36. 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
