Machining is one of the most precise and reliable manufacturing methods, creating components with tight tolerances, high strength, and excellent durability. Whether used for aerospace, medical devices, industrial machinery, or automotive parts, machining ensures superior performance and longevity. However, not all materials are equally suited for the process.
The choice of material affects machining speed, tool wear, production cost, and final part performance. Metals and plastics behave differently under cutting forces, heat generation, and surface finishing techniques, so selecting the right one is essential for efficient production and long-term reliability.
Machining Metals: Strength, Durability, and Workability
Metals remain the gold standard for machined components due to their strength, wear resistance, and temperature stability. The most commonly used metals include aluminum, stainless steel, carbon steel, and titanium, each offering distinct advantages depending on application needs.
Aluminum: Lightweight, Corrosion-Resistant, and Fast to Machine
Aluminum is a favorite in aerospace, automotive, and industrial manufacturing due to its high strength-to-weight ratio and ease of machining.
Among aluminum alloys, 6061 is the most common, offering excellent machinability, corrosion resistance, and moderate strength. It is widely used in structural components, frames, and aerospace parts. For applications demanding higher strength, 7075 aluminum is preferred, though it is harder to machine and more expensive.
One of aluminum’s greatest benefits is its low cutting forces, which result in faster machining speeds and reduced tool wear, making it one of the most cost-effective metals to machine.
Stainless Steel: Strength and Corrosion Resistance with Machining Challenges
Stainless steel is indispensable in medical, marine, food-processing, and industrial applications due to its superior corrosion resistance and high durability.
303 stainless steel is the easiest to machine, making it suitable for fasteners, fittings, and industrial components. 304 stainless steel is more common and offers stronger corrosion resistance, though it is more difficult to machine due to work hardening. 316 stainless steel provides the highest corrosion resistance, making it ideal for marine and chemical processing applications, but it demands slow machining speeds and specialized tooling.
Despite its strength, stainless steel wears down cutting tools quickly and generates significant heat, increasing machining costs and cycle times compared to aluminum.
Carbon Steel: Affordable Strength for Industrial Applications
Carbon steel is a cost-effective alternative to stainless steel, offering high mechanical strength and machinability but requiring protective coatings to prevent rust.
1018 carbon steel is widely used due to its low cost and easy machinability, making it ideal for shafts, gears, and general-purpose industrial components. 1045 carbon steel offers greater hardness and wear resistance, making it more suitable for load-bearing applications.
While carbon steel is easier to machine than stainless steel, it lacks the corrosion resistance of stainless alloys, requiring additional plating or protective treatments.
Titanium: Aerospace-Grade Strength at a High Cost
Titanium offers exceptional strength, corrosion resistance, and weight savings, making it essential for aerospace, medical implants, and high-performance automotive parts. However, it is one of the most difficult and costly metals to machine.
Grade 5 titanium (Ti-6Al-4V) is the most commonly used alloy, balancing high strength and moderate machinability. It is extremely heat-resistant, but it also wears out cutting tools quickly and requires slow feed rates to avoid material deformation.
Due to its high cost and machining difficulty, titanium is reserved for applications where strength, corrosion resistance, and weight reduction are critical.
Machining Plastics: Lightweight, Chemical-Resistant, and Cost-Effective
Plastics are often machined as an alternative to metals in applications requiring chemical resistance, weight reduction, or electrical insulation. Some plastics are as easy to machine as metals, while others present unique challenges due to softness, thermal expansion, and material melting.
Delrin (Acetal): The Gold Standard for Machined Plastics
Delrin, also known as Acetal (POM), is one of the best machinable plastics, widely used for gears, bushings, and precision mechanical components.
It offers low friction, high wear resistance, and excellent dimensional stability, making it a top choice for low-maintenance parts. Unlike softer plastics, Delrin cuts cleanly and holds tight tolerances, making it ideal for precision machining applications.
Nylon: Impact-Resistant but Moisture-Sensitive
Nylon is a strong, flexible plastic used in industrial bushings, gears, and impact-resistant parts. However, it absorbs moisture, which can cause dimensional instability in humid environments.
It machines relatively well but tends to generate heat, which can lead to melting and poor surface finishes if not machined with sharp tools and controlled feed rates.
PTFE (Teflon®): The Ultimate Chemical-Resistant Plastic
PTFE is valued for its extreme chemical resistance, low friction, and high-temperature stability, making it ideal for seals, gaskets, and medical applications. However, it is soft and deforms easily, requiring specialized techniques to machine precisely.
Because PTFE is prone to cold flow and dimensional creep, machining tolerances must be carefully controlled to prevent part deformation over time.
PEEK: The Aerospace-Grade High-Performance Plastic
PEEK is one of the strongest and most heat-resistant machinable plastics, used in aerospace, medical implants, and high-performance automotive applications.
It offers exceptional mechanical strength, thermal stability, and resistance to harsh chemicals, but it is abrasive and requires carbide tooling to prevent excessive wear. Due to its high cost and machining challenges, PEEK is reserved for specialized, high-end applications.
Comparing Machining Costs and Difficulty
Material choice significantly affects machining speed, tool life, and production costs.
Aluminum remains the most cost-effective metal to machine due to fast cutting speeds and low tool wear. Stainless steel and carbon steel are moderate in cost, but stainless steel requires specialized tooling. Titanium is the most expensive and difficult metal to machine, increasing production time and tooling costs.
Among plastics, Delrin and Nylon are affordable and easy to machine, while PTFE and PEEK require specialized tooling and careful machining techniques due to softness or abrasiveness. PEEK, in particular, is very expensive, making it viable only for extreme environments requiring high-temperature and chemical resistance.
Choosing the Right Material for Machining
Selecting the right material depends on cost, machinability, durability, and performance requirements.
Aluminum is ideal for fast, cost-effective machining with moderate strength. Stainless steel is best for corrosion-resistant, high-strength applications, while carbon steel provides a strong, low-cost alternative. Titanium is reserved for high-performance, weight-sensitive applications, despite its machining challenges.
For plastic machining, Delrin and Nylon offer affordable strength and wear resistance, while PTFE and PEEK are necessary for extreme chemical and heat resistance.
At RapidMade, we specialize in precision machining for both metals and plastics, offering expert material selection and manufacturing solutions tailored to your needs.
For custom machining services and expert consultation, visit rapidmade.com or contact info@rapidmade.com.
