Nylon Applications: Bushings, Gears, Sheaves & More
Nylon finds its widest use in applications that combine moderate-to-high compressive loads, sliding or rotating motion, and the need for corrosion-free, self-lubricating contact. Its tensile strength of ~12,000 psi, low coefficient of friction (0.20–0.35 dry, lower in filled grades), and machinability make it a practical first choice for bushings, gears, sheaves, wear pads, and rollers across industrial, food processing, and marine environments.
TL;DR
- Primary use cases: sleeve bushings, spur/helical gears, sheaves, cam followers, wear pads, and rollers
- Choose MoS₂-filled (Nylatron GS) for dry-running bearings; oil-filled (Nyloil) for intermittent or oscillating motion
- Unfilled natural Nylon 6 is FDA-compliant — use it in food contact zones; filled grades are not food-safe
- Moisture affects dimensions — leave proper shaft clearance (see bushing section below)
- Cast nylon handles larger cross-sections and shock loads better than extruded; size up to cast when OD exceeds 3"
Sleeve Bushings and Plain Bearings
The single largest application for machined nylon is plain sleeve bushings. Nylon offers several advantages over bronze, cast iron, and sintered metal bearings in many medium-duty applications:
- No seizure with steel shafts: nylon will wear rather than seize, even at momentary lubrication loss
- Corrosion immunity: no rust, no galvanic reaction with aluminum or stainless steel housings
- Noise reduction: plastic-on-steel contact is quieter than metal-on-metal
- Emergency dry-running: nylon can survive brief dry-running that would destroy a bronze bearing
Grade and Clearance Selection
| Operating Condition | Recommended Grade | Shaft Clearance (per inch of diameter) |
|---|---|---|
| Continuous rotation, light load, dry | Nylatron GS (MoS₂) | 0.003"–0.005" |
| Continuous rotation, heavy load, dry | Nylatron GS | 0.003"–0.005" |
| Oscillating / reciprocating, dry | Nyloil (oil-filled) | 0.004"–0.006" |
| Intermittent, occasional lube | Nylon 6 natural | 0.003"–0.005" |
| Food zone, dry | Nylon 6 natural or Nyloil (food-grade oil) | 0.004"–0.006" |
Machine nylon bushings dry (low ambient humidity, stable shop temperature). If the bushing will operate in a humid or wet environment, add 0.001"–0.002" per inch of diameter to shaft clearance to account for moisture-driven expansion. Nylon absorbs 2–9% moisture — see the full discussion in the nylon properties guide.
Press-fit retention: Nylon bushings are commonly pressed into housings. Use 0.001"–0.003" interference per inch of OD for aluminum housings; reduce to 0.0005"–0.001" for steel. Avoid over-pressing — nylon will cold-flow under excessive compression over time, reducing effective interference.
PV Ratings for Nylon Bearings
PV (pressure × velocity) is the key operating limit:
| Grade | Max PV (dry, continuous) |
|---|---|
| Nylon 6 unfilled | 3,000 psi·ft/min |
| Nylatron GS (MoS₂) | 8,000–10,000 psi·ft/min |
| Nyloil (oil-filled) | 6,000–8,000 psi·ft/min |
For applications requiring PV above 10,000 psi·ft/min dry, consider cotton phenolic in flooded oil service, or PEEK for high-temperature/high-PV combination.
Gears — Spur, Helical, and Worm
Nylon is one of the most common materials for cut plastic gears in industrial machinery. The reasons are consistent:
- Shock absorption: nylon's lower modulus relative to steel allows it to absorb tooth-impact loads that would chip or crack metal gears
- Quiet operation: plastic-on-steel or plastic-on-plastic meshing reduces transmission noise significantly vs. all-metal gearsets
- Self-lubricating surface: MoS₂-filled grades run dry against steel pinions without galling
- Re-cut when worn: a worn nylon gear is re-machined or replaced at a fraction of the cost of a hardened steel equivalent
Gear Application Guidelines
Spur and helical gears: Cast Nylon 6 (natural or Nylatron GS) handles most industrial spur/helical applications. Use cast stock for gear blanks above 3" diameter — extruded rod has higher residual stress that can cause distortion on heavy stock removal.
Worm gears: Nylon worm gears work well against steel worms when lubrication is available; running dry against steel worms requires MoS₂-filled nylon (Nylatron GS) and careful PV management.
Drive vs. driven: In steel-drives-plastic configurations, the plastic gear should be the slower-rotating element (typically the driven gear) to minimize heat generation at the mesh. Tooth speed above 1,500 ft/min in continuous dry service pushes past nylon's safe operating range — reduce tooth speed or add lubrication.
Glass-filled nylon for gears: GS-30 (33% glass fiber) doubles gear stiffness and reduces wear depth, but increases abrasion on the mating steel gear and is more brittle at tooth tips. Specify glass-filled nylon gears only when mating against hardened steel (60+ Rc) and when tooth geometry provides adequate root thickness.
