Industry News
Which Metal Materials Should be Chosen for Custom CNC Parts?
2026-06-29
Introduction: Why Material Selection Directly Determines the Success or Failure of a CNC Project
At FRIMA, we machine thousands of bespoke parts every year for clients across various sectors, including agriculture, automotive, healthcare and industrial equipment. One question we are asked most frequently is: What material should I use for my part?
This is a crucial question. Choosing the right material ensures reliable part performance, efficient machining and a manageable budget; choosing the wrong material, however, can lead to severe tool wear, poor surface quality, premature part failure, and even final costs far exceeding the budget.
The good news is that modern CNC machine tools can machine an extremely wide range of metals — from free-cutting soft aluminium to high-strength titanium alloys, all with precision. The real challenge lies in selecting the most suitable material for your specific application.
In the following sections, FRIMA will guide you through the most commonly used metals for CNC machining, their core properties, machining characteristics and typical applications. By the end, we hope you will have a clear framework for material selection, enabling you to make the best decisions when commissioning custom CNC parts.
Four Key Considerations When Selecting Materials for CNC Machining
Before going into detail about the various types of metals, let us first outline the four key criteria that our engineers at FRIMA focus on when recommending materials to our clients.
1. Mechanical Performance Requirements
What functions must the component fulfil? Key indicators include:
• Strength: tensile strength, yield strength, hardness
• Toughness: impact resistance and resistance to crack propagation
• Weight: strength-to-weight ratio for aerospace or portable equipment applications
• Wear resistance: a key consideration for components subject to friction or wear
2. Operating Conditions
In what environment will the components operate?
• Corrosion resistance: Will they be exposed to moisture, chemicals or salt spray
• Temperature range: Extreme high or low temperatures can significantly alter material properties
• Electrical and thermal conductivity: Key performance indicators for applications such as electronic components and heat sinks
3. Machinability
How difficult is the material to machine?
• Tool wear rate: Highly abrasive or high-hardness materials can drive up tooling costs
• Chip control: Materials that break up easily result in more stable and efficient machining
• Surface finish potential: Some materials are naturally better suited to achieving a high-quality surface finish
• Machining speed: The faster the cutting speed, the lower the unit cost
4. Total Cost
The total cost extends far beyond the price of raw materials:
• Cost of materials per unit volume
• Cost of machining time and tool wear
• Cost of post-processing operations (heat treatment, electroplating, oxidation, etc.)
• Scrap rate and material wastage
The 'best' material is never the cheapest raw material, but rather the solution with the lowest overall cost, provided it meets the performance requirements.
A Comprehensive Guide to the Most Commonly Used Metal Materials in CNC Machining
Below are the metal materials most commonly used in FRIMA' s manufacturing processes, along with their respective advantages, disadvantages and typical applications.
1. Aluminium Alloys
Aluminium alloys are by far the most popular materials for CNC machining.
Key Characteristics:
• Excellent machinability, with high cutting speeds and minimal tool wear
• High strength-to-weight ratio, resulting in significant weight savings
• Good natural corrosion resistance
• Excellent thermal and electrical conductivity
• Easily sourced and offering good value for money
Common Grades:
• 6061-T6: The 'all-rounder' aluminium for CNC machining. It offers balanced overall performance, good machinability and moderate strength. It is the preferred choice for brackets, housings, panels and general structural components.
• 7075-T6: Significantly stronger than 6061, approaching the strength of steel whilst maintaining a lightweight profile. Slightly more difficult to machine, with slightly lower corrosion resistance. Commonly used in aerospace structural components, high-stress parts and high-performance equipment.
• 5052: Excellent corrosion resistance, particularly suitable for marine environments. Slightly less strong than 6061, making it an ideal choice for sheet metal and housing components.
Applications:
General-purpose structural components, housings, brackets, aerospace components, heat sinks, and all applications requiring lightweight construction.
At FRIMA, aluminium alloy is the material we machine most frequently. Its excellent machinability allows us to use higher spindle speeds and feed rates, resulting in shorter lead times and lower unit costs.
