Reference numbers printed in red indicate sizes covered by:
l BS 1806: Dimensions of toroidal sealing rings (‘O’ rings) and
their housings (inch sizes),
l BS ISO 3601-1: Fluid power systems — ‘O’ rings Part 1: Inside
diameters, cross-sections, tolerances and designation codes,
and
l SAE AS 568: American National Standard Aerospace size
standard for ‘O’ rings.
Although the basic range is in inches, the ‘O’ rings can of course
be used for sealing metric dimensioned components. Chart 50
includes suggested metric shaft and cylinder sizes for which each
individual ‘O’ ring is suitable. (Note: these figures are NOT merely
direct metric conversions of inch sizes. Also, separate ranges of
back-up rings are available for metric shafts and cylinders