ANSI limits and fits calculator works in line with ANSI B4.1 standard which is based on inch units. According to nominal size and fit type selection among running and sliding [RC], locational clearance [LC], locational transition [LT], locational interference [LN], force and shrink [FN] fits, size limits for hole/shaft are calculated with schematic representation of the fit. ANSI tolerance calculator is applicable to non-threaded cylindrical parts.
Limits of sizes that calculated are the extreme values, within which the actual size of the dimension shall lie, at the standard temperature of 20C or 68F.
Nominal size: The size of a feature of perfect form as defined by the technical drawing.
Deviation: The difference between a size and the corresponding nominal size.
Upper deviation: The difference between the maximum limiting size and the corresponding nominal size of a feature.
Lower deviation: The difference between the minimum limiting size and the corresponding nominal size of a feature.
Tolerance: The difference between the maximum and minimum size limits of a part.
Clearance Fit: A fit type where clearance exists between assembled parts under all tolerance conditions.
Interference Fit: A fit type where interference exists between assembled parts under all tolerance conditions.
Transition Fit: A fit type where clearance or interference can exist between assembled parts depending on tolerance conditions.
Hole Basis Fit System: A fit system in which hole lower deviation is zero. In other words the lower limit of size of hole is equal to nominal size. The required fit (clearance, interference etc.) is obtained by keeping hole as defined and applying various tolerance classes to shaft.
Allowance: The difference between the maximum material limits of mating parts. Minimum clearance (+ allowance) or maximum interference (- allowance) between parts depending on the fit type.
GD&T: A means of dimensioning and tolerancing a part with respect to relationship and function of that part. GD&T is used to define how a part feature relates the other part features in the same part or in a mating part; it’s a way to dimension and tolerance with respect to part’s function, the way it works.