🧪 PEEK
PEEK Machining in Lewiston, ME — Unfilled, Glass-Filled, and Carbon-Filled PEEK Components
Polyether ether ketone — PEEK — sits at the top tier of engineering thermoplastics, and the decision to specify it over competing polymers is always driven by a combination of requirements that only PEEK satisfies simultaneously: continuous service temperature to 480 degrees Fahrenheit, tensile strength of 14,000 psi unfilled rising to 24,000 psi carbon-filled, chemical resistance that survives steam autoclaving, and dimensional stability under moisture and temperature cycling that softer polymers cannot match. Lewiston's precision CNC shops, built on the discipline of defense component manufacturing, apply the same first-article inspection rigor and material traceability to PEEK machining that they do to titanium and stainless — buyers get polymer components held to metal-world standards.
AS9100ISO 9001ISO 13485
Unfilled PEEK: Baseline Properties and Where It Fits in Lewiston's Defense Work
Unfilled PEEK (Victrex 450G or equivalent) is the reference material against which the filled grades are measured. Tensile strength of 14,000 psi, flexural modulus of 600,000 psi, and continuous service temperature of 480 degrees Fahrenheit give unfilled PEEK a performance envelope that overlaps with aluminum alloy in many structural applications while offering electrical insulation and chemical resistance that aluminum cannot provide. For Lewiston's defense electronics supply chain — seals, bushings, and connector bodies in radar and communications hardware — unfilled PEEK's low dielectric constant (3.2 at 1 MHz) and loss tangent (0.003) make it a functional electrical insulator in high-frequency assemblies.
Machining unfilled PEEK requires sharp tooling and conservative parameters to avoid heat buildup that causes local melting and surface smearing. High-speed steel tooling is adequate for light cuts; carbide is preferred for production volumes where tool life matters. Cutting speeds of 400 to 800 surface feet per minute with 0.005 to 0.010 inch depth of cut produce clean surfaces without burning. Compressed air cooling is preferred over liquid coolant, which can cause thermal shock stress in semi-crystalline PEEK and introduce moisture that affects tight-tolerance bores during machining. Lewiston shops machine unfilled PEEK bores to plus or minus 0.001 inch diameter with surface finishes of 32 Ra on bearing surfaces.
Material sourcing for unfilled PEEK destined for defense components requires documented Victrex or equivalent certification — not generic description — and lot traceability. Lewiston suppliers working under AS9100 retain material certifications and can provide first-article inspection reports with 100 percent dimensional data on all critical features. For defense applications where outgassing in vacuum environments matters, buyers should specify outgassing testing per ASTM E595 and confirm the PEEK compound meets TML less than 1.0 percent and CVCM less than 0.1 percent.
Glass-Filled PEEK: Improved Stiffness for Structural Defense Components
Adding 30 percent glass fiber to PEEK roughly doubles the flexural modulus from 600,000 psi to 1,100,000 psi and improves the compressive strength from 17,000 psi to 21,000 psi, while the continuous service temperature and chemical resistance remain essentially unchanged. For Lewiston's aerospace-defense buyers, glass-filled PEEK (GF30 PEEK) is the grade of choice when the component must function as a load-bearing structural member: standoffs, mounting brackets, bearing retainers, and structural spacers in assemblies where deflection under load must be predictable and minimal.
The glass fiber reinforcement does introduce wear considerations: glass-filled PEEK is significantly more abrasive than unfilled PEEK and will cause accelerated wear on mating metal surfaces in sliding contact. Lewiston shops specify this limitation to buyers at the design stage — glass-filled PEEK is a poor choice for sliding bushings against steel shafts. Carbon-filled or unfilled PEEK is the correct selection for sliding interfaces; glass-filled PEEK is for structural support where contact is static or non-sliding.
Machining GF30 PEEK requires carbide tooling — the glass fiber abrades high-speed steel quickly — and aggressive chip clearance to prevent recutting of glass fiber fragments. Carbide end mills with PVD TiAlN coating significantly outlast uncoated carbide in glass-filled PEEK. Tolerance capability on GF30 PEEK is slightly more demanding than unfilled PEEK due to the anisotropic nature of the fiber-reinforced material: dimensions parallel to the mold flow direction in the stock material may differ from those perpendicular to it by 0.001 to 0.003 inch on a 6-inch span. Lewiston shops working with GF30 PEEK plate and rod account for this by identifying material orientation on drawings and aligning critical dimensions to the more stable axis.
