Technical Guide · Fabrication
Cut FRP Like Glass, Not Like Wood
FRP dust is abrasive and the fibers itch; treat cutting like machining fiberglass — not sawing timber.
| Task | Recommended Tool | Practice |
|---|---|---|
| Cutting panel to length | Carbide-tipped circular saw / abrasive cut-off | Wet-cut to control dust; support both sides of cut |
| Notching / opening | Jig saw with carbide blade, or router | Round internal corners to avoid stress cracks |
| Drilling bolt holes | Carbide-tipped masonry/glass drill, low speed | Back the panel; do not force; clear dust |
| Edge trimming | Router / grinder with carbide bit | Light pass; finish with file |
| Grinding / shaping | Angle grinder with abrasive disc | PPE; wet where possible; avoid overheating |
Carbide-tipped tools are essential; standard HSS blades dull instantly on glass fibers. Always wear a dust mask, eye protection and gloves.
Protect the Crew
- Respiratory: a P100 / P3 dust mask for dry cutting; prefer wet-cutting to suppress dust at source.
- Eyes & skin: safety glasses and long sleeves; fiberglass dust irritates skin — wash with cold water, not hot.
- Ventilation: in enclosed spaces, use local exhaust; do not let dust accumulate on ledges.
Restore the Barrier After Cutting
A factory panel has a resin-rich C-veil on its faces. A field cut breaks that barrier: glass fibers are exposed at the edge, and chemicals or moisture can wick along them. Seal every cut edge with a brush coat of matching resin (polyester or vinyl ester, as supplied) or apply FRP flat-bar edge banding. This is a one-minute job that prevents years of edge degradation.
Re-Clip and Re-Check
Re-clip every support
A cut panel must be re-fastened at every support intersection; never leave a cut edge unclipped.
Round corners
Square internal notches are stress raisers; round them to ≥ 10 mm radius to prevent fatigue cracking.
Respect bearing
After trimming, ensure ≥ 50 mm bearing on the support; do not cut so short that the bar bears only on its edge.
Clean grit face
Sawdust on a grit-top surface ruins wet grip; brush it clean before hand-over.
A Safe Field Procedure
- Mark the cut line on the panel face; support the panel on both sides of the cut.
- Clamp the panel to stop chatter; use a carbide-tipped blade at moderate speed.
- Wet-cut or use extraction to control dust; wear P100 mask and eye protection.
- Cut on the waste side of the mark; finish the edge with a file or router.
- Round internal corners to >= 10 mm radius; do not leave square notches.
- Seal the cut edge with matching resin or banding once cured.
Bolts and Clips
Drill at low speed with a carbide-tipped or masonry/glass bit; back the panel with wood to prevent splintering on the exit side. Do not force the drill - FRP chips rather than swarfs. Clear dust from the hole, use a backing plate under any bolted clip, and torque to snug only (4-20 N by bolt size), never steel-style pretension. Larger holes for clips are often slotted to allow thermal movement.
When to Let the Mill Do the Work
Every field cut costs labor, dust control, edge sealing and re-clipping - and risks a botched notch. Where openings are known before shipment (pump cut-outs, manhole frames, stair landings), factory-prefabricated panels are faster and cleaner: the mill cuts on a saw table, seals edges under controlled conditions and ships ready to lay. Reserve on-site cutting for dimensions discovered at installation - minor trimming, fitting around existing steelwork and last-minute hole locations. Tell ZeAllgrate your cut-out drawings at order stage and most field work disappears from the schedule. When you must cut on site, follow the sequence above, seal every edge, and re-clip every support after the cut.
Fiberglass Dust Does Not Just Vanish
Collect cuttings and dust in bags, not swept into the drainage: cured FRP dust is inert but abrasive, and fines in a plant sump are an irritant to housekeeping and personnel. Wipe tools and work faces with a damp cloth. Reuse off-cuts for small openings where length allows. Because cut edges are the weak point, dispose of any bar that is more than lightly trimmed rather than forcing a short piece into service where its bearing length is compromised.
References
- Industry molded grating engineering guide (manufacturer PDF) — field fabrication and cutting guidance. Manufacturer technical data available upon request.
- Industry pultruded grating metric design manual (manufacturer PDF) — pultruded bar cutting and drilling. Manufacturer technical data available upon request.
- OSHA 29 CFR 1910.23; FRP composite fabrication health & safety practice (respirable dust, PPE).
Drilling and Fastener Guidance
Bolt holes in FRP are drilled, never punched, and the drill size is matched to the fastener with working clearance. A clip or bolt of 12 mm nominal diameter is typically drilled at 13–14 mm to allow thermal movement and easy placement; undersized holes force the fastener in and create local stress. Drill from the top surface and back up the panel to limit exit chipping, run at low speed with light feed pressure, and clear the flutes regularly — FRP dust binds and overheats HSS drills quickly, which is why carbide-tipped tooling is the standard.
Edge Sealing in Chemical Service
A cut edge exposes glass fibres that were previously sealed inside the resin laminate. In dry, indoor service this is normally acceptable; in chemical splash zones, washdown areas or marine environments, seal cut edges with an FRP resin sealant or band the edge with FRP flat bar to restore the barrier that protects the fibres from wicking and chemical attack. The same logic applies to drilled holes in corrosion-critical decks — seal the hole with a compatible resin or use a rubber grommet where a fastener passes through.
Field Cutting Checklist
- Mark and dry-fit panels before cutting; transfer openings from the site drawing, not from memory.
- Support both sides of every cut so the blade never climbs a free edge.
- Use wet cutting or a dust collector; wear dust mask, eye protection and gloves.
- Radius internal corners of openings (min ~5 mm) to prevent crack initiation.
- Deburr cut edges with a file or light router pass; seal edges in corrosive service.
- Verify the remaining section around openings against the load chart before final fixing.
Factory vs. Site Fabrication
Where openings, notches and irregular edges are known before delivery, factory fabrication is the higher-quality option: panels are machined to drawing, edges are sealed, and the cut plan is checked against the support layout during production. Site fabrication remains essential for field adjustments, and the practice above — correct tooling, backing, wet cutting and edge sealing — is exactly what turns a field cut into a factory-quality edge.
Where openings, notches and irregular edges are known before delivery, factory fabrication is the higher-quality option: panels are machined to drawing, edges are sealed, and the cut plan is checked against the support layout during production. Site fabrication remains essential for field adjustments, and the practice above — correct tooling, backing, wet cutting and edge sealing — is exactly what turns a field cut into a factory-quality edge.Need Prefabricated Panels?
Send drawings with cut-outs and hole locations — ZeAllgrate ships ready-to-lay panels, reducing on-site cutting to zero.