Seals · ISO 3601-1 (fluid power — O-rings, inside diameters and cross-sections)

PTFE Metric O-Rings (ISO 3601)

Temperature range, chemical and fluid compatibility, hardness and the full dimensional range for this compound.

PTFE Metric O-Rings (ISO 3601) are supplied to polytetrafluoroethylene (thermoplastic, not an elastomer). Corrosion behaviour is near-universal chemical resistance; no elastic recovery, so it is used as a back-up or energised seal, the material is non-magnetic, and the usable service range is approx. -200 °C to +260 °C. In practice this grade is chosen for chemical service and low friction rather than for elastic sealing.

Grade: polytetrafluoroethylene (thermoplastic, not an elastomer)
Corrosion resistance: Near-universal chemical resistance; no elastic recovery, so it is used as a back-up or energised seal
Magnetic response: Non-magnetic
Service temperature: approx. -200 °C to +260 °C

Property values are typical for the grade. Certified mechanical test data is available on request for production orders.

PTFE Metric O-Rings (ISO 3601) combine the dimensional form of ISO 3601-1 (fluid power — O-rings, inside diameters and cross-sections) with the material properties of grade polytetrafluoroethylene (thermoplastic, not an elastomer): near-universal chemical resistance; no elastic recovery, so it is used as a back-up or energised seal, non-magnetic, service range approx. -200 °C to +260 °C. This page summarizes the grade data, its corrosion behavior in service, the comparable grades, and the sizes supplied.

Why Choose PTFE for Metric O-Rings (ISO 3601)

Chosen for chemical service and low friction rather than for elastic sealing. For metric o-rings (iso 3601), this matters when near-universal chemical resistance; no elastic recovery, so it is used as a back-up or energised seal is the primary requirement.

Mechanical & Physical Properties

Grade designation	polytetrafluoroethylene (thermoplastic, not an elastomer)
Magnetic response	Non-magnetic
Service temperature	approx. -200 °C to +260 °C
Corrosion characteristic	Near-universal chemical resistance; no elastic recovery, so it is used as a back-up or energised seal

Galvanic & Galling Considerations

Galvanic and galling behavior do not apply to metric o-rings (iso 3601) in PTFE — the relevant compatibility questions are chemical: confirm the elastomer against the fluid, the temperature and any cleaning agents in service, and check the gland or groove dimensions give the intended compression on the section.

Comparable Grades

For metric o-rings (iso 3601), consider an energised or spring-loaded PTFE seal where recovery is required, or FKM where the chemistry allows an elastomer. Elastomer selection is decided by the medium, the temperature range and whether the seal is static or dynamic — not by strength.

Sizes of Metric O-Rings (ISO 3601) Available in PTFE

Cross-section (mm)	Typical inside-diameter range (mm)	Common compounds	Notes
1.0	1.0 u2013 20	NBR, FKM, EPDM, silicone	miniature and pneumatic
1.5	2.0 u2013 40	NBR, FKM, EPDM, silicone	small pneumatic and instrument
1.78	1.78 u2013 50	NBR, FKM, EPDM	nearest metric equivalent to the 1/16 in section
2.0	3.0 u2013 100	NBR, FKM, EPDM, silicone	general hydraulic and pneumatic
2.5	5.0 u2013 150	NBR, FKM, EPDM	general hydraulic
3.0	6.0 u2013 200	NBR, FKM, EPDM	general hydraulic
3.5	10 u2013 250	NBR, FKM	hydraulic
4.0	12 u2013 300	NBR, FKM	hydraulic and larger flanges
5.0	20 u2013 400	NBR, FKM	large flanges and covers
5.33	20 u2013 400	NBR, FKM	nearest metric equivalent to the 3/16 in section
6.0	25 u2013 500	NBR, FKM	large covers and housings

Technical Drawing

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Specification

Item / category Standard Size(s) Material / finish Quantity

Business Information

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Notes

Dimensions & Specifications (ISO 3601-1 (fluid power — O-rings, inside diameters and cross-sections))

