CNC Machining PEEK in the UK: Grades, Tolerances & Cost Guide
PEEK is one of the most capable engineering thermoplastics available for precision-machined components.
It offers an unusual combination of high-temperature performance, chemical resistance, mechanical strength and dimensional stability.
But there is an important detail that engineers and purchasing teams sometimes overlook:
Not all PEEK is the same material.
A component machined from unfilled PEEK can behave very differently from an identical component manufactured from 30% carbon-fibre-filled PEEK.
A glass-filled grade may be excellent for a highly loaded structural component but unsuitable for a particular sliding bearing.
And a specialist bearing grade containing PTFE, graphite and carbon fibre may outperform a conventional reinforced grade in a demanding wear application.
For UK manufacturers sourcing CNC-machined PEEK components, choosing the correct material is therefore just as important as choosing the machining supplier.
At Axion Precision, we support engineering companies with precision CNC machining of engineering polymers, including unfilled and reinforced PEEK.
This guide explains how to select the appropriate grade, specify realistic tolerances and prepare a manufacturing quotation that reflects the component's actual operating requirements.
What is PEEK, and why is it used for precision components?
PEEK stands for polyether ether ketone.
It is a semi-crystalline, high-performance thermoplastic belonging to the PAEK family of polymers.
Compared with common engineering plastics such as acetal, nylon and ABS, PEEK offers particularly strong performance in demanding thermal, chemical and mechanical environments.
Its useful characteristics include:
High continuous-service temperature capability.
Excellent resistance to many chemicals.
Low moisture absorption compared with many other engineering thermoplastics.
Good mechanical strength and stiffness.
Resistance to hydrolysis and steam exposure.
Useful electrical insulation properties in unfilled grades.
Good dimensional stability when correctly processed and machined.
According to the manufacturer's March 2026 technical data, unfilled VICTREX PEEK 450G has a melting temperature of approximately 343°C, a glass-transition onset around 143°C and a tensile modulus of approximately 4 GPa at 23°C. Victrex
These properties make PEEK attractive for components that conventional plastics may struggle to accommodate.
However, high melting temperature should not be confused with an unlimited operating temperature.
Mechanical properties change with temperature, loading and duration of exposure.
For highly loaded components, engineers should evaluate creep, stiffness and the relevant grade's temperature-dependent mechanical data.
The four main PEEK material options
For many CNC machining projects, the initial material decision involves four categories.
PEEK gradeMain advantageTypical applicationUnfilled PEEKDuctility and balanced propertiesInsulators, precision housings, general engineering componentsGlass-filled PEEK GF30Increased stiffness and creep resistanceStructural supports, spacers, loaded componentsCarbon-filled PEEK CF30High stiffness and dimensional stabilityPrecision supports, loaded bushes, mechanical componentsSpecialist bearing-grade PEEKOptimised friction and wear characteristicsSliding bearings, thrust washers, guides and bushes
These categories are useful starting points, but they are not interchangeable specifications.
A drawing should identify the required material grade, not simply state “PEEK”.
Unfilled PEEK: the general-purpose option
Unfilled PEEK is the natural starting point for many precision components.
It provides a useful combination of mechanical performance, chemical resistance and ductility without introducing reinforcing fibres.
Typical applications include:
Electrical insulating components.
Precision spacers.
Instrument housings.
Chemical-resistant fittings.
Valve components.
Bushes operating under suitable loads.
Specialist mechanical components.
One advantage of unfilled PEEK is that it generally offers greater elongation before failure than highly reinforced grades.
That can be important for components containing:
Snap features.
Thin sections.
Press-fit interfaces.
Localised stress concentrations.
Features that experience limited elastic deformation.
The manufacturer's data for unfilled PEEK 450G reports tensile strain at break of approximately 25%, compared with approximately 1.7% for its 30% carbon-fibre-reinforced 450CA30 grade under the stated test conditions. Victrex
The practical implication is important.
Adding reinforcement increases stiffness, but it can significantly reduce ductility.
A stiffer material is not automatically a better material.
Glass-filled PEEK GF30: when stiffness matters
Glass-filled PEEK typically contains approximately 30% glass-fibre reinforcement by weight.
