PEEK CNC machining guide
(definition, advantages, processes,materials and tips)

Updated: June 12, 2024

What is PEEK (polyether ether ketone)?

Polyetheretherketone (PEEK) is one of the highest-performing, semi-crystalline thermoplastics. PEEK plastic material offers a combination of superlative properties that allow PEEK to effectively replace metal in some of the most severe end-use environments.

The chemical structure of PEEK is shown as below.

The molecular structure of PEEK gives rise to a valuable array of high-performance characteristics. Aryl groups contribute to modulus, thermal stability, and flame retardancy. Ether linkages impart toughness and ductility, while ketones provide long-term thermal oxidative resistance.

peek chemical structure

What are the properties of PEEK material?

Polyetheretherketone (PEEK) is a versatile engineering plastic known for its exceptional combination of properties.

PEEK Density

The PEEK material density is about 1.3 to 1.4g/cm3. Compared with metal, it is low density and that is one of the reasons why it can be used as a substitute material for metals.

With excellent mechanical performance, high temperature and chemical stability, PEEK’s lightweight properties make it suitable for aerospace and automotive industries. It can reduce the components overall weight, thus improving fuel efficiency, reducing loads and cutting cost.

PEEK Thermal Properties

The melting point of PEEK is about 343°C (649°F), and PEEK operating temperature is around -60°C to +250°C (-76°F to +482°F). PEEK is high temperature resistance, and maintains its stability and performance in elevated temperature environments.

The glass transition temperature (Tg) of PEEK typically ranges from approximately 143°C to 160°C (289°F to 320°F). With a high Tg, PEEK can maintain its stiffness, strength, and durability without excessively softening or losing structural stability at high temperatures.

This allows PEEK to perform exceptionally well in applications requiring operation under elevated temperatures, such as automotive engines, aerospace, and high-temperature chemical environments.

The thermal conductivity of PEEK is relatively low, typically ranging from 0.25 to 0.4 W/(m·K) at room temperature. This low thermal conductivity contributes to its good thermal insulation properties, making PEEK suitable for applications where thermal insulation is important.

The thermal expansion coefficient of PEEK is generally from 50 to 70 × 10^-6 per °C.Compared to some other materials, the thermal expansion coefficient of PEEK can be considered relatively low.

In precision engineering applications or situations where tight tolerances need to be maintained, PEEK’s low thermal expansion coefficient helps ensure that components maintain their dimensions over a range of operating temperatures.

This helps prevent issues such as warping, distortion, or improper fit due to temperature changes, making PEEK suitable for use in applications where dimensional accuracy and stability are critical.

Due to PEEK’s high heat resistance and thermal conductivity, PEEK performances well at very high temperature. It is why PEEK is used as a high performance engineering thermoplastic material.

PEEK Chemical Properties

PEEK has excellent resistance to wide ranges of chemicals, including acids, bases, solvents and hydrocarbons. PEEK’s chemical resistance makes it suitable for application in environments exposed to corrosive substances, such as chemical processing, oil and gas, and automotive industries.

PEEK also has good resistance to degradation from radiation and sterilizations processes, making it suitable for medical and aerospace applications.

PEEK Mechanical Properties

The tensile strength of PEEK is about 90 to 120 MPa (megapascals). Compared to some other materials, it is relatively high, especially for a thermoplastic polymer.

The high tensile strength of PEEK makes it suitable for a wide range of applications where strong, durable materials are required. It allows PEEK to withstand high mechanical loads and stresses without experiencing significant deformation or failure.

This property is particularly advantageous in industries such as aerospace, automotive, medical devices, and oil and gas, where components are subjected to demanding mechanical conditions.

PEEK plastic has high harness and impact resistance. The Rockwell M hardness is 105 (ISO 2039-2) and 100 (ASTM D785), which is high. The high hardness makes PEEK to maintain stability with high loads and abrasion.

Overall, PEEK has good mechanical properties, high hardness, good impact resistance, and high tensile strength. These characteristics makes PEEK suitable for automotive, aerospace and medical device industries.

Peek Electrical Properties

The typical electrical resistivity of PEEK is 10^15 to 10^16 ohm·cm. The dielectric constant of PEEK is about 3.2 to 3.3. PEEK has good insulation performance and arc resistance.

