Custom Machined Insulators
Electrical insulators are where precision machining and dielectric performance intersect. A machined insulator must hold its geometry — typically to tolerances of ±0.001" or better on critical features — while also meeting the dielectric withstand voltage, tracking resistance, and moisture performance specified by the design. Federal Materials specializes in machined plastic insulators for switchgear, motor controls, utility equipment, high-voltage assemblies, and semiconductor tooling.
We machine insulators in all major dielectric plastics: G10, FR4, phenolic (XX, CE, LE), PEEK, Vespel, Torlon, and PTFE. Every electrical insulator order can include dielectric withstand (hipot) testing and a material certification. You supply the print — we manufacture to it.
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Request a Quote →Insulator Types We Machine
- Flat insulating plates and separator plates — routed profiles, drilled grid patterns, slots
- Standoff insulators — hex, round, threaded rod insulators for PCB and switchgear assemblies
- Coil form insulators — turned from rod; transformer and motor winding forms
- Arc barrier insulators — complex profiles for circuit breaker and contactor arc quenching
- Phase barrier and interphase insulators — switchgear separation plates
- Insulating bushings and sleeves — dielectric bushings for bolt and shaft pass-throughs
- Terminal board insulators — drilled grid, slotted, and routed terminal panels
- High-voltage and RF insulators — contoured for field control and low-loss RF applications
- Custom prototype insulators — from print or sketch, same-week quoting
Material Selection Guide
| Material | Continuous temp | Dielectric strength | Best for |
|---|---|---|---|
| G10 / Epoxy-Glass | 285°F | 500 V/mil | General electrical, moderate environments |
| FR4 / Epoxy-Glass | 285°F | 500 V/mil | UL-listed, flame-retardant assemblies |
| XX Phenolic | 220°F | 450 V/mil | Economical, switchgear production parts |
| CE Phenolic | 220°F | 450 V/mil | Better impact, canvas-reinforced |
| PEEK | 480°F | 480 V/mil | High-temp, chemical-resistant insulators |
| Vespel (SP-1) | 550°F | 400 V/mil | Extreme temperature, hard vacuum |
| PTFE | 500°F | 500 V/mil | Chemical-resistant, low-loss RF |
Not sure which material to specify? Include operating temperature, voltage level, and environment in your RFQ and our application engineers will recommend.
Typical Tolerances
| Dimension type | Production tolerance |
|---|---|
| Critical turned dims (OD/ID) | ±0.0005" (fiberglass/PEEK/Vespel) |
| General machined dims | ±0.005" |
| Hole location (CNC milled) | ±0.002" |
| Flatness (plates ≤ 12") | ±0.003" |
| Thread form | 2B/3B per print |
Finish Options
| Finish | Description |
|---|---|
| As-machined | Clean, deburred — standard for fiberglass and high-performance plastics |
| Hot oil dip | Standard for phenolic insulators — seals cut surfaces, enhances moisture resistance |
| Edge routing / chamfer | Per drawing callout |
| No metallic coating | Insulating parts must not be inadvertently plated — confirm with application engineering if any secondary process is planned |
Standard Turnaround
| Stage | Lead time |
|---|---|
| Quote response | Same business day |
| Prototype / first article (1–5 pcs) | 3–5 business days |
| Short run (6–50 pcs) | 5–10 business days |
| Production run (50+ pcs) | 10–15 business days |
Materials We Stock (Insulator Stock Shapes)
| Material | Forms stocked | Notes |
|---|---|---|
| G10 | Sheet, rod, tube | NEMA LI-1 GP03 |
| FR4 | Sheet, rod | NEMA LI-1 FR4, UL94 V-0 |
| XX Phenolic | Sheet, rod | NEMA LI-1 XX |
| CE Phenolic | Sheet, rod, tube | NEMA LI-1 CE |
| PEEK | Rod, plate | ASTM D6262 |
| PTFE | Rod, sheet, tube | ASTM D4894 |
| Vespel | Rod, plate | DuPont-certified SP-1, SP-21 |
Quality & Inspection
- Dimensional inspection — in-process and final to print; CMM first-article on request
- Dielectric withstand (hipot) testing — standard offering for electrical insulators; specify voltage and test method (AC/DC) on RFQ
- Megohm / insulation resistance testing — available for high-resistance applications
- Material certification — lot-traceable C of C to applicable NEMA, ASTM, or MIL spec
- Visual inspection — delamination, voids, edge condition, surface finish
- Hot oil dip process log — for phenolic parts
Get a quote on
Request a Quote →More Related Guides
- Machined Arc Chutes — arc-quenching components
- Custom Machined Standoffs — threaded insulating standoffs
- Custom Machined Washers — dielectric washers and shims
- Custom Machined Bushings — insulating sleeve bushings
- G10 vs. FR4 — key material differences
- CNC Milling Thermoset Sheet