Carbon-Filled PEEK: Maximum Wear Resistance for High-Performance Applications
Carbon-fiber-filled PEEK (CF30 PEEK) combines the base polymer's thermal and chemical resistance with a 30 percent carbon fiber loading that increases tensile strength to 24,000 psi and flexural modulus to 2,000,000 psi — approaching aluminum in stiffness — while providing inherent electrical conductivity and superior tribological properties. The carbon fiber acts as a solid lubricant in sliding contact applications, reducing the coefficient of friction to 0.10 to 0.15 against steel (versus 0.35 to 0.45 for unfilled PEEK) and enabling dry-running bearing and bushing applications that would otherwise require lubrication.
For Lewiston's defense and aerospace customers, CF30 PEEK components appear in aircraft hydraulic system components, semiconductor processing equipment vacuum seals, and precision bearing retainers in gyroscopic systems. The material's electrical conductivity — bulk resistivity of approximately 10 to 100 ohm-cm — prevents electrostatic charge buildup, which is critical in semiconductor cleanroom environments and in defense electronics where ESD events can damage sensitive circuits.
Machining CF30 PEEK is the most tooling-demanding of the three PEEK grades. Carbon fiber is abrasive to standard carbide, and diamond-coated tooling is frequently specified for high-volume CF30 PEEK machining to maintain dimensional consistency across a production run. Lewiston shops with diamond tooling capability can hold bore diameters to plus or minus 0.0005 inch over a production run of 500 pieces, which is important for bearing retainer applications where bore diameter directly affects bearing preload. All CF30 PEEK components should be deburred with a plastic or nylon scraper rather than steel to avoid embedding metal particles in the part surface.
Thermal and Dimensional Stability in Southern Maine's Precision Environment
PEEK's semi-crystalline structure gives it dimensional stability superior to amorphous thermoplastics, but thermal management during machining and storage still requires attention in Lewiston's manufacturing environment. Annealing semi-crystalline PEEK stock before precision machining — holding at 300 degrees Fahrenheit for two to four hours — relieves residual stresses from the extrusion process and prevents dimensional drift during and after machining. Lewiston shops with temperature-controlled inspection rooms (68 to 72 degrees Fahrenheit per ASME Y14.5) verify critical dimensions only after parts have fully equilibrated from the machining operation.
For southern Maine's construction industry — PEEK wear pads on hydraulic cylinder guides, bushings in construction equipment pivot points exposed to mud and hydraulic fluid — the material's resistance to hydrolysis even in boiling water and its FDA compliance for food-contact incidental applications are secondary benefits over the primary driver of wear life. A PEEK bushing in a construction equipment application running in hydraulic fluid typically outlasts nylon or acetal bushings by a factor of three to five, justifying the higher material cost on high-cycle applications.
Dimensional stability across temperature is quantified by PEEK's coefficient of thermal expansion: 25 ppm per degree Fahrenheit for unfilled, 14 ppm for GF30, and 9 ppm for CF30. For components that assemble with metal hardware — aluminum housings, steel brackets — the differential CTE must be accounted for in the clearance fit specification. Lewiston shops routinely perform this calculation at the design review stage and recommend fit classes that accommodate the operating temperature range without binding or excessive play.
Certification and Traceability for PEEK in Defense and Medical Applications
PEEK components for AS9100-scoped defense programs or ISO 13485-scoped medical devices require full material traceability from the polymer lot number through final part inspection. Lewiston shops operating under AS9100 maintain incoming material inspection records documenting resin lot, certificate of conformance from the polymer supplier (Victrex, Solvay, or equivalent), and any testing performed — tensile coupon testing is occasionally required for safety-critical structural PEEK parts to verify that the specific lot meets minimum mechanical properties.
For medical device applications involving PEEK implants or reusable surgical instrument components — a growing segment as southern Maine's medical manufacturing sector develops — ISO 13485 certification at the machining shop is required, and material must be medical-grade PEEK (Victrex PEEK 450G medical grade or equivalent) with a full biocompatibility package including ISO 10993 testing data. Lewiston's proximity to New England's medical manufacturing corridor in Massachusetts and New Hampshire positions local shops to serve this market as their quality systems mature.