The high electrical resistivity and relatively low dielectric constant makes PEEK a preferred material for electrical and electronic application, such as electrical equipment and cable insulation.

PEEK’s excellent arc resistance makes it suitable for high voltage environment such as aerospace and power systems.

Peek UV Resistance

Most materials are susceptible to damage from extended exposure to outdoor weather conditions. To assess the impact of prolonged exposure to high levels of ultraviolet (UV) radiation, such as that found in sunlight, an Atlas water-cooled weathering test instrument was utilized, employing a Xenon Arc light source.

Like other materials, PEEK is susceptible to damage from exposure to outdoor weather conditions. Thus PEEK does not have good UV resistance. PEEK will become yellower and darker if exposed to sunlight or high levels of ultraviolet (UV) radiation for a long time.

PEEK Water Absorption

Polyetheretherketone (PEEK) has low water absorption, and the water absorbed has minimal impact on the mechanical properties of PEEK.

PEEK Flammability

PEEK has a V-0 flammability rating, indicating excellent flame resistance, and emits very low levels of smoke and toxic gases when exposed to flame.


PEEK is made from specific petroleum derivatives, and the production process is complex, requiring a high degree of purification and fine processing, so PEEK materials are more expensive. Another reason is that there are fewer producers of PEEK materials worldwide, and competition is not as fierce, which is also the reason for its higher price.

What Are the Grades of Polyether Ether Ketone (PEEK)?

There are various PEEK manufacturers globally, and the classification may vary for each manufacturer. However, overall, PEEK can be divided into the following four categories.

  1. Unfilled PEEK,
  2. 30% glass filled PEEK
  3. 30% carbon filled PEEK
  4. Bearing grade PEEK(also called carbon fiber-reinforced with graphite PEEK, PTFE PEEK)
  5. Medical grade PEEK

Unfilled PEEK

Unfilled PEEK is the most common grade and for general purpose application. Unfilled PEEK has the highest toughness, elongation, and fatigue resistance among all grades. There are different colors for unfilled PEEK, mostly white, tan/light brown, and black.

30% glass filled PEEK

30% glass-reinforced PEEK incorporates glass fibers, reducing PEEK’s expansion rate and enhancing its flexural modulus by 30%. Consequently, it becomes a more robust and rigid alternative to the unfilled grade, well-suited for structural applications requiring stability, particularly in high-temperature environments.

Despite its increased strength, this variant of PEEK may experience higher wear when paired with other components. It is available in light grey/tan or black color options.

30% carbon filled PEEK

PEEK reinforced with 30% carbon fibers has heightened stiffness and compressive strength while greatly reducing its expansion rate. This carbon-filled PEEK is specifically engineered for superior wear resistance and load-bearing capabilities. Additionally, it has 3.5 times greater thermal conductivity than unfilled PEEK. These properties make carbon-reinforced PEEK an ideal choice for plastic bearings. 30% carbon-filled PEEK is available in black color due to the incorporation of carbon fibers.

Bearing grade PEEK

Bearing grade PEEK varies among manufacturers, but typically contains a 20% infusion of PTFE and carbon fiber reinforced with graphite. It has the lowest coefficient of friction and highest machinability compared to all other PEEK grades. Bearing grade PEEK exhibits excellent wear characteristics in mating, friction, and load-bearing applications, making it an optimal material choice for bearings across various industries. Due to these exceptional properties, this specific PEEK grade is labeled as “bearing grade.” It is commonly available in grey or black colors.

Medical grade PEEK

Medical-grade PEEK, also known as implant-grade PEEK or PEEK-OPTIMA, is designed for medical applications. It offers exceptional biocompatibility, radiolucency, mechanical properties, chemical resistance, and sterilizability. Used in various medical devices and implants, medical-grade PEEK contributes to improved patient outcomes and quality of life by providing structural support, stability, and reliability in the healthcare industry.

Below are world-famous PEEK manufacturers and the PEEK grades they provide.

