Nylon Plastic — Sheet, Rod & Bar Stock Guide

Nylon (polyamide, PA) is the most widely used engineering thermoplastic for machined wear parts. It combines a tensile strength around 12,000 psi with a low coefficient of friction, continuous-use temperature up to 200°F, and cost-effective machinability — making it the go-to material for bushings, gears, sheaves, wear pads, and rollers across industrial, food, and marine applications.

TL;DR

• Two main production routes: cast Nylon 6 (large cross-sections, low residual stress) and extruded Nylon 6/6 (tighter tolerances, smaller stock)
• Nylon absorbs 2–9% moisture by weight, which affects dimensions and mechanical properties — plan for it in close-tolerance parts
• Filled grades — MoS₂ (Nylatron GS), oil-filled (Nyloil), glass-filled (GS-30) — target specific performance gaps
• FDA-compliant in unfilled natural grades; filled grades (MoS₂, glass) are NOT food-safe
• Stock forms: sheet, rod, tube, and hex bar; rod up to 12" diameter, cast plate up to 24" × 96"
• Competes primarily against Delrin for precision parts, UHMW for abrasion resistance, PEEK for high-temperature duty, and phenolic composites for wet/oiled bearings

Cast vs. Extruded Nylon: The First Decision

The single most consequential choice when ordering nylon stock is production method. Cast and extruded nylon have different internal structures, size ranges, and performance characteristics — selecting the wrong one creates problems even if the alloy chemistry is identical.

Cast Nylon 6

Cast nylon is polymerized directly in the mold from caprolactam monomer. The process is low-pressure and allows very large cross-sections without internal stress. Key characteristics:

• Available sizes: rod to 12" diameter, plate to 24" × 96" × 4" thick, tube to large bore
• Internal stress: near zero — the part solidifies from the outside in without pressure, so stress cracking on machining is rare
• Crystallinity: higher than extruded, which yields slightly better modulus and creep resistance
• Grade examples: Nylatron GS (MoS₂-filled), Nylatron NSM (oil-filled), standard natural Nylon 6

Extruded Nylon 6/6

Extrusion forces molten Nylon 6/6 through a die under pressure, then cools it. The result is a denser skin and tighter dimensional control over the length of the bar.

• Available sizes: typically rod to 4" diameter, sheet to ½" thick in standard stock
• Dimensional tolerance: tighter length tolerances than cast — better for CNC bar-feed operations
• Nylon 6 vs. 6/6 chemistry: Nylon 6/6 (hexamethylenediamine + adipic acid) has a slightly higher melting point (~500°F vs. 430°F for Nylon 6) and marginally better stiffness. Moisture absorption is comparable.
• Residual stress: higher than cast; deep cuts can release stress and cause deflection on thin walls

Mechanical and Thermal Properties at a Glance

For a full breakdown including electrical properties and chemical resistance, see the nylon mechanical and thermal properties guide.

Moisture Absorption: The Critical Variable

No other common engineering thermoplastic has moisture absorption as central to its performance profile as nylon. Water acts as a plasticizer in the polyamide chain: absorbed moisture reduces stiffness and hardness, increases toughness, and — critically for machinists — changes dimensions.

• At 50% relative humidity equilibrium, a nylon 6 part can expand approximately 0.010"–0.015" per inch
• At full saturation, linear expansion can exceed 1–2% depending on cross-section
• Tensile strength drops ~15–20% from dry to saturated; impact strength increases

Practical implications:

1. Machine to finish dimension in the conditioned state if possible (dry from bag, or conditioned to job environment)
2. Add clearance on bore fits — a bushing machined dry in winter will tighten after equilibrating in a humid shop or outdoor installation
3. Vacuum-bag or seal cut stock to delay moisture uptake between operations
4. For close-tolerance applications, consider Delrin — it absorbs under 0.25% moisture and is dimensionally far more stable

Nylon Grades — Filled vs. Unfilled

The unfilled natural grade covers the majority of applications. Filled grades solve specific problems:

MoS₂-Filled — Nylatron GS

Molybdenum disulfide powder (typically 2–3% loading) is mixed into the cast Nylon 6 matrix. MoS₂ acts as a dry lubricant at the crystalline level, reducing the coefficient of friction and improving wear life by 5–10× over unfilled nylon in dry-running conditions.

Use when: dry-running bushings, gears, or cams where no external lubrication is possible. Color: black.

Oil-Filled — Nyloil (Cast Nylon 6)

Internally lubricated with food-grade or mineral oil dispersed through the matrix. Oil migrates to the wear surface under load, providing continuous lubrication without external oil supply.

Use when: intermittent or oscillating motion, food-zone applications where external grease is restricted. Nyloil qualifies under FDA 21 CFR 177.1500.