2. Carbon Steel
Carbon steel comes in a wide variety of grades, offers excellent value for money and has a broad range of applications, making it a fundamental material in the industrial sector.
Key Characteristics:
• Low-carbon steel offers good machinability
• Excellent strength and toughness
• Extremely versatile, a wide range of hardnesses can be achieved through heat treatment
• Cost-effective
• Poor corrosion resistance (requires electroplating or coating for protection when used outdoors)
Common Grades:
• 1018: A representative low-carbon steel, offering good machinability, excellent ductility and low cost. It is highly suitable for general-purpose parts, brackets, jigs and fixtures, as well as components requiring welding or surface carburising and quenching.
• 1045: A medium-carbon steel with higher strength than 1018; after heat treatment, it can achieve a hardness of HRC 45–55. It is commonly used for medium-load components such as shafts, gears and pins.
• A36: Structural steel with properties similar to 1018; sheets and sections are readily available. Suitable for structural components and welded assemblies.
Applications:
General-purpose structural components, shafts, gears, pins, jigs, and applications requiring strength whilst prioritising low cost.
3. Free-cutting Steel
If you are seeking the highest machining efficiency from steel, free-cutting steel is well worth considering.
Key Characteristics:
• Exceptional machinability — fine, brittle chips and long tool life
• Excellent surface finish
• Faster machining speeds directly reduce unit costs
• Mechanical properties are slightly lower than those of standard carbon steel of the same grade
Common Grades:
• 12L14: The most widely used free-cutting steel. The addition of lead significantly improves chip evacuation and surface quality, making it ideal for the automated production of high-volume, precision small parts.
• 1215: A lead-free, environmentally friendly version of free-cutting steel that retains excellent machining performance. Suitable for applications where lead content is restricted (such as certain medical and food-related applications).
Applications:
High-volume production, precision small parts, threaded components, and all projects requiring the highest levels of machining efficiency and surface quality.
At FRIMA, for high-volume projects with low strength requirements and no need for welding, we typically recommend 12L14. Compared to standard 1018 steel, it offers a 20–30% improvement in machining efficiency, resulting in significant cost savings on large orders.
4. Alloy Steel
When the strength, toughness or hardenability of ordinary carbon steel fails to meet requirements, alloy steel is the solution.
Key Characteristics:
• Superior strength, toughness and hardenability compared to carbon steel
• A wide range of hardness and toughness combinations can be achieved following heat treatment
• Better wear resistance
• Slightly more difficult to machine than carbon steel
• Higher material costs
Common Grades:
• 4140: The most classic alloy structural steel. After heat treatment, it offers an excellent balance of strength, toughness and wear resistance (typically HRC 28–35, though higher values are possible). Widely used in high-stress industrial components such as shafts, gears, bolts and hydraulic components.
• 4340: A high-end alloy steel with superior toughness and hardenability compared to 4140. Used in critical load-bearing applications such as aerospace components and high-performance automotive parts.
• 4130: Lower strength grade than 4140, but with better machinability and weldability. Suitable for structural tubing, bicycle frames and general-purpose high-strength components.
Applications:
High-strength components, shafts, gears, fasteners, hydraulic components, and parts requiring specific mechanical properties achieved through heat treatment.
5. Stainless Steel
Stainless steel combines excellent corrosion resistance with good mechanical properties and is widely used.
Key Characteristics:
• Excellent corrosion resistance (varies significantly between grades)
• Good strength and toughness
• Some grades can be heat-treated for strengthening (precipitation-hardening types)
• More difficult to machine than carbon steel
• Higher material cost
Common Grades:
• 304 (18-8): The most commonly used austenitic stainless steel. It offers good corrosion resistance, excellent formability and is non-magnetic. Used in food processing equipment, medical devices, kitchenware and general-purpose corrosion-resistant components.
• 316: Offers superior corrosion resistance to 304, with particularly strong resistance to salt spray and chloride corrosion. Used in marine environments, chemical processing equipment, medical implants and similar applications.
• 17-4 PH: A precipitation-hardening stainless steel. After heat treatment, it can achieve a hardness of HRC 38–44 and offers high strength. It combines high strength, corrosion resistance and good machinability. It is used in aerospace components, medical devices and high-strength fasteners, amongst others.
