Tolerance is the limit of random (unintentional) deviation of a dimension from its nominal value. Allowance is the amount of designed (intentional) deviation between two mating dimensions in a fit, which, in combination with their respective tolerances, results into a maximum and minimum clearance or interference.
Regarding this, what is clearance and tolerance?
Tolerance is nothing but the allowance given to adjust dimensional errors during manufacturing as manufacturing to the required exact dimension is both difficult and expensive. Clearance on the other hand means how much gap or empty space is between two mating parts. It is more related to fits concept of metrology.
What is maximum clearance?
Maximum and minimum clearance. The maximum clearance of a fit is the difference between the upper bound of the orifice diameter and the lower bound of the shaft diameter.