Drawing requirements for PEEK defense components should call out the specific PEEK grade (unfilled, GF30, CF30), the polymer compound designation (not generic PEEK), surface finish requirements, and any post-machining treatments such as ultrasonic cleaning per MIL-PRF-680 for contamination-sensitive applications. Lewiston shops packaging PEEK components for defense programs use ESD-safe bags for CF30 PEEK (conductive) and standard polyethylene bags for unfilled and GF30 grades.
Frequently Asked Questions
For a sliding bearing bushing in aerospace-defense where dry running or minimal lubrication is the design intent, CF30 (carbon-fiber-filled) PEEK is the correct choice. The carbon fiber provides a coefficient of friction of 0.10 to 0.15 against a hardened steel shaft and extends wear life significantly over unfilled PEEK. The electrical conductivity of CF30 PEEK also prevents ESD charge buildup in sensitive electronics assemblies. If the application involves high structural load with no sliding (a static standoff or press-fit sleeve), GF30 PEEK's higher compressive strength and stiffness is the better selection. Unfilled PEEK is appropriate when electrical insulation is required and sliding wear is not a concern. Communicate the specific load, speed, mating material, and lubrication condition to your Lewiston supplier at the design stage for the best grade recommendation.
PEEK's density is 0.048 lb/in3 compared to 6061 aluminum at 0.098 lb/in3 — PEEK weighs roughly half as much as aluminum at the same volume. For weight-critical aerospace-defense components like structural brackets, connector housings, and insulating standoffs, this is a significant advantage. However, PEEK's stiffness (Young's modulus of 580,000 psi unfilled vs. 10,000,000 psi for aluminum) means that equivalent deflection under load requires a larger PEEK cross-section, which recovers some of the weight savings. CF30 PEEK at 2,000,000 psi modulus closes this gap significantly. For applications where the primary driver is electrical insulation combined with structural function — mounting plates for RF assemblies, insulating spacers in power electronics — PEEK delivers aluminum-comparable structural performance with complete electrical isolation, which aluminum cannot provide at any weight. Lewiston shops can help buyers run a simple beam deflection comparison at the design stage.
Unfilled PEEK machines to surface finishes of 16 to 32 Ra on turned surfaces with sharp carbide tooling and appropriate feeds — 16 Ra is achievable on final finishing passes at 0.002 inch depth of cut and 0.003 inch per revolution feed rate. Bored surfaces used as bearing seats reach 16 Ra with a final boring pass. GF30 PEEK typically achieves 32 to 63 Ra on standard machining, with glass fibers protruding at the surface above the polymer matrix on rough cuts; a finish pass at reduced depth produces cleaner surfaces. CF30 PEEK produces 32 to 63 Ra on standard machining, with diamond tooling improving to 16 to 32 Ra on precision bearing surfaces. For optical or sealing surfaces requiring better than 16 Ra, lapping with aluminum oxide or diamond paste on PEEK achieves 4 to 8 Ra and is available through Lewiston finishing operations. All finish specifications should be documented on the drawing with appropriate surface texture symbols per ASME Y14.36.
PEEK injection molding is available through specialty polymer processors in New England for volumes that justify tooling investment, typically above 500 to 1,000 pieces per year. Tooling cost for PEEK injection molding runs 15,000 to 40,000 dollars depending on part complexity, because PEEK's processing temperature (700 to 750 degrees Fahrenheit) requires hardened steel tooling rather than the aluminum tooling sufficient for lower-temperature polymers. Cycle times are longer than commodity polymer molding due to the crystallization requirements — parts must be cooled slowly to achieve the semi-crystalline structure that delivers PEEK's mechanical properties; quench-cooled PEEK is predominantly amorphous and significantly weaker. For defense and aerospace quantities below 500 pieces per year, machined PEEK from rod or plate stock remains more economical than injection molding. Lewiston shops serving the defense sector primarily machine from stock. The crossover analysis should include tooling amortization, cycle time, and inspection cost at the projected annual volume.
Last updated: July 2026
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