G-10 Fabrication and CNC Machining for OEM Electrical and Industrial Applications
G-10 is the workhorse glass-epoxy laminate of OEM electrical engineering. High dielectric strength, exceptional structural rigidity, dimensional stability across temperature and humidity — it’s the material specified when a part has to insulate and hold up mechanically in the same job. Wm. F. McGraw & Co. fabricates G-10 to your drawings in-house at our Riverview, Michigan facility: CNC-machined, drilled, tapped, routed, and finished, in volumes from one prototype to repeat production runs.
Below is what we fabricate, the specs that matter, and the comparison engineers actually need before they commit a grade.
What G-10 Is
G-10 is a high-pressure thermoset industrial laminate built from continuous woven glass cloth impregnated with an epoxy resin binder, then cured under heat and pressure. The result is a rigid, dimensionally stable composite sheet that combines mechanical strength with high dielectric performance — the two properties OEM electrical buyers can’t get from a thermoplastic alone.
G-10 carries a NEMA designation (per NEMA LI 1) — engineers spec it as NEMA G-10 when they want consistency across vendors. You’ll also see it sold under trade names: Garolite (the McMaster-Carr brand), Micarta, and Bakelite — all refer to the same base NEMA grade, with minor variations by supplier.
G-10 has a flame-retardant equivalent called FR-4. The two materials are mechanically and dielectrically identical; FR-4 adds a brominated flame retardant to achieve a UL 94 V-0 rating. If your application requires UL flame compliance, spec FR-4. If it doesn’t, G-10 is the standard — and a slightly cheaper choice. Most engineers spec one or the other depending on whether the part lives inside a regulated enclosure.
G-10 Properties
Typical values for standard G-10 epoxy glass laminate. Specific values vary by manufacturer and thickness — request the datasheet for safety-critical applications.
| Property | Typical Value (G-10) | Why It Matters |
|---|---|---|
| Flexural strength (LW / CW) | 65,000 / 55,000 psi | Carries structural load — bus bar supports, standoffs, panels |
| Tensile strength (LW) | 45,000 psi | Holds under tension without elongation |
| Compressive strength (perpendicular) | 60,000 psi | Survives mounting pressure and mechanical loading |
| Dielectric strength (perpendicular) | 500–750 V/mil | High electrical insulation — isolates conductors at voltage |
| Continuous service temperature | Up to 285°F (140°C) | Holds properties at typical switchgear/electronics temps |
| Glass transition (Tg) | ~130–150°C | Defines the upper service envelope |
| Water absorption (24 hr) | ≤ 0.10% | Stable in humid environments; properties don’t drift |
| Specific gravity | ~1.8 g/cm³ | Lightweight vs metal alternatives |
| Thermal expansion (CTE) | Low — comparable to glass | Dimensionally stable across temperature swings |
| NEMA designation | G-10 (per NEMA LI 1) | Industry-standard grade specification |
| Flame rating | Not rated (spec FR-4 for UL 94 V-0) | G-10 is non-FR; FR-4 is the flame-retardant equivalent |
| Cryogenic performance (G-10 CR variant) | Properties retained to cryogenic temperatures | One of few composites usable in cryogenic equipment |
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Why These Numbers Matter
- 500–750 V/mil dielectric strength makes G-10 suitable for any standard low- and medium-voltage insulation application, with safety margin.
- Compressive and flexural strength above 50,000 psi means a G-10 part doesn’t just insulate — it can carry real mechanical load (bus bar weight, mounting forces, mechanical impact).
- Water absorption below 0.1% means properties don’t drift in humid plants, marine environments, or chemical-exposure applications.
- Low CTE means G-10 holds its dimensions across the temperature swings typical of industrial equipment.
