CNC Cutting and Engraving Phenolic Garolite Circuit Board Blanks and Insulating Panels
Garolite and phenolic laminate show up in maker shops almost entirely as knife scales and spoilboard material, but the same sheet stock has a second life as electrical insulating panels, standoffs, terminal strip bases, and non-conductive jig plates — and machining it for that purpose asks for different settings and different respect for the dust than machining it for a knife handle does.
What's Actually in the Sheet
"Garolite" and "phenolic" aren't one material. The common grades differ in both resin and reinforcement, and that difference changes what each is good for electrically and mechanically.
GradeReinforcementDielectric strengthContinuous temp ratingTypical use Phenolic (XX, LE grades)PaperModerate~120°CGeneral insulating standoffs, low-cost terminal boards G10Woven glass cloth + epoxyHigh~130°CInsulating jig plates, structural non-conductive brackets G11Woven glass cloth + epoxy (high-temp resin)High~170°CSame as G10 where higher heat survival is needed FR4Woven glass cloth + epoxyHigh~130°CBare circuit board substrate, flame-retardant insulating platesIf the part is a pure insulator — a standoff, a barrier board behind a high-voltage terminal, a non-conductive mounting plate inside an electronics enclosure — G10 or G11 is the usual pick over paper phenolic once the application sees any meaningful voltage or vibration, since the glass weave resists cracking far better than paper-reinforced phenolic.
Feeds, Speeds, and Bit Selection
Glass-reinforced grades (G10/G11/FR4) are abrasive the same way fiberglass is abrasive — they eat high-speed steel bits quickly and dull carbide noticeably faster than wood or aluminum does. Solid carbide, single or double O-flute bits run cooler and clear chips better than multi-flute geometry here; compression bits help control edge chipping on thicker sheet. Keep spindle speed moderate and feed rate steady rather than slow — a bit that dwells too long in one spot from being fed too slowly builds heat that can delaminate the glass-resin bond right at the cut edge. Paper phenolic cuts more like a dense hardwood and is far more forgiving of standard wood-cutting router bits and feeds.
Drilling, Tapping, and Edge Finishing
Standoff and terminal-board applications usually need clean through-holes for screws or press-fit hardware; back the hole with sacrificial material to avoid blowout on exit, same as you would drilling plywood. Paper phenolic is porous at a cut edge and will wick moisture over time in damp environments — sealing exposed edges with a thin epoxy or lacquer coat on anything going into an enclosure near humidity or coolant is worth the extra step. Glass-reinforced grades don't have that wicking problem but do leave a resin-rich, slightly fuzzy edge that benefits from a light sand or a single light finishing pass.
Safety: This Dust Is Not Wood Dust
Glass-reinforced garolite dust contains fine glass fibers along with cured epoxy particulate — this is a respiratory and skin irritant in the same family as fiberglass dust, not a nuisance dust you can shrug off with a dust mask rated for wood. Run real dust extraction at the cut, wear a properly fitted P100 respirator rather than an N95 paper mask, and wear long sleeves and gloves when handling freshly cut edges — the glass fibers at a cut edge can embed in skin the same way fiberglass insulation does. Never clear chips with compressed air aimed at your body or face, and vacuum the machine and surrounding area rather than brushing dust into the air.
Treated right, G10 and phenolic are some of the most useful insulating stock a electronics-adjacent shop can keep on hand — cheap, machinable with tooling you already own, and far more durable than 3D-printed standoffs for anything that sees real mechanical load or heat near live electrical parts.