Contract CNC Material Selection: Aluminum, Steel, Stainless | ARK CNC

As ARK CNC, we perform contract manufacturing of complex geometry parts using state-of-the-art CNC lathe (C-axis capable) and vertical machining (milling) centers at our facility in Bayrampaşa, Istanbul. Adhering to tight tolerances (H7, g6, etc.) in your technical drawings is crucial for your project's success, as is selecting the correct raw material suitable for the part's operating environment.

The question "How to Choose Material in Contract Manufacturing?" is one of the most challenging issues for engineers and purchasers. Incorrect material selection can lead to premature part deformation, assembly problems, or unnecessarily high manufacturing costs.

In this technical guide, we will compare the three most common basic metal types used in CNC manufacturing—Aluminum, Carbon Steel, and Stainless Steel—in terms of their technical properties, machinability, corrosion resistance, and cost structures.

1. Aluminum Alloys: Lightweight and High Machinability

Aluminum is one of the most preferred materials in contract CNC manufacturing due to its weight, which is approximately one-third that of steel, and its high machinability. It has very high thermal and electrical conductivity.

When to Choose?

• If Lightweight is Critical: Aerospace, automotive, medical, and defense industry parts.

• Fast and Low-Cost Production: Machining complex 3D geometries with high material removal rates (HSM).

• Thermal Management: Heat sinks and cooling blocks.

Commonly Used Aluminum Alloys:

• Aluminum 6061: The most common alloy, general-purpose, easy to machine, offering good corrosion resistance and weldability.

• Aluminum 7075: Known as aircraft aluminum. Has high strength competing with steel. Ideal for plastic and blow molding dies.

2. Carbon Steels: Strength, Hardness, and Economic Solutions

Carbon steels offer much higher strength, hardness, and wear resistance compared to aluminum. Raw material costs are generally lower; however, machining times are longer compared to aluminum.

When to Choose?

• High Load-Bearing Capacity: Machine bodies, shafts, spindles, gears, and fasteners.

• Wear Resistance: Technical parts to which surface hardening (carburizing, nitriding) will be applied.

• Budget Constraints: Economic solutions in high-volume serial manufacturing projects.

Commonly Used Steel Alloys:

• Steel 1018 (Mild Steel): Low carbon, extremely easy to machine and weld general manufacturing steel.

• Steel 4140 (Alloy Steel): Offers high strength and toughness. Can be hardened by heat treatment; ideal for machine shafts and heavy-duty brackets.

3. Stainless Steel: Corrosion Resistance and Hygiene

Stainless steel offers excellent corrosion resistance in addition to the strength of carbon steel. Thanks to its chromium content, it forms a passive oxide layer that prevents rusting. However, due to its high hardness, it is more difficult to machine, and cutting tool wear is high.

When to Choose?

• Harsh Operating Conditions: Parts exposed to chemicals, pressure, or high humidity.

• Food and Medical Sector: Surfaces requiring hygiene, easy cleaning, and sterilization.

Commonly Used Stainless Alloys:

• Stainless Steel 304: The most common corrosion-resistant stainless type. Food equipment and standard contract parts.

• Stainless Steel 316: Offers higher corrosion resistance than 304 (suitable for environments with chlorides and seawater). Ideal for medical parts and marine applications.

• Stainless Steel 420: Can achieve high hardness through heat treatment. Preferred for mold parts and wear-resistant details.

CNC Material Comparison Table

Property	Aluminum Alloys	Carbon Steels	Stainless Steel
Strength / Weight	Very High	Low	Medium
Machinability	Excellent (Very Fast)	Good - Medium	Difficult (Low Speed)
Corrosion Resistance	Medium (Uncoated)	Low (Coating Required)	Very High
Raw Material Cost	Medium	Low	High
Thermal Conductivity	Very High	Medium	Low

ARK CNC: Precision Material Expertise in Istanbul

With our experience since 2003, we provide reliable engineering solutions for correct raw material selection, ISO 286 tolerance requirements, and contract manufacturing methods for your projects.

To review our machining capabilities, you can visit our Services page; by sending your technical drawings in STEP, IGES, or DXF format via the Contact Form , you can receive engineering support and a quote within 24 hours.