Nylon and acetal are two of the most common engineering plastics used for gears, bushings, rollers, bearings, wear pads, spacers, guides and other mechanical parts. At first glance, they can appear interchangeable because both provide good wear resistance, relatively low friction, corrosion resistance and much lower weight than metals.
In actual engineering applications, however, the differences between nylon and acetal can become significant. Nylon generally offers better toughness, impact resistance and load-bearing capability, while acetal is usually preferred when dimensional stability, low moisture absorption, precision machining and consistent clearances are more important.
This difference becomes especially important for CNC machined parts. A nylon component may meet its drawing tolerance immediately after machining but change dimensions after absorbing moisture. Acetal normally undergoes much smaller moisture-related dimensional changes and is therefore frequently selected for precision gears, bushings, fixtures and sliding components.
The correct choice is not simply “nylon is stronger” or “acetal is easier to machine.” Engineers need to consider the exact nylon and POM grade, loading mode, temperature, humidity, wear conditions, tolerance and expected service life.
나일론이란 무엇인가?
Nylon is the common name for a family of polyamide materials, often abbreviated as PA. Nylon 6 and Nylon 66 are among the most widely used engineering grades, although PA11, PA12 and other specialized polyamides are also available.
Nylon combines good mechanical strength with toughness, wear resistance, fatigue resistance and impact performance. It is frequently used for gears, bearings, wheels, rollers, sprockets, guide blocks, cable components and structural mechanical parts.
One of nylon’s defining characteristics is its ability to absorb moisture from the surrounding environment. Water molecules enter the polymer and act as a plasticizer. This changes both the dimensions and mechanical behavior of the material.
As moisture content increases, nylon can become tougher and less brittle, but stiffness and dimensional stability can decrease. This property is extremely important when designing precision CNC components.
아세탈이란 무엇인가요?
Acetal is the common engineering name for polyoxymethylene, or POM. It is a semi-crystalline engineering thermoplastic known for high stiffness, low friction, good wear resistance and particularly good dimensional stability.
Acetal absorbs much less moisture than conventional nylon. This makes it suitable for components where bearing clearance, hole diameter, gear geometry or other dimensions must remain relatively stable as ambient humidity changes.
POM also machines very cleanly compared with many engineering plastics. Sharp tools can produce accurate bores, threads, grooves and turned diameters with excellent surface finish.
This is why acetal is widely used for CNC machined gears, rollers, valve parts, bushings, electrical insulators, fixtures, jigs and precision mechanical components.
Acetal vs Delrin: Are They the Same?
Acetal, POM and Delrin are frequently used as if they mean exactly the same material, but there is an important distinction.
Acetal refers to the overall POM family. POM is available primarily as homopolymer and copolymer.
Delrin is a well-known commercial brand of acetal homopolymer, commonly referred to as POM-H.
Acetal copolymer is generally referred to as POM-C.
POM-H typically provides slightly higher stiffness, strength and hardness. POM-C usually provides better chemical resistance, improved resistance to hot water and hydrolysis, and reduced risk of centerline porosity in larger stock shapes.
For CNC machining, buyers should specify the actual required grade instead of simply writing “Delrin” when any generic POM material would be acceptable.
나일론 6 대 나일론 66
“Nylon” is also not one single material.
Nylon 6 and Nylon 66 are commonly machined into industrial components, but they have somewhat different characteristics.
Nylon 6 generally provides good toughness and impact resistance and is widely available as cast and extruded stock. Nylon 66 normally offers greater stiffness, higher heat resistance and higher mechanical strength under comparable conditions.
Both materials absorb substantially more moisture than acetal.
This means that choosing Nylon 66 instead of Nylon 6 does not eliminate the main dimensional-stability issue that distinguishes nylon from POM.
If humidity-related size change is unacceptable, moving from PA6 to PA66 may not solve the underlying design problem. Acetal, PA12 or another lower-moisture material may deserve consideration.
Nylon vs Acetal: Which Is Stronger?
There is no useful single answer unless the exact grades and loading conditions are specified.
Nylon can provide excellent tensile strength, impact resistance and toughness. Reinforced nylon grades can achieve substantially greater stiffness and strength than unfilled material.
Acetal also provides high strength and stiffness, but its main engineering advantage is often the consistency with which those properties and dimensions are maintained in different humidity conditions.
For a structural component subjected to impact or shock loading, nylon may be the better choice.
For a precision mechanical component where a bore, gear tooth or running clearance must stay within a narrow range, acetal may provide better functional performance even if another material has a higher published tensile-strength value.
The Biggest Difference: Moisture Absorption
For many engineering applications, moisture absorption is the most important difference between nylon and acetal.
