The tolerance values of this standard are intended as deviations from the nominal dimensions reported in the drawing of the rough castings, for which no tolerance indication has been provided on the executive drawing. The measurements of the dimensions are intended as referring to axes or starting planes of tracing, specifically indicated on the drawing of the castings or defined by agreement between the foundry and the customer. 2 The draft values and any excess metal are not considered in the nominal dimensions, but can be agreed upon when ordering between the foundry and the customer; they must be added to the external dimensions and removed from the internal dimensions. In order to avoid witnesses after mechanical machining, the allowances must, in any case, be greater than the values of the deviations of the internal and external dimensions.
UNI 7451-1975 history
1984UNI 7451-1984 Malleable iron castings cast in molding sand or soil, with offset values stated without deviation and machining allowances
1975UNI 7451-1975 Can forge iron sand or molding sand castings. Deviation without deviation statement