1. ASSEMBLY• the mating of parts to give a combined operation. • In previous centuries, and before, fit in assemblies was often not considered, or when it did matter, each piece was custom fitted. • Modern methods of mass production means that some fundamental methods of fitting are necessary. • The three basic methods of fitting are, - Fitting - One part is made to size, and then a second part is made to fit it. - Selective Assembly - parts are made to loose general tolerances, and then the results are sorted into tolerance ranges. (e.g. bearings, solar cells, etc) - Interchangeable Assembly - Parts are made to tighter tolerances, and as a result assembly of randomly selected parts will yield a good fit. This is essential for modern assembly lines. • The basic categories of fits are, - Clearance - a gap is always present between parts - Transitional - the parts will have a gap sometimes, other times the parts will touch - Interference - both parts will always be in full contact 1.1 THE BASICS OF FITS1.2 C.S.A. B97-1 1963 LIMITS AND FITS(REWORK)1.3 CSA MODIFIED FITS1.4 CSA LIMITS AND FITS1.5 THE I.S.O. SYSTEM1.6 PRACTICE PROBLEMS |