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

What Are Metric O-Rings (ISO 3601) Used For?

Typical applications, the industries that specify metric o-rings (iso 3601), and how to choose the right size, material and finish for the joint.

Metric O-Rings (ISO 3601) are used for containing fluid or excluding contamination at a static or dynamic interface. They are manufactured to ISO 3601-1 (fluid power — O-rings, inside diameters and cross-sections), and selection is driven by the inside diameter, the fit and tolerance the assembly requires, and the service environment.

Primary duty
Containing fluid or excluding contamination at a static or dynamic interface
Governing standard
ISO 3601-1 (fluid power — O-rings, inside diameters and cross-sections)
Inside diameter range
1 mm to 6 mm
Category
Seals

Application notes are general engineering guidance. Verify the property class and any approval requirement against your own design calculation.

What Are Metric O-Rings (ISO 3601) Used For? application image

Metric O-Rings (ISO 3601) are used primarily for containing fluid or excluding contamination at a static or dynamic interface. This page lists the industries and assemblies where they are specified, the selection criteria that matter for each application, installation practice, and the cases where a different fastener type is the correct choice. Parts are supplied to ISO 3601-1 (fluid power — O-rings, inside diameters and cross-sections). Stocked across roughly 1 mm to 6 mm, they cover light-duty and instrument-scale work.

Typical Applications for Metric O-Rings (ISO 3601)

The most common settings where these are specified:

  • General machine building: fastening covers, brackets, motors and sub-assemblies on production equipment.
  • Maintenance & repair (MRO): a stocked size for servicing existing plant where the original fastener spec must be matched.
  • Fabrication & metalwork: bench and on-site assembly of steel frames, enclosures and weldments.

How to Specify Metric O-Rings (ISO 3601) for Your Application

  • Size: Select on inside diameter, and confirm it against the mating feature in the assembly. This product spans 1 mm–6 mm; check the full table below for the exact dimensions of each size.
  • Material: Choose the material and finish for the service environment — plated steel for general use, stainless for corrosion resistance.
  • Environment: For damp, coastal or chemical exposure prefer A4/316 stainless or a suitable coating; indoors, plated steel or A2 is usually sufficient.
  • Standard: This product is supplied to ISO 3601-1 (fluid power — O-rings, inside diameters and cross-sections). Quoting the standard on your order guarantees interchangeable dimensions between suppliers.

Where Metric O-Rings (ISO 3601) Are Not the Right Choice

Match the fastener to the load, environment and whether the joint must be reopened; the wrong class or style is the usual cause of joint failure.

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.

Request a Quote

The form below follows the current technical drawing configuration. Change the drawing values above and the request details update automatically.

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Specification
Business Information

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

Cross-section (mm)Typical inside-diameter range (mm)Common compoundsNotes
1.01.0 u2013 20NBR, FKM, EPDM, siliconeminiature and pneumatic
1.52.0 u2013 40NBR, FKM, EPDM, siliconesmall pneumatic and instrument
1.781.78 u2013 50NBR, FKM, EPDMnearest metric equivalent to the 1/16 in section
2.03.0 u2013 100NBR, FKM, EPDM, siliconegeneral hydraulic and pneumatic
2.55.0 u2013 150NBR, FKM, EPDMgeneral hydraulic
3.06.0 u2013 200NBR, FKM, EPDMgeneral hydraulic
3.510 u2013 250NBR, FKMhydraulic
4.012 u2013 300NBR, FKMhydraulic and larger flanges
5.020 u2013 400NBR, FKMlarge flanges and covers
5.3320 u2013 400NBR, FKMnearest metric equivalent to the 3/16 in section
6.025 u2013 500NBR, FKMlarge covers and housings
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.

  1. Wire rod feeding into a cold heading machine
    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.

  2. Thread rolling machine producing bolt threads
    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.

  3. Baskets of bolts staged for heat treatment
    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.

  4. Zinc plated bolts in a treatment basket
    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

What are Metric O-Rings (ISO 3601) used for?

Containing fluid or excluding contamination at a static or dynamic interface. They are supplied to ISO 3601-1 (fluid power — O-rings, inside diameters and cross-sections).

Which industries use Metric O-Rings (ISO 3601)?

They are commonly specified in general machine building, maintenance & repair (mro) and fabrication & metalwork, among other sectors.

How do I choose the right size of Metric O-Rings (ISO 3601)?

Select on inside diameter and on the fit the assembly requires. This product is available from 1 mm to 6 mm; the full dimension table on this page lists each size.

Are Metric O-Rings (ISO 3601) made to a recognized standard?

Yes — they are manufactured to ISO 3601-1 (fluid power — O-rings, inside diameters and cross-sections), so dimensions are interchangeable between suppliers when you quote the standard on your order.

Can I get a quote for Metric O-Rings (ISO 3601) in the size and material I need?

Yes. Use the technical drawing and quote form on this page to set the size and options, then send the exact configuration to our team for pricing and lead time.