PEEK Machining
Unfilled, glass-filled and medical-grade PEEK parts, stress-relieved and machined to tight tolerances for medical, semiconductor, oil and gas, and aerospace customers.
High-Performance Plastic, Machined Without the Cracks
PEEK is the plastic you choose when nothing else survives: continuous service to 480°F (250°C), outstanding chemical resistance, metal-level strength, and excellent wear properties. It's also unforgiving to machine — internal stress causes cracking and warpage if the stock isn't handled correctly. IsoCNC runs PEEK machining for medical, semiconductor, oil and gas, and aerospace customers in North America and Europe, with annealed stock and stress-relief cycles built into the process rather than added as an afterthought.
PEEK Grades We Machine
- Unfilled PEEK (natural) — the standard grade. Best ductility and chemical resistance; the default for medical and food-contact parts
- 30% glass-filled PEEK — higher stiffness and dimensional stability, lower thermal expansion. Note: glass fibers are abrasive, so we run carbide or PCD tooling and expect faster tool wear
- 30% carbon-filled PEEK — highest strength and wear resistance of the common grades; used for bearings, seals, and structural parts
- Bearing-grade PEEK (PTFE/graphite-filled) — low-friction grade for bushings and wear pads
- Medical-grade PEEK — biocompatible grades with full material certification for medical device components; tell us your regulatory requirements when quoting
We source PEEK stock with material certificates and lot traceability on request — important for medical machining and other regulated industries, where the certificate for the resin batch has to follow the part.
Machinability and How We Cut It
CNC machining PEEK cleanly is mostly about discipline, not exotic equipment. Our shop-floor approach:
- Annealed stock only — we start with stress-relieved rod and plate; heavily machined parts get intermediate annealing (typically 2–4 hours at 300–350°F / 150–175°C) between roughing and finishing to prevent post-machining movement
- Sharp tooling, controlled coolant — PEEK can be machined dry or with coolant; we prefer compressed air or mist for medical parts to avoid contamination, with sharp carbide or diamond-coated tools
- Heat management — PEEK is a thermal insulator, so heat stays in the cut. Reduced cutting speeds and sharp tools prevent melting, smearing, and surface damage
- Glass-filled caution — abrasive fillers destroy standard tooling fast; we quote filled grades with an appropriate tool-wear allowance instead of discovering it mid-run
Tolerances and Surface Finishes
PEEK holds tighter tolerances than most plastics. General features machine to ±0.005 in (±0.13 mm); critical features to ±0.002 in (±0.05 mm) with annealed stock and controlled finishing. Note that PEEK absorbs moisture and grows slightly — for the tightest work we recommend final machining after conditioning, and we verify dimensions by CMM inspection before shipment.
As-machined surface finish runs Ra 3.2 µm (125 µin) standard, to Ra 0.8 µm (32 µin) on sealing and bearing surfaces. PEEK machined parts are almost always used as-machined — no plating or coating required, which is part of the material's appeal. See surface finishes for what applies to plastics.
Typical PEEK Parts
Medical device components and surgical instrument parts, semiconductor wafer-handling components, valve seats and seals, pump wear rings, electrical insulators, connectors, bearing cages, and oil-and-gas downhole components. Most PEEK work runs on 3-axis milling and CNC turning; thin-wall manifolds and complex multi-face geometries route to 5-axis machining.
PEEK Machining — Capability Summary
| Capability | Specification |
|---|---|
| Grades available | Unfilled, 30% glass-filled, 30% carbon-filled, bearing grade, medical grade |
| Stress relief | Annealed stock standard; intermediate annealing for tight-tolerance parts |
| General tolerance | ±0.005 in (±0.13 mm); precision features to ±0.002 in (±0.05 mm) |
| As-machined finish | Ra 3.2 µm (125 µin); to Ra 0.8 µm (32 µin) on request |
| Finishes | As-machined, bead blast (matte); no plating or anodizing on PEEK |
| Batch range | 1 pc prototype to 1,000+ pcs production |
| Documentation | Material certificates and lot traceability on request |
Drawing Tips for PEEK Parts
- Name the grade on the drawing. “PEEK” alone gets quoted as unfilled natural; if you need glass- or carbon-filled stiffness, or a medical grade with certification, say so — the resin cost difference is significant.
- Balance your material removal. Parts machined heavily from one side of a plate will move. If the design allows, rough symmetrically or leave the part slightly oversized for a final finishing pass after stress relief — and note the flatness-critical faces so we plan the sequence.
- Be realistic on tolerances across temperature swings. PEEK’s thermal expansion is far higher than metal; a bore toleranced at room temperature will measure differently in service. Tell us the operating temperature if the fit matters.
- Threads: prefer metal inserts for repeated assembly. PEEK threads work for single-assembly joints, but tapped threads in service equipment wear — a threaded insert is cheap insurance.
Quote Your PEEK Parts
Send STEP files and drawings with your grade and any regulatory requirements — we'll return pricing, lead time, and DFM feedback within 1–2 business days. For other engineering plastics, see the full materials page or our plastic CNC machining overview.
Quote Your PEEK Parts
Send STEP files and drawings with your grade and any regulatory requirements — we'll return pricing, lead time, and DFM feedback within 1–2 business days.
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