The reinforcement improves properties such as:
Stiffness.
Resistance to deformation under sustained loading.
Dimensional stability.
Strength under certain loading conditions.
This makes GF30 attractive for structural components that must maintain their geometry under mechanical loading.
For example, consider a precision spacer installed between two metal components.
The spacer must maintain a controlled separation while experiencing a sustained compressive load.
If unfilled PEEK deforms excessively over time, a glass-filled grade may provide improved performance.
The material manufacturer Ensinger specifically identifies its TECAPEEK GF30 material as suitable for components experiencing high static loads over extended periods, including elevated-temperature applications. Ensinger Plastics
Why GF30 may be unsuitable for sliding bearings
Glass fibres are relatively hard.
When exposed at a sliding surface, they can increase abrasion of the mating component.
For example, a glass-filled PEEK bush running against a relatively soft metal shaft may produce undesirable shaft wear.
Ensinger explicitly cautions that glass-filled PEEK is less suitable for some bearing and wear applications because the glass fibres can abrade mating surfaces. Ensinger Plastics
This is an important distinction.
GF30 can be an excellent structural material without being the best bearing material.
If the component slides, rotates or experiences repeated frictional contact, the complete material pair needs to be evaluated.
Carbon-filled PEEK CF30: strength and dimensional stability
Carbon-filled PEEK commonly contains 30% carbon-fibre reinforcement.
The carbon fibres significantly increase stiffness and can improve resistance to deformation under sustained loading.
Carbon-filled PEEK can also provide improved thermal conductivity compared with unfilled PEEK.
That can be useful in components where heat must dissipate from a loaded contact region.
Typical applications include:
Precision bushes.
Structural supports.
Loaded spacers.
Mechanical guides.
High-stiffness components.
Components requiring improved dimensional stability.
Ensinger's TECAPEEK CF30 technical information identifies improved creep strength, high rigidity and increased thermal conductivity among its principal advantages. Ensinger Plastics
How much stiffer is CF30?
Manufacturer data provides a useful comparison.
The March 2026 VICTREX technical datasheets report approximately:
Unfilled PEEK 450G: 4 GPa tensile modulus.
Carbon-filled PEEK 450CA30: 28 GPa tensile modulus.
That represents approximately seven times the tensile modulus under the specified test conditions. Victrex
However, these figures relate to particular material grades and test specimens.
Properties in machined stock can depend on the stock manufacturing process, fibre orientation and component geometry.
The values should not be treated as universal design allowables.
Nevertheless, the difference illustrates why carbon-filled PEEK can be attractive where stiffness is a primary requirement.
Is PEEK CF30 suitable for sliding bearings?
Potentially, yes.
Carbon-filled PEEK can offer useful wear characteristics and may perform well in selected sliding applications.
However, there is an important distinction between:
Carbon-fibre-reinforced PEEK
and
A purpose-developed PEEK bearing grade.
They are not necessarily the same thing.
A material described as CF30 is generally reinforced primarily to improve mechanical properties.
A specialist bearing grade may contain a combination of additives selected specifically to reduce friction and wear.
This distinction matters when specifying components such as:
Plain bearings.
Sliding bushes.
Thrust washers.
Linear guides.
Wear rings.
Bearing cages.
For a highly loaded static spacer, CF30 may be entirely appropriate.
For a continuously sliding bush, a dedicated bearing grade may offer a better solution.
What is bearing-grade PEEK?
The term bearing-grade PEEK can describe several proprietary formulations.
One established example uses a combination of:
Carbon fibre.
Graphite.
PTFE.
These ingredients perform different functions.
Carbon fibre can improve stiffness and load-carrying capability.
Graphite can contribute to favourable sliding behaviour.
PTFE can reduce friction in suitable applications.
For example, Ensinger's TECAPEEK PVX material contains 10% carbon fibre, 10% graphite and 10% PTFE.
The manufacturer specifically identifies good sliding and wear properties as principal characteristics. Ensinger Plastics
Why the exact bearing grade matters
Two suppliers may both offer a material described as:
PEEK BEARING GRADE
But the formulations may differ.
Differences can include:
Reinforcement percentage.
Lubricating additives.
