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

NBR (Nitrile) Metric O-Rings (ISO 3601)

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

NBR (Nitrile) Metric O-Rings (ISO 3601) are supplied to acrylonitrile-butadiene rubber, typically 70 Shore A. Corrosion behaviour is good resistance to mineral oil, grease and hydraulic fluid; poor in ozone and weathering, the material is non-magnetic, and the usable service range is approx. -30 °C to +100 °C. In practice this grade is the default elastomer for oil and hydraulic sealing.

Grade: acrylonitrile-butadiene rubber, typically 70 Shore A
Corrosion resistance: Good resistance to mineral oil, grease and hydraulic fluid; poor in ozone and weathering
Magnetic response: Non-magnetic
Service temperature: approx. -30 °C to +100 °C

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

NBR (Nitrile) (acrylonitrile-butadiene rubber, typically 70 Shore A) is the default elastomer for oil and hydraulic sealing. When metric o-rings (iso 3601) are specified in this grade, the dimensions remain per ISO 3601-1 (fluid power — O-rings, inside diameters and cross-sections); the material determines corrosion behavior (good resistance to mineral oil, grease and hydraulic fluid; poor in ozone and weathering) and the service temperature range (approx. -30 °C to +100 °C). Both are covered below with the size table.

Why Choose NBR (Nitrile) for Metric O-Rings (ISO 3601)

The default elastomer for oil and hydraulic sealing. For metric o-rings (iso 3601), this matters when good resistance to mineral oil, grease and hydraulic fluid; poor in ozone and weathering is the primary requirement.

Mechanical & Physical Properties

Grade designation	acrylonitrile-butadiene rubber, typically 70 Shore A
Magnetic response	Non-magnetic
Service temperature	approx. -30 °C to +100 °C
Corrosion characteristic	Good resistance to mineral oil, grease and hydraulic fluid; poor in ozone and weathering

Galvanic & Galling Considerations

Galvanic and galling behavior do not apply to metric o-rings (iso 3601) in NBR (Nitrile) — 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 FKM where temperature or chemical exposure is higher, or EPDM where the medium is water, steam or brake fluid rather than oil. 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 NBR (Nitrile)

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

Customize the parameters below — every spec field is editable, and the drawing redraws to match the values you choose. Changing the size will snap the other fields to that size's standard values; you can then override any individual value.

Sends the selected values to the quote form below.

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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

When should I move from acrylonitrile-butadiene rubber, typically 70 Shore A 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 NBR (Nitrile) 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.

Which finish is best for outdoor Metric O-Rings (ISO 3601)?

For outdoor service in steel, hot-dip galvanizing gives the longest life; zinc-flake (Geomet/Delta-Tone family) gives a thinner film with excellent salt-spray performance; standard zinc plating is the lowest-cost option for general indoor / shielded outdoor use.

What's the service temperature limit for NBR (Nitrile)?

The practical service range is approx. -30 °C to +100 °C.

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.