⚪ DELRIN / ACETAL
Delrin & Acetal Parts for Lexington, KY Manufacturing
If a plastic part in Lexington has to slide, mesh, snap, or hold a precise dimension, odds are it is acetal. Sold most famously under DuPont's Delrin brand, acetal is the engineering plastic that automotive and equipment shops reach for when they need metal-like rigidity, low friction, and tight tolerances at a fraction of metal's cost and weight. The practical choice almost always comes down to homopolymer versus copolymer, a distinction that changes machinability, chemical resistance, and how the part behaves over time.
ISO 9001IATF 16949
The Precision Plastic Behind Lexington's Moving Parts
Acetal, technically polyoxymethylene or POM, is one of the most machinable and dimensionally stable engineering plastics available. It has high stiffness, excellent fatigue resistance, a naturally low coefficient of friction, good wear properties, and resistance to fuels, solvents, and many chemicals. Those traits make it the default material for gears, bearings, bushings, rollers, cams, snap-fit fasteners, and precision mechanical parts throughout central Kentucky's automotive and equipment supply chains.
For a buyer, acetal hits a sweet spot. It machines faster and cleaner than most plastics, holds tight tolerances, and costs far less than high-performance polymers like PEEK while still behaving in a metal-like way for moderate loads and temperatures. It is the obvious upgrade from nylon when a part needs better dimensional stability and lower moisture absorption, and the obvious choice over metal when weight, corrosion, noise, or self-lubrication matter.
The one thing buyers must get right is the polymer type. 'Acetal' on a print is ambiguous, and the difference between homopolymer and copolymer is real enough to change part performance, so the spec should always state which one.
Homopolymer (Delrin) vs Copolymer
Acetal homopolymer, the family DuPont sells as Delrin, has slightly higher tensile strength, stiffness, and hardness than copolymer, plus better creep resistance and fatigue endurance. That makes it the choice for high-load mechanical parts, precision gears, and components where maximum stiffness and surface hardness matter. Its one notable quirk is a tendency toward a small amount of internal centerline porosity in extruded rod, which can occasionally show on the centerline of a turned part, something to discuss with the supplier for critical parts.
Acetal copolymer has marginally lower mechanical properties but better resistance to hot water, strong bases, and certain chemicals, and it does not suffer the centerline porosity issue, giving more uniform structure through the cross-section. It is often preferred for parts exposed to hot water or aggressive chemistry, and for thicker sections where porosity would be a concern.
Delrin 150 is a specific, widely stocked homopolymer grade, a general-purpose, high-molecular-weight acetal used broadly for machined mechanical parts. When a Lexington buyer specifies Delrin 150, they are getting a known, repeatable homopolymer with predictable machining and mechanical behavior. The practical guidance: default to homopolymer (Delrin) for stiffness and load, switch to copolymer for hot-water or chemical exposure and for thick cross-sections.
Machining, Molding, and What to Confirm
Acetal is a pleasure to machine. It cuts cleanly with sharp tooling, produces manageable chips, and holds tight tolerances, which is why it is a favorite for turned and milled precision parts. The main cautions are heat and stress: acetal has a high coefficient of thermal expansion, so parts grow and shrink noticeably with temperature, and machinists must account for that when holding tight tolerances, often letting parts stabilize at room temperature before final measurement. Aggressive machining can also release internal stresses, so annealing is sometimes used for the tightest-tolerance work.
For production volumes, acetal injection molds extremely well, producing precise gears, clips, and mechanical parts at high rates, which is why so much automotive interior and mechanical hardware in the region is molded acetal. The decision between machining and molding follows volume and geometry as it does with most plastics.
When sourcing in the Lexington corridor, confirm the supplier states homopolymer versus copolymer clearly, understands acetal's thermal expansion when quoting tight tolerances, and for any food-contact or medical application, can supply the appropriate FDA-compliant or medical grade with documentation. ManufacturingBase lets buyers compare machining and molding shops and filter by the certifications their end use requires.
