ISO 7649:1991

Specifies the nominal dimensions and tolerances which affect the interchangeability between clutch housings for spring-loaded clutches and mating parts. All other dimensions and tolerances are left to the discretion of the component manufacturer. Does not apply to engines for aircraft and passenger cars; it may be used for other engine applications where no specific International Standard exists. Clutch housings of size codes 1 to 4 in table 1 are recommended for commercial vehicles and buses.