Nylon is hygroscopic. It absorbs water from humidity and direct water exposure.
The amount depends on the exact nylon grade, component thickness, temperature, humidity and exposure time.
As moisture enters nylon, the component can swell. Its stiffness and strength can also change.
Acetal has much lower moisture absorption. This allows it to retain dimensions more consistently in changing environmental conditions.
This explains why acetal is frequently preferred for precision mechanical components even when nylon provides adequate strength.
Why Can a CNC Machined Nylon Part Change Size After Inspection?
This is a common problem reported by machinists.
A component may be machined and inspected in a temperature-controlled shop while the nylon is relatively dry. After the part is shipped to a customer in a more humid location, the material absorbs moisture.
The resulting swelling can alter bores, outer diameters, thicknesses and center distances.
The machinist may have produced exactly what the drawing requested at the time of inspection, yet the component can later move outside tolerance.
This is not necessarily evidence of poor CNC accuracy. It can be a material-selection and environmental-conditioning issue.
For precision nylon components, engineers should therefore define the expected conditioning state and operating environment instead of assuming that the dry-machined dimension will remain constant indefinitely.
Can Nylon Hold Tight CNC Tolerances?
Nylon can be machined accurately, but specifying extremely tight tolerances without considering its environmental behavior can create unrealistic requirements.
Machine capability is only one part of tolerance control.
A machine shop may be able to produce a bore accurately to the specified value, but humidity, temperature, residual stress and clamping deformation may later create greater dimensional variation than the cutting process itself.
This is why metal-style tolerances should not automatically be applied to nylon components.
For critical fits, engineers should first ask how much dimensional variation the assembly can tolerate throughout its complete service environment.
Is Acetal Better for Tight Tolerances?
In most conventional precision plastic applications, yes.
Acetal combines relatively high stiffness, low moisture absorption and good machinability. These characteristics make it easier to maintain repeatable bore diameters, thicknesses and mating dimensions.
This does not mean that every acetal component can automatically hold extremely tight metal-like tolerances.
POM still has much greater thermal expansion than typical metals, and large machined stock can contain residual stress. Thin walls can also distort when excessive fixture pressure is released.
However, when choosing between standard nylon and acetal for a humidity-sensitive precision component, acetal is usually easier to control.
Nylon vs Acetal for CNC Machining
Both materials can be milled, turned, drilled, bored and threaded using conventional CNC equipment.
The cutting behavior is noticeably different.
Acetal is widely considered one of the easier engineering plastics to machine. It can produce excellent surface finishes with sharp tooling and appropriate chip evacuation.
Nylon tends to be more flexible. Cutting forces can push slender features away from the tool, and the material can produce long, stringy chips during turning and drilling.
For both materials, tools should be extremely sharp. The goal is to cut the polymer cleanly rather than generate heat by rubbing.
Why Do Nylon Chips Become Long and Stringy?
Nylon is tough and ductile, so chips often remain connected rather than breaking like those generated from many metals.
During CNC turning, a continuous nylon chip can wrap around the workpiece, chuck or tool.
This creates more than a cosmetic problem. Accumulated chips can interfere with the cutting zone and increase heat.
Machining strategies may therefore require chip-breaking geometry, interrupted tool paths, controlled pecking or manual and automated chip removal depending on the operation.
Acetal can also generate long chips, but its machining behavior is often more predictable and manageable in precision work.
Heat Control When Machining Nylon and Acetal
Heat is one of the most important machining concerns for both materials.
Plastic conducts heat much less efficiently than metals. Heat generated at the cutting edge can therefore remain concentrated near the tool and workpiece.
As the component warms, it expands.
If the machinist measures the part while it is warm and corrects the tool based on that measurement, the component may become undersized or oversized after returning to room temperature.
Sharp cutters, effective chip evacuation and suitable cutting conditions help reduce heat generation.
Air blast or appropriate coolant may be used depending on the material, machine and application.
Excessive heat should be avoided when machining POM because thermal decomposition of acetal can release formaldehyde-containing fumes.
Workholding and Clamp Distortion
Plastic components are easier to deform during fixturing than steel or aluminum components.
If a thin nylon or acetal part is heavily clamped, it may be machined accurately while held in the distorted condition. When the fixture is released, the component springs into a different shape.
The machinist may then observe changes in flatness, diameter or wall geometry.
This problem is particularly important for large rings, thin plates, bearing retainers and thin-wall bushings.
Workholding should provide enough force to prevent movement without unnecessarily deforming the blank.
Residual Stress in Machined Plastic Stock
Extruded and molded plastic stock can contain residual stresses from manufacturing.
