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Machined Delrin and Acetal Parts by Application

Acetal earns its place where parts slide, turn or carry load for years and have to keep their size. These are the applications buyers send most often and what each one puts on the drawing.

Get matched with an acetal shopSee parts by application
Low frictionRuns against steel with little or no lubricant
Low water uptakeAbout 0.2 percent in 24 h, so dimensions hold when wet
Creep resistanceKeeps its shape under a held load
Electrical insulatorDoes not conduct, holds size

Typical parts, grades and drawing callouts

The grades and callouts listed are the ones most often seen in each application, not a rule. Your drawing decides.

ApplicationTypical partsCommon gradeCallouts to expect
Gears and power transmissionSpur and helical gears, worm wheels, sprockets, camsHomopolymer, PTFE-filled for dry runningGear data, backlash, mating material
Bearings and bushingsPlain bushings, thrust washers, slide blocks, rollersHomopolymer, PTFE-filledBore tolerance after press fit, PV limit, running clearance
Conveying and packagingStar wheels, timing screws, guide rails, wear stripsCopolymer, food contact gradesFood contact statement, flatness, edge breaks
Fluid handlingValve seats, pump impellers, manifold blocks, fittingsCopolymer for hot water, homopolymer for stiffnessSealing face finish, thread spec, media and temperature
Electrical and electronicsInsulators, spacers, terminal blocks, test fixturesUnfilled acetal, ESD grades for handlingSurface resistivity, flatness, hole positions
Medical and lab equipmentInstrument handles, housings, cams, fixture partsCopolymer, medical-grade POM where requiredMaterial traceability, cleaning method, biocompatibility if patient contact
Automotive and mobilityPrototype clips, fuel system parts, gear trains, bushingsHomopolymer or copolymer per OEM specOEM material spec, PPAP or first article report

Grade details and properties are on the acetal grades page.

Application by application

What changes from one use to the next and what to mention on the RFQ so the right shops see it.

  • GearsMachined acetal gears run quietly against steel or nylon and need no grease in light duty. Tooth form, module or diametral pitch, quality class and the mating gear belong on the drawing. Machined acetal gear design
  • Bushings and bearingsAcetal bushings suit low to moderate speeds and loads. Press fits close the bore, so the drawing should state the bore size after installation, not just before. Bushing design
  • Conveying and packagingStar wheels, timing screws and guide rails are often cut from plate in copolymer for washdown resistance. Large flat parts need stress-relieved stock to stay flat.
  • Fluid handlingValve seats, impellers and manifold blocks in cold or warm water. Copolymer handles hot water and alkaline cleaners better than homopolymer. Sealing faces carry the only fine-finish callout.
  • ElectricalInsulating spacers, terminal blocks and test fixtures where the part must not conduct and must hold hole positions. ESD grades cover electronics handling.
  • Medical and labInstrument handles, housings and fixture parts in low volumes. If the part touches a patient, the resin grade and its biocompatibility file matter more than the machining.
  • AutomotivePrototype and bridge parts machined in the production resin before tooling is cut, so fit and function can be tested early. Machining vs moulding

What to put on the RFQ for each application

A shop that already makes your kind of part reads these as routine. Leaving them out makes quotes hard to compare.

  • Grade and substitutionHomopolymer or copolymer, filled or not, and whether an equivalent is acceptable.
  • Service conditionsTemperature, media, load and whether the part runs dry. They decide the grade more than anything else.
  • Critical featuresBores, gear teeth and sealing faces, with the tolerance and the temperature at which they are measured. See machining processes.
  • DocumentsMaterial certificate, food contact statement or a first article report.
  • QuantityPrototype quantity and expected annual volume. Lead times explained

Questions about acetal applications

Why use acetal instead of nylon for gears and bushings?

Acetal absorbs far less water than nylon, so its dimensions stay put in humid or wet service. It is also stiffer and has lower friction against steel. Nylon keeps more toughness under impact and at low temperatures.

Is machined Delrin safe for food contact?

Some grades are. Food contact depends on the specific resin and its compliance documents, such as FDA 21 CFR or EU 10/2011, not on the word Delrin. Ask for the compliance statement for the exact stock the shop will use.

When should acetal parts be moulded instead of machined?

Machining suits prototypes and runs up to a few thousand pieces, or parts too thick for moulding. Above that, an injection mould usually pays for itself, provided the design is stable.

Can acetal parts be used outdoors?

Natural acetal degrades under long UV exposure, turning chalky and brittle. Black UV-stabilised grades last much longer outdoors. Say on the RFQ if the part will see sunlight.

Related pages

Background reading: polyoxymethylene on Wikipedia.

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