BS ISO 6621-2:2003

Foreword
Introduction
1 Scope
2 Normative references
3 Terms and definitions
4 Measuring principles
  4.1 General measuring conditions
  4.2 Ring characteristics and their measurement
      4.2.1 Ring width (in millimetres)
      4.2.2 Radial wall thickness, a[1] (in millimetres)
      4.2.3 Total free gap m, p (in millimetres)
      4.2.4 Closed gap, s[1] (in millimetres)
      4.2.5 Tangential force, F[t] (in newtons)
      4.2.6 Diametral force, F[d] (in newtons)
      4.2.7 Ovality, U (in millimetres)
      4.2.8 Point deflection, W (in millimeters)
      4.2.9 Light tightness (percentage of ring circumference)
      4.2.10 Taper on peripheral surface (in micrometres or
             degrees)
      4.2.11 Barrel on peripheral surface, t[2], t[3]
             (in millimetres)
      4.2.12 Land width, h[4], h[5] (in millimetres)
      4.2.13 Land offset (in millimetres)
      4.2.14 Plating/coating thickness (in millimetres)
      4.2.15 Nitrided case depth (in millimetres)
      4.2.16 Keystone angle (in degrees)
      4.2.17 Obliqueness (in degrees)
      4.2.18 Twist (in millimetres)
      4.2.19 Unevenness T[er], T[eu]
      4.2.20 Helix (axial displacement of gap ends)
             (in millimetres)
      4.2.21 Free flatness (in millimetres)
      4.2.22 Surface roughness Ra, Rz (in micrometres)
Bibliography

Describes the principles to be used in the measuring for inspection purposes of piston rings for both reciprocating internal combustion engines and compressors working under analogous conditions. Applicable to all such rings of a diameter greater than or equal to 200 mm.