Reference Chart

CNC Plastics & Polymer Grades Chart

Q: What is the best plastic for CNC machined gears?

Delrin (Acetal/POM) is the best plastic for CNC machined gears. It has low friction, high stiffness, and excellent machinability. It holds tight tolerances and resists wear. Nylon 6/6 is also a good choice when you need more impact strength.

Q: What is the difference between PEEK and Delrin?

PEEK handles much higher temperatures than Delrin. PEEK works up to 480 degrees Fahrenheit. Delrin tops out at 180 degrees. PEEK is also stronger and resists more chemicals. But PEEK costs much more and is harder to machine. Use Delrin for general parts. Use PEEK when you need high heat or chemical resistance.

Q: Which CNC plastics are FDA food-safe?

HDPE, Delrin (Acetal), UHMW-PE, and PTFE (Teflon) are all FDA compliant for food contact. HDPE is the most common choice for food-safe CNC parts like cutting boards and conveyor guides. Always check with your resin supplier for the exact FDA-compliant grade.

Q: Do any CNC plastics absorb moisture?

Yes. Nylon 6/6 absorbs the most moisture of common CNC plastics. It can soak up 2 to 3 percent of its weight in water. This causes parts to swell and change size. Delrin, PEEK, and UHMW absorb very little moisture. If your part will be in a wet area, pick a low-absorption plastic.

Compare 12 common engineering plastics used in CNC machining. This chart shows tensile strength, max service temp, machinability, and typical uses. Pick the right plastic for your next project.

Material ▲	Trade Name ▲	Tensile (ksi) ▲	Flexural Mod (ksi) ▲	Max Temp (°F) ▲	Machinability ▲	FDA Safe ▲	Common CNC Uses ▲
Acetal (POM)	Delrin	10	410	180	Excellent	Yes	Gears, bushings, fixtures, low-friction slides
PEEK	Victrex / KetaSpire	16	600	480	Good	No	Aerospace brackets, medical implants, semiconductor fixtures
Nylon 6/6	Zytel / Nylatron	12	410	220	Good	No	Gears, bearings, structural brackets, rollers
UHMW-PE	Tivar / Lennite	5.8	110	180	Fair	Yes	Wear strips, conveyor guides, liners
Polycarbonate	Lexan / Makrolon	9.5	345	270	Good	No	Clear housings, shields, sight glasses
Acrylic (PMMA)	Plexiglas / Lucite	10	450	160	Good	No	Optical parts, display panels, light guides
PTFE	Teflon	3.5	80	500	Fair	Yes	Seals, bearings, electrical insulators, gaskets
PEI	Ultem	15.2	480	340	Good	No	Aerospace connectors, electrical housings, test sockets
G-10/FR-4	Garolite	40	550	280	Good	No	Electrical insulators, fixtures, PCB tooling plates
PVC	Type I PVC	7.5	400	140	Good	No	Chemical tanks, valve bodies, duct fittings
HDPE	High-Density PE	4.5	145	180	Good	Yes	Food-safe parts, cutting boards, tank liners
PAI	Torlon	21	630	500	Difficult	No	High-load bearings, seals, aerospace wear parts

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Tips for Machining Plastics

Use sharp, polished cutting tools. Dull tools create heat and melt the plastic.
Keep feed rates high enough to make chips, not dust. Small feeds cause rubbing and heat buildup.
Avoid coolant on acrylic and polycarbonate. It can cause stress cracks. Use compressed air instead.
UHMW and PTFE are soft and flexible. Use light clamping pressure and support the part well.
Clear chips often. Plastic chips can re-weld to the cut surface if they stay in the cut zone.
PEEK and Torlon need slow speeds and steady feeds. They are strong but sensitive to heat.
G-10/FR-4 creates fine glass dust. Always use dust collection and wear a respirator.
FDA-safe grades must come from certified resin lots. Ask your supplier for the certificate.

Frequently Asked Questions

What is the best plastic for CNC machined gears?

Delrin (Acetal/POM) is the top pick for CNC gears. It has low friction, high stiffness, and cuts very clean. It holds tight sizes well and wears slowly. Nylon 6/6 is also a solid choice when you need more impact strength. Both are easy to machine on standard CNC mills and lathes.

What is the difference between PEEK and Delrin?

PEEK handles much more heat than Delrin. PEEK works up to 480 degrees. Delrin tops out at 180 degrees. PEEK is also stronger and fights off more chemicals. But PEEK costs a lot more and takes more care to machine. Use Delrin for general parts. Use PEEK when you need high heat or harsh chemical contact.

Which CNC plastics are FDA food-safe?

HDPE, Delrin, UHMW-PE, and PTFE (Teflon) all meet FDA rules for food contact. HDPE is the most popular pick for food-safe CNC parts like cutting boards and guides. Always ask your resin supplier for the FDA-grade certificate to make sure you have the right lot.

Do any CNC plastics absorb moisture?

Yes. Nylon 6/6 soaks up the most water of the common CNC plastics. It can take in 2 to 3 percent of its weight. This makes parts swell and change size. Delrin, PEEK, and UHMW absorb very little water. If your part will get wet, pick a plastic with low water uptake.

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CNC Plastics & Polymer Grades Chart

Tips for Machining Plastics

Frequently Asked Questions

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