FR5 Tube — IDs, ODs, Wall Thicknesses & Lengths
FR5 tube is hollow cylindrical stock produced from NEMA FR-5, a flame-retardant glass-fabric/epoxy thermoset composite rated for continuous service to 180 °C (355 °F). Combining the high tensile strength (63,000 psi) and dielectric reliability of the epoxy-glass family with a UL 94HB flame-retardant rating, FR5 tube is specified for insulating sleeves in fire-rated wiring enclosures, coil forms in high-temperature transformers, conduit through hot zones, and structural spacer tubes in critical power assemblies where open flame risk cannot be tolerated.
At a glance:
- Wall thickness range: 0.062" to 0.500"+ (ID/OD combinations vary)
- Standard lengths: 12" to 48" nominal; longer cuts available
- Wall tolerance: ±0.010" typical
- Material: NEMA FR-5, glass-fabric/epoxy flame-retardant thermoset
- Production method: Filament-wound or compression-molded tube
- Color: Natural yellow-green
Standard Tube Size Table
FR5 tube is stocked in common ID/OD combinations at Ready Plastics:
| ID | OD | Wall | Standard Length | Notes |
|---|---|---|---|---|
| 0.500" | 0.750" | 0.125" | 24" & 48" | Insulating sleeve blank |
| 0.750" | 1.000" | 0.125" | 24" & 48" | |
| 1.000" | 1.375" | 0.187" | 24" & 48" | Coil form blank |
| 1.250" | 1.625" | 0.187" | 24" & 48" | |
| 1.500" | 2.000" | 0.250" | 24" & 48" | Conduit/sleeve |
| 2.000" | 2.500" | 0.250" | 24" & 48" | |
| 2.500" | 3.000" | 0.250" | 24" | Structural spacer |
| 3.000" | 3.750" | 0.375" | 24" | Large bore insulating tube |
Custom ID/OD and wall specifications 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 tube is used where hollow insulating forms must survive high temperatures in fire-rated environments:
- Insulating sleeves in fire-rated wiring enclosures — flame-retardant resin meets code requirements for exposed insulation in enclosed power systems
- Coil forms and transformer bobbins — dimensionally stable under winding tension; tolerates varnish impregnation cures
- Conduit through high-temperature zones — protects conductors passing through motor housings or heat-generating assemblies
- Structural spacer tubes in MCC and switchgear — electrically isolates and mechanically separates live bus components
- High-voltage guide tubes and probe sleeves in test fixture assemblies
- Bearing liners in applications combining heat and electrical isolation requirements
Machining FR5 Tube
FR5 tube cuts cleanly on band saws and chop saws with carbide-tipped blades. For precision ID and OD turning, use a lathe with carbide insert tooling at moderate surface speeds — feeds should be light enough to avoid delaminating the tube wall. When drilling through the wall thickness, back the tube section with a sacrificial plug to eliminate exit-face breakout. Bonding flanges to tube ends with structural epoxy adhesive is straightforward; surface preparation with 80-grit abrasion ensures good adhesion. Epoxy-glass tube is not heat-formable — all bends and shapes must be achieved by machining or by procuring purpose-formed sections.
Related
- FR5 Glass Epoxy — Line Card
- FR5 Rod — solid round bar for machined standoffs and insulators
- FR5 Sheet — flat stock for panels, barriers, and motor liners
- G11 Tube — non-flame-retardant high-temperature epoxy-glass tube
- FR4 Tube — standard-temperature flame-retardant glass-epoxy tube (130 °C service)