Learn what 6063 aluminum is, how it performs in CNC machining, common CNC machined 6063 aluminum parts, key properties, machining challenges, and how 6063 compares with maraging steel for custom precision components.
What Is 6063 Aluminum?
6063 aluminum is a heat-treatable aluminum-magnesium-silicon alloy in the 6xxx series. It is best known for excellent extrudability, clean surface appearance, good corrosion resistance, and very good response to anodizing. For CNC machining buyers, the most important point is that 6063 is not chosen only because it is “aluminum.” It is usually selected when a part needs a lightweight body, a smooth visible surface, and enough strength for housings, frames, covers, profiles, brackets, and precision machined features.
Alloy Family and Basic Material Identity
In engineering discussions, 6063 is often described as an architectural or extrusion aluminum alloy, but that does not mean it is limited to building products. It belongs to the same broad 6xxx family as 6061 and 6082, yet its balance is different: 6063 favors formability, surface quality, and finishing performance more than maximum strength. This makes it attractive for CNC machined aluminum parts where appearance, corrosion resistance, and cost stability matter as much as load capacity.
Why Magnesium and Silicon Matter
The magnesium and silicon in 6063 form Mg2Si strengthening phases after heat treatment. In practical CNC machining, this means 6063 can be supplied in tempers such as T5 and T6 with useful mechanical strength while retaining the clean cutting behavior expected from aluminum. The alloy also has relatively low density, high thermal conductivity, and a naturally protective oxide film, which help it fit many custom CNC machining applications where parts must be light, stable, and easy to finish.
| Element | Typical 6063 Composition Range | Machining Relevance |
| Aluminum | Balance | Base metal; provides low density and good corrosion resistance |
| Magnesium | 0.45-0.90% | Combines with silicon for heat-treatable strength |
| Silicon | 0.20-0.60% | Improves response to aging and helps stable extrusion behavior |
| Iron | Up to 0.35% | Controlled impurity; excess can affect surface finish |
| Copper | Up to 0.10% | Kept low to preserve corrosion resistance |
| Manganese, Chromium, Zinc, Titanium | Usually low limits | Small additions or residuals; normally not the main design driver |
Is 6063 Aluminum Commonly Used for CNC Machining?
6063 aluminum is commonly used for CNC machining, especially when the starting stock is an extrusion, bar, tube, or profile that already approximates the final shape. It is not always the first choice for highly loaded structural parts, but it is a very practical material for CNC milled and CNC turned components that need accurate holes, flat sealing faces, slots, grooves, threads, and clean external surfaces. Many buyers compare 6063 aluminum CNC machining with 6061 because both materials are available, affordable, and easy to finish.
When 6063 Is a Strong CNC Choice
6063 becomes especially useful when a component combines extruded geometry with secondary machining. A profile can be extruded first, then CNC machined to add mounting holes, pockets, end faces, threaded features, countersunk holes, grooves, and mating surfaces. This route often lowers material waste compared with machining a complex shape entirely from billet.
Common CNC Operations for 6063 Aluminum
6063 supports common machining operations, but the process plan should consider its relatively softer behavior compared with stronger aluminum grades. Sharp tools, stable workholding, and controlled chip evacuation are important because the alloy can smear if tools are dull or if cutting heat is poorly managed. Typical operations include the following:
- CNC milling for slots, pockets, mounting surfaces, and enclosure features.
- CNC drilling and tapping for assembly holes, threaded inserts, and fastener locations.
- CNC turning for round sleeves, spacers, bushings, knobs, and tube-end features.
- Deburring and edge finishing to protect anodized surfaces and improve assembly fit.
What Parts Are Usually Made from CNC Machined 6063 Aluminum?
6063 aluminum is widely used for CNC machined parts that must look clean, assemble accurately, and remain lightweight. It is common in visible hardware, device structures, protective frames, mounting rails, control panels, and parts produced from extruded profiles. Instead of thinking of 6063 as a material for one industry, it is better to think of it as a practical alloy for parts where the machined geometry is added to an attractive, corrosion-resistant aluminum body.
