Comparison
Acetal vs nylon
Two strong, machinable plastics for gears, bushings and moving parts. How they differ, which parts suit each, and how they machine.
The main difference
The difference is water
On paper, the two are close in strength and stiffness. Acetal takes up very little water, so its size and stiffness stay the same in humid air, washdown or under water. Nylon keeps taking up moisture until it matches its surroundings.
As nylon takes up water, it
- Grows
- Its size increases slightly, which can tighten a bore or loosen a fit.
- Gets tougher
- It takes shock better, which helps in wet, heavy-duty service.
- Loses stiffness
- It gives a little more under load than it does dry.
In dry service, that rarely matters. In wet service, it can use up a close fit.
| Acetal | ||
|---|---|---|
| Copolymer | 0.20% | |
| Delrin® homopolymer | 0.25% | |
| Nylon | ||
| Cast nylon 6 | 0.6–1.2% | |
| Nylon 6/6 | 1.2% | |
Typical published values for unfilled grades. The lighter part of the cast nylon bar is its range. Immersed for long periods, nylon 6/6 can take up as much as 8–9%.
What moves a part’s sizeProperties
Four common grades side by side
Each plastic comes in two grades you’ll see most often on drawings. Typical values, dry and unfilled.
| Nylon | Acetal | |||
|---|---|---|---|---|
| Property | Cast nylon 6 | Nylon 6/6 | Copolymer | Delrin® homopolymer |
| Tensile strength psi | 10,000–13,500 | 12,400 | 9,800 | 10,000 |
| Stiffness flexural modulus, psi | 420,000–500,000 | 410,000 | 370,000 | 420,000 |
| Impact strength notched Izod, ft-lb/in | 0.7–0.9 | 1.2 | 1.0 | 1.5 |
| Max continuous service in air, °F | 230 | 210 | 195 | 185 |
| Water uptake 24 h immersion | 0.6–1.2% | 1.2% | 0.20% | 0.25% |
| Stock sizes rod, tube and plate | Very large shapes | Standard sizes | Standard sizes | Standard sizes |
| Usually chosen for | Large sheaves, gears and wear parts from one piece. | Smaller strong parts, including ones that run warm. | General precise parts. Stable in hot water and cleaners, and consistent through thick stock. | Parts that need a little more stiffness and strength. |
Typical published values for natural, unfilled grades. Nylon’s values change as it takes up moisture. Filled grades differ.
-
Nylon
Cast nylon 6
- Tensile strength psi
- 10,000–13,500
- Stiffness flexural modulus, psi
- 420,000–500,000
- Impact strength notched Izod, ft-lb/in
- 0.7–0.9
- Max continuous service in air, °F
- 230
- Water uptake 24 h immersion
- 0.6–1.2%
- Stock sizes rod, tube and plate
- Very large shapes
- Usually chosen for
- Large sheaves, gears and wear parts from one piece.
-
Nylon
Nylon 6/6
- Tensile strength psi
- 12,400
- Stiffness flexural modulus, psi
- 410,000
- Impact strength notched Izod, ft-lb/in
- 1.2
- Max continuous service in air, °F
- 210
- Water uptake 24 h immersion
- 1.2%
- Stock sizes rod, tube and plate
- Standard sizes
- Usually chosen for
- Smaller strong parts, including ones that run warm.
-
Acetal
Copolymer
- Tensile strength psi
- 9,800
- Stiffness flexural modulus, psi
- 370,000
- Impact strength notched Izod, ft-lb/in
- 1.0
- Max continuous service in air, °F
- 195
- Water uptake 24 h immersion
- 0.20%
- Stock sizes rod, tube and plate
- Standard sizes
- Usually chosen for
- General precise parts. Stable in hot water and cleaners, and consistent through thick stock.
-
Acetal
Delrin® homopolymer
- Tensile strength psi
- 10,000
- Stiffness flexural modulus, psi
- 420,000
- Impact strength notched Izod, ft-lb/in
- 1.5
- Max continuous service in air, °F
- 185
- Water uptake 24 h immersion
- 0.25%
- Stock sizes rod, tube and plate
- Standard sizes
- Usually chosen for
- Parts that need a little more stiffness and strength.