Mechanical stiffness.
Compressive properties.
Thermal expansion.
Wear characteristics.
Electrical properties.
Available stock dimensions.
For repeat production, the exact grade should be controlled.
A suitable drawing specification might identify a particular manufacturer's material and grade, together with any approved equivalent.
This helps prevent a supplier substituting a material that appears similar but performs differently.
PEEK bearing design: the shaft matters too
Selecting a suitable polymer is only half the problem.
A sliding bearing is a system containing at least two interacting surfaces.
Consider a PEEK bush operating on a stainless-steel shaft.
The bearing's performance will depend on:
Shaft material.
Shaft hardness.
Surface roughness.
Bearing pressure.
Sliding speed.
Lubrication.
Temperature.
Contamination.
Alignment.
Operating duty cycle.
A material that performs well against hardened steel may behave differently against anodised aluminium.
Likewise, a bush that operates successfully under intermittent movement may not be suitable for continuous high-speed rotation.
Pressure and velocity
Bearing applications are often assessed using the relationship between contact pressure and sliding velocity.
This is commonly expressed as a PV value.
For a simple plain-bearing assessment:
PV = bearing pressure × sliding velocity
The result provides a useful initial indication of operating severity.
However, allowable PV values depend on the material, lubrication, geometry and test conditions.
A published PV limit should not be treated as a guarantee of service life.
For critical applications, representative testing may be necessary.
CNC machining PEEK: why it differs from machining aluminium
PEEK can be machined using conventional CNC equipment.
However, its behaviour is different from that of metals.
PEEK has:
Lower thermal conductivity than aluminium.
Greater thermal expansion than many metals.
Different cutting-force and chip-formation behaviour.
Potential residual stresses from stock manufacture.
Greater sensitivity to workholding pressure in some geometries.
These differences influence machining strategy.
Axion's CNC milling service includes engineering polymers such as PEEK alongside aluminium, stainless steel and other engineering materials.
Heat management
Excessive local heat can affect surface quality and dimensional accuracy.
Sharp cutting tools, appropriate feeds and speeds, effective chip evacuation and suitable cooling strategies are therefore important.
The correct coolant strategy depends on the material grade and application.
For medical, food-contact or contamination-sensitive components, cleaning requirements should be defined before machining.
Tool wear
Glass and carbon fibres can increase tool wear compared with unfilled polymer.
This may influence:
Tool selection.
Cutting parameters.
Surface finish.
Tool replacement frequency.
Manufacturing cost.
For repeat-production reinforced PEEK components, tooling strategy can become an important part of the quotation.
Workholding
A thin-walled PEEK component can deform if clamped excessively.
If the component is machined while distorted, it may spring back after removal from the fixture.
This can produce an unexpected dimensional error even when the machine has followed the programmed toolpath accurately.
The solution may involve improved fixturing, lighter clamping or a revised machining sequence.
PEEK machining tolerances: what is realistic?
PEEK can be machined to tight tolerances, but the correct tolerance depends on the component.
A short, thick-walled bush is very different from a large, thin-walled housing.
Important factors include:
Component size.
Wall thickness.
Material grade.
Stock condition.
Temperature.
Internal stress.
Workholding.
Machining sequence.
Inspection conditions.
For general engineering features, tolerances around ±0.1 mm may be relatively straightforward.
Features requiring ±0.05 mm or tighter may need additional process control, depending on geometry and material.
These are illustrative design considerations, not guaranteed Axion machining capabilities.
The actual tolerance should be reviewed against the drawing.
Thermal expansion can affect inspection
Consider a 100 mm dimension in unfilled PEEK.
The manufacturer's technical data for PEEK 450G reports an average coefficient of linear thermal expansion of approximately 55 × 10⁻⁶/K below its glass-transition temperature. Victrex
Using a simplified linear expansion calculation:
ΔL = α × L × ΔT
For a temperature change from 20°C to 40°C:
ΔL = 55 × 10⁻⁶ × 100 × 20
ΔL ≈ 0.11 mm
That is approximately 0.11 mm of theoretical expansion over a 100 mm length.
The actual dimensional response depends on grade, orientation and operating conditions, but the example illustrates an important point.