Frequently Asked Questions
They are closely related but not interchangeable terms, and the distinction matters when you spec a part. 'Acetal' is the generic name for the polymer family polyoxymethylene (POM), and it comes in two types: homopolymer and copolymer. 'Delrin' is DuPont's brand name for their acetal homopolymer specifically. So all Delrin is acetal, but not all acetal is Delrin, much of the acetal on the market is copolymer made by other manufacturers. The practical differences: homopolymer (Delrin) has slightly higher tensile strength, stiffness, hardness, and fatigue and creep resistance, making it the choice for high-load mechanical parts and precision gears. Copolymer has marginally lower mechanical properties but better resistance to hot water and strong bases, and it avoids the small centerline porosity that homopolymer extruded rod can show. When a print just says 'acetal,' it is ambiguous, and a good supplier will ask which type you want. Always specify homopolymer or copolymer (or a named grade like Delrin 150) so you get consistent, predictable part behavior rather than whatever the shop happens to stock.
The decision turns on load, chemical exposure, and section thickness. Choose homopolymer (Delrin family) when stiffness, surface hardness, fatigue resistance, and creep resistance under load are the priority, which covers most precision gears, high-load bearings, cams, and structural mechanical parts. Homopolymer's slightly higher mechanical properties make it the default for demanding moving parts, and that is why it dominates Lexington's automotive and equipment mechanical work. Choose copolymer when the part will see hot water, steam, or strong bases, because copolymer resists those conditions better and will not degrade the way homopolymer can in hot aqueous or alkaline environments. Also lean toward copolymer for thick cross-sections, because homopolymer extruded rod can develop a small amount of centerline porosity that may appear on the center of a turned part, while copolymer has more uniform structure through the section. If your application is general-purpose, room-temperature, and not chemically aggressive, either works and homopolymer's mechanical edge usually wins. State the chosen type explicitly on your print, and discuss centerline porosity with your supplier for any critical part turned from large-diameter rod.
Acetal has a relatively high coefficient of thermal expansion compared to metals, meaning it grows and shrinks noticeably with temperature changes, and it can also release internal stresses when material is removed during machining. Both effects threaten tight tolerances. The thermal expansion issue shows up two ways: a part machined while warm from cutting will measure differently once it cools to room temperature, and a finished part will change size in service if its operating temperature differs from the shop. Experienced machinists handle this by minimizing heat buildup with sharp tooling and appropriate speeds, by letting parts stabilize at a controlled room temperature before taking final measurements, and by designing and inspecting to the temperature the part will actually see in use. The internal-stress issue is handled with annealing: heating the stock or rough-machined part through a controlled cycle relieves locked-in stresses so the part does not warp or move after final machining. For the tightest-tolerance acetal work, a shop may rough-machine, anneal, then finish-machine. When sourcing near Lexington, confirm your shop accounts for thermal expansion in its tolerancing and anneals when the tolerance band demands it.
For a large class of moderate-load, moderate-speed applications, yes, and that is exactly why acetal is so common in Lexington's automotive and equipment supply chains. Acetal offers a naturally low coefficient of friction and good wear resistance, so it can run as a self-lubricating gear or bushing without grease in many applications, which simplifies assembly and maintenance. It is far lighter than metal, will not corrode, runs quieter, and damps vibration better, and it costs much less than high-performance plastics. Its high stiffness and excellent fatigue resistance let it transmit real mechanical loads while holding tight tolerances. The limits are temperature and load: acetal softens and loses strength as temperature rises (continuous service generally stays well below 100 C), and it cannot match metal for very high loads, high speeds with heat generation, or extreme stiffness requirements. It also expands more with temperature than metal, which must be designed around in close-fitting gear and bushing applications. The practical answer most engineers reach: use acetal to replace metal gears, bushings, rollers, and cams in light to moderate duty where weight, corrosion, noise, or self-lubrication matter, and stay with metal for high-load, high-temperature, or high-precision-under-heat duty.
Yes. Acetal is available in grades certified for food contact and medical use, and Lexington's mix of medical-device manufacturing and general engineering shops supports sourcing them. FDA-compliant acetal grades meet the requirements for repeated food contact and are used in food-processing equipment, beverage components, and similar applications, while medical-grade acetal carries additional documentation and may meet USP Class VI or comparable biocompatibility testing for certain device applications. The important point for buyers is that compliance comes from the specific certified grade and its documentation, not from acetal generically, so you must specify the compliant grade on your print and require the supplier to provide the certification paperwork tracing the material lot. Acetal copolymer is often favored for hot-water and steam-cleaned food and medical applications because of its better hot-water resistance. When sourcing through ManufacturingBase, filter for shops with the relevant quality system (ISO 13485 for medical-device work), specify the exact FDA or medical grade you need, and require lot traceability and certification documentation up front. A shop experienced in regulated work will handle this routinely; confirm the capability before placing the order.
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Last updated: July 2026
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