Typical Part Categories
The parts below show where 6063 aluminum CNC machining is most useful. In many cases, the component begins as a bar, extrusion, or tube, and machining creates the critical dimensions that extrusion alone cannot control. This is why 6063 is common for custom aluminum CNC parts that need both efficient raw material use and precise local features.
| Part Type | Why 6063 Is Used | CNC-Machined Features |
| Enclosures and covers | Lightweight, clean finish, good anodizing response | Milled pockets, screw bosses, gasket surfaces, ports |
| Heat sink bodies and rails | Good thermal conductivity and extrusion-friendly geometry | Flat contact faces, holes, slots, end machining |
| Frames and brackets | Low weight and good corrosion resistance | Mounting holes, counterbores, threaded locations |
| Lighting and display parts | Attractive surface after anodizing | Visible faces, grooves, precision edges |
| Tube and sleeve components | Available as tube or round stock | Turned diameters, chamfered ends, internal holes |
| Automation and equipment parts | Cost-effective for light-duty structures | Slots, locating surfaces, tapped holes |
Parts That May Need a Different Alloy
6063 is not ideal for every aluminum CNC machining project. If the part carries high mechanical loads, requires higher thread strength, or must resist severe impact, 6061-T6, 6082, 7075, or a steel grade may be better. The decision should be based on function, not only on availability. For cosmetic covers, brackets, rails, and profile-based components, 6063 is often excellent. For highly stressed aerospace-style links or compact load-bearing arms, a higher-strength material is usually safer.
Why Do Users Choose Maraging Steel for CNC Machined Parts?
Although this article focuses on 6063 aluminum, maraging steel appears in the same material-selection discussion because it represents the opposite design direction. Users do not choose maraging steel for low cost, low weight, or easy anodizing. They choose it when a precision part needs very high strength, high toughness, good dimensional stability after aging, and the ability to machine in a softer condition before final hardening. This is why maraging steel is often considered for tooling, high-performance mechanical parts, aerospace-related components, and demanding prototype work.
Main Reasons for Choosing Maraging Steel
Maraging steel is usually selected when ordinary aluminum alloys cannot provide the required strength or service margin. Its low-carbon martensitic structure can be aged to very high strength levels, while maintaining useful toughness. For CNC machining, one of its strongest advantages is the ability to rough and finish many features before aging, then obtain high strength with relatively predictable dimensional change.
Selection Logic in CNC Projects
The buyer’s question is often not “Which material is easier to machine?” but “Which material gives the required performance after machining?” Maraging steel can justify its higher cost when the part is compact, highly loaded, or must retain tight geometry after heat treatment. Typical reasons include the following:
- Very high tensile and yield strength after aging heat treatment.
- Good toughness compared with many high-hardness steels.
- Low carbon content, which helps reduce decarburization concerns during heat treatment.
- Dimensional stability during aging, important for precision CNC machined steel parts.
- Ability to machine before final aging, reducing the need for extensive hard machining.
Chemical Composition of 6063 Aluminum and Maraging Steel
Chemical composition explains why 6063 aluminum and maraging steel behave so differently in CNC machining. 6063 is an aluminum alloy with modest magnesium and silicon additions. Maraging steel, especially common 18Ni grades such as 18Ni-300, is a low-carbon, high-nickel steel strengthened by intermetallic precipitation during aging. Because the alloy systems are completely different, they should not be treated as direct substitutes. They solve different engineering problems.
6063 Aluminum Composition
6063 composition is intentionally controlled for extrusion quality, surface appearance, corrosion resistance, and heat-treatable strength. Low copper content supports corrosion resistance, while magnesium and silicon provide the basis for aging response. In CNC machining, this chemistry helps explain why 6063 cuts easily but may not provide the same strength margin as 6061-T6 or 7075-T6.
Typical Composition Range
Actual certificates may vary by standard and supplier, so a production drawing should reference the required material standard and temper. The following values are typical for 6063 aluminum and should be used as engineering guidance rather than a substitute for a material certificate.
| Material | Key Alloying Elements | Typical Balance | Material Character |
| 6063 aluminum | Mg 0.45-0.90%, Si 0.20-0.60%, Fe up to 0.35%, Cu up to 0.10% | Aluminum balance | Lightweight, corrosion resistant, finish-friendly |
| 18Ni-300 maraging steel | Ni about 18%, Co, Mo, Ti, very low carbon | Iron balance | Ultra-high strength after aging, stable precision steel |
Maraging Steel Composition
Maraging steel composition is built around nickel, cobalt, molybdenum, titanium, and very low carbon. The low carbon content separates it from conventional carbon-strengthened tool steels. After aging, fine precipitates strengthen the martensitic matrix. For CNC machined parts, this is why maraging steel can offer strength levels far beyond 6063 aluminum while still being machinable before final aging.
