations must be planned from the design stage onward, a point covered more broadly in our article on post-machining treatments.

Strategies Tailored to Each Aluminum Grade

Machining aluminum well isn’t just a matter of choosing “aluminum”: grade selection, anticipating thermal distortion, managing burrs, and properly holding thin-walled parts all make the difference between a part that’s right the first time and a costly series of rework.

At G.M. Précision, we tailor our machining strategies to each aluminum grade to ensure precision and efficiency. Have an aluminum project that needs evaluating? Request a quote today.