When CNC machining removes material from one side, the original stress balance changes. The remaining material may warp.
This can affect both nylon and acetal.
For high-precision components or parts requiring extensive material removal, manufacturers may rough-machine the blank first, allow it to stabilize and then perform finishing operations.
Annealing may also be appropriate for selected plastic grades and geometries.
Material suppliers’ recommended heat-treatment procedures should be followed because incorrect heating can create additional distortion rather than solving it.
Nylon vs Acetal for Gears
Both materials are widely used for gears.
Nylon gears are valued for toughness, impact absorption, noise reduction and resistance to shock loading. Nylon can be useful when the gear must survive intermittent impact or misalignment.
Acetal gears offer excellent dimensional stability and low friction. They are particularly useful for precision gear trains where tooth geometry, backlash and center distance must remain consistent.
Moisture must be considered when using nylon gears. Dimensional swelling can change backlash and tooth engagement.
Therefore, a high-impact gear may favor nylon, while a small precision gear operating in changing humidity may favor acetal.
Nylon vs Acetal for Bushings and Bearings
Both materials have good wear properties and can operate without continuous external lubrication in suitable applications.
Nylon is often chosen for heavily loaded wear components where toughness and impact resistance matter.
Acetal offers low friction, excellent machinability and stable dimensions, making it attractive for precision bushings and bearing surfaces.
For a bushing operating on a fixed metal shaft, moisture expansion of nylon can reduce the designed running clearance.
If that clearance is already small, swelling can increase friction or even cause binding.
Acetal is therefore often preferable when clearance control is more important than maximum impact toughness.
Nylon vs Acetal for Rollers and Wheels
Nylon is commonly used for larger industrial rollers and wheels because of its toughness, abrasion resistance and ability to absorb shock.
It can perform well in conveyors, material-handling equipment and heavy mechanical systems.
Acetal may be preferable for smaller precision rollers, guide wheels and components where low friction and dimensional consistency are more important.
Load, shaft fit, humidity and impact level should all be considered before choosing between them.
Nylon vs Acetal for Sliding Components
Both materials can work well for wear strips, guides and sliding parts.
Acetal’s low friction and dimensional stability make it a strong choice for precision linear guides, valve components and machine sliding elements.
Nylon may be more suitable where heavy impact or rough service is expected.
Modified grades containing lubricants, PTFE or other additives can further change friction and wear performance, so base-polymer comparisons should not replace testing of the actual material grade.
Which Has Better Creep Resistance?
Both nylon and acetal are thermoplastics and can deform gradually under continuous load.
Acetal generally provides very good creep resistance and dimensional stability for precision mechanical applications.
Nylon can also carry substantial loads, but moisture, temperature and sustained stress can alter its long-term deformation behavior.
For components such as permanent spacers, loaded bushings, precision supports or clamped plastic parts, engineers should use long-term creep data rather than simply comparing short-term tensile strength.
Which Is Better for Press Fits?
Press fits in engineering plastics require more caution than equivalent metal fits.
With nylon, moisture-induced expansion can increase interference after assembly. Stress relaxation and creep can also change holding force over time.
Acetal provides more predictable dimensions, making it easier to design precision fits.
However, excessive interference can still crack or permanently deform POM components.
For critical assemblies, the interference should be designed from the mechanical and environmental properties of the specific material rather than applying a metal press-fit value directly to plastic.
Nylon vs Acetal for Threads
Both materials can be CNC threaded.
Acetal generally produces clean machined threads because of its rigidity and good cutting behavior.
Nylon threads can also perform well, particularly where toughness is useful, but the material can deflect during machining and may change dimensions with moisture.
For repeatedly assembled joints or high sustained loads, metal inserts may provide better thread durability than repeatedly loading the polymer itself.
Which Material Is Better Around Water?
This question needs to separate chemical resistance from dimensional stability.
Nylon can operate in many wet environments, but it absorbs water and changes dimensions.
Acetal absorbs much less water and generally maintains dimensions more consistently.
For precision components exposed to humidity or intermittent water contact, POM is therefore often preferred.
However, chemical environment and water temperature also matter. Hot water, steam, chlorine and cleaning chemicals can affect polymer grades differently, so the exact service condition should be evaluated rather than assuming that “water resistant” means suitable for every aqueous environment.
When Should You Choose Nylon?
Choose nylon when toughness, impact resistance, fatigue performance or heavy-duty wear behavior is more important than extremely stable dimensions.
Typical applications include industrial wheels, larger gears, wear pads, sprockets, rollers, guides and components exposed to shock loading.
Nylon may also be a good choice when a component benefits from vibration and impact absorption.