Cross-section (mm)	Typical inside-diameter range (mm)	Common compounds	Notes
1.0	1.0 u2013 20	NBR, FKM, EPDM, silicone	miniature and pneumatic
1.5	2.0 u2013 40	NBR, FKM, EPDM, silicone	small pneumatic and instrument
1.78	1.78 u2013 50	NBR, FKM, EPDM	nearest metric equivalent to the 1/16 in section
2.0	3.0 u2013 100	NBR, FKM, EPDM, silicone	general hydraulic and pneumatic
2.5	5.0 u2013 150	NBR, FKM, EPDM	general hydraulic
3.0	6.0 u2013 200	NBR, FKM, EPDM	general hydraulic
3.5	10 u2013 250	NBR, FKM	hydraulic
4.0	12 u2013 300	NBR, FKM	hydraulic and larger flanges
5.0	20 u2013 400	NBR, FKM	large flanges and covers
5.33	20 u2013 400	NBR, FKM	nearest metric equivalent to the 3/16 in section
6.0	25 u2013 500	NBR, FKM	large covers and housings

Applications & Industries

Where Metric O-Rings are used, and what decides the specification in each case. Stocked from 1.0 to 6.0 (inside diameter).

Industries that specify Metric O-Rings

Hydraulics Port, cover and piston seals.
Pneumatics Cylinder and valve seals.
Food and beverage EPDM and silicone compounds.
Chemical plant FKM for aggressive media.
Hydraulics & pneumatics Static and dynamic sealing in cylinders and valve bodies.
Process & food equipment Sealing at joints that are cleaned and inspected.

Typical applications

specifying inside diameter, cross-section and compound together
matching the compound to the fluid and the temperature
checking the groove dimensions give the right squeeze
using a back-up ring at high pressure
sealing a joint against fluid or air pressure
excluding dust and moisture from a housing

Service conditions to specify against

Sealed joints: Used where the fixing has to keep water or air out as well as hold — the elastomer, not the fastener, decides service life.

Where to use something else

Do not substitute an NBR ring for an FKM one because the dimensions match; the size fits and the compound fails, which looks like a leak with no cause.

Full application guide: where Metric O-Rings are used, how to specify them, and the cases they are wrong for

Inside the plant

Manufactured in our own plant

This part is cold-formed, threaded, heat-treated and finished in-house. The stages below are where its class and finish are actually decided.

01

Cold heading

Wire rod is drawn to size and cold-formed into blanks. Forming rather than cutting keeps the grain flow continuous around the head, which is where a bolt is most likely to fail.

Head dimensions and under-head radius checked at set-up and per shift.
02

Thread rolling

Threads are rolled between hardened dies rather than cut. Rolled threads are stronger in fatigue than cut threads and hold pitch and flank angle far more consistently across a batch.

Go / no-go ring gauges to ISO 965 tolerance class 6g.
03

Heat treatment

Quench-and-temper brings carbon and alloy steel to the property class ordered — 8.8, 10.9 or 12.9 — with the furnace charge tracked so a finished lot can be traced back to it.

Core hardness and tensile tested per lot to ISO 898-1.
04

Surface treatment

Zinc, zinc-nickel, hot-dip galvanizing, black oxide, phosphate and Dacromet, selected against the service environment rather than against the price list.

Coating thickness and neutral salt spray hours to ISO 9227.

Frequently Asked Questions

Are PTFE Metric O-Rings (ISO 3601) magnetic?

PTFE Metric O-Rings (ISO 3601) are non-magnetic.

What corrosion resistance do PTFE Metric O-Rings (ISO 3601) offer?

PTFE Metric O-Rings (ISO 3601) provide near-universal chemical resistance; no elastic recovery, so it is used as a back-up or energised seal with a service range of approx. -200 °C to +260 °C.

When should I move from polytetrafluoroethylene (thermoplastic, not an elastomer) to class 8.8 for Metric O-Rings (ISO 3601)?

Step up to class 8.8 when the joint preload approaches the proof load of the current class. The higher class adds preload at the same diameter, often saving size and weight.

Is PTFE prone to hydrogen embrittlement?

Class 10.9 and above can be susceptible to hydrogen embrittlement when electroplated. Specify post-plating baking, or use mechanical-zinc / zinc-flake finishes which avoid the cathodic plating step.

How do I request a quotation?

Use the technical drawing on this page to pick the exact configuration, then submit it with the quote form. We respond within one business day.