CompanyPEEK Grades Provided
EvonikMedical grade PEEK
VictrexUnfilled PEEK,
30% glass filled PEEK
30% carbon filled PEEK
Bearing grade PEEK
SolvayUnfilled PEEK,
30% glass filled PEEK
30% carbon filled PEEK
Bearing grade PEEK
Zypeek(China)Unfilled PEEK,
30% glass filled PEEK
30% carbon filled PEEK
Bearing grade PEEK
Pfluon(China)Unfilled PEEK,
30% glass filled PEEK
30% carbon filled PEEK
Bearing grade PEEK
Jdsep(China)Unfilled PEEK,
30% glass filled PEEK
30% carbon filled PEEK
carbon fiber used in peek

How is PEEK part manufactured?

PEEK components can be processed via different methods, including injection molding, extrusion, compression molding, CNC machining and 3d printing.

PEEK Injection Molding

Injection molding is a commonly used method of processing polyether ether ketone (PEEK). In this process, PEEK pellets are melted and injected into the mold cavity at high pressure. Once the material has cooled and solidified, the mold opens and the finished PEEK part is ejected.

Injection molding can produce complex shapes and high volume parts with excellent dimensional accuracy and surface quality. It is widely used in the aerospace, automotive, medical device and electronics industries to manufacture a variety of PEEK parts.

PEEK Extrusion

For PEEK extrusion process, PEEK pellets are heated to a molten state, and then the molten material is extruded through an extruder to form continuous profiles, sheets, or films.

PEEK extruded products have excellent heat, chemical, and mechanical resistance, and can be used to manufacture a variety of applications such as tubing, sheets, and films.

PEEK Compression Molding

In PEEK compression molding process, PEEK pellets are heated to a molten state and then placed in a pre-designed mold. By applying pressure, the molten PEEK material is filled into the mold to form the desired shape of the part. The material then cools and solidifies, the mold opens and the final PEEK part is removed.

PEEK compression molding method is suitable for producing parts with intricate details or thicker sections.

PEEK CNC Machining

PEEK CNC machining is a common manufacturing method where computer numerical control (CNC) machines are used to precisely cut, mill, drill, and shape PEEK material to produce parts of desired shapes and sizes. PEEK material is relatively hard, but precise machining can be achieved through CNC machining methods, making it suitable for producing various PEEK parts, including components and prototypes.

PEEK CNC machining is suitable for parts with precision machining and complex shapes.  CNC machining is the ideal choice for manufacturing PEEK parts requiring high accuracy and surface quality.

PEEK has high dimensional stability and well-balanced mechanical properties. This combination of properties contributes to the excellent machinability of PEEK material. In PEEK plastic machining, high tool infeeds and feed rates can be utilized, making PEEK CNC machining still considered the fastest and most efficient manufacturing process for producing precision components.

PEEK 3D Printing

PEEK 3D printing is a three-dimensional printing technique using polyether ether ketone (PEEK) material. It is an additive manufacturing process that creates three-dimensional objects by stacking layers of PEEK material one on top of another.

PEEK 3D printing is typically performed using techniques such as fused deposition modeling (FDM) or selective laser sintering (SLS). PEEK 3d printing technique allows for the production of parts with complex geometries and internal structures without the need to create costly molds.

PEEK 3D printing is suitable for applications that require high-temperature and corrosion-resistant properties, such as in aerospace, automotive, medical, and engineering.PEEK 3D printing also offers the convenience of customization and rapid prototyping and thus has a wide range of applications.

PEEK CNC Machining VS PEEK 3D Printing VS PEEK Injection Molding VS PEEK Compression Molding

PEEK extrusion process is usually to make PEEK profiles, sheets, and films, which may need further machining processes to get the final PEEK components. PEEK CNC machining, PEEK 3D printing, PEEK injection molding, and PEEK compression molding are all processes that can produce more complex PEEK parts. Each process has its unique advantages and suitability for parts of varying complexity and requirements.

Choosing the right process depends on factors such as specific design requirements, production costs, lead times and part characteristics.