G-10 vs FR-4 vs G-11 vs GPO-3
Four glass-laminate grades cover almost every OEM electrical-insulation application. The differences come down to resin system, reinforcement, flame rating, and how each material trades cost against high-temperature or arc-resistance performance.
| Property | G-10 | FR-4 | G-11 | GPO-3 |
|---|---|---|---|---|
| Resin system | Epoxy | Epoxy + FR additive | Epoxy (high-temp) | Polyester |
| Reinforcement | Woven glass cloth | Woven glass cloth | Woven glass cloth | Chopped glass mat |
| Continuous service | ~285°F | ~285°F | ~330°F | ~285°F |
| Flame rating (UL 94) | Not rated | V-0 | Not rated | V-0 |
| Arc / track resistance | Good | Good | Good | Best (UTR) |
| Mechanical strength | Highest | Highest | High at temperature | Moderate |
| Relative cost | $$ | $$ | $$$ | $$ |
| Best for | Structural insulation, PCB, cryogenics | Same as G-10 + flame rating | G-10 at higher temp | Switchgear barriers, arc shields |
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How to Choose Between Them
Structural strength + dielectric, no flame rating required
The dominant choice for bus bar supports, terminal boards, PCB fixtures, and cryogenic equipment.
Everything G-10 offers, plus UL 94 V-0 flame rating
Typical for regulated enclosures, PCB substrates, and electronics housings.
Operating temperature pushes above G-10’s envelope
High-temperature epoxy holds mechanical and dielectric performance to roughly 330°F continuous.
Arc/track resistance and flame retardance are the primary requirements
Switchgear barriers, mounting plates, and high-voltage hardware. Polyester resin with chopped glass mat outperforms G-10 in arc environments.
Substitution Note
FR-4 can almost always substitute for G-10 (same base properties, plus flame rating). G-10 cannot substitute for FR-4 when a flame rating is specified.
How do I get a quote?
Tell us what you’re building. We’ll come back with the right grade and the right fabrication approach for your application.
G-10 Grades and Variants We Fabricate
“G-10” is a NEMA designation, not a single product. Within the designation, several variants serve specialized applications:
Standard G-10
The base epoxy-glass laminate — specified for general structural insulation, bus bar supports, terminal boards, standoffs, and most OEM electrical applications. Light green to yellowish natural color, available in sheet, rod, and tube form.
G-10 CR (Cryogenic Grade)
A G-10 variant engineered to retain mechanical and dielectric properties at cryogenic temperatures. Used in MRI equipment, aerospace cryogenic systems, superconducting magnets, and physics-experiment structural supports. One of the few rigid composites that doesn’t embrittle at very low temperatures.
Garolite / Micarta / Bakelite
Trade names for G-10 sold under various brands. Garolite is McMaster-Carr’s brand; Micarta and Bakelite are historical trade names that have stuck in the industry. All refer to the same NEMA G-10 grade with minor manufacturer variations. Spec by NEMA grade and we’ll match the right material.
Cut-to-Size G-10 Sheet
For shops that fabricate in-house, we cut G-10 sheet to your dimensions and ship. Standard stock thicknesses run from thin sheet through thick block; less common thicknesses available on request.
Our G-10 Fabrication Capabilities
We fabricate G-10 in-house at our Riverview, Michigan facility. CNC machining, cutting, drilling, tapping, routing, and finishing all happen under one roof — quality, lead time, and tolerance stay with us. For broader context on our thermoset processing depth, see our materials manufacturing capability page.
CNC Machining
Milling, drilling, tapping, profiling to drawing on multi-axis centers.
Cut-to-Size
Sheet stock cut to your exact dimensions.
Drilling & Counterboring
Clean bores with consistent hole-to-hole tolerance.
Tapping
Threaded mounting holes machined to spec.
Routing & Profiling
Perimeter cuts, contoured edges, custom shapes.
Tight Tolerance Control
±0.005″ standard, tighter on request.
Prototype to Repeat Production
From a single replacement standoff to fleet quantities.
Drawing-to-Part Service
Send us a print, get the part.
On G-10 Machining
G-10 is rigid and dimensionally stable but the woven fiberglass reinforcement is genuinely abrasive on tooling. Cutting it cleanly requires carbide or diamond-coated tools, rigid workholding, controlled feeds, and proper dust collection. Without those, you get delamination, fuzzy edges, premature tool wear, and a workplace dust problem. We’ve fabricated G-10 long enough that our tooling, feeds, and dust management are dialed in for both prototype runs and production volumes.
