POM acetal and nylon gears, bushings and sliding parts for material selection
Material Decision · Gears · Bushings · Sliding Parts

POM (Acetal) vs Nylon for Bushings, Gears and Sliding Parts

Choosing between POM and nylon for injection-molded gears, bushings and sliding parts is mainly a question of motion, fit and long-term dimensional behavior. POM is usually the safer starting point when low friction, low moisture uptake and repeatable shaft or bore clearance are critical. Nylon becomes more attractive when toughness, impact resistance or higher mechanical loading matters more than moisture-driven dimensional change. The decision should be based on the real service condition, not tensile strength alone.

Engineering Quick Answer

Choose POM when

Low-friction sliding is important, the part must hold a stable bore or shaft fit, humidity exposure could change function, or gear backlash and running clearance need to remain predictable.

Choose Nylon when

The part must absorb shock, tolerate repeated impact, carry higher mechanical load, or benefit from greater toughness and flexibility while some moisture-driven dimensional change can be managed.

Neither material should be frozen from a datasheet value alone. Load, contact condition, lubrication, humidity and functional fit should be defined first. For the broader resin-selection framework, see our injection molding material selection guide .

Quick Material Decision

POM vs Nylon: Quick Engineering Decision

POM and nylon solve different mechanical design problems. Use this table to screen the choice around friction, moisture stability, impact loading, fit and long-term service conditions before moving into grade-level validation.

POM vs nylon comparison for gears, bushings and sliding parts
Decision Factor POM / Acetal Nylon
Sliding friction Often the safer default for low-friction motion and predictable running clearance. Can work well, but wear depends more strongly on grade, load, mating surface and lubrication.
Moisture stability Low moisture uptake generally makes functional dimensions easier to stabilize. Moisture absorption can change dimensions between dry, conditioned and service states.
Impact & structural duty Better suited where dimensional control matters more than repeated shock or high strain. Often the stronger choice where toughness, impact or structural loading dominates.
Gear stability Strong candidate when backlash, tooth geometry and center distance must remain predictable. Humidity and conditioning can influence gear geometry and backlash.
Shaft / bore fit Usually easier to manage where bushing ID and repeatable shaft clearance are critical. Fit should be reviewed in the conditioned state expected during service.
Creep under load Long-term load, temperature and bearing pressure still require validation. Long-term load also requires validation, including moisture and conditioning effects.
Noise & motion quality Often suitable where stable clearance supports controlled gear or sliding motion. Can also run quietly, depending on grade, geometry and service environment.
Best starting point Precision motion: gears, bushings and sliders where friction and dimensional stability dominate. Tough mechanical duty: parts where impact, toughness and load capacity dominate.

This table is for early material screening. Final selection still depends on the actual load, speed, humidity, lubrication, service temperature and required functional clearance.

POM acetal gears bushings rollers and sliding parts for precision motion applications
POM Decision Zone

When POM Is Better for Gears, Bushings and Sliding Parts

POM is usually the stronger starting point when a molded mechanical part depends on predictable motion and dimensional control more than impact flexibility. For gears, bushings and sliding parts, its low moisture uptake and stable molded behavior can make backlash, bore clearance and sliding fit easier to manage across normal service conditions. That advantage matters most when function is sensitive to small changes in geometry.

01

Precision Motion and Repeatable Fit

Choose POM first when the design depends on stable bore diameter, gear geometry or running clearance. It is especially useful where a shaft, gear or guide must continue to move freely without large humidity-driven dimensional change.

02

Low-Friction Mechanical Interfaces

POM is widely used as a starting material for sliding and rotating interfaces because it can combine low friction with good dimensional stability. The final wear result still depends on load, speed, mating material, surface condition and lubrication.

03

Typical POM-Favored Parts

Common candidates include precision gears, bushings, rollers, linear guides, sliding blocks and other molded motion components where repeatable clearance matters. The design should still be checked against the actual service load and operating environment.

POM should not be treated as the automatic winner. If repeated impact, high strain or flexible deformation is the dominant requirement, nylon may remain the better material family to evaluate.

Nylon molded clips brackets and load-bearing functional parts requiring toughness and impact resistance
Nylon Decision Zone

When Nylon Is Better for Tough, Load-Bearing Parts

Nylon becomes the stronger candidate when a molded part must absorb impact, tolerate repeated strain or carry mechanical load without brittle behavior. Compared with POM, many nylon grades offer a more forgiving balance of toughness, fatigue resistance and structural performance. The tradeoff is that moisture conditioning can change dimensions, so close shaft fits, gear clearances and other precision interfaces require additional attention.

01

Impact and Repeated Strain

Nylon is often preferred for clips, flexible arms, brackets and impact-exposed features because it can tolerate deformation and repeated mechanical strain better than a more dimensionally rigid material choice.