 ProsConsComplex GeometriesMechanical PerformanceAccuracy & Repeatability
CNC Machining Peek1. High precision and accuracy.
2. Ability to produce complex geometries.
3. Suitable for prototype,small to medium batch production.
1. Longer lead times compared to other processes.
2. Higher cost, especially for small quantities.
3. Material waste during machining process.
3D Printing PEEK1. Ability to produce complex geometries without the need for molds.
2. Rapid prototyping and customization capabilities.
3. Reduced material waste.
1. Lower mechanical properties compared to machined or molded parts.
2. Limited choice of PEEK filaments suitable for 3D printing.
3. Surface finish may not be as smooth as other methods.
Injection Molding PEEK1. High production volumes with low unit cost for mass production.
2. Excellent repeatability and consistency.
3. Wide range of material options and surface finishes.
1. Initial tooling cost can be high.
2. Longer lead times for tooling fabrication.
3. Limited ability to modify designs after tooling is made.
Compression Molding PEEK1. Lower tooling cost compared to injection molding.
2. Suitable for large and thick parts.
3. Can accommodate various fillers and additives.
1. Longer cycle times compared to injection molding.
2. Limited to simpler geometries compared to injection molding.
3. Potential for material degradation due to prolonged heating.

PEEK CNC Machining Processes

PEEK has excellent machinability, allowing for the production of complex and high-precision components through CNC machining. Processes such as turning, milling, threading, and drilling can be used to manufacture PEEK parts suitable for prototyping, small batch, or medium batch production.

PEEK Milling

PEEK milling is the process of using milling machines or CNC mills to shape and cut PEEK material into desired forms, dimensions, and surface finishes. 

PEEK plastic milling involves rotating a cutting tool with multiple flutes or edges, while simultaneously moving the PEEK workpiece in relation to the tool to remove material and create features such as slots, pockets, and contours.

PEEK milling is commonly used in various industries to manufacture components such as gears, housings, and structural parts from PEEK material.

Effective part fixturing is crucial in PEEK CNC milling, because high spindle speeds and fast travel are recommended to minimize frictional heat buildup and material pullout.

Tools with positive geometry is preferred.

It is advisable to use climb milling instead of conventional milling because climb milling offers improved chip removal, reduced tool wear, and a superior surface finish.

If possible, use end mills with 4 flutes. Generally, keep milling stepovers restricted to 25% of the tool diameter, and limit depths of cut to 50% of the tool diameter to achieve the best possible surface finish.

peek face milling

PEEK Turning

PEEK turning is the process of machining PEEK rods on a lathe or turning machine to achieve desired shapes, dimensions, and surface finishes. This turning process involves rotating the PEEK workpiece while a cutting tool removes material from its surface to create cylindrical or contoured features. PEEK turning is commonly used in manufacturing industries to produce various components such as bushings, seals, and medical implants from PEEK material.

For turning tools, it is recommended to use positive geometries with ground peripheries. The best options are fine-grained C-2 carbide or PCD tools. To avoid distortion, it is suggested to apply 360° chuck pressure.

When turning thin-walled, tubular shapes, it is advisable to use machined soft jaws or pie jaws.

Improving roundness can be achieved by rough-turning the chuck area of the stock.

To prevent thin-walled PEEK-turned parts from compressing and distorting, internal plugs should be used.

peek turning

PEEK Drilling

PEEK drilling is to make holes or cavities in PEEK rods or plates with drilling equipment. It can be done by different drilling techniques, such as conventional drilling, peck drilling, , or through-hole drilling. Due to PEEK’s high temperature resistance and mechanical strength, PEEK drilling may require special drill bits and cutting parameters to achieve precise peek machined parts.

Careful measures must be taken to minimize heat build-up when drilling holes deeper than twice their diameter. When drilling, it is best to use a drill with a low helix angle and flood coolant. Peck drilling is recommended to remove chips and swarf. To remove chips and prevent excessive heat buildup, coolant fed drills are preferred.

For larger diameter holes, it is best to use a two-step process by drilling a pilot hole up to 1/2 inch in diameter and then reaming the hole to the final diameter. Holes up to 1/2-inch diameter can be drilled with standard carbide drills. Holes up to 2 inches in diameter can be drilled with an interchangeable insert drill bit similar to the Iscar Chamdrill. For milling setups, a pocket design is recommended.

To avoid backside breakout, consider milling from both sides or leaving a 0.005-0.010-inch allowance that can then be removed with a small milling cutter.

PEEK Threading

For threading by CNC turning, single-point inserts with flood coolant are recommended.

For tapped holes, two fluted, non-coated spiral carbide taps are recommended with a cutting fluid. Tight tolerance tapped holes may require a tap one size larger than typically needed for tapping aluminum or steel.

