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1.1 This European Standard specifies the dimensional tolerances for steel drop and vertical press forgings made under hammers and presses. The first part of this European Standard applies to hot forgings in the delivery condition, made in carbon and alloy steels. The tolerances specified apply to forgings not exceeding 250 kg in mass or 2 500 mm maximum dimension. Tolerances for heavier or larger forgings shall be agreed at the time of enquiry and order. This European Standard does not apply to upset forgings made on horizontal forging machine (see prEN 10243-2). 1.2 The tolerances shown in this European Standard cover both forgings to normal requirements and forgings to a closer range of tolerances. These two grades of tolerances are identified as follows : - forging grade F with tolerances providing an adequate standard of accuracy for the majority of applications and capable of being complied with by commonly used forging equipment and production methods ; - forging grade E providing closer tolerances to assist in acommodating those instances in which the normal manufacturing standards are inadequate. While grade E (close) tolerances may be applied to all dimensions on one forging, it is more economical to apply them only to those specific dimensions on which closer tolerances are essential. This grade should not be specified unless the additional forging cost entailed can be justified by a consequent saving in overall cost. The tables showing dimensional tolerances are based on the R20 series of preferred numbers (see ISO 3). The annex A gives for information some examples of application of these tolerances for different types of closed die forgings. 1.3 Any occasional instances may necessitate the use of tolerances wider than those indicated, e.g. specially complicated designs and steels having particularly difficult forging characteristics. In such cases these standard tolerances can form only a basis on which to agreed modifications appropriate to the particu