It is the property of long products and indicates the alignment with the axial axis.
In bars and specially in cold drawn products, the straightness tolerance is of vital importance, since for later transformations of these products in automatic machines bars with high straightness properties are needed to avoid vibrations and stoppages.
The straightness property is guaranteed by the straightness tolerance which is the maximum allowable deviation in mm per meter or in % with respect to the total length of the bar.