When threading by CNC milling, floating tap heads can help minimize tap breakage, which is common with smaller-sized taps.

Below is a table to show PEEK CNC machining parameters.

Turning PEEK.025”300-800 FT/MIN. .004-.025”
Face milling PEEK0.035”    500 – 800 .006 – .035”
¼.250”270-450 FT/MIN..002”
½.250”270-450 FT/MIN..003”
¾.250”270-450 FT/MIN..005”
1.250”270-450 FT/MIN..008”
.750” up.015”

PEEK CNC Machining Tips

Below are general machining tips for CNC machining PEEK.


Though PEEK material is stronger and stiffer than most plastic, it is still much softer compared with metals. Thus fixturing is critical for successful peek plastic machining.

Minimize jaw pressure when chucking the PEEK stock or PEEK plate to prevent deformation.Ensure adequate support for thin sections to prevent deflection caused by the cutting tool. Adjust cut depths to be shallower as the part thickness decreases.


Compared with other CNC machining plastics like Nylon and Acetal, all PEEK grades are more abrasive on tooling,  especially for grades reinforced with glass and/or carbon fiber. The part geometry design, tolerance requirement and PEEK grade will also influence the selection of tools.

Carbide tooling with polished surfaces is typically sufficient for the unfilled grades and low production volumes, but it tends to dull fairly quickly. Diamond-coated or polycrystalline tooling (PCD) is recommended for grades containing glass or carbon fibers, as well as for higher production volumes, tightly tolerance parts, and reinforced grades.


PEEK polymer has low thermal conductivity and high thermal expansion, which can result in stock overheating during aggressive machining, leading to dimensional issues when the part cools.

Coolant is recommended for machining PEEK, with both water-soluble and petroleum-based options suitable for chip removal and thermal management of both the stock and tooling. Proper coolant usage can prolong tool life and enhance surface finish.

Alternatively, air, preferably from a cold air gun, can be used for small parts or instances where cleanup is challenging.

PEEK has lower elongation compared to many other plastics. Deep hole drilling into heavy cross-sections without adequate coolant can potentially cause cracking.


As a high-performance engineering plastic with excellent machinability, in general, PEEK machining does not require any annealing treatment. However, there are specific scenarios where annealing may be necessary before or after rough machining.

When the PEEK machined parts is relatively long or has large dimensions, there is a risk of excessive stress or deformation during machining. In such cases, annealing after rough machining is recommended to relieve stress.

If the wall thickness of the PEEK component is thin, annealing may be necessary to prevent warping or distortion.

PEEK components with strict surface finish requirements or tight tolerance specifications may also benefit from annealing to ensure dimensional stability and surface quality.

For more information about PPEK annealing, please refer to our blog What is annealing peek for machining.

What is the tolerance of PEEK in machining?

Although PEEK has high strength and machining performance, it is still a plastic material. The tolerances for CNC machining PEEK components typically adhere to ISO 2768 MK. Tighter tolerances can also be achieved with extensive machining experience.

What is the surface finishes for CNC Machining PEEK?

Unfilled PEEK is usually tan or beige. Standard finishes for PEEK machined parts are as machined, machining marks are visible. PEEK components are usually used for functional parts while the appearance is not critical, so it is acceptable to leave the parts as machined.

Paints and coatings are difficult to bond to its surface considering PEEK’s polymeric structures.
To achieve a smoother surface and improved aesthetic, secondary processes like sanding and polishing may be used to get a higher-quality finish.

What are the advantages of machining PEEK?

The unique molecular structure of PEEK makes it have many high-performance characteristics. Aryl groups provide modulus, thermal stability, and flame retardant. Ether linkages provide toughness and ductility. PEEK plastic polymer provides long-term thermal oxidative resistance.

Below are key properties of PEEK plastic material.

  • Outstanding chemical resistance to a wide range of organic compounds, acids, and bases.
  • High mechanical strength, maintaining performance even at temperatures exceeding 250°C (480°F)
  • Exceptional wear and abrasion resistance
  • Best-in-class fatigue resistance, ensuring durability under repeated stress
  • Excellent resistance to hydrolysis, even in boiling water and superheated steam environments
  • Low moisture absorption, ensuring dimensional stability over time
  • Superior dielectric properties with minimal loss at high temperatures and frequencies
  • Ease of melt processing during manufacturing
  • High purity, suitable for demanding applications requiring precise material properties.