Common G-10 Parts and Applications
G-10 shows up across the OEM electrical and electronic equipment spectrum. The parts we fabricate most often:
| Part Type | Typical Industry | Why G-10 |
|---|---|---|
| Bus bar supports + standoffs | Switchgear, power electronics | Structural + dielectric, low moisture absorption |
| Terminal boards + barrier strips | Motors, generators, controls | Dimensional stability + insulation |
| PCB test fixtures + ICT plates | Electronics manufacturing | Tight tolerance, repeatable, dielectric |
| Wave solder pallets + SMT carriers | Electronics assembly | Holds dimensional accuracy at elevated temperature |
| Insulator panels + mounting plates | Switchgear, industrial controls | Structural insulation, machinable to drawing |
| Cryogenic supports + brackets (G-10 CR) | Aerospace, scientific equipment, MRI | Properties retained at cryogenic temperatures |
| Battery insulators + module brackets | Electric vehicles, energy storage | Lightweight + dielectric + dimensional stability |
| High-voltage insulators | Transformers, switchgear | High dielectric strength + low moisture |
| Coil structures + circuit-breaker parts | Motors, transformers | Holds tight tolerance through cure and service |
| Phase shifters + dielectric gaskets | RF / microwave electronics | Low dielectric loss, dimensional precision |
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Industries We Serve with G-10
G-10 anchors a long list of OEM applications. Each industry below links to its dedicated page with broader material recommendations and case examples.
Switchgear →
Bus bar supports, standoffs, mounting plates, and structural insulators for low- and medium-voltage switchgear cabinets.
Transformers →
Laminate insulators, structural supports, and dielectric components in transformer construction.
Power Electronics →
Bus bar supports, standoffs, terminal boards, and structural insulators for inverters, drives, and converters.
Motor Applications →
Terminal boards, structural supports, phase barriers, and machined precision components.
Generators →
Terminal boards, stator-coil structural supports, and high-voltage insulators.
Electric Vehicles →
Battery module brackets, structural insulators, and dielectric components for EV power systems.
Aerospace →
Structural composites and dielectric components for cabin and avionics electrical systems, plus G-10 CR for cryogenic aerospace applications.
Medical →
Machined components for diagnostic imaging equipment (including MRI cryogenic systems via G-10 CR), surgical instruments, and dielectric medical devices.
Electronics Manufacturing →
PCB test fixtures, ICT bed-of-nails plates, wave-solder pallets, and SMT carriers, where dimensional stability under repeated thermal cycling is critical.
Why OEMs Choose WMF McGraw for G-10
Domestic fabrication, the full glass-laminate family in one shop, and tooling configured specifically for G-10’s abrasive reinforcement.
US-domestic fabrication, not overseas machining
Most low-cost G-10 machining online is overseas. Domestic fabrication means controlled lead times, no IP risk on your drawings, no surprise customs delays, and direct English-speaking engineering support. For OEMs that ship product on a schedule, that’s not a premium — it’s the baseline.
The full glass-laminate family
Most fabricators specialize in G-10 and FR-4, then stop. We fabricate G-10, FR-4, G-11, G-7, G-9, and GPO-3 — the full range. If your application needs a less-common grade, you’re not compromising on the material to find a fabricator.
Engineering support, not just quoting
Send us a drawing, a sample, or a description of the application. If G-10 is the right material, we’ll quote it. If FR-4 or G-11 is a better fit for your operating envelope, we’ll tell you before we cut. The wrong material in the right shape is still a failed part.
Tolerance control
G-10’s abrasiveness means generic plastic-machining setups produce mediocre parts. Our tooling, feeds, fixturing, and dust management are configured specifically for the glass-laminate family. Standard tolerance is ±0.005″; tighter is available where the application justifies it.
Prototype through production
One-off prototype, low-volume run, or recurring production — we support all three. Many of our OEM customers start with a prototype and scale into ongoing supply with us.
Frequently Asked Questions
Quick answers about grades, substitution, machining, tolerances, and quoting.
What’s the difference between G-10 and FR-4?
Is Garolite the same as G-10?
What is G-10’s maximum operating temperature?
What is G-10’s dielectric strength?
Can G-10 be used at cryogenic temperatures?
Is G-10 difficult to machine?
What tolerances can you hold on G-10 parts?
Do you ship G-10 sheet stock or only fabricated parts?
How do I get a quote?
Request a G-10 Fabrication Quote
Tell us what you’re building. Send your drawing or describe the application — we’ll come back with the right G-10 grade, the right fabrication approach, and a quote, usually within one to two business days.