A polymer component can change dimension significantly between inspection temperature and operating temperature.
If a PEEK component must maintain a precise fit at elevated temperature, the operating clearance should be calculated using the appropriate material data.
Why stress relief matters in PEEK machining
Engineering-polymer stock can contain residual stresses introduced during manufacture.
Machining removes material and can redistribute those stresses.
In some geometries, this may cause:
Warping.
Bowing.
Changes in flatness.
Changes in bore diameter.
Dimensional movement after machining.
For particularly demanding components, the manufacturing plan may involve rough machining, controlled stress relief and subsequent finishing operations.
However, stress-relief procedures must follow the stock manufacturer's recommendations.
An arbitrary heating cycle can introduce additional dimensional changes or alter material properties.
The need for stress relief should therefore be considered during quotation rather than added automatically to every PEEK component.
Thin walls and deep pockets
Thin-walled PEEK components can be difficult to hold securely during machining.
For example, consider a rectangular PEEK housing containing a deep internal pocket.
The remaining walls may be only 1 mm thick.
Potential manufacturing problems include:
Wall deflection.
Vibration.
Distortion during clamping.
Dimensional movement after machining.
Poor surface finish.
If the wall thickness is not functionally critical, increasing it may improve manufacturability.
Similarly, deep pockets requiring long-reach cutters can increase machining time and tool deflection.
Axion's CAD and design-for-manufacture support can help identify these issues before the component is released for production.
Machining PEEK bushes and sleeves
Bushes are among the more common precision components manufactured from engineering polymers.
A typical bush may contain:
An external locating diameter.
An internal sliding bore.
A flange.
A chamfer.
A retaining feature.
Although the geometry appears simple, several dimensions may be functionally critical.
Internal diameter
The bore must provide the intended clearance with the mating shaft.
This clearance may need to account for operating temperature and environmental conditions.
External diameter
If the bush is installed into a housing, the external diameter determines the fit.
An interference fit can also alter the internal bore diameter after installation.
Wall thickness
Very thin walls can deform during machining or assembly.
Surface finish
The sliding surface may require a controlled finish appropriate to the shaft material and operating conditions.
Flange geometry
The flange may carry axial loading and must be designed for the relevant compressive stresses.
For these components, a drawing containing only nominal dimensions is often insufficient.
The intended fits and operating conditions should also be communicated.
Should you use a metal or PEEK bush?
PEEK can be an attractive alternative to certain metal bearing materials.
Potential advantages include:
Reduced weight.
Corrosion resistance.
Electrical insulation in appropriate grades.
Compatibility with selected chemicals.
Useful sliding properties.
Elimination of some metal-to-metal contact.
However, PEEK is not automatically superior to bronze, stainless steel or other conventional bearing materials.
Metallic bearings may offer advantages in:
Stiffness.
Thermal conductivity.
Dimensional stability under certain loads.
High contact pressures.
Particular lubrication regimes.
The correct choice depends on the application.
For example, replacing a bronze bush with PEEK without reconsidering wall thickness and running clearance may produce an unsuitable design.
Material substitution should therefore involve an engineering review rather than simply replacing the material callout on an existing drawing.
How to reduce the cost of CNC-machined PEEK components
PEEK is a relatively expensive engineering polymer.
That makes material utilisation especially important.
The most economical manufacturing approach is not always the one with the shortest machining cycle.
1. Select the correct grade
Do not specify CF30 if unfilled PEEK meets the requirement.
Likewise, do not specify a specialist bearing formulation for a static spacer unless its properties are needed.
2. Avoid unnecessary material removal
A component machined from a large solid billet may generate substantial waste.
Where available and appropriate, rod, plate or tube stock closer to the final geometry can reduce material consumption.
3. Review stock sizes before finalising the design
A small increase in external diameter may require purchasing the next available stock size.
For expensive polymers, that can materially affect the quotation.
4. Apply tolerances selectively
A precision bearing bore may require close control.
The overall length of a non-critical spacer may not.
Over-tolerancing increases machining and inspection costs.
5. Avoid unnecessary complexity
Deep pockets, very thin walls, inaccessible features and excessive surface-finish requirements can increase manufacturing time.