By CNC machining, PEEK machined parts can achieve high accuracy, high repeatability and tight tolerance.

What are the limitations of machining PEEK?

Tough PEEK plastic is considered to be a reliable alternative to some metals, there are indeed some limitations for machining peek material.

For extremely intricate or organic designs, 3D printing might offer advantages in terms of feasibility and cost-effectiveness than CNC machining PEEK.

Annealing PEEK may be required to minimize internal stress and heat-related cracks for complicated PEEK parts.

What are the applications of machining PEEK?

Aerospace industry

PEEK is often used to manufacture critical components such as nozzles, turbine blades, seals and turbine bearings. Its high-temperature resistance meets the needs of aero-engines, while its lightweight and corrosion-resistant properties make it widely used in aerospace applications.

Also, PEEK materials are used to manufacture structural components for spacecraft, helping to realize lightweight designs and improve the load capacity and fuel efficiency of spacecraft.

Automotive industry

PEEK is widely used in the manufacture of engine components for high-performance vehicles, such as throttle valves, piston rings and cylinder liners.

Its heat and wear resistance enables it to maintain stability in high temperature, high pressure, and high-speed environments, while its lightweight and excellent mechanical properties help improve fuel efficiency and performance of vehicles.

In addition, PEEK is commonly used in the manufacture of automotive interior parts such as instrument panels, door handles, and seat adjusters to provide comfort and durability.

Semiconductor industry

PEEK is used as an encapsulant and insulating layer for semiconductor devices to protect circuit boards and chips from external environmental interference and damage.

Its excellent insulating properties and chemical resistance enable it to meet semiconductor device requirements for stability and reliability, while its high-temperature stability helps to cope with high-temperature handling in semiconductor processes.

Petroleum industry

PEEK is often used as a manufacturing material for key components such as oil well tools, valves and pipeline connectors. Its corrosion resistance and high-temperature resistance enable it to cope with the harsh environment in the oil extraction and transportation process, ensuring the safe and stable operation of oil equipment.

In addition, PEEK is also widely used as seals and anti-corrosion materials in petrochemical plants to improve the durability and reliability of equipment.

Mechanical equipment

PEEK is often used in the manufacture of high-performance bearings, gear seals, and other key components. Its wear resistance and high-temperature resistance enable it to maintain stability in heavy-duty, high-speed mechanical systems, extending the service life of equipment and reducing maintenance costs.

In addition, PEEK is also commonly used in wind power, hydropower, and other new energy equipment, key components of manufacturing, to improve energy efficiency and equipment reliability.

Electronic industry

PEEK is widely used in the manufacture of connectors, sockets, and electronic insulation parts. Its excellent insulation properties and high-temperature resistance can ensure the stable operation and safety performance of electronic equipment.

In addition, PEEK is also used as an electronic heat dissipation material to improve the heat dissipation efficiency and performance stability of electronic equipment.

Medical industry

PEEK is commonly used in the manufacture of orthopedic implants and surgical instruments, such as artificial joints, interbody fusion devices and surgical forceps. Its biocompatibility and mechanical strength make it ideal for use in medical devices for a variety of orthopedic surgeries and treatments.

For more information about PEEK application, read our blog Applications of Polyetheretherketone (PEEK) Introduction.

cnc machining peek parts suppliers


PEEK is a commonly used engineering plastic in CNC machining, but due to its high price, the material cost is relatively high. Therefore, in the machining process, you need to pay attention to the selection of tools, the use of coolant, and anealing treatment of the material.

When choosing a PEEK CNC machining manufacturer, you need to consider whether you have experience in PEEK machining, whether you can provide raw material certificates, and other factors.

ECOREPRAP Author Lucas


Lucas is a technical writer at ECOREPRAP. He has eight years of CNC programming and operating experience, including five-axis programming. He also spent three years in CNC engineering, quoting, design, and project management. Lucas holds an associate degree in mold design and has self-taught knowledge in materials science. He’s a lifelong learner who loves sharing his expertise.

Learn More about Lucas.

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