02

Higher Mechanical Duty

Load-bearing components may favor nylon when toughness, fatigue resistance or structural support matters more than moisture-stable dimensions. Actual performance still depends on grade, temperature, load direction and duty cycle.

03

Know the Dimensional Tradeoff

Nylon should be challenged when function depends on a tightly controlled bushing ID, shaft clearance or gear geometry. Moisture absorption does not automatically rule nylon out, but its conditioned service dimensions must be considered.

If nylon is already the preferred material family, the next decision is the grade. Use our PA6 vs PA66 material selection guide to compare the nylon options separately rather than expanding that decision inside this POM vs nylon page.

POM and nylon bushing shaft fit comparison under dry and humid service conditions
Dimensional Stability

Humidity, Dimensional Stability and Shaft Fit

Moisture exposure can change the functional dimensions of nylon after molding, which matters when a gear, bushing or sliding part depends on a controlled clearance. POM generally absorbs less moisture, so bore size, gear geometry and shaft fit are easier to keep predictable across changing humidity. With nylon, the important question is not only the molded dimension, but the dimension the part will hold after conditioning and during actual service.

Nylon

Dry Size Is Not Always Service Size

A nylon component measured shortly after molding may not represent its stabilized service condition. Moisture uptake can change bore diameter, gear geometry or assembled clearance, so the expected conditioning state should be defined before a close fit is approved.

POM

Lower Moisture Sensitivity Helps Fit Control

POM is often easier to manage where a bushing ID, shaft clearance or gear relationship must remain consistent. Its lower moisture uptake reduces one major source of dimensional variation, although molding shrinkage and geometry still need to be considered.

Fit

Design Around Functional Clearance

For a shaft-and-bushing pair, define the operating clearance rather than reviewing each molded dimension in isolation. For gears, backlash and center distance should be evaluated in the expected service state, especially when nylon is being considered.

Separate molding shrinkage from moisture-driven dimensional change. Use the plastic resin shrinkage rate chart for early resin screening. If the required shaft, bore or positional tolerance is unusually tight, confirm whether it is realistically production-feasible in the tolerance feasibility guide rather than expanding that topic inside this material comparison.

Tribology Decision

Friction, Wear and Lubrication: What Changes the Choice?

POM is often the safer starting point for low-friction gears, bushings and sliding parts, but material family alone does not determine wear life. Load, sliding speed, mating material, surface condition and lubrication can change the result. Nylon can also perform well in moving interfaces when toughness or load capacity matters, so the comparison should reflect the actual contact condition rather than a general claim that one resin always wears better.

Contact Conditions to Define

Load Contact pressure
Speed Sliding or rotation
Lubrication Dry, grease or oil
Mating Surface Steel, polymer or coating
01

Dry Sliding Often Favors POM

POM is commonly considered first where a bushing, guide or gear must run with limited lubrication and stable clearance. Its combination of low friction and dimensional stability can be useful, but actual wear still depends on pressure, speed and mating-surface condition.

02

Lubrication Can Change the Ranking

Grease or oil can reduce friction and wear for either material family, so a dry-running comparison may not represent the real application. The lubricant must also be compatible with the selected resin grade and the expected service temperature.

03

Noise and Wear Must Be Tested in Context

Quiet motion does not come from resin selection alone. Gear geometry, backlash, shaft alignment, surface finish and mating material can all affect noise and wear. Use the real assembly condition when evaluating POM against nylon.

Avoid absolute statements such as “POM always has lower friction” or “nylon always lasts longer.” Tribological performance is grade- and application-dependent; material selection should be based on the actual load, speed, lubrication and mating interface.

Geometry & Functional Fit

Geometry and Fit Checks That Can Change the POM vs Nylon Decision

Material choice should follow the geometry that controls function. Gear backlash, press fit, wall thickness and contact stress can shift a POM vs nylon decision even when both materials look acceptable from datasheet properties.

Gear

Gear Geometry Can Shift the Choice

POM often suits precision motion, while nylon may be favored when toughness matters more. Tooth and hub geometry can change backlash, noise and deformation enough to alter that starting assumption.

  • tooth thickness and pitch;
  • backlash and center distance;
  • hub stiffness and load path.
Bushing

Bushing Fit Is More Than Bore Size

POM may favor stable clearance, but thin walls, press fit and sustained bearing pressure can change the risk. Nylon remains viable where toughness matters and dimensional variation can be controlled.

  • wall thickness around the bore;
  • press-fit interference;
  • shaft clearance and bearing pressure.
Slider

Sliding Geometry Controls Contact Stress

For guides and sliding blocks, contact area and load distribution can matter as much as nominal friction. Narrow bearing surfaces or edge loading can create wear even with a suitable resin.