Sheaves, Pulleys, and Cable Guides
Cast nylon 6 is the preferred plastic for machined sheave wheels and cable guide pulleys in overhead cranes, hoists, marine rigging, and agricultural equipment. Key properties driving sheave selection:
- Groove wear resistance: the hardened nylon groove surface resists wire-rope abrasion significantly better than softer plastics
- Re-bore tolerance: worn sheaves can be re-machined to accept a new bushing and returned to service — cast nylon's low residual stress makes re-boring reliable
- Corrosion immunity: nylon sheaves are standard in saltwater and chemical environments where steel sheaves corrode and seize
- Weight savings: cast nylon is 1.13–1.16 g/cc vs. 7.8 g/cc for steel — significant for overhead rigging
Bore sizing: Nylon sheave bores must account for moisture expansion. For marine environments, use a minimum shaft clearance of 0.005" per inch of bore diameter in addition to standard bearing clearance.
Wire rope grooving: Use a groove radius 10–15% larger than the wire rope radius to distribute contact load and reduce groove wear rate. Sharp-bottomed grooves concentrate load and accelerate nylon wear.
Wear Pads and Wear Strips
Nylon wear pads provide replaceable bearing surfaces in steel frameworks, guide rails, and reciprocating machinery. Compared to the main competitor (UHMW polyethylene) for wear pad applications:
| Criterion | Nylon 6 | UHMW |
|---|---|---|
| Abrasion resistance | Good | Excellent (6× nylon) |
| Compressive strength | 14,000–18,000 psi | 3,000–5,000 psi |
| Dimensional stability | Fair (moisture-sensitive) | Excellent |
| Surface for heavy loads | Good — stiff | Poor — cold-flows under sustained load |
| Cost | Similar | Similar |
When to choose nylon over UHMW for wear pads: Use nylon when the pad carries sustained compressive loads above ~1,500 psi (UHMW cold-flows at these levels), or when the pad is part of a precision guide where dimensional accuracy matters more than raw abrasion life.
Attachment: Nylon wear pads are countersunk-bolted or bonded with structural epoxy. For bolted pads, use oversized holes with washers to allow for thermal and moisture expansion — do not clamp the nylon so tightly that it cannot move.
Rollers and Conveyor Components
Cast nylon tube, bored and trued on a lathe, produces a conveyor roller with integrated bushing surfaces at both ends. Natural Nylon 6 is used in food-safe zones; black MoS₂-filled nylon for dry continuous-rotation duty; smooth-turned natural for paper and film handling where low friction is needed to avoid surface marking.
Sizing: Design roller walls for maximum bending stress no greater than 30–50% of tensile strength. Verify wall section before committing to nylon on long-span, heavy-load rollers — upsize the wall or switch to heavier cast sections as required.
Food Processing and Food Zone Applications
Unfilled natural Nylon 6 and Nylon 6/6 comply with FDA 21 CFR 177.1500 for food-contact use. This covers conveyor components, sorting gates, hopper liners, cam followers, and any other part with incidental contact with food product.
Practical food-zone guidance:
- Use natural (off-white) or blue grades — blue pieces are visible under metal detection if a part breaks
- Never use MoS₂-filled (Nylatron GS), glass-filled, or graphite-filled grades in direct food contact
- Nyloil is FDA-compliant only when the specific oil used meets FDA 21 CFR 178.3570 (white mineral oil) — confirm with supplier
- Nylon absorbs moisture from food and cleaning cycles — account for dimensional growth in close-clearance parts
- For wash-down environments with caustic cleaners, confirm nylon's chemical resistance against the specific cleaner concentration; strong alkaline cleaners above pH 12 can attack nylon over extended exposure
See the complete regulatory detail in the nylon FDA food-grade guide.
Marine Applications
Nylon's corrosion immunity and self-lubrication make it standard in marine hardware: sheaves, rollers, rudder pintles, and steering pivot bushings. Natural nylon withstands seawater immersion indefinitely — the polyamide is not attacked by sodium chloride. Submerged parts fully saturate over weeks to months; machine bores to the larger (saturated) dimension to prevent in-service tightening.
UV limitation: Nylon yellows and degrades under long-term UV exposure. For above-waterline structural parts, specify black carbon-loaded nylon or switch to UHMW or HDPE Marine board.
Cam Followers and Tire Chocks
Cam followers: Nylon (Nylatron GS) runs quietly against steel cams in packaging and textile machinery. Check PV limit against Nylatron GS specifications before specifying for high-speed continuous-rotation followers.
Tire chocks: Cast nylon 6 heavy plate (2"–4" thick) is machined into aircraft and heavy-truck wheel chocks. High compressive strength (14,000–18,000 psi), friction against concrete, low weight, and weathering resistance make it a practical alternative to wood or steel.
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