The designer must still account for moisture absorption, particularly for precision holes, fitted shafts or closely controlled assemblies.
When Should You Choose Acetal?
Choose acetal when machining accuracy, low friction, moisture resistance and dimensional consistency are primary requirements.
Typical components include precision gears, bushings, valve components, electrical parts, guide rollers, spacers, bearing cages, jigs and fixtures.
Acetal is especially useful when the component moves between different humidity environments or when a small dimensional shift could affect clearance or assembly.
Common Mistakes When Choosing Nylon or Acetal
One common mistake is selecting material entirely from tensile strength. The highest-strength material is not automatically the best choice for a precision mechanical part.
Another mistake is treating all nylon grades as identical. PA6, PA66, PA12, cast nylon and reinforced polyamides can behave very differently.
The same applies to acetal. POM-H and POM-C have different advantages.
A third mistake is specifying extremely tight tolerances on nylon without considering humidity and temperature.
Finally, engineers sometimes compare raw-material price while ignoring manufacturing cost. A material that machines more consistently and creates fewer rejected precision components may reduce the total part cost even if its raw stock is slightly more expensive.
How Tuofa CNC Germany Selects Nylon and Acetal for CNC Parts
At Tuofa CNC Germany, the choice between nylon and acetal starts with the application rather than the material name alone.
For a precision bushing or gear, dimensional stability, shaft clearance, humidity and operating temperature are considered before recommending a material.
For a heavily loaded roller or wear component, impact resistance and toughness may become more important.
During CNC machining, sharp tooling and controlled workholding are used to reduce heat and deformation. Large material removal may be divided between rough and finish machining when dimensional stability is critical.
For nylon components, environmental conditions are especially important. Buyers should identify whether the part will operate dry, outdoors, underwater or in a high-humidity environment.
This information can be just as important as the nominal machining tolerance.
FAQs About Nylon vs Acetal
Is Acetal Easier to Machine Than Nylon?
Generally yes. Acetal’s stiffness, chip behavior and dimensional stability make it one of the easiest engineering plastics to CNC machine accurately. Nylon can also be machined successfully but tends to be more flexible and moisture sensitive.
Which Material Holds Tighter Tolerances?
Acetal generally provides better dimensional stability and is easier to use for tight-tolerance components, particularly when environmental humidity changes.
Which Is Better for Gears?
Nylon is useful for tough, impact-resistant gears, while acetal is frequently preferred for precision gears requiring stable tooth geometry and low friction.
Which Is Better for Bushings?
Acetal is often preferred when shaft clearance must remain consistent. Nylon can be advantageous for heavy loads and impact, but moisture swelling must be included in the clearance design.
Does Nylon Expand When It Gets Wet?
Yes. Nylon absorbs moisture and can swell. The amount depends on the specific polyamide, part geometry, humidity, temperature and exposure duration.
Does Acetal Absorb Water?
Yes, but much less than conventional nylon. Its low water absorption is one reason POM is widely used for precision mechanical parts.
Is Delrin Nylon?
No. Delrin is a brand of acetal homopolymer, or POM-H. Nylon belongs to the polyamide family.
Can Nylon Replace Delrin?
Sometimes, but not automatically. The replacement may change moisture sensitivity, friction, impact behavior, stiffness and dimensional stability. The application should be reviewed before substitution.
Can Acetal Replace Nylon?
Acetal can replace nylon in some gears, bushings and precision mechanical components, particularly where dimensional stability is important. It may not provide the same impact response or other properties required from a particular nylon grade.
Why Did My Nylon Part Go Out of Tolerance After Machining?
Possible causes include moisture absorption, temperature change, residual stress and deformation caused by machining or workholding. Inspection conditions and service conditions should therefore be considered when troubleshooting dimensional change.
결론
Nylon and acetal are both excellent engineering plastics, but they solve different manufacturing problems.
Nylon is usually the stronger choice when toughness, impact resistance, fatigue performance and heavy-duty wear are priorities. Acetal becomes more attractive when a part requires stable dimensions, low friction, good machinability and minimal sensitivity to humidity.
For CNC machined components, this distinction can determine whether a part continues to function after leaving the machine shop. A nylon bore may change as the material absorbs moisture, while an acetal component generally maintains its geometry more consistently.
Material selection should therefore consider more than strength and price. Engineers should define the actual nylon or POM grade, loading condition, operating temperature, humidity, wear requirement, expected service life and realistic tolerance before choosing between nylon and acetal.
When these conditions are understood, both materials can provide reliable and economical alternatives to metal for gears, bushings, bearings, rollers and other precision mechanical components.