Linen Phenolic Rod
Linen phenolic rod is the precision bushing stock of the phenolic laminate family — the fine, tightly woven linen fabric reinforcement produces a denser, smoother-machined surface than cotton phenolic, supporting tighter bore tolerances, better surface finish after turning, and improved performance in instrument-class and precision-bearing applications.
TL;DR — Linen Phenolic Rod Quick Facts
| Property | Value |
|---|---|
| Typical diameters | 1/2" – 6" (standard stock) |
| Standard length | 4 ft (48") |
| OD tolerance (NEMA LI 1) | +0.025" / −0.000" up to 1½"; +0.062" up to 6" |
| Color | Natural tan/cream; black available |
| Lead time (standard stock) | 1–3 business days |
| Price tier | $$$ — premium over cotton phenolic; lower than glass laminate |
Standard Sizes — Linen Phenolic Rod
Per NEMA LI 1 (Industrial Laminated Thermosetting Products):
| Nominal Diameter | OD Tolerance | Standard Length |
|---|---|---|
| 1/2" – 1½" | +0.025" / −0.000" | 4 ft |
| Over 1½" – 3" | +0.031" / −0.000" | 4 ft |
| Over 3" – 6" | +0.062" / −0.000" | 4 ft |
Commonly stocked diameters: ½, ⅝, ¾, 1, 1¼, 1½, 2, 2½, 3, 4, 5, 6 inches.
Linen phenolic rod is stocked in smaller diameters than cotton phenolic; the fine-weave fabric does not lend itself to the large-diameter compression molding that cotton phenolic rod routinely achieves at 10–12" diameter. For diameters above 6", consider cotton phenolic rod (NEMA Grade C/CE) or consult for special order.
Properties Relevant to Rod Form
Linen phenolic rod uses finer-filament linen woven fabric versus the heavier cotton weave. This translates to:
- Higher surface smoothness after turning (achievable Ra 32–63 μin vs. 63–125 μin for cotton phenolic)
- Tighter achievable bore tolerances (Class 2 fit bores are routine in linen phenolic)
- Marginally higher flexural and tensile strength in-plane
- Slightly lower impact toughness than cotton — trade-off for the finer weave
| Property | NEMA Grade L | NEMA Grade LE |
|---|---|---|
| Tensile Strength (lengthwise) | 12,000 psi (83 MPa) | 11,500 psi (79 MPa) |
| Compressive Strength (flatwise) | 34,000 psi (234 MPa) | 33,000 psi (228 MPa) |
| Flexural Strength (lengthwise) | 16,000 psi (110 MPa) | 15,000 psi (103 MPa) |
| Hardness (Rockwell M) | 105–120 | 100–115 |
| Dielectric Strength (LE grade) | — | 250+ V/mil |
| Continuous Use Temperature | 250°F (121°C) | 250°F (121°C) |
| Density | 1.37 g/cc | 1.37 g/cc |
| Coefficient of Friction (dry) | 0.13–0.22 | 0.13–0.22 |
Grade L is the precision mechanical grade: highest strength for linen phenolic, smallest fiber diameter for best machined surface. Grade LE (linen, electrical) adds enhanced electrical insulation performance — dielectric strength exceeds 250 V/mil — for precision insulators and precision bearing components in live-metal electrical assemblies.
For the complete datasheet, see the Linen Phenolic properties page.
Typical Applications — Rod Form
Linen phenolic rod earns its premium over cotton phenolic where smooth bore finish and tight dimensional tolerance are non-negotiable:
Precision bushings and instrument bearings — Linen phenolic bushings in scientific instruments, precision measurement equipment, and metrological apparatus where surface finish in the bore must not introduce stick-slip artifacts. The fine linen weave minimizes fiber pull-out during boring, producing a smoother bore surface.
Gear blanks for instrument drives — Small-diameter linen phenolic rod (up to 2") machined into fine-pitch spur and helical gears for instrument panels, office machinery, and scientific devices. The fine weave supports clean involute profiles with minimal material tears.
Shaft end covers and thrust washers — Precision-turned thrust washers in pumps and gear sets where dimensional stability under thermal cycling is more critical than impact resistance.
Electrical relay and switchgear actuators — Grade LE rod machined into actuator pins, cam followers, and pivot bushings in relay assemblies where both close-tolerance motion and electrical isolation are required simultaneously.
Aircraft and military instrument components — Linen phenolic rod to NEMA LE specifications cross-references to MIL-I-24768/13 (Type FBG-LE) for defense electronics and avionics instrument components requiring QPL-traceable documentation.
Precision spacers in electronic assemblies — Turned standoffs and spacers in high-frequency electronic chassis where low dissipation factor (compared to cotton phenolic) reduces signal loss.
Machining Notes — Rod
Linen phenolic rod machines similarly to cotton phenolic but rewards extra attention to cutting geometry because the finer fabric can produce a smoother finish when parameters are optimized.
Tooling: Sharp solid-carbide tooling; PCD inserts for production volume. Positive rake (5°–10°) reduces cutting force and minimizes sub-surface fiber breakage that causes bore roughness.
Cutting parameters (turning):
- Surface speed: 450–650 SFM
- Feed rate (roughing): 0.004–0.008 IPR
- Feed rate (finishing): 0.001–0.002 IPR for Ra ≤ 32 μin
- Depth of cut: 0.010"–0.020" for finishing passes
Boring precision bores: Spring-back is 0.001"–0.002" after boring. Target undersized, withdraw, measure with air gauge or plug gauge, then take the final cleanup pass. For Class 2 bore fits (H7/h6 system), honing after boring to 180–240 grit is recommended for consistent finish.
Coolant: Dry or light air blast preferred. Avoid flood coolant on thin-wall sections — moisture absorption in linen phenolic is ~1% over 24 hours, and wet machining of thin bores can cause dimensional shift before the part is inspected.
Surface finish: Achievable Ra 16–32 μin with sharp carbide and fine feed. Below Ra 16 μin is possible with PCD tooling and very fine feed (0.0005 IPR); consult tooling manufacturer for RPM/feed optimization at this finish level.
See the Linen Phenolic Machining Guide for complete specifications.
Standards and Compliance
| Standard | Scope |
|---|---|
| NEMA LI 1 | Industrial laminated thermosetting products — minimum properties per grade, dimensional tolerances |
| MIL-I-24768/13 | Type FBG-LE — military grade linen phenolic, electrical grade |
| MIL-I-24768/14 | Type FBG-L — military grade linen phenolic, mechanical grade |
| ASTM D709 | Standard specification for laminated thermosetting materials |
Request a Certificate of Conformance citing NEMA LI 1 Grade L or LE. For MIL applications, confirm manufacturer QPL status before order.
Get a quote on NEMA Grade L or LE rod — precision bushing stock, cut to length
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