Preferred tolerances and fits charts according to ANSI B4.1 standard.
Running and Sliding Fits [RC]: Intended to provide a similar running performance, with suitable lubrication allowance, through out the range of sizes. The clearances for the first two classes, used chiefly as slide fits, increase more slowly with diameter than the other classes, so that accurate location is maintained even at the expense of free relative motion.
Note: There is no symbol in the standard for the shaft tolerance of RC9.
Locational clearance fits [LC]: Intended for parts which are normally stationary, but which can be freely assembled or disassembled. They run from snug fits for parts requiring accuracy of location, through the medium clearance fits for parts such as ball, race and housing, to the looser fastener fits where freedom
Note: There are no symbols in the standard for the shaft tolerances of LC10 and LC11.
Locational transition fits [LT] : A compromise between clearance and interference fits, for application where accuracy of location is important, but either a small amount of clearance or interference is permissible.
Locational interference fits [LN] : are used where accuracy of location is of prime importance and for parts requiring rigidity and alignment with no special requirements for bore pressure. Such fits are not intended for parts designed to transmit frictional loads from one part to another by virtue of the tightness of fit, as these conditions are covered by force fits.
Force Fits [FN] : Force or shrink fits constitute a special type of interference fit, normally characterized by maintenance of constant bore pressures throughout the range of sizes . The interference therefore varies almost directly with diameter, and the difference between its minimum and maximum value is small to maintain the resulting pressures within reasonable limits.
Note: There is no symbol in the standard for the shaft tolerance of FN1.