Common Metal Materials for CNC Machining: Properties, Applications and Material Selection Guide

 

Common Metal Materials for CNC Machining: Properties, Applications and Material Selection Guide

 

Selecting the right metal material is one of the most important decisions in CNC machining. Material choice affects not only the mechanical performance of the final part, but also machining efficiency, tooling cost, surface finish, and overall production cost.

 

In this guide, we summarize the most commonly used metal materials in CNC machining, their key properties, typical applications, and important machining considerations.

Computer Numerical Control Material Categories Overview

The most common CNC machining metals can be divided into six categories:

1. Carbon Steels
2.  Alloy Steels
3. Stainless Steels
4. Cast Iron
5.  Aluminum Alloys
6. Specialty Metals

Each category offers unique advantages depending on strength, corrosion resistance, weight, wear resistance, and budget requirements.

 

1. Carbon Steels (Widely Used and Cost-Effective)

 

Q235 Mild Steel

Properties

• Good ductility and excellent weldability
• No heat treatment required
• Low hardness (HB 120–160)

Typical Applications

• Machine frames
• Welded bases
• Safety guards
• Sheet metal components

Machining Considerations

• Material tends to adhere to the cutting edge, which can cause burr formation
• Sharp tooling is recommended

 

45 Steel (Equivalent to AISI 1045 Medium Carbon Steel)

Properties

• Offers an excellent balance of strength and toughness after quenching and tempering
• Typical hardness: HRC 22–28
• Good machinability

Typical Applications

• Gears
• Shafts
• Couplings
• Bolts
• Mold bases

Machining Considerations

• Surface finish is easy to control after heat treatment
• Widely used for general-purpose mechanical components

 

T10 / T12 High Carbon Tool Steel

Properties

• High hardness after quenching (HRC 58–62)
• Excellent wear resistance
• High brittleness and low impact toughness

Typical Applications

• Files
• Taps
• Gauges
• Punches

Machining Considerations

• Readily machined in the annealed condition
• Grinding is required after hardening

 

2. Alloy Steels (For High-Strength and Critical Components)

 

40Cr (Equivalent to AISI 5140 Alloy Steel)

Properties

• Good hardenability
• 20–30% higher strength than 1045 steel Excellent overall mechanical performance after quenching
• and tempering

Typical Applications

• Engine connecting rods
• Critical gears
• Spindles
• High-strength bolts

Machining Considerations

• Offers good machinability in the tempered condition
• Excessive work hardening should be avoided

 

20CrMnTi Carburizing Steel

Properties

• Surface hardness after carburizing: HRC 58–62
• Tough and ductile core: HRC 35–42
• Excellent wear resistance and impact strength

Typical Applications

• Automotive transmission gears
• Bevel gears
• Wear-resistant shafts

Machining Considerations

• Final finishing is typically performed by grinding after carburizing
• Heat treatment distortion must be controlled

 

38CrMoAl Nitriding Steel

Properties

• Surface hardness after nitriding can reach HV 900–1100
• Excellent thermal stability
• Good core toughness

Typical Applications

• Precision lead screws
• High-pressure plungers
• Extruder screws

Machining Considerations

• Components are fully machined before nitriding
• No cutting operations are normally performed after nitriding

 

3. Stainless Steels (Corrosion-Resistant Materials)

 

304 Austenitic Stainless Steel

Properties

• Non-magnetic in the annealed condition
• Good general corrosion resistance
• Severe work hardening tendency
• Low thermal conductivity

Typical Applications

• Food processing equipment
• Medical devices
• Chemical vessels
• Decorative tubing

Machining Considerations

• Sharp tooling is essential
• Lower feeds and generous coolant application are recommended
• Prone to built-up edge (BUE)

 

316L Stainless Steel

Properties

• Contains molybdenum for improved chloride and seawater resistance
• Low carbon content provides excellent weldability

Typical Applications

• Marine components
• Medical implants
• Chemical valves

Machining Considerations

• More difficult to machine than 304
• High-performance tool coatings are recommended

 

420 / 440C Martensitic Stainless Steel

Properties

• Heat treatable to HRC 56–60
• High hardness and excellent wear resistance
• Magnetic

Typical Applications

• Surgical instruments
• Bearings
• Corrosion-resistant knives
• Molds

Machining Considerations

• Best machined in the annealed condition
• Grinding is required after hardening
• Grinding burn should be carefully controlled

 

4. Cast Irons (Excellent Damping and Dimensional Stability)

 

HT200 / HT250 Gray Cast Iron

Properties

• High compressive strength
• Excellent vibration damping capacity
• Good wear resistance
• Brittle with low tensile strength

Typical Applications

• Machine tool beds
• Columns
• Bases
• Flywheels

Machining Considerations

• Produces short, powder-like chips
• Carbide tooling is recommended
• Dust extraction may be necessary during dry machining

 

QT400-18 / QT600-3 Ductile Iron

Properties

• Mechanical strength comparable to steel
• Better impact toughness and fatigue resistance than gray iron

Typical Applications

• Crankshafts
• Steering knuckles
• Hydraulic valve bodies

Machining Considerations

• Generates higher cutting forces than gray cast iron
• Wear-resistant tooling is recommended

 

5. Aluminum Alloys (Lightweight and Highly Machinable)

 

6061-T6 Aluminum Alloy

Properties

• Medium strength
• Good corrosion resistance
• Excellent anodizing response
• Good weldability

Typical Applications

• Consumer electronics housings
• Bicycle frames
• Heat sinks
• Structural components