Conditions
Which way it leans
How a part runs usually points to one or the other. General guidance: if your drawing names the plastic, we machine to it.
Usually nylon when
- Dry, heavily loaded wear
- Dry, it outwears acetal, especially in oil- or MoS₂-filled grades.
- Large parts and thick sections
- Cast nylon comes in large rod, tube and plate, so big sheaves and gears can be machined from one piece.
- The part runs warmer
- It’s rated to about 210–230°F continuous, against 185–195°F for acetal.
- It runs against steel rope or chain
- It’s gentle on the mating metal and takes shock loads well.
Usually acetal when
- Wet service, washdown or humid air
- It takes up very little water, so it keeps its size and stiffness.
- Close fits and bores that must stay put
- Its size doesn’t drift with the humidity after machining.
- Small, precise parts
- It cuts cleanly into threads, small bores and fine gear teeth.
- Hot water and alkaline cleaners
- Copolymer acetal holds up to them better than nylon.
Both
Food lines
Both come in food-contact and metal-detectable grades. Compliance comes with the grade’s supplier documentation.
Parts
Parts in each
The plastic each part is most often made in, and what tips the choice. We machine any of these in either plastic, or another one, to your drawing.
| Part | Usually | What tips it |
|---|---|---|
| Sheaves | Nylon | Tough, quiet and gentle on wire rope and cable. Large sheaves come from one piece of cast nylon. |
| Bearing blocks | Nylon | Cast nylon comes in the thick sections large blocks need, and carries a shaft quietly. |
| Timing gears | Either | Cast nylon for large gears and shock loads. Acetal for small, precise gears and wet service. |
| Sprockets | Either | Nylon for heavier chain and shock loads. Acetal for smaller sprockets and wet service. |
| Bushings | Either | Filled nylon for dry, heavy loads. Acetal for wet or submerged bushings and close fits. |
| Rollers | Either | Nylon to carry heavy loads quietly. Acetal for a hard surface that stays round and to size when wet. |
| Wear rings | Either | Filled nylon for sliding against metal. Acetal where the ring runs wet and must hold its size. |
| Pistons | Either | Nylon where the piston takes shock. Acetal to hold groove and bore sizes. |
| Spacers | Either | Nylon for general duty. Acetal where the length must hold in wet service. |
| Washers | Either | Nylon for general duty. Acetal for thin washers that must stay flat and to size. |
| Plungers | Acetal | Stiff and slick in a bore, and it holds its size when wet. |
| Spools | Acetal | Machines cleanly into fine lands and grooves that must hold their size. |
| Housings | Acetal | Clean bores, pockets and threads that stay where the drawing puts them. |
In our Aurora shop
How they machine
We machine both every day. Acetal is one of the easiest plastics to machine; nylon takes more care, during the cut and after it.
Acetal
Usually toward the tighter end of our range
- Under the cutter
- Free-cutting, with short, clean chips.
- Detail
- Holds threads, small bores and fine gear teeth.
- After the cut
- Stays to size, wet or dry.
What we do
We keep thin walls and bores cool as we cut, so they hold shape and size, and deburr every edge and bore.
Nylon
Where it lands depends on how wet the part runs
- Under the cutter
- Tougher and gummier, with stringy chips and burrs.
- Detail
- Holds features well, with more care at thin walls and edges.
- After the cut
- Can move as it takes up moisture.
What we do
We deburr edges and bores, allow for moisture on close fits, and confirm the critical dimensions with your quote.
Questions
Acetal and nylon FAQs
Something else? Call (630) 904-2525.
Yes. We machine the part in the plastic you choose. If the drawing leaves it open, we’ll suggest suitable plastics with your quote.
Standard grades are similar in price. For large parts, cast nylon usually costs less than acetal. The price of a machined part depends mostly on the machining.
Delrin® is a well-known brand of acetal homopolymer, and many buyers use the name for any acetal. If your drawing specifies Delrin, we machine the part in Delrin. Delrin® is a registered trademark; CDS is not affiliated with its owner.
Acetal machiningHave a part in acetal or nylon?
Send a drawing, a sample or the worn part. We machine in either plastic, and suggest one with your quote if the drawing leaves it open.