PEEK Machining and Supply in Concord, NH — Unfilled, Glass-Filled, and Carbon-Filled Grades

Unfilled PEEK is the baseline grade — polymer chain only, no reinforcing filler — and it is the default specification for medical implant components because its biocompatibility is fully characterized under ISO 10993 and ASTM F2026. Tensile strength runs 14,500 psi (100 MPa), flexural modulus approximately 550,000 psi (3.8 GPa), and the material retains dimensional stability to 260 degrees C under load. Unfilled PEEK machines to tight tolerances with surface finishes suitable for bearing and sealing surfaces; its homogeneous structure means there are no filler particles to create surface roughness variation or to introduce anisotropic properties that complicate tolerance prediction. Glass-filled PEEK — typically 30 percent short glass fiber — increases flexural modulus to roughly 1.4 million psi (9.6 GPa) and improves compressive strength and creep resistance at elevated temperature. The trade-off is reduced impact toughness compared to unfilled PEEK and the introduction of abrasive glass fibers that accelerate cutting-tool wear. Glass-filled PEEK is specified in Concord aerospace programs for connector bodies, valve seats, and structural insulators where stiffness under combined mechanical and thermal load is the primary design requirement. It is generally not used for implant applications because the glass fiber reinforcement is not biocompatible in long-term implant service. Carbon-filled PEEK — 30 percent carbon fiber — takes the stiffness advantage further, reaching flexural modulus above 2 million psi (14 GPa) while also delivering improved thermal conductivity (critical for dissipating frictional heat in bearing applications) and inherent lubricity from the carbon fiber. Compressive strength exceeds 25,000 psi. This grade is the choice for PEEK bushings, bearing rings, and wear pads in aerospace actuators, semiconductor processing equipment, and precision motion systems where the combination of stiffness, low friction, and chemical resistance in aggressive environments outperforms any alternative polymer. Carbon-filled PEEK requires diamond tooling for precision finishing because carbon fibers are extremely abrasive.

PEEK machines well compared to most engineering polymers, but it is not forgiving of poor tooling or sloppy process control. The primary failure mode in PEEK machining is thermal damage: the material's low thermal conductivity means heat generated at the cutting edge stays in the workpiece longer than it would in metal, and localized overheating above 260 degrees C causes surface discoloration, micro-cracking, and dimensional instability as the material approaches its glass transition temperature. For unfilled PEEK, sharp uncoated or TiN-coated carbide tooling at surface speeds of 300–500 SFM with moderate feed rates and light depths of cut produces clean, predictable results. Air blast or minimum-quantity lubrication is preferred over flood coolant to avoid thermal shock and to prevent coolant contamination of medical parts that must be cleaned to biocompatibility standards. Tool sharpness matters more than on metals — a dulled edge that would still cut steel acceptably will generate excess heat in PEEK and immediately degrade surface quality. Glass-filled and carbon-filled PEEK require diamond tooling (CVD diamond-coated inserts or PCD tooling) for production runs. The abrasive filler content destroys uncoated or TiN-coated carbide at a rate that makes anything beyond prototype quantities uneconomical. Diamond-coated end mills run at 600–800 SFM on carbon-filled PEEK and maintain acceptable tool life for hundreds of parts before requiring replacement. Surface finish achievable on PEEK with sharp diamond tooling is Ra 16–32 microinch in a single milling pass, suitable for most sealing and bearing surface requirements without secondary grinding. Tight-tolerance PEEK features — bore diameters held to +/-0.0005 inch for implant taper fits, for example — require stress relief before finish machining. PEEK semi-finished stock carries residual stress from extrusion or compression molding; rough machining releases this stress and allows the material to reach a new equilibrium before the final tolerance pass. Concord shops doing implant-grade PEEK work typically rough machine to within 0.010–0.020 inch of finish dimension, stress relieve at 150 degrees C for 2–4 hours, and then finish-machine to final print. This two-stage process adds cycle time but is non-negotiable for holding ISO 13485 first-article tolerances.

PEEK stock — rod, plate, and tube — is available through specialty plastics distributors with same-day or next-day reach into Concord. The key brand most specifications reference is Victrex PEEK, which sets the baseline for mechanical properties and biocompatibility data. Solvay's KetaSpire and Evonik's VESTAKEEP are equivalents with comparable properties, and most buyers accept them as alternates unless the print specifically calls out the Victrex brand. For medical implant programs, the material specification on the purchase order should include: the specific grade (450G for unfilled implant-grade, for example), a certificate of conformance to ASTM F2026, lot traceability to the polymer manufacturer's production batch, and biocompatibility data package per ISO 10993. Some OEMs require that the PEEK stock be purchased directly from the polymer manufacturer's medical-grade distribution channel rather than through a general plastics distributor, to ensure the chain of custody documentation meets FDA 21 CFR Part 820 quality system requirements. Concord shops regularly working on Class III implant components maintain approved supplier lists for PEEK stock that have already gone through the OEM's supplier qualification process. For aerospace PEEK — connector bodies, insulator discs, radome structural components — the specification requirements are less stringent on biocompatibility but more demanding on dimensional stability and lot-to-lot consistency of mechanical properties. AMS 3678 covers glass-filled PEEK for aerospace applications. Stock certification to AMS 3678 with a tensile and flexural modulus test report is typically required for FAIR-controlled aerospace programs. Lead times on stock items run 1–5 business days; custom extrusions in non-standard diameters or large-volume plate orders require 2–4 week lead times from the polymer producer.