Physical Properties of 6063 Aluminum and Maraging Steel
Physical properties strongly affect CNC machining strategy, part weight, heat behavior, and long-term performance. 6063 aluminum has low density and high thermal conductivity, making it suitable for lightweight structures and heat-spreading parts. Maraging steel is much denser and much stronger, but it also creates higher cutting forces, heavier parts, and more demanding tool conditions. These differences are central when comparing 6063 aluminum vs maraging steel for CNC machining.
Key Physical Property Comparison
The table below summarizes practical values engineers often consider before choosing between 6063 aluminum and maraging steel. Exact numbers depend on temper, heat treatment, supplier, and testing condition, so the values should be treated as typical ranges for early material selection.
| Property | 6063 Aluminum | Maraging Steel 18Ni-300 | CNC Design Meaning |
| Density | About 2.69-2.70 g/cm3 | About 8.0 g/cm3 | Maraging steel is roughly three times heavier |
| Elastic Modulus | About 69 GPa | About 180-200 GPa | Steel is much stiffer under the same geometry |
| Thermal Conductivity | About 200 W/m-K | Much lower than aluminum | 6063 is better for heat-spreading parts |
| Coefficient of Thermal Expansion | About 23.4 µm/m-°C | Lower than aluminum | 6063 changes size more with temperature |
| Melting Range | About 616-654 °C | Much higher steel melting range | Not a machining limit, but relevant to thermal exposure |
What These Properties Mean for Part Design
For a lightweight enclosure, frame, rail, or cover, 6063 aluminum usually provides a better weight-to-cost balance. For a compact part that must resist high stress, maraging steel may allow a smaller cross-section. The important point is that density, stiffness, and thermal expansion can be as important as tensile strength. A 6063 aluminum part may need thicker walls or ribs to match the stiffness of steel, while a maraging steel part may need more careful cost and machining planning.
Mechanical Properties of 6063 Aluminum and Maraging Steel
Mechanical properties decide whether a CNC machined component can survive load, assembly, vibration, and repeated handling. 6063 aluminum in T5 or T6 temper provides useful strength for many commercial and industrial parts, but it is not an ultra-high-strength alloy. Maraging steel, after aging, can reach extremely high strength and hardness. This difference explains why the two materials are rarely selected for the same mechanical reason.
Typical Mechanical Property Comparison
The values below are general selection data, not final design allowables. For production parts, engineering teams should confirm the exact temper, heat treatment, bar or extrusion direction, and certified mechanical properties. In CNC machining, the most important practical question is whether the machined features, threads, thin walls, and assembly interfaces can handle the required service loads.
| Property | 6063-T6 Aluminum Typical | 18Ni-300 Maraging Steel Aged Typical | Practical Meaning |
| Ultimate tensile strength | About 240 MPa | Often above 2000 MPa | Maraging steel is far stronger |
| Yield strength | About 214 MPa | Often above 1900-2100 MPa | 6063 is for light to moderate loads |
| Hardness | Around 70-75 HB | Can exceed 50 HRC after aging | Tool wear is much higher in aged steel |
| Elongation | Often around 8-12% depending on product form | Good for a very high-strength steel | Both can be usable, but failure modes differ |
| Fatigue performance | Moderate; design geometry matters | High strength helps, but surface quality still matters | Avoid sharp internal corners in both materials |
How Strength Changes Machining Decisions
With 6063, the machining challenge is usually not machine power; it is surface finish, burr control, thin-wall distortion, and avoiding scratches before anodizing. With maraging steel, cutting force, heat, tool wear, and post-machining aging control become much more important. If maraging steel is machined after aging, it behaves like a hard high-strength steel and may require carbide tooling, conservative parameters, rigid fixturing, and sometimes grinding or EDM for critical features.
What Users Discuss Most About 6063 Aluminum CNC Machining
Common user concerns around 6063 aluminum are practical rather than theoretical. Buyers usually want to know whether it machines cleanly, whether it can be anodized beautifully, whether it is strong enough compared with 6061, and whether it will scratch, bend, or deform during machining and shipping. These are useful questions because 6063 is often selected for parts that customers can see and touch, not only for hidden structural pieces.
