FR5 Rod — Diameters, Lengths & Tolerances
FR5 rod is round bar stock produced from NEMA FR-5, a flame-retardant glass-fabric/epoxy thermoset laminate engineered for high-temperature electrical insulation service. Rated to 180 °C (355 °F) continuous, with a UL 94HB flammability rating and tensile strength of 63,000 psi, FR5 rod delivers the mechanical and dielectric performance of G11 with the added assurance of flame-retardant resin chemistry — making it the preferred rod stock for bus bar hardware, high-voltage standoffs, and insulating components in fire-rated enclosures and critical power systems.
At a glance:
- Diameter range: 0.250" to 4.0"
- Standard lengths: 4 ft and 8 ft
- OD tolerance: ±0.005" on smaller diameters; ±0.010" on larger diameters
- Material: NEMA FR-5, glass-fabric/epoxy flame-retardant thermoset
- Production method: Compression-molded and ground to round
- Color: Natural yellow-green
Standard Diameter Table
FR5 rod is stocked in the following standard sizes at Ready Plastics:
| Diameter | Standard Lengths | Notes |
|---|---|---|
| 0.250" | 4 ft & 8 ft | Standoff and spacer blank |
| 0.375" | 4 ft & 8 ft | |
| 0.500" | 4 ft & 8 ft | |
| 0.750" | 4 ft & 8 ft | |
| 1.000" | 4 ft & 8 ft | Popular insulator turning blank |
| 1.500" | 4 ft & 8 ft | |
| 2.000" | 4 ft | |
| 3.000" | 4 ft | Larger structural blanks |
Custom diameters and cut-to-length pieces are available on request.
Mechanical & Electrical Properties
| Property | Value |
|---|---|
| Tensile strength | 63,000 psi (430 MPa) |
| Flexural strength (LW, 0.125") | 75,000 psi (515 MPa) |
| Shear strength | 22,000 psi (150 MPa) |
| Bond strength | 2,200 psi (15 MPa) |
| Hardness (Rockwell M) | 112 |
| Izod impact strength (49 °C, LW) | 12.00 ft·lb/in |
| Specific gravity | 1.82 |
| Water absorption (24 hr) | 0.20% |
| Flammability rating | UL 94HB |
| Maximum continuous service temp | 180 °C (355 °F) |
Typical Applications
FR5 rod is machined into high-temperature, flame-rated insulating components across electrical and industrial sectors:
- High-voltage standoffs and insulators — flame-retardant chemistry meets fire-safety requirements in enclosed switchgear
- Bus bar support hardware — mechanically robust at sustained bus temperatures
- Motor and transformer spacers — resists thermal degradation in continuously energized assemblies
- Insulating shafts and drive couplings — isolates ground loops in drive systems
- Terminal block bodies — combines electrical insulation with flame safety in high-density wiring panels
- Test and measurement fixture components for elevated-temperature dielectric testing
Machining FR5 Rod
FR5 rod machines similarly to G11 on CNC lathes and mills. Use sharp carbide insert tooling with moderate cutting speeds and positive rake geometry to produce clean surface finishes without edge delamination. Dry machining with air blast for chip removal is preferred; conventional coolants are compatible but should be cleared from finished surfaces. Saw-cutting with carbide-tipped blades provides clean square ends. Like all thermoset glass-epoxy materials, FR5 will not re-soften — final dimensions must be achieved by machining, not by thermal forming.
Related
- FR5 Glass Epoxy — Line Card
- FR5 Sheet — flat laminate stock for panels and bus bar insulation
- FR5 Tube — hollow sections for coil forms and insulating conduit
- G11 Rod — non-flame-retardant counterpart with identical mechanical and thermal class
- FR4 Rod — lower-temperature flame-retardant glass-epoxy rod (130 °C service)