Machining Considerations

• Tends to form built-up edge
• Polished carbide or diamond tooling is recommended
• High-pressure coolant improves chip evacuation

 

7075-T6 Aluminum Alloy

Properties

• Very high strength, approaching that of some mild steels
• Lower ductility than 6061
• Poor weldability

Typical Applications

•  Aircraft structural parts
• Missile components
• High-stress tooling
• Drone parts

Machining Considerations

• Residual stresses may cause thin-wall distortion
• Machining sequence should be carefully planned

 

A380 Die-Cast Aluminum Alloy

Properties

• Excellent castability and dimensional stability
• Suitable for complex thin-wall components

Typical Applications

• Engine brackets
• LED heat sink housings
• Pump bodies

Machining Considerations

• A light skim cut is recommended to remove the dense surface layer before finish machining

 

6. Specialty Metals (High Performance, Challenging to Machine)

 

H62 Brass

Properties

• Excellent machinability
• Smooth surface finish
• Good corrosion resistance
• Good electrical conductivity

Typical Applications

• Plumbing fittings
• Valve cores
• Instrument components

Machining Considerations

• Supports high-speed machining
• Minimal burr formation
• Dry machining is often possible

 

T2 Copper (Pure Copper)

Properties

• Extremely high electrical and thermal conductivity
• Very soft and prone to deformation

Typical Applications

• Busbars
• Heat spreaders
• Sealing gaskets

Machining Considerations

• Requires very sharp tooling
• Generous coolant application is recommended
• Rigid workholding is essential

 

Inconel 718 Nickel-Based Superalloy

Properties

• Retains high strength at elevated temperatures above 600°C
• Severe work hardening tendency
• Poor thermal conductivity

Typical Applications

• Jet engine blades
• Nuclear reactor components
• Turbine disks

Machining Considerations

• Premium carbide or ceramic inserts are required
• Very low cutting speeds are recommended
• Machine rigidity is critical

 

Ti-6Al-4V (TC4) Titanium Alloy

Properties

• Exceptional strength-to-weight ratio
• Excellent biocompatibility
• Low thermal conductivity
• High chemical affinity with cutting tools

Typical Applications

• Orthopedic implants
• High-performance connecting rods
• Aerospace fasteners
• Deep-sea equipment

Machining Considerations

• Light cuts should be avoided to minimize work hardening
• Generous coolant application is essential
• Sharp coated tools are recommended

 

CNC Machining Material Comparison Table

Material	Machinability	Main Advantages	Main Drawbacks	Relative Cost
45 Steel	Excellent	Balanced performance and cost	Limited hardenability	★
40Cr	Very Good	High strength	Requires preheating for welding	★★
304 Stainless Steel	Moderate	Corrosion resistance	Work hardening	★★★
HT250 Cast Iron	Very Good	Vibration damping	Lower tensile strength	★
6061 Aluminum	Excellent	Lightweight and fast machining	Limited high-temperature wear resistance	★★
Brass H62	Excellent	Superb surface finish	Lower strength	★★
TC4 Titanium	Poor	Highest specific strength	Very difficult to machine	★★★★★
Inconel 718	Poor	Outstanding high-temperature strength	Extremely difficult to machine	★★★★★

 

 

How to Choose the Right CNC Machining Material

 

Choose 45 Steel or 40Cr If:

• You need a cost-effective solution
• Strength and toughness are both important
• The parts are shafts, gears, or structural components

 

Choose 6061 Aluminum If:

• Lightweight design is required
• Fast machining and anodizing are important
• Parts are for electronics, automation, or aerospace

 

Choose 304 or 316L Stainless Steel If:

• Corrosion resistance is critical
• Parts will be used in food, medical, or marine environments

 

Choose HT250 Cast Iron If:

• Vibration damping is required
• You are machining large machine bases or housings

 

Choose Titanium or Inconel If:

• Parts must withstand extreme temperatures or harsh environments
• Aerospace, medical, or energy applications are involved

 

Final Thoughts

Material selection directly impacts machining cost, production efficiency, and product performance.

 

As a general rule:

• For balanced performance and cost, choose 45 steel or 40Cr.
• For lightweight components, choose 6061 aluminum.
• For corrosion resistance, choose 304 or 316L stainless steel.
• For high wear resistance, choose 440C or tool steel.
• For vibration damping and large cast structures, choose HT250.
• For aerospace and high-temperature applications, choose titanium or Inconel.

 

By understanding the properties, applications, and machining challenges of each material, engineers and buyers can make more informed decisions and optimize both performance and manufacturing cost.

 

Need Help Selecting the Right Material for Your CNC Machined Parts?

Choosing the right material is critical to achieving the best balance of performance, machinability, and cost. Whether you need carbon steel, stainless steel, aluminum, brass, titanium, or high-temperature alloys, our engineering team can help you select the most suitable material for your application.

 

At XSH Precision, we specialize in precision CNC machining of complex metal components for industries including aerospace, medical, laser systems, automation, and industrial equipment.

Why Work With XSH Precision?

• 15+ years of CNC machining experience
• Expertise in machining difficult materials such as Ti-6Al-4V (TC4) and Inconel 718
• Tight tolerances up to ±0.005 mm
• Prototype to production capabilities
• Competitive pricing and reliable delivery

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Send us your drawings or material requirements, and our engineers will provide:

• Material selection recommendations
• Design-for-manufacturing (DFM) suggestions
• Competitive pricing
• Fast lead times

 

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