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 traces of crude oil after mechanical processing, the allowances must, in any case, be greater than the values of the deviations of the internal and external dimensions.
UNI 7601-1976 history
1984UNI 7601-1984 Ductile iron cast in molding sand or soil, offset values without deviation and machining allowance stated
1976UNI 7601-1976 Pig iron castings with molded sand casting or sand cast spherical graphite. Offset value without deviation specification