⚪ DELRIN / ACETAL

Delrin & Acetal Machining in Boise, ID

If a Boise part needs to slide, mesh, or snap without binding, odds are it is machined from Delrin or acetal. This semi-crystalline polymer family delivers the low friction, high stiffness, excellent machinability, and dimensional stability that make it the default for gears, bushings, fittings, and precision mechanical parts across the Treasure Valley. The trick is knowing when to spec Delrin homopolymer versus an acetal copolymer, and finding a shop that machines it to the tight tolerances these parts demand.

ISO 9001ISO 13485

Why Acetal Dominates Precision Polymer Parts

Acetal, the polymer family that includes DuPont's Delrin brand, hits a sweet spot of properties that few plastics match. It is stiff and strong yet machines like a dream, holds tight tolerances, offers a low coefficient of friction with good wear resistance, resists moisture absorption, and stays dimensionally stable across a useful temperature range. For Boise mechanical designers, that combination makes it the obvious choice for moving parts: gears, cams, bushings, rollers, and bearings that need to run smoothly without lubrication. Its low moisture absorption is a quiet but important advantage over nylon. Nylon swells as it absorbs water, shifting dimensions and degrading tight-tolerance fits; acetal stays put. For Treasure Valley parts that must hold precise dimensions in humid or wet service, fittings, manifolds, valve components, acetal is the more reliable choice. Acetal also machines faster and cleaner than almost any other engineering plastic. It produces clean chips, takes fine surface finishes, and lets Boise shops hold tolerances in the low thousandths of an inch on turned and milled features. That machinability keeps part cost down, which is part of why acetal is so widely specified for production mechanical components.
01

Delrin Homopolymer vs Acetal Copolymer

The acetal family splits into two chemistries, and the difference matters for demanding parts. Delrin homopolymer, including the Delrin 150 grade, offers slightly higher tensile strength, stiffness, and surface hardness, plus better creep resistance and fatigue performance. It is the choice for highly loaded mechanical parts, precision gears, and components where maximum stiffness and strength carry the day. Delrin 150 is a medium-viscosity general-purpose homopolymer grade widely stocked as rod and plate. Acetal copolymer trades a small amount of peak mechanical performance for better chemical resistance, particularly to hot water and alkaline environments, and improved long-term thermal stability. Critically, copolymer has a more uniform internal structure and is less prone to the centerline porosity that can occur in the core of large homopolymer sections. For parts machined from large-diameter stock, or parts that must seal or run in hot or chemically aggressive service, copolymer is often the safer pick. The practical guidance for Boise buyers: for highly loaded gears and stiff structural parts, lean Delrin homopolymer; for parts from thick stock, sealing applications, or hot-water and chemical exposure, lean copolymer. For many general bushings and brackets, either works and availability or cost decides. Tell the supplier the load, environment, and stock size and they will confirm the right chemistry.

02

Holding Tolerance and Avoiding Surprises

Acetal machines exceptionally well, but tight-tolerance work still demands attention to thermal expansion and internal stress. Acetal has a relatively high coefficient of thermal expansion compared to metals, so a part measured warm off the machine reads different cold, and parts running across a temperature range need that expansion designed into the fit. For Boise precision work, inspecting at controlled temperature and accounting for expansion in the print prevents fits that bind or rattle in service. Internal stress matters on precision parts machined from large stock. As material is removed, residual stress can release and shift dimensions, so for the tightest work shops rough machine, stress relieve via a controlled anneal, then finish machine. This is less critical than for PEEK but still worth specifying on close-tolerance gears and bearings. Centerline porosity in large homopolymer sections is another reason to consider copolymer or to source from billet sized to keep the core out of critical features. Finish and inspection round out a good acetal part. Acetal takes a fine machined finish and can be polished where low friction matters, and a shop with real quality-inspection capability will verify gear geometry, bore size, and critical dimensions before shipping. For medical-device acetal parts, ISO 13485 and material traceability apply, so match the certification to the application up front.