6063 vs 6061 Questions
The most common comparison is 6063 vs 6061 aluminum for CNC machining. 6061-T6 usually offers higher strength and broader structural use, while 6063 usually offers smoother extruded surfaces and excellent anodizing appearance. Therefore, 6063 is not automatically “worse”; it is simply optimized for different priorities. If the part is a visible enclosure, trim, rail, or profile-based component, 6063 can be the better choice. If the part is highly loaded, 6061 may be safer.
Questions Buyers Often Raise
These questions should be answered early in quoting because they affect material choice, machining method, and finishing plan. A clear drawing, target surface finish, and final use case will usually prevent wrong assumptions.
- Will 6063-T6 be strong enough for threaded holes and repeated assembly?
- Should I choose 6063 or 6061 for anodized CNC aluminum parts?
- Can 6063 be machined without visible tool marks on cosmetic surfaces?
- Will thin 6063 aluminum walls warp during CNC milling?
- Is 6063 suitable for heat sink machining or only for extrusions?
Surface Finish and Anodizing Concerns
6063 is often chosen because it anodizes well, but machining marks do not disappear automatically after anodizing. In fact, anodizing can make inconsistent tool paths, scratches, dents, or polishing differences more visible. For cosmetic CNC machined 6063 aluminum parts, the supplier should define which surfaces are cosmetic, which edges require controlled deburring, and whether bead blasting, brushing, polishing, or direct anodizing is expected before production begins.
CNC Machining Challenges of 6063 Aluminum
6063 aluminum is generally easy to machine, but “easy” does not mean risk-free. Its softer and more ductile cutting behavior can create built-up edge, burrs, smeared surfaces, and edge deformation if machining parameters are not controlled. Because many 6063 parts are visible, even small scratches or inconsistent tool marks can become quality problems. The best process is one that protects both dimensions and appearance.
Built-Up Edge and Surface Smearing
Built-up edge occurs when aluminum sticks to the cutting edge, reducing sharpness and damaging the machined surface. This is more likely with dull tools, poor chip evacuation, low cutting speed, or insufficient lubrication. On 6063 aluminum, built-up edge can produce cloudy faces, torn edges, or inconsistent finishes that become obvious after anodizing.
How to Reduce Built-Up Edge
The solution is to keep the cut clean and cool while preventing chips from rubbing the finished surface. In production, the following measures are commonly used:
- Use sharp polished carbide tools designed for aluminum machining.
- Apply suitable coolant or mist lubrication to reduce adhesion.
- Use chip loads that cut rather than rub the material.
- Avoid recutting chips in pockets, grooves, and deep features.
- Replace tools before edge wear affects cosmetic surfaces.
Burrs, Thin Walls, and Workholding Marks
6063 can form burrs around holes, slots, and thin edges. Thin-wall parts can also flex under clamping force, causing dimensional error after release. For anodized or visible parts, vise marks and fixture scratches are another concern. These problems are not solved by material selection alone; they require careful fixturing, toolpath planning, and handling control.
How to Control Deformation and Burrs
A stable CNC machining plan uses soft jaws, protected contact surfaces, balanced roughing, and light finishing passes. Burrs should be removed consistently, but over-deburring can change edge geometry or harm cosmetic appearance. For tight-tolerance 6063 aluminum CNC parts, inspection should include flatness, hole position, thread quality, and finish-sensitive surfaces.
How to Improve CNC Machining Results for 6063 Aluminum
Good results with 6063 aluminum come from matching the part design, stock form, machining sequence, and finishing requirement. Since 6063 is often supplied as extrusion, the starting geometry can save cost, but extrusion tolerance may be looser than CNC tolerance. The machining plan should identify which faces are functional, which faces are cosmetic, and which surfaces can remain as-extruded.
Design Measures Before Machining
Design choices can reduce cost and improve quality before a single chip is cut. Avoid unnecessarily deep pockets, extremely thin walls, and sharp internal corners. Use realistic corner radii, sufficient thread engagement, and consistent wall thickness where possible. If the component will be anodized, cosmetic faces should be identified on the drawing so the machining supplier can protect them through cutting, deburring, cleaning, and packaging.
Useful Drawing Notes for 6063 CNC Parts
A clear drawing prevents misunderstandings between buyer and manufacturer. For CNC machined 6063 aluminum parts, the most useful notes are not long; they are specific. Consider adding the following where relevant:
- Specify alloy and temper, such as 6063-T5 or 6063-T6.
