• 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
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