6. Provide realistic production quantities
A quotation for five components may use a different manufacturing approach from an order for 500.
Providing anticipated annual demand can help the supplier evaluate the most economical process.
PEEK versus acetal: is the extra cost justified?
PEEK is significantly more expensive than acetal in many commercial applications.
However, that does not mean it is poor value.
PEEK may be justified when the component requires:
Higher operating temperatures.
Greater resistance to certain chemicals.
Improved mechanical performance under demanding conditions.
Specialist wear properties.
Performance beyond the capability of conventional engineering plastics.
Acetal may be entirely suitable for:
General-purpose bushes.
Low-temperature spacers.
Simple mechanical guides.
Precision components operating under moderate conditions.
If acetal meets the engineering requirements, specifying PEEK may unnecessarily increase component cost.
Conversely, replacing PEEK with acetal purely to reduce material cost may introduce unacceptable performance risks.
The decision should be based on the operating requirements and validated material properties.
Material traceability and certification
For some industries, purchasing PEEK components involves more than confirming the nominal material grade.
Applications may require:
Material certificates.
Batch traceability.
Specific resin or stock-shape manufacturers.
Controlled manufacturing processes.
Defined cleaning procedures.
Regulatory or application-specific documentation.
This is particularly important in regulated applications.
For example, a general industrial PEEK grade should not automatically be assumed suitable for an implantable medical device.
Where specific approvals or biological testing are required, the exact certified material and supply route must be established.
Likewise, a supplier should not substitute one nominally equivalent PEEK grade for another without reviewing any applicable qualification requirements.
What should UK buyers include in a PEEK machining RFQ?
A complete request for quotation helps avoid material substitutions, manufacturing assumptions and unexpected costs.
Include the following information.
3D CAD model
Provide a STEP file showing the finished geometry.
Engineering drawing
Include critical dimensions, tolerances, threads and surface-finish requirements.
Material grade
Specify unfilled PEEK, GF30, CF30 or the exact bearing-grade formulation.
Where necessary, identify the manufacturer and commercial grade.
Operating temperature
Include both normal and maximum operating temperatures.
Mechanical loading
Describe relevant static, cyclic or impact loading.
Sliding conditions
For bearings and bushes, provide the shaft material, operating speed, load and lubrication conditions.
Chemical exposure
Identify chemicals, cleaning agents or process fluids.
Quantity
Provide immediate order quantity and anticipated repeat demand.
Inspection requirements
Identify critical dimensions and any required inspection documentation.
Material certification
Specify traceability or other certification requirements where applicable.
Delivery requirements
State the required delivery date and whether the order is for prototypes or production.
This information allows the supplier to assess the complete manufacturing requirement rather than simply pricing the geometry.
CNC machining PEEK components with Axion Precision
Axion Precision provides CNC machining support for engineering companies throughout the UK.
Our precision CNC milling capabilities include engineering polymers such as PEEK, alongside aluminium, stainless steel and other materials.
We also provide CNC turning and mill-turn manufacturing for rotational components such as bushes, sleeves, spacers and precision fittings.
For components requiring material selection or geometry optimisation, our mechanical-design capabilities can support the transition from initial CAD to a manufacturable component.
Axion is based in Poole, Dorset, serving customers across the South Coast and wider UK.
Whether the requirement is a single development component or a repeat-production batch, selecting the appropriate material grade and manufacturing process is essential.
Request a quote for CNC-machined PEEK parts
If you are sourcing precision PEEK components, send Axion Precision your CAD model and engineering drawing.
We can review requirements involving:
Unfilled PEEK.
Glass-filled PEEK.
Carbon-filled PEEK.
Specialist bearing-grade PEEK.
Precision bushes and sleeves.
Structural polymer components.
Complex CNC-machined polymer parts.
If you are unsure whether unfilled PEEK, CF30, GF30 or a specialist bearing grade is appropriate, include the operating conditions with your enquiry.
The material choice can then be considered alongside component geometry, tolerances, quantity and manufacturing cost.
Need a quotation for CNC-machined PEEK components?
Send your CAD files and request a quote from Axion Precision
Axion Precision — Poole, Dorset, UK
