PEEK CNC machining is where plastics work starts to look like metal work. Polyetheretherketone is a high-performance thermoplastic with continuous service temperatures around 480 F, excellent chemical resistance, low moisture absorption and good strength and wear behavior. It is also expensive stock, so scrap is costly and process planning matters. Wexmar machines unfilled, 30 percent glass-filled, 30 percent carbon-filled and bearing-grade PEEK on CNC lathes, Swiss-type machines and horizontal machining centers at our shop in Canastota, New York.
Machinability of PEEK
Like other plastics, PEEK is not rated on the AISI 1212 steel scale. It cuts freely and forms manageable chips, but the limits are heat, residual stress, clamping and dimensional stability. PEEK has low thermal conductivity, so heat stays at the cut and can build stress into the surface layer. Filled grades add a second issue: glass and carbon fibers are abrasive and wear cutting edges quickly, which changes size and finish over a long run if tool life is not managed.
Tolerances and surface finish
On precision PEEK turned parts we typically hold plus or minus 0.001 in. on small diameters and bores and plus or minus 0.002 in. on larger turned and milled features. Critical tolerances on thin walls or large parts are reviewed per drawing. Unfilled PEEK routinely reaches 32 Ra on turned sealing surfaces; filled grades typically finish at 32 to 63 Ra, since exposed fibers limit how smooth the surface can get. Parts are inspected at controlled shop temperature on our CMMs, with reports available through our inspection and quality program.
Tooling, heat and stress gotchas
- Anneal before and between operations. Stress-relieved stock is the starting point. For tight parts, the roughed part is annealed again before finishing so it does not move after release.
- Tool material. Sharp carbide works well on unfilled PEEK. On glass and carbon-filled grades, diamond-coated or PCD tools hold size far longer.
- Heat control. Air blast or water-soluble coolant keeps the surface cool. Overheating leaves internal stress that can lead to cracking or warpage later.
- Drilling. Deep holes in PEEK are pecked with sharp drills and moderate feed. Drilling hot or too aggressively can crack the part, particularly in filled grades.
- Clamping. Full-contact soft jaws and light, even pressure prevent distortion that shows up as out-of-round bores after unclamping.
- Burrs and fibers. Unfilled PEEK leaves fine burrs that trim cleanly. Filled grades can show fiber fuzz on edges, which is controlled with sharp tools and finish passes.
Annealing and finish options
PEEK annealing cycles run several hours with controlled ramp-up and cool-down, and are performed through qualified outside processors or specified on the stock from the mill. PEEK parts typically ship as machined. Specialized cleaning, marking or packaging, when a drawing requires it, is arranged through qualified outside processors.
Common PEEK parts
- Seals, backup rings and valve seats for high-pressure and high-temperature fluid systems (CNC lathes)
- Bushings, thrust washers and wear rings in pumps and compressors (lathes)
- Electrical insulators, standoffs and connector bodies (Swiss-type, to 32 mm diameter)
- Manifold blocks, pump housings and analytical instrument components (horizontal machining centers)
- Wafer and part handling components for process equipment
- Medical hardware such as instrument components and fixtures (non-implant)
Small PEEK parts in volume run efficiently on our Swiss machining cells, where bar feeders reduce handling and remnant waste on costly bar.
Cost index vs 6061 aluminum
| Material | Approx. machinability (1212 = 100) | Cost index vs 6061 | Notes |
|---|---|---|---|
| 6061-T6 aluminum | ~180 | 1.0 | Baseline |
| Delrin / acetal | Not rated; cuts freely | 1.0 | Lower heat limit |
| PTFE | Not rated; cuts freely | 1.4 | Chemical resistant, creeps under load |
| 316 stainless | ~36 | 2.5 | Metal alternative for pressure parts |
| Ultem (PEI) | Not rated; cuts freely | 3.0 | High heat, lower cost than PEEK |
| PEEK | Not rated; cuts freely | 4.5 | High heat, chemical and wear resistance |
These values are typical and illustrative for a comparable part; actual quotes depend on geometry, quantity, tolerances and mill pricing. If the temperature and chemical demands are lower, Ultem machining is often a less costly alternative.
Applications and industries
PEEK machining services support fluid power and pump OEMs, oil and gas instrumentation, analytical and laboratory equipment builders, electrical and connector manufacturers, aerospace hardware programs and medical hardware makers. Material certs and lot traceability are available on request. From Canastota in Central New York, parts ship nationwide by parcel or LTL.
Getting a quote
To price PEEK parts, upload a drawing for an instant estimate or call (315) 400-2654. A human estimator confirms every quote, including grade selection and stock availability.