Glass-Filled — GS-30 / Nylon GF33

33% short-glass-fiber reinforcement roughly doubles the flexural modulus (to ~900,000 psi) and cuts the coefficient of thermal expansion nearly in half. Stiffness, creep resistance, and dimensional stability all improve significantly.

Trade-offs: brittle at notches, abrasive to mating surfaces, and NOT food-safe. See the detailed nylon grades comparison for selection tables.

Unfilled Natural Nylon 6 / 6/6

The baseline. FDA-compliant in natural (off-white) form. Best toughness and impact resistance of all nylon grades. Correct choice for general-purpose bushings, wear pads, and structural shapes where moisture is controlled.

Common Applications

Nylon's combination of moderate strength, self-lubricating character, and machinability puts it in a wide range of service environments:

For application-specific detail — including load ratings, operating clearances, and grade selection by environment — see the nylon applications guide.

Stock Forms and Available Sizes

Sheet / Plate

• Extruded Nylon 6/6: typically up to 2" thick, 24" × 48" or 48" × 96" panels
• Cast Nylon 6: plate up to 4" thick, 24" × 96" in standard stock; custom thicknesses available

Rod

• Extruded: ¼" through 4" diameter in 6' or 12' lengths
• Cast: ½" through 12" diameter; larger diameters in shorter billets

Tube

• Cast Nylon 6 tube: 1" to 12"+ OD, varied wall thicknesses for bushing and roller applications

Hex Bar

• Nylon 6/6 extruded hex: ½" through 2½" across-flats, typically 6' lengths; used for machined nuts, standoffs, and fittings

Full dimensional availability is covered in the nylon specifications page.

How Nylon Compares to Competing Materials

The most common substitution question is nylon vs. Delrin. The short answer: use Acetal when dimensional stability and moisture immunity matter most; use Nylon when toughness, impact resistance, and higher compressive load capacity are the priorities. Full comparison data:

• Nylon vs. Delrin — See Acetal vs. Nylon comparison
• Nylon vs. UHMW — UHMW wins on abrasion resistance and noise; Nylon wins on stiffness and compressive strength
• Nylon vs. PEEK — PEEK handles 480°F continuous vs. Nylon's 200°F; PEEK is 10–15× the cost
• Nylon vs. Cotton Phenolic — Cotton phenolic excels in oiled/wet bearing service; Nylon handles dry-running better

See the nylon comparisons index for structured data tables across all competing materials.

Machining Overview

Nylon machines cleanly with carbide or sharp HSS tooling. Key considerations:

• Use sharp, positive-rake tools to shear rather than plow — dull tools generate heat that melts the surface
• Chips are stringy and can wrap around tooling; use chip breakers or compressed air
• Avoid flood coolant (introduces moisture); use compressed air or dry machine where possible
• Thermal expansion is significant — rough-cut and let stock return to room temperature before finishing to final dimension
• Supported wall thickness minimum: ~3/16" for most grades; glass-filled is more brittle and prone to delamination at thin walls

Full tooling parameters, RPM/feed tables, and fixturing advice in the nylon machining guide.

FDA and Food-Safety Status

Unfilled natural Nylon 6 and Nylon 6/6 comply with FDA 21 CFR 177.1500 for food-contact applications. USDA acceptance also applies to certain natural grades. Critical limitation: any filled grade — MoS₂, glass-fiber, or graphite — is not approved for direct food contact. Blue-colored grades (Nylatron NSM) are designed to be metal-detector visible, which is useful for food processing lines but does not inherently convey FDA status.

Detailed regulatory citations, grade-by-grade FDA status, and USDA/3-A compliance notes are in the nylon FDA and food-grade guide.

Frequently Asked Questions

Can nylon be used outdoors? Unfilled nylon has moderate UV resistance — it will yellow and degrade over multi-year outdoor exposure. Black grades (carbon-black loaded) offer better UV stability. For long-term outdoor structural service, consider black polyethylene (UHMW or HDPE) instead.

What is the maximum continuous service temperature? 200°F (93°C) for unfilled nylon. Glass-filled grades raise this slightly to ~230°F due to restricted polymer chain mobility. Nylon should not be used in steam or hot-water environments — hydrolytic degradation accelerates above 180°F.

Does nylon bond with adhesives? Nylon is difficult to bond without surface preparation. Abrade the surface, clean with isopropyl alcohol, then use a structural epoxy or cyanoacrylate formulated for polyamides. Solvent bonding is not practical — nylon has limited solvent susceptibility.

Full FAQ with 10+ answered questions at the nylon FAQ.

Related Guides

More related guides

Cross-cluster suggestions to help shoppers and engineers explore adjacent topics:

Applications

• Bushings Bearings
• Wear Strips Guide Rails
• Gears

Industries

• Food Beverage
• Automotive

Compare to other materials

• Acetal Vs. Nylon
• Nylon Vs. Uhmw
• Nylon Vs. Cotton Phenolic

Frequently asked questions — Nylon FAQ