272 HANDBOOK OF MECHANICAL DESIGN 



Class 1. Thickness Tolerances 



Thickness tolerances shall apply to the over-all thickness of a forging. When 

 applied to drop-hammer forgings, they shall apply to the thickness in a direction per- 

 pendicular to the main or fundamental parting plane of the die. When applied to 

 upset forgings, they shall apply to the thickness in a direction parallel to the direction 

 of travel of the ram, but only to such dimensions as are inclosed by the die. 



Class 2. Width and Length Tolerances 



Width and length tolerances shall be ahke and shall apply to the width and/or 

 length of a forging. When applied to drop-hammer forgings, they shall apply to the 

 width or length in a direction parallel to the main or fundamental parting plane of the 

 die, but only to such dimensions as are enclosed by and actually formed by the die. 

 When apphed to upset forgings, they shall apply to the width or length in a direction 

 perpendicular to the direction of travel of the ram. 



Width and length tolerances shall consist of three subdivisions: 



Class 2a. Shrinkage and die wear tolerance. , 



Class 26. Mismatching tolerance. 



Class 2c. Trimmed size tolerance. 



Class 2a. Shrinkage and Die Wear 



Shrinkage and die wear tolerances shall apply to that part of the forging formed 

 by a single die block only. They shall not apply to any dimension crossing the part- 

 ing plane. They shall be the sum of the shrinkage tolerances and the die wear toler- 

 ances as given in the following table. The shrinkage tolerances and die wear 

 tolerances shall not be applied separately, but shall only be used as the sum of the 

 two. They shall not be so applied as to include draft or variation thereof. 



SHRINKAGE PLUS DIE WEAR 



(Inches) 



