Top 5 Metals Used in CNC Machining and Their Applications

CNC machining plays a pivotal role in manufacturing across aerospace, automotive, medical, and industrial sectors, largely due to its ability to work with a broad range of metals.
Each metal offers distinct advantages in machinability, strength, thermal resistance, or corrosion protection—making material selection a critical factor in functional part performance.

This guide explores the top five metals used in CNC machining, their key characteristics, and common applications, helping engineers, designers, and procurement teams make informed choices based on use-case requirements.

1. Aluminum – Lightweight and Highly Machinable

Aluminum is the most widely used metal in CNC machining due to its excellent machinability, light weight, and cost-effectiveness.

Key Characteristics:

• Density: ~2.7 g/cm³ (lightweight)

• Corrosion resistance: Naturally forms an oxide layer

• Thermal conductivity: High, ideal for heat dissipation

• Machinability: Excellent (low cutting forces, good chip removal)

• Finish: Accepts anodizing, polishing, bead blasting

Common Grades:

• 6061: General-purpose, high strength-to-weight ratio

• 7075: Aerospace-grade, stronger but less corrosion resistant

• 2024: Used where high fatigue strength is required

Applications:

• Aerospace brackets and structural frames

• Automotive engine housings and manifolds

• Consumer electronics enclosures

• Robotics and automation components

• Heat sinks, drone parts, and lighting frames

Why it’s chosen: Aluminum combines machinability with performance and is ideal for both prototyping and production. It is often the go-to choice for CNC machining services where quick turnaround and precision are critical.

2. Stainless Steel – Corrosion-Resistant and Strong

Stainless steel is preferred when strength, durability, and corrosion resistance are priorities.
It’s widely used in industries that demand hygienic, oxidation-resistant parts, such as medical, food processing, and marine.

Key Characteristics:

• Density: ~7.8 g/cm³

• Corrosion resistance: Excellent in 304/316 grades

• Strength and hardness: High mechanical strength

• Machinability: Moderate; slower speeds and rigid tooling required

• Surface finish: Polishes to a smooth, hygienic surface

Common Grades:

• 304: General-purpose, widely used, excellent corrosion resistance

• 316: Enhanced corrosion resistance (chloride-resistant)

• 303: Modified for better machinability

Applications:

• Surgical instruments and orthopedic implants

• Marine fasteners and pumps

• Industrial valves and pipe fittings

• Kitchen and food-processing equipment

• Aerospace fuel system components

Why it’s chosen: Stainless steel is ideal for harsh environments where both mechanical strength and corrosion resistance are essential.

3. Steel Alloys – Tough and Wear-Resistant

Carbon and alloy steels are known for their toughness, hardness, and excellent mechanical properties under stress.
CNC machining of steel is common in automotive, defense, tooling, and construction applications.

Key Characteristics:

• Density: ~7.85 g/cm³

• Strength: High tensile and yield strength

• Hardness: Can be heat treated for wear resistance

• Machinability: Varies by grade; typically requires coolant and rigid tooling

• Surface treatment: Supports coatings, plating, and painting

Common Grades:

• 1018: Low carbon, good weldability and machinability

• 4140: Chromoly steel, excellent fatigue resistance

• 1045: Medium carbon steel, balances strength and machinability

• A36: Common structural steel

Applications:

• Gears, shafts, axles, and drive train components

• Tooling and dies

• Structural frames and brackets

• High-stress machine parts

• Firearms and defense equipment

Why it’s chosen: Steel alloys offer unmatched strength and durability, making them ideal for load-bearing and impact-resistant parts.

4. Brass – Easy to Machine and Electrically Conductive

Brass is a copper-zinc alloy that is widely used in CNC machining due to its ease of machining, aesthetic appeal, and excellent electrical conductivity.

Key Characteristics:

• Density: ~8.4–8.7 g/cm³

• Machinability: Excellent; among the easiest metals to machine

• Corrosion resistance: Good in non-acidic environments

• Conductivity: High electrical and thermal conductivity

• Surface finish: Bright, gold-like appearance

Common Grades:

• C360 (Free-Cutting Brass): Best for high-speed machining

• C260 (Cartridge Brass): Better corrosion resistance

• C464 (Naval Brass): Marine-grade brass with added strength

Applications:

• Electrical connectors and terminals

• Decorative hardware and plumbing fixtures

• Instrument components

• Valves and threaded parts

• Precision fittings and fasteners

Why it’s chosen: Brass is ideal for parts requiring tight tolerances, low friction, and excellent machinability, especially in electrical and aesthetic applications.

5. Titanium – High Strength-to-Weight Ratio and Biocompatibility

Titanium is a premium metal used in CNC machining for demanding applications where strength, weight, and corrosion resistance are critical.
It is most commonly seen in aerospace and medical environments.

Key Characteristics:

• Density: ~4.5 g/cm³ (strong yet lightweight)

• Strength: Comparable to steel, but half the weight

• Corrosion resistance: Excellent, including saltwater and chemicals

• Biocompatibility: Non-reactive in the human body

• Machinability: Poor to moderate (requires sharp tools, low speed)

Common Grades:

• Grade 2: Commercially pure, more ductile

• Grade 5 (Ti-6Al-4V): Most commonly used, combines strength and corrosion resistance

• Grade 23: Medical-grade version of Grade 5

Applications:

• Aerospace structural components

• Orthopedic and dental implants

• Military hardware

• Motorsport parts

• High-performance marine and industrial tools

Why it’s chosen: Titanium offers unmatched strength-to-weight performance, making it irreplaceable in environments where performance and weight savings matter.

Summary Table: Top 5 Metals for CNC Machining

Final Thoughts

Choosing the right metal is just as important as selecting the correct machining process.
Each material offers distinct advantages based on strength, cost, corrosion resistance, and application-specific needs. Whether you're building a high-stress aerospace component or an electrically conductive part, understanding the properties of these top metals ensures optimal performance and cost-efficiency.

Reliable CNC machining services should help guide your selection based on part geometry, tolerance, and functional requirements—ensuring you receive the best possible outcome for both prototyping and production.