PEEK CNC Machining Services
PEEK is a high-performance, semi-crystalline thermoplastic rated for continuous use to 250 C, resistant to most chemicals, and the default plastic for aerospace, oilfield, medical and semiconductor parts where engineering polymers are required.
Unfilled, glass-filled and carbon-filled grades
Tolerances to +/-0.05 mm on critical features
Bearable grade rod, plate and near-net shapes
What Is PEEK?
Why PEEK earns its premium over commodity plastics, and what changes on the machine.
PEEK (polyetheretherketone) is a semi-crystalline engineering thermoplastic built around the diphenyl ketone backbone. Unfilled PEEK has a tensile strength of about 100 MPa and a continuous service temperature of 250 C, and resists attack from most organic and inorganic chemicals except strong concentrated acids. Those numbers put it closer to a metal replacement than to a typical plastic.
Grades and when to use them
Unfilled PEEK is the toughest and most ductile grade. Glass-filled PEEK (typically 30 percent glass) raises stiffness and stability at the cost of impact resistance. Carbon-filled PEEK adds electrical conductivity for static dissipative parts and bears higher load at temperature. Bearing grades add PTFE, graphite or carbon fibre to lower the coefficient of friction against steel without external lubrication.
How PEEK is machined
PEEK cuts cleanly with sharp carbide and standard geometry, but the material is sensitive to heat above its glass transition near 143 C. Use moderate cutting speeds, positive rake, and water-based or air coolants rather than cutting fluid, because coolant absorption creates a long-term dimensional change. The result is a part that holds tolerance and remains chemically clean on delivery.
Related capabilities: CNC Machining, CNC Milling, CNC Turning, 5-Axis Machining. Dimensional limits, thread rules and surface roughness grades are listed on the tolerances and specifications page, and volume-based routing is covered under production solutions.
PEEK Mechanical Properties
Typical values at room temperature for the condition most often machined. Use them for material screening, then confirm against the mill certificate for the exact heat and product form.
| Property | Typical value |
|---|---|
| Density | 1.31 g/cm3 |
| Ultimate tensile strength | 100 MPa (14.5 ksi) |
| Tensile yield strength | 0.2 percent offset 70 MPa (10 ksi) |
| Elongation at break | about 30 to 45 percent |
| Elastic modulus | 3.6 GPa |
| Continuous service temperature | 250 C in air |
| Melting point | 343 C |
| Glass transition temperature | 143 C |
| Moisture absorption at saturation | about 0.5 percent |
| Flammability | UL 94 V-0 at 1.5 mm without flame retardant additives |
Typical room-temperature values compiled from public ASM, MatWeb and mill datasheets. Actual values vary with temper, section thickness and product form; request the EN 10204 3.1 certificate for critical applications.
Machining Characteristics of PEEK
How the material behaves in the cut, and what that means for tooling, fixtures, cycle time and achievable tolerance.
Carbide tooling
Standard sharp carbide with polished flutes gives clean cuts and long tool life; diamond coating helps in volume production.
Heat management
Keep cutting energy moderate. Above 143 C the material begins to transition and dimensional behaviour shifts, so air blast or water-based cooling is preferred over petroleum-based cutting oils.
Stress cracking
Notch-sensitive at high stress concentrations. Specify generous internal radii on hubs, bosses and locking features.
Tapping and threading
PEEK taps well with oversize tap drills. Standard threads should be oversize by 75 to 80 percent to avoid strip-out under thermal cycling.
Avoid swelling creep
Coupled parts that combine metal and plastic must allow for the higher thermal expansion of PEEK; otherwise thermal cycling strips fitted threads.
Sterilisation
Withstands gamma, EtO and steam sterilisation cycles used in pharmaceutical and medical manufacturing.
Design and Machining Checklist
Practical rules that reduce cost and scrap on PEEK parts. Share them with your design team before the drawing is frozen.
- Specify glass-filled PEEK for structural components where stiffness and dimensional stability at temperature drive the design.
- Use carbon-filled PEEK where static dissipation or extra strength over glass-filled are needed, particularly for semiconductor components.
- Cut PEEK dry or with water-based coolants; avoid petroleum lubricants that may be absorbed and later leach out.
- Allow for thermal expansion of about 50 um per metre per C when designing metal-to-PEEK assemblies.
- Use generous radii of 0.5 mm minimum on all internal corners to avoid notch-driven cracking.
- Consider PEEK bearing grades for unlubricated bushings and wear rings; PTFE and graphite fillers drop friction by half.
Surface Finishing Options
Finishes are selected for corrosion resistance, wear, appearance, electrical behaviour or cleanliness. Specify only what the function needs.
As-Machined
Ra 0.4 to 1.6 um with no tool chatter, suitable for many sealing and bearing surfaces.
Bead Blasting
Fine glass-bead finish that gives a uniform satin appearance and removes light handling marks.
Polishing
Mechanical polish to a glossy finish for medical and semiconductor flow components where cleanliness is critical.
Bonding and Welding
PEEK bonds with structural adhesives and can be heat welded above its melting point; ultrasonic staking is widely used for assembly.
Steam and Chemical Sterilisation
Withstands repeated autoclaving and aggressive cleaning agents without property loss.
Annealing
Post-machining annealing at 200 to 250 C relieves residual stress and stabilises dimensions for tight tolerances.
Typical Applications
Where PEEK is most often specified, and why it wins against the alternatives.
Aerospace and defence
Brackets, manifolds, fasteners and bushings used in airframes and engines, where high temperature and fire performance are mandatory.
Oil and gas downhole
Back-up rings, seal carriers, bearings and electrical connectors that survive sour service to 200 C.
Medical and dental
Instrument handles, sterilisation trays and trial implants that must survive repeated autoclaving.
Semiconductor
Wafer carriers, chambers and handling components that combine chemical resistance with low outgassing.
Food and pharmaceutical
Mixer parts, valve seats and pump components in contact with aggressive cleaning chemicals.
Industrial bearings and seals
Unlubricated bushings and wear rings in pumps, mixers and conveyor systems.
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