ISO INTERNATIONAL 6621-2 STANDARD Third edition 2020-03 Internal combustion engines - Piston rings Part 2: Inspection measuring principles Moteursa combustion interne-Segments de piston- Partie 2:Principes de mesure pour inspection Reference number ISO 6621-2:2020(E) O ISO 2020 ISO 6621-2:2020(E) COPYRIGHTPROTECTEDDOCUMENT @ISO2020 Allrights reserved.Unless otherwise specified,or required in the context of its implementation,no part of this publication may be reproduced or utilized otherwise in any form or by any means,electronic or mechanical,including, photocopying.or posting on the internet or an intranet,without prior written permission.Permission can be requested from either IsO at the address below or IsO's member body in the country of the requester. ISO copyright office CP 401-Ch.de Blandonnet 8 CH-1214 Vernier,Geneva Phone:+41227490111 Fax:+41227490947 Email:[email protected] Website:www.iso.org Published in Switzerland ii ISO 2020-All rights reserved 6621-2:2020(E) ISO Contents Page Foreword Introduction 1 Scope 2 Normativereferences 3 Terms and definitions 4 Measuring principles 4.1 General measuring conditions 4.2 Characteristics and measuring principles ... 4.2.1 Ring width 4.2.2 Radial wall thickness ,a1 4.2.3 Total free gapm ,p .... 4.2.4 Closed gap , S1 4.2.5 Tangential force ,Ft (in Newton) 4.2.6 Diametral force,Fa (in Newton) ... 4.2.7 Ovality,U(inmillimetres) 4.2.8 Point deflection,W(in millimetres) 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 , t2 , t3 ( in millimetres) 18 4.2.12 Land width,h4 ,h s ( 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) 25 4.2.19 Unevenness Te, Teu. 26 4.2.20 Helix (axial displacement ofgap ends )( in millimetres) 4.2.21 Free flatness (in millimetres) 4.2.22 Surface roughness Ra, Rz(in micrometers) 28 4.2.23 Circumferential waviness Bottom sideface(inmicrometres) 28 Bibliography ISO 2020- All rights reserved