- Mark cosmetic surfaces and required surface roughness.
- Define anodizing type, color, masking areas, and acceptable color variation.
- Call out tight tolerances only where function requires them.
- Define deburring requirements without rounding critical edges excessively.
Manufacturing Measures During Machining
During machining, the supplier should use sharp tools, controlled clamping, and stable cutting parameters. A separate finishing pass often improves surface consistency. For long extruded parts, stress release, straightness, and fixture support should be reviewed before final machining. For batches, first article inspection is useful to confirm that extrusion variation and CNC datum selection do not create cumulative error.
6063 Aluminum vs Maraging Steel in CNC Machinability
6063 aluminum and maraging steel are both machinable, but their machining behavior, cost structure, and design intent are completely different. 6063 is fast to cut, light, easy to finish, and suitable for visible aluminum parts. Maraging steel is selected for strength and dimensional stability after aging, but it demands more tool control, slower machining, and higher material cost. The right choice depends on whether the part needs lightweight appearance or extreme mechanical performance.
Machinability Comparison Table
The table below gives a practical comparison for CNC material selection. It is especially useful when a buyer asks whether a high-strength steel can replace aluminum, or whether aluminum can reduce weight in a part originally designed from steel.
| Factor | 6063 Aluminum | Maraging Steel | Better Choice When |
| Cutting speed and cycle time | Fast machining, low cutting force | Slower machining, higher cutting force | 6063 for cost-efficient production |
| Tool wear | Low with proper aluminum tooling | Moderate to high, especially after aging | 6063 for long tool life |
| Weight | Very light | Heavy | 6063 for portable or weight-sensitive parts |
| Strength | Moderate | Extremely high after aging | Maraging steel for compact high-load parts |
| Finishing | Excellent anodizing response | Can be polished or coated, but not anodized like aluminum | 6063 for colored cosmetic aluminum |
| Dimensional stability after heat treatment | Temper is usually selected before machining | Aging can be controlled with predictable change | Maraging steel for post-machining strengthening |
| Typical cost | Lower material and machining cost | Higher material and processing cost | 6063 for appearance and economy |
How to Choose Between Them
Choose 6063 aluminum when the design priority is lightweight construction, visible anodized finish, good corrosion resistance, efficient extrusion-based stock, and moderate strength. Choose maraging steel when the priority is very high strength, high toughness, compact geometry, or precision performance after aging. In many real projects, the comparison ends quickly: if the part must be light and cosmetic, 6063 is the logical path; if the part must carry extreme load in a small envelope, maraging steel may justify its cost.
Conclusion
6063 aluminum is a practical CNC machining material for lightweight, corrosion-resistant, and appearance-sensitive parts such as enclosures, frames, rails, brackets, sleeves, and profile-based components. It machines easily, anodizes well, and works best when strength requirements are moderate. Maraging steel belongs to a different performance class: it is heavier and more expensive, but offers exceptional strength and dimensional stability after aging. For most cosmetic and extrusion-based CNC aluminum parts, choose 6063. For compact, highly loaded precision parts, consider maraging steel.
FAQ
Is 6063 aluminum good for CNC machining?
Yes. 6063 aluminum is good for CNC machining when the part needs moderate strength, low weight, good corrosion resistance, and a clean anodized surface. It is especially useful for extruded profiles that need secondary CNC milling, drilling, tapping, or end machining. For highly loaded parts, 6061-T6 or a stronger alloy may be better.
Is 6063 aluminum stronger than 6061 aluminum?
Usually no. 6061-T6 generally provides higher strength than 6063-T5 or 6063-T6. However, 6063 often provides better extrusion quality and surface appearance, which is why it is widely used for visible frames, rails, trim, housings, and anodized parts. Strength is only one part of the material selection decision.
Can 6063 aluminum be anodized after CNC machining?
Yes. 6063 aluminum is well known for good anodizing response. However, anodizing will not hide machining scratches, dents, or inconsistent tool paths. Cosmetic surfaces should be defined on the drawing, and machining, deburring, cleaning, and packaging should protect those areas before finishing.
When should maraging steel replace 6063 aluminum?
Maraging steel should be considered when the part needs very high strength, high toughness, compact load-bearing geometry, or dimensional stability after aging. It should not replace 6063 for ordinary lightweight cosmetic parts because it is heavier, more expensive, and slower to machine. The two materials serve different design goals.