  • contact length and bearing area;
  • edge loading or misalignment;
  • functional running clearance.

Keep the review at part-function level. Tooling details belong in a dedicated manufacturing review; include geometry here only when it can materially change the POM-versus-nylon decision.

Buyer Verification

What Evidence Should a Supplier Provide Before Material Freeze?

A POM-versus-nylon decision should be supported by evidence tied to the actual part function, not only a generic resin datasheet. Before the material is frozen, confirm the grade, service condition and functional risks that could change gear motion, bushing fit or sliding performance.

01

Exact Resin Grade

Confirm the commercial grade, reinforcement level and supplier datasheet rather than approving only “POM” or “nylon” as a material family.

02

Conditioning State

For nylon, define whether dimensions and performance are being evaluated dry-as-molded, conditioned or under expected service humidity.

03

Functional Fit Requirement

Identify the actual operating requirement such as shaft clearance, bushing ID, gear backlash or sliding running clearance.

04

Relevant CTQ Evidence

Measure only the dimensions that control function and confirm that the proposed inspection method matches the real assembly requirement.

05

Functional Trial Evidence

Where fit or motion is critical, use molded-sample assembly, gear engagement or shaft-fit testing to confirm the design assumption.

06

Wear and Lubrication Assumption

For moving interfaces, document load, mating material and lubrication condition so material approval reflects the real contact environment.

Once the material, fit and functional risks are defined, the next step is production feasibility. Our custom injection molding process can then review how the selected resin, part geometry and CTQ requirements translate into tooling and production control.

Material Freeze Gate

When You Should Not Choose POM or Nylon Yet

Do not freeze POM or nylon while the service condition or functional requirement is still undefined. Resolve these six inputs first; otherwise, even a technically suitable resin can fail in the real assembly.

Operating Temperature Is Unknown

Define continuous and peak temperature first. Heat can change stiffness, creep response and long-term fit in both material families.

Load and Duty Cycle Are Undefined

Static load, impact and continuous motion create different demands. Define load direction, magnitude and operating cycle before comparing material strength.

Functional Clearance Is Not Defined

A gear or bushing decision needs the required backlash, shaft clearance or interference. Nominal dimensions alone are not enough.

Humidity Exposure Is Unclear

Nylon service dimensions depend on moisture condition. Define the expected environment and conditioning state before approving a close-fit application.

Chemical Exposure Drives the Design

When oils, cleaners, fuels or solvents are critical, verify compatibility at the exact resin-grade level rather than by material family.

No Functional Test Is Defined

If wear, noise, backlash or shaft fit is critical, keep the material decision provisional until the real assembly can be functionally checked.

Material freeze is appropriate only after service conditions, loading and functional fit are defined. Then POM or nylon can be judged against the actual engineering requirement instead of a generic property ranking.

Engineering FAQ

POM vs Nylon FAQ for Gears, Bushings and Sliding Parts

These are the final questions buyers and engineers commonly ask before choosing POM or nylon for molded mechanical parts.

Is POM the same as acetal?

Yes. POM, or polyoxymethylene, is commonly called acetal. It is widely used for gears, bushings and sliding parts where low friction and dimensional stability matter. The exact grade still affects wear, shrinkage and service performance.

Is Delrin the same as POM?

Delrin is a trade name for an acetal homopolymer; POM is the broader polymer family. Specify the actual resin grade rather than assuming every POM or acetal grade has the same mechanical and wear behavior.

Is POM or nylon better for bushings?

POM is often preferred when low friction, stable bore size and predictable shaft clearance matter most. Nylon may be better when toughness or shock loading dominates. Load, speed, lubrication, humidity and operating clearance should decide the final choice.

Which material is better for plastic gears?

POM often suits precision gears because low moisture uptake helps keep backlash and tooth geometry predictable. Nylon can be attractive when toughness or impact resistance matters more. Gear load, lubrication, noise and service environment should drive the decision.

How does moisture affect nylon shaft or bore fit?

Nylon can absorb moisture after molding, changing bore diameter and shaft clearance. For close-fit parts, define whether dimensions are being evaluated dry, conditioned or at expected service humidity before freezing the functional fit.

When should I request a DFM review before choosing the resin?

Request a review when resin choice depends on tight fit, gear backlash, thin walls, sustained load, wear life or uncertain service conditions. Material, geometry and molding feasibility should then be checked together before tooling assumptions are frozen.

Before Material Freeze

Review Gear, Bushing and Shaft-Fit Risk

Send the drawing, load, service environment and required fit. We can review whether POM, nylon or another resin family is the safer starting point before tooling is locked.

Review Gear, Bushing and Shaft-Fit Risk