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ISO3601-1

ISO3601-1: Inside diameters, cross-sections, tolerances and designation codes

ISO3601-1 specialises in the inside diameters, cross-sections, tolerances and designation codes for O Rings used in fluid power systems for aerospace and standard industrial installations.

Inside diameters, Cross-sections & Tolerances

Tolerances and dimensions defined are adequate for any rubber material if the right tooling is obtainable. In this part of ISO3601, the following symbols are used:

  • O Ring inside diameter – d1
  • O Ring cross-section diameter – d2

Typical O Ring configuration

ISO3601-1

The composite of inside diameters and cross-section diameters should be selected conditional to the installation. For industrial installations, 2 classes of inside diameter tolerances are defined, Class A and Class B. Class A O Rings have tighter I.D. tolerances rather than Class B O Rings. They are also adequate for aerospace and industrial installations if the housing or installation demand tighter tolerances. Class B O Rings have tolerances and dimensions adequate for standard-purpose installations.

In significant instances, the conformity with the restraints of the shape variations and surface blemishes should be deliberated aside from the dimensional tolerances – see ISO3601-3.

Graphical comparison of inside diameter tolerances for Class A and Class B O Rings

ISO3601-1

Key:

X – O Ring inside diameter (d1) (in mm)

Y – ± tolerances (in mm)

1 – Class A tolerance

2 – Class B tolerance

Designation codes

O Rings for standards industrial installations that comply with ISO3601-1 should be denominated as follows:

  • The word ‘’o-ring’’ followed by ‘’-‘’ (hyphen)
  • ‘’ISO3601-1’’ followed by ‘’-‘’ (hyphen)
  • The size code and ‘’A’’ or ‘’B’’ for the inside diameter tolerance class, followed by ‘’-‘’ (hyphen)
  • The nominal inside diameter and cross-section dimensions, divided by an ‘’x’’ and followed by a ‘’-‘’ (hyphen)
  • The grade letter ‘’N’’, ‘’S’’ or ‘’SC’’ in accordance with ISO3601-3

O Rings for aerospace installations that comply with ISO3601-1 should be denominated as follows:

  • The word ‘’o-ring’’ followed by a ‘’-‘’ (hyphen)
  • ‘’ISO3601-1’’ followed by a letter ‘’A’’ (to denominate an aerospace installation), followed by a ‘’-‘’ (hyphen)
  • The size code, followed by a ‘’-‘’ (hyphen)
  • The nominal inside diameter and cross-section dimensions, divided by an ‘’x’’ and followed by a ‘’-‘’ (hyphen)
  • The grade letter ‘’N’’, ‘’S’’ or ‘’CS’’, in accordance with ISO3601-3

Click here to see the ISO3601 overview (Pt1, Pt2, Pt3, Pt4, Pt5)

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E & OE. M Barnwell Services endeavour to make sure that all content is correct. Information has been gathered from manufacturing partners.