Applications:
Corrosion-resistant components, food and medical equipment, marine applications, aerospace components, and parts requiring both strength and corrosion resistance.
6. Tool Steel
Tool steel is specifically designed for cutting tools, moulds and wear-resistant components — but is also widely used in mass-produced parts requiring extremely high hardness and wear resistance.
Key Characteristics:
• Extremely high hardness and wear resistance after heat treatment
• Good toughness (varies by grade)
• Excellent dimensional stability after heat treatment
• Difficult to machine in the hardened state
• High material cost
Common Grades:
• A2: Air-hardening tool steel, offering a balance of wear resistance and toughness. Used for punches, dies, shear blades, forming tools, etc.
• D2: High-carbon, high-chromium tool steel. Offers exceptional wear resistance but relatively low toughness. Used for long-life dies, cutting tools and highly wear-resistant components.
• S7: Impact-resistant tool steel. Superior toughness compared to D2 and A2, with slightly lower hardness. Used for impact tools, chisels, shear blades, etc.
Applications:
Cutting tools, dies, punches, shear blades, and all applications requiring extreme wear resistance.
7. Copper and Copper Alloys (Brass, Bronze)
Copper and its alloys offer outstanding electrical conductivity, thermal conductivity, corrosion resistance and workability.
Key Characteristics:
• Excellent electrical and thermal conductivity
• Good corrosion resistance
• Exceptional workability (particularly brass)
• Copper possesses natural antimicrobial properties
• Higher material cost than steel and aluminium
Common Alloys:
• Pure copper (C110): Offers the very best electrical and thermal conductivity. Used in electrical contacts, busbars, heat sinks, earthing components, etc.
• Brass (C360): Undoubtedly the metal with the best machinability. Excellent chip removal, good surface finish and corrosion resistance. Used in fittings, valves, connectors, decorative components and high-volume precision parts.
• Bronze: Outstanding wear resistance and self-lubricating bearing properties. Used in bearings, bushings, gears, marine components, etc.
Applications:
Electronic components, heat sinks, valves, fittings, bearings, decorative parts. Brass, in particular, is a favourite for FRIMA’s high-volume projects; its machinability allows us to achieve extremely fast cycle times whilst maintaining excellent surface quality.
8. Titanium and Titanium Alloys
Titanium has the highest strength-to-weight ratio of any commonly used metal, whilst also offering outstanding corrosion resistance.
Key Characteristics:
• Unrivalled strength-to-weight ratio amongst all commonly used metals
• Extremely high corrosion resistance (superior to stainless steel in many environments)
• Excellent biocompatibility (suitable for medical implants)
• Extremely difficult to machine — requires rigid clamping, sharp cutting tools and specialised process parameters
• Very high material cost
Common Grades:
• Ti-6Al-4V (TC4/5 grade titanium): The most widely used titanium alloy. It offers high strength and relatively good machinability among titanium alloys. Used in aerospace components, medical implants and high-performance automotive parts.
• Pure titanium (Grade 2 titanium): Industrial-grade pure titanium. Slightly lower strength, but with better formability and corrosion resistance. Used in chemical engineering and marine corrosion-resistant applications.
Applications:
Aerospace components, medical implants, high-performance automotive parts, and applications requiring the ultimate in strength-to-weight ratio and corrosion resistance.
9. Magnesium Alloys
Magnesium is the lightest structural metal and is the material of choice for applications requiring extreme weight reduction.
Key Characteristics:
• Extreme lightness — 35% lighter than aluminium
• Excellent machinability (even superior to aluminium)
• Good dimensional stability
• Lower strength than aluminium
• Fine magnesium swarf is flammable; special protective measures are required during machining
• Moderate corrosion resistance
Applications:
Aerospace components, lightweight structural parts, handheld devices, and all applications where extreme weight reduction is the primary objective.
