Unfilled, glass-filled, and carbon-filled PEEK machined in the United States — with the stress management and annealing discipline the material actually requires.
PEEK — polyetheretherketone — sits at the top of the engineering-thermoplastic pyramid, and it is the one polymer routinely specified as a direct replacement for metal. Continuous service to roughly 250°C, near-total immunity to industrial chemistry, inherent flame resistance, excellent wear behavior, and biocompatibility in implantable grades: no other machinable plastic covers all of it at once. It also machines well — semi-crystalline, rigid, clean-chipping — provided the shop respects two things most metal-first shops miss. First, heat: PEEK insulates rather than conducts, so cutting heat stays at the surface, and an overheated cut leaves a glazed, amorphous skin with degraded chemical resistance. Sharp tooling, moderate engagement, and cooling planned per grade keep the surface crystalline and honest. Second, stress: extruded PEEK stock carries residual manufacturing stress, and hogging a pocket into it releases that stress unevenly. The part that measured perfectly on the machine can bow measurably days later. That is why heavily machined PEEK parts get intermediate stress-relief annealing between roughing and finishing in our plastics workflow — the material relaxes in the oven, then the finish pass lands final dimensions on a part that has stopped moving.
The default and most forgiving grade — toughest, most ductile, best surface finish, and the correct choice for seal seats, valve components, and anything with a sliding or sealing surface. Natural (tan) unfilled PEEK is also the base for FDA-compliant and, in dedicated implantable grades, biocompatible medical work.
Thirty percent glass fiber buys substantially higher stiffness, better creep resistance under sustained load, and a lower thermal expansion coefficient — the grade for structural parts that hold dimension at temperature. The trade-offs: the glass is abrasive to tooling and to any softer mating surface, so it never belongs on a wear or seal interface.
Carbon fiber delivers the highest stiffness and best strength-to-weight in the family, improved wear performance, and enough conductivity for static dissipation — which is why carbon-filled and dedicated ESD PEEK grades populate semiconductor wafer-handling equipment. Machines abrasively; tooling and cycle are planned accordingly.
PEEK stock is genuinely expensive, and specifying it where a lesser polymer serves is the most common money leak we see on plastic prints. If the requirement is dielectric strength and moderate heat, Ultem (PEI) does it at a fraction of the cost. If it is precision and low friction at room temperature, Delrin is the answer. We will tell you when the drawing can step down.
PEEK runs across the same platforms as our metal work, with plastics-specific setup. Manifold blocks, wafer-handling components, and instrument bodies run on VMCs with travels to 32.5" × 20.5" × 20.1", with complex multi-face geometry consolidated onto the 5-axis trunnion mill (19" table, 18,000 RPM spindle, 60 tools) — the high spindle speed range suits small sharp cutters in plastics well. Turned PEEK seal components and connector bodies run on lathes with 1.625" to 3.05" bores, and small-diameter production parts run on Swiss-type platforms from .812" to 1.50" bar. Work-holding is deliberately gentle — soft jaws, nests, light clamping — because PEEK will elastically deform under fixture pressure and record the error in the finished dimension. Dimensional inspection happens at controlled temperature, because a warm PEEK part genuinely is a different size than a cold one.
Three industries anchor PEEK demand. Semiconductor equipment uses it for wafer-handling, test sockets, and process-chamber hardware because it tolerates aggressive chemistry and plasma environments without particulating. Medical programs use it for surgical instruments and implant-adjacent components that need repeated autoclave sterilization, radiolucency, or a bone-like modulus. Oil and gas puts it downhole — seal rings, back-up rings, connector insulators, and sensor packaging that must survive heat, pressure, and sour chemistry simultaneously. Around those anchors sits general instrumentation and aerospace work: high-temperature insulators, bushings that run where nylon melts, and structural clips replacing metal for weight.
PEEK is one of the most dimensionally stable machinable polymers — low moisture absorption, modest thermal expansion for a plastic, and good creep resistance — and with stress-relief annealing in the process we routinely hold ±.0005" or better on critical features, quoting tighter per-feature tolerances where the design demands them. It still is a polymer: its expansion with temperature is several times steel's, and it takes up a small amount of moisture that moves tenths on a precision bore between a dry oven and a humid summer floor. Prints toleranced in metal-class microns get a conversation, not a silent quote. Machined finishes run clean and smooth off sharp tooling; vapor polishing is not applicable to PEEK, but fine machined finishes, tumbling for edge break, and inspection documentation through first article inspection cover what regulated programs need.
Extruded PEEK carries residual stress; heavy material removal releases it unevenly and the part moves after it leaves the machine. Intermediate annealing lets the material relax before the finish pass lands final dimensions — and restores surface crystallinity that cutting heat can disturb.
Unfilled for toughness, seals, and medical; glass-filled for stiffness and stability at temperature (never on a wear interface); carbon-filled for maximum stiffness and static dissipation in semiconductor handling. Filled grades machine abrasively and are quoted accordingly.
Routinely ±.0005" or better on critical features with stress management and temperature-controlled inspection, tighter quoted per-feature. Thermal expansion and slight moisture uptake, not the machining, set the practical limit.
The full engineering-plastics family — Delrin, UHMW, PTFE, polycarbonate, and more.
The step-down when dielectric strength and heat matter but PEEK's price does not fit.
The precision plastic for room-temperature bushings, gears, and instrument work.
The metal PEEK most often replaces — and sometimes shouldn't.
Tight-tolerance process discipline applied to polymer work.
5-axis milling, Swiss turning, and inspection across an ISO 9001:2015 certified production network.