Frequently Asked Questions

Delrin is a brand name, DuPont's trade name for acetal homopolymer, while acetal is the generic polymer family that includes both homopolymer and copolymer chemistries. So all Delrin is acetal, but not all acetal is Delrin. The meaningful technical distinction is between homopolymer and copolymer. Homopolymer, including grades like Delrin 150, offers slightly higher tensile strength, stiffness, surface hardness, creep resistance, and fatigue performance, making it the choice for highly loaded mechanical parts and precision gears. Copolymer trades a small amount of peak mechanical performance for better chemical resistance, especially to hot water and alkaline environments, improved long-term thermal stability, and a more uniform internal structure that resists the centerline porosity sometimes found in the core of large homopolymer sections. For Boise buyers, the practical rule is to lean homopolymer for highly loaded gears and maximum stiffness, and copolymer for parts machined from thick stock, sealing applications, or hot and chemically aggressive service. Tell your supplier the load, environment, and stock size and they will recommend the right chemistry.
Choose acetal when dimensional stability and tight tolerance matter, especially in moist or wet service. The key differentiator is moisture absorption: nylon absorbs water and swells, shifting dimensions and loosening or tightening precision fits over time, while acetal absorbs very little moisture and stays dimensionally stable. For Treasure Valley parts that must hold precise dimensions in humid or wet environments, fittings, manifolds, valve components, and bushings, acetal is the more reliable choice. Acetal is also stiffer, machines faster and cleaner, and holds tighter tolerances, which lowers part cost on production mechanical components. Nylon still has its place where its higher toughness, impact resistance, and abrasion resistance are the priority, or where some moisture absorption is acceptable. But for gears, bearings, and precision parts that must run smoothly and hold tolerance without dimensional drift, acetal usually wins. The decision comes down to whether your part prioritizes dimensional stability and machinability, favoring acetal, or maximum toughness and impact resistance, where nylon may edge ahead.
Yes, acetal is one of the most machinable engineering plastics and Boise precision shops routinely hold tolerances in the low thousandths of an inch on turned and milled features. It produces clean chips, takes fine surface finishes, and machines fast, which is part of why it is so widely specified. That said, two factors require attention on the tightest work. First, acetal has a relatively high coefficient of thermal expansion compared to metals, so a part measured warm off the machine reads differently when cold, and parts running across a temperature range need that expansion designed into the fit. Good shops inspect at controlled temperature and account for expansion in the print. Second, internal stress in material machined from large stock can release as material is removed, shifting dimensions, so for the closest-tolerance gears and bearings shops rough machine, stress relieve with a controlled anneal, then finish machine. A shop with genuine quality-inspection capability verifies gear geometry, bore size, and critical dimensions before shipping, which is what you want for precision acetal work.
Centerline porosity is a known issue in the core of large-diameter acetal homopolymer stock. During the extrusion and cooling of thick rod, the center cools and solidifies last, and the material can develop voids or low-density regions along the centerline. If a machined part exposes that core in a critical feature, a sealing surface, a pressure boundary, or a precision bore, the porosity can cause leaks or dimensional problems. There are two reliable ways to avoid it. First, specify acetal copolymer instead of homopolymer for parts machined from large stock; copolymer has a more uniform internal structure and is far less prone to centerline porosity. Second, size the stock so the critical features stay out of the centerline region, or machine the part from billet selected to keep the core away from sealing and load-bearing surfaces. For Boise parts that must seal or hold pressure, raise this with your supplier at quote time so they select the right chemistry and stock size. An experienced shop flags porosity risk before machining rather than discovering it at inspection or in the field.
Acetal is used in medical devices, but suitability depends on the specific grade and application, and the supplier requirements differ from general industrial work. Medical-grade acetal is available and used for instrument components, handles, and mechanical parts where its stiffness, low friction, and dimensional stability are valuable. For medical-device parts, you need a supplier with an ISO 13485 quality system and full material traceability, since the device industry requires documented certification of the material and controlled processes, not just a part that meets the print. A general ISO 9001 machine shop can machine acetal geometrically, but medical work should go to a shop holding ISO 13485. Note that not every application is a fit, some implant or long-term-contact uses require materials with specific biocompatibility approvals, and certain sterilization methods affect acetal, so confirm the grade is rated for your sterilization process. When sourcing in Boise, specify the medical application, sterilization method, and certification requirement in the RFQ, and filter suppliers for ISO 13485 so the part lands at a qualified shop.

Related Pages

Delrin / Acetal in NampaDelrin / Acetal CNC MachiningDelrin / Acetal Swiss MachiningDelrin / Acetal EDM / Wire EDMDelrin / Acetal Laser CuttingDelrin / Acetal Stamping

Last updated: July 2026

Find Delrin / Acetal Manufacturers in Boise, ID

Search verified Boise shops that work in Delrin / Acetal.

Search Manufacturers →Get Your Shop Listed (Free)

No logins. No email gates. Just results.