Comparison Table of the Machinability of Common Materials
To help you compare at a glance, here' s how the most common CNC materials stack up in terms of machinability (higher = easier/faster to machine)：
|
Material |
Machinability Rating |
Relative Cost |
Typical Strength |
|
Brass (C360) |
100% (Best) |
Medium |
Low-Medium |
|
Magnesium |
90% |
High |
Low-Medium |
|
Aluminum 6061 |
85% |
Low-Medium |
Medium |
|
12L14 Steel |
80% |
Low |
Medium |
|
1018 Steel |
65% |
Low |
Medium |
|
4140 Steel (annealed) |
50% |
Medium |
High |
|
304 Stainless |
40% |
Medium-High |
Medium-High |
|
17-4 PH Stainless |
45% |
High |
High |
|
Tool Steel (annealed) |
30% |
High |
Very High |
|
Titanium Ti-6Al-4V |
20% |
Very High |
Very High |
Note: Machinability ratings are approximate and depend on specific material condition, tooling, and machine setup.
Below Are Our Recommended Solutions for Common Application Types
|
Application |
Our Top Recommendation |
Why |
|
General-purpose parts, enclosures, brackets |
6061 Aluminum |
Great machinability, good strength, cost-effective |
|
High-volume precision parts |
12L14 Steel or Brass |
Excellent machinability, great surface finish, fast cycle times |
|
High-strength structural parts |
4140 Steel (Q&T) |
Excellent strength and toughness balance, cost-effective |
|
Corrosion-resistant parts |
304 or 316 Stainless |
Excellent corrosion resistance, good mechanical properties |
|
Electrical/thermal components |
Copper or Aluminum |
Excellent conductivity, good machinability |
|
Aerospace / weight-critical |
7075 Aluminum or Titanium |
Highest strength-to-weight ratios |
|
Wear parts / tooling |
D2 or A2 Tool Steel |
Extreme hardness and wear resistance |
|
Food / medical equipment |
316 Stainless or 17-4 PH |
Corrosion-resistant, cleanable, biocompatible options |
Conclusion
No single metal is a 'one-size-fits-all' solution; the correct choice depends on the part' s function, operating environment, production volume and budget. Aluminium alloys are the most popular all-rounders, but steel, stainless steel, brass, copper, titanium and magnesium each have their own unique applications where they are irreplaceable.
Most importantly, find an experienced CNC machining partner to help you weigh up the various trade-offs and select the optimal material solution for your project.
Get a Free Materials Review and Quotation Now
If you are working on a CNC machining project and are unsure which material to choose for your parts, FRIMA' s engineering team is always on hand to assist. Simply send your drawings and technical specifications to info@frimaparts.com, or complete the online quotation form on our website, and we will respond within 24 hours with professional advice and a competitive quotation.
Frequently Asked Questions (FAQ)
Q1: What is the easiest metal to machine using CNC?
A: Brass (particularly C360 free-cutting brass) is generally considered to offer the best machinability, with smooth chip removal and excellent surface finish. Aluminium alloys (especially 6061) are a close second and, due to their favourable strength-to-weight ratio, have a wider range of applications.
Q2: What is the cheapest metal for CNC machining?
A: In terms of raw material prices, low-carbon steels such as 1018 and A36 are usually the cheapest. However, when considering the overall cost, aluminium alloys are often more economical, as they can be machined much faster, resulting in lower labour and machine-hour costs.
Q3: Can CNC machine tools machine titanium alloys?
A: Yes, but titanium is one of the most challenging metals to machine. It requires extremely rigid clamping, sharp carbide cutting tools, specialised cutting parameters and appropriate cooling methods. FRIMA has extensive experience in machining titanium alloys and has served numerous clients in the aerospace and medical sectors.
Q4: Is stainless steel significantly more difficult to machine than ordinary steel?
A: Yes. Stainless steel, particularly austenitic grades such as 304 and 316, is significantly more difficult to machine than carbon steel. It work-hardens rapidly, produces long, sticky chips and causes greater tool wear, which means slower cutting speeds and higher unit costs.
Q5: Is it best to choose the material with the highest strength?
A: Not necessarily. Using a material with a strength that exceeds requirements will only increase costs, including both higher material costs and slower machining speeds. The optimal strategy is to select the material with the lowest strength that meets the performance requirements, thereby ensuring reliability whilst keeping costs under control.