PEEK Machining in Lima, OH — Unfilled, Glass-Filled, and Carbon-Filled Grades for Defense and Oil Equipment

Unfilled PEEK (natural, ivory-colored stock) is specified when chemical resistance and mechanical performance at elevated temperature are the primary requirements. With a tensile strength of approximately 14,000 psi, flexural modulus of 600,000 psi, and continuous service temperature to 480 degrees F (with short-term excursions to 572 degrees F), unfilled PEEK outperforms PTFE in strength while matching or exceeding its chemical inertness. For Lima's oil equipment sector — seals, valve seats, piston rings, and check valve components in crude oil and refined product service — unfilled PEEK resists hydrocarbons, H2S, CO2, and the brine chemistry common in upstream and midstream equipment. Machining unfilled PEEK in Lima shops uses carbide tooling at 500-800 SFM with positive-rake insert geometry, achieving Ra 32-63 microinch as-machined on turned surfaces. Unlike filled grades, unfilled PEEK generates clean, predictable chips and does not abrade tooling aggressively, so standard carbide inserts have acceptable tool life. Tolerances of ±0.001 inch on bored diameters and ±0.002 inch on turned ODs are routine; tighter tolerances require accounting for PEEK's thermal expansion coefficient of approximately 2.6 x 10-5 per degree F, which means parts inspected at 68 degrees F will change dimensionally in hot process service. Buyers specifying PEEK seals for elevated temperature service should confirm the dimensional requirement at operating temperature, not just at room temperature.

Glass-filled PEEK (typically 30% short glass fiber by weight) multiplies the unfilled grade's flexural modulus to approximately 1,400,000 psi and raises tensile strength to 24,000 psi, while reducing the coefficient of thermal expansion by roughly half. These properties make 30% GF-PEEK the preferred grade for structural brackets, electrical connector bodies, and bearing retainers where dimensional stability under thermal cycling matters more than impact toughness. In Lima's defense electronics supply chain — components destined for integration into armored vehicle systems at the JSMC — glass-filled PEEK is used for printed circuit board standoffs, connector insulators, and wire routing clips that must survive temperature cycles from -65 degrees F to +300 degrees F without relaxing fastener preload or cracking at mounting holes. The glass filler makes the material mildly abrasive to tooling, so Lima shops use PCD (polycrystalline diamond) or coated carbide inserts for high-volume production to maintain tool life and surface finish consistency. Electrical properties of glass-filled PEEK — dielectric strength of approximately 480 V/mil and volume resistivity above 10^16 ohm-cm — are relatively unaffected by the glass addition, preserving the insulating performance that makes unfilled PEEK attractive for electronics applications. Glass-filled PEEK does absorb slightly more moisture than unfilled (approximately 0.1% vs. 0.06% at saturation), which buyers should account for in tight-clearance bearing designs.

Carbon-filled PEEK (typically 30% carbon fiber by weight) is the grade of choice for bearing surfaces, wear pads, and seal rings in Lima's oil equipment and industrial machinery applications. The carbon fiber reinforcement raises the PV limit (pressure-velocity product) approximately four times compared to unfilled PEEK — to roughly 10,000 psi-ft/min in dry sliding service — and adds a degree of thermal conductivity (approximately 2 W/m-K vs. 0.25 W/m-K for unfilled PEEK) that helps dissipate frictional heat in high-speed bearing applications. Allen County shops machine carbon-filled PEEK with PCD tooling exclusively in production environments due to the carbon fiber's extreme abrasiveness. At 500-700 SFM with positive-rake PCD inserts and light depths of cut, carbon-filled PEEK turns to Ra 32 microinch on critical bore and OD surfaces. EDM is not applicable to PEEK grades because the polymer chars rather than erodes cleanly. Buyers specifying carbon-filled PEEK bearing bushings for pump shafts running in hydrocarbon service should provide shaft OD tolerance and shaft surface finish — the PEEK bushing ID is typically machined to provide 0.001-0.002 inch diametral clearance at operating temperature, requiring coordination between the machined bushing tolerance and the thermal expansion at operating conditions.