NEMA L

NEMA L is the mechanical-grade linen phenolic laminate — woven linen (cotton/flax blend with finer threads than canvas) impregnated with phenolic resin, producing a laminate with a smoother machined surface than canvas phenolic (NEMA C), preferred for precision mechanical parts that require close dimensional tolerances and a fine surface finish.

TL;DR

Chemistry & Reinforcement

Linen phenolic uses a finer-weave woven textile (linen — typically a cotton/flax blend with thread counts higher than standard canvas) saturated with phenolic resin. The smaller thread diameter and tighter weave geometry result in:

• Reinforcement: Fine-weave linen or linen/cotton fabric
• Resin: Phenol-formaldehyde (phenolic)
• Color/finish: Tan to light brown; smoother cross-section texture than canvas phenolic
• Density: ~1.30–1.36 g/cc

The practical consequence of the finer weave: when NEMA L is machined, turned, or ground, the surface finish (Ra) achieved is significantly smoother than NEMA C. Canvas phenolic, with its coarser fabric weave, leaves a slightly fibrous or textured surface after machining. Linen phenolic turns and mills with a finish approaching paper phenolic while retaining most of the impact advantage of a woven reinforcement.

Key Properties

Typical Applications

Linen phenolic grade L is selected when the finer surface finish of linen reinforcement matters more than maximum impact toughness:

• Precision spur gears and pinions — instrument gears in clocks, calculators, and metrology equipment where tooth form accuracy and surface smoothness reduce noise and backlash.
• Fine-tolerance bushings — press-fit bushings in instrument pivots and light-duty shafts where a smooth bore surface reduces break-in wear.
• Cams and followers — profiled cam surfaces benefit from the smoother linen finish; mating metal followers see less abrasion.
• Instrument panels and dials — linen phenolic machines to tight flatness tolerances and holds a smooth face for marking and engraving.
• Precision spacers and shims — close-tolerance spacer stacks where surface roughness would introduce stack-up error.
• Textile machinery guides — yarn guides and thread-tension surfaces where the fine linen finish prevents fiber snagging.

Standard Sizes

Thin sheet (1/16 to 1/8 in.) is common for instrument panels and spacer applications. Rod is frequently ordered for turning gear and bushing blanks.

Standards Reference

1. NEMA LI 1 — Grade L is defined with mechanical minimums (flexural, impact) and dimensional tolerances. NEMA LI 1-2020 is current.
2. MIL-I-24768/5 — Military specification, Type CFM (Cotton-fabric Fine-weave, Mechanical). QPL certification for defense programs.
3. ASTM D709 — test method backbone for all laminated thermosetting materials; underlies NEMA LI 1 property requirements.

Comparison to Neighbor Grades

Choose L when: surface finish and dimensional precision in machined parts are more important than maximum impact toughness. Choose C when the primary driver is impact strength and canvas texture is acceptable. Choose LE when the same fine-finish linen laminate must also serve as an electrical insulator.

More related guides

Linen phenolic grades

• NEMA LE Linen Phenolic Electrical Grade

Compare linen to other phenolic families

• Canvas Phenolic C Mechanical Grade
• Canvas Phenolic CE Electrical Grade
• Paper Phenolic XX Mechanical Grade

All grades index

• NEMA Grades Directory