CAMBBIA STEEL. 363 



RULES FOR PROPORTIONS OF BOLTS AND 

 NUTS. 



Franklin Institute Standard. 



The dimensions of nuts and bolts are determined by the 

 following rules, which apply to both square and hexagon. 



Short diameter of rough nut = 1 X diameter of bolt + f in. 



Short diameter of finished nut = 1 X diameter of bolt + 

 &in. 



Thickness of rough nut = diameter of bolt. 



Thickness of finished nut = diameter of bolt ^ in. 



Short diameter of rough head = 1| X diameter of bolt + | in. 



Short diameter of finished head = 1 X diameter of bolt -f- 

 A in. 



Thickness of rough head = \ of short diameter of head. 



Thickness of finished kead = diameter of bolt ^ in. 



In 1864, a committee of the Franklin Institute recommended 

 the above system of screw threads and bolts which was devised 

 by Mr. William Sellers, of Philadelphia. This system as far 

 as it relates to screw threads is generally used in the United 

 States, but the proportions of bolt heads and nuts are not 

 adhered to because the sizes of bar required to make the nuts 

 are special and extra work is necessary to make the bolt heads. 

 Sizes of nuts and bolt heads in accordance with the Manufacturers' 

 Standard are given on pages 369, 370 and 371. 



