ISO INTERNATIONAL STANDARD 6698 Second edition 1989-12-01 Cycles - s Screw threads used to assemble freewheels onbicycle hubs Cycles -- Filetages utilises pour I'assemblage des roues libres sur les moyeux de bicyclettes Reference number ISO 6698 : 1989 (E) Coovriaht International Oraanization for Standardizatior ISO 6698 : 1989 (E) Foreword iso (the International Organization for Standardization) is a worldwide federation of Standards is normally carried out through IsO technical committees. Each member body interested in a subject for which a technical committee has been established has the right to be represented on that committee. International organizations, govern- mental and non-governmental, in liaison with iso, also take part in the work. ISo collaborates closely with the International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization. Draft International Standards adopted by the technical committees are circulated to the member bodies for approval before their acceptance as International Standards by the ISo Council. They are approved in accordance with ISO procedures requiring at least 75 % approval by the member bodies voting. International Standard ISO 6698 was prepared by Technical Committee ISO/Tc 149, Cycles. This second edition cancels and replaces the first edition (is0 6698 : 1981), of which it constitutes a minor revision. ISO 1989 All rights reserved. No part of this publication may be reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from the publisher. International Organization for Standardization Case postale 56.CH-1211 Geneve 20·Switzerland Printed in Switzerland ii Coovriaht Intemational Oroanization for Standardization ISO 6698 : 1989 (E) Introduction Inch screw threads of British Standard Cycle (B.S.C.) thread profile are used exten- sively throughout the world for various applications on bicycle components, and have been standardized in national standards. The purpose of this document is to provide an International Standard for the particular screw thread used to assemble freewheels on bicycle hubs: it is based on the use of the IsO basic thread profile and complies as far as is practicable with existing International Standards for general purpose screw threads. The change to an iSO system of screw threads will inevitably take a long time to com- plete in view of the milions of bicycles now in use which employ B.S.C. thread profile inch screw threads and for which replacement spare parts will be required. For this reason,in orderto minimize changes inproductionmethods duringthechangetothe International Standard, and also to secure satisfactory interchangeability with the B.S.C. screw threads now used, the ISO screw thread in this International Standard has the same pitch as that of the 1,37 in × 24 t.p.i. B.S.C. screw thread it is intended to replace; this means that the pitch is in inch units (turns per inch or t.p.i.) but all other dimensions are specified in metric units. A 1 3/8 (1,375) in × 24 t.p.i screw thread of ISO basic profile has been adopted in this international Standard. The basic pitch diameter of this thread differs by only 0,003 mm from that of the 1,37 in × 24 t.p.i. B.S.C. thread, but, due to the smaller crest truncation of the iSO profile (see figure 1) interference may occur at the major diameter when an ISO hub thread made towards its upper limit is assembled with a B.S.C. freewheel thread made towards its lower limit on major diameter. The possi- bility of interference occurring in this manner is considered to be unlikely in practice because of the effect of the manufacturing tolerances (negative on the hub and positive on the freewheel) and the usual practice of using high-crested screwing taps. However, a practical investigation has been carried out and has confirmed that there is little possibility of any interference arising in practice. Coo