306 TOWERS AND TANKS FOR WATER-WORKS. 



The overturning and resisting moment of the water-tower 

 shall be calculated from the assumed wind pressure, resisted 

 by the weight of the structure when empty, but anchorage shall 

 in all cases be provided. 



SHOP WORK. 



As soon as received at the shop, all material shall be assorted 

 and carefully and accurately laid out for punching, machining, 

 shearing, and rolling. 



Plates exceeding three-eighths (f) inches shall be planed 

 to a bevel by machining; all other plates may be sheared. 



Plates under five-eighths (f) inch may be punched with 

 sharp and well-conditioned punch and dies away from the sur- 

 faces in contact. The punch shall be one-sixteenth (1/16) 

 inch greater diameter than that of the rivet proposed to be used. 



Plates having a thickness between five-eighths (f) inch and 

 seven-eighths (|) inch must be punched to correspond to the 

 diameter of the rivet to be used and afterwards reamed one- 

 sixteenth (1/16) inch larger, while plates exceeding that thickness 

 shall be drilled from the solid metal. 



In general all bends in the metal must be made cold, especially 

 in the case of the cylinder and bottom plates, but detail pieces 

 may be bent hot without annealing. 



If a steel piece in which the full strength is required has been 

 partially heated, the whole must be subsequently annealed. 



In laying out plates, lap-joints will be allowed only for con- 

 necting plates less than seven-eighths (J) inch thick; all other 

 joints must be of the butt-strap type. 



When " scarfing" is necessary, the temperature of the re- 

 heated metal shall not be more than would be necessary to ignite 

 hard wood when placed in contact. 



Flanging or bending shall be done by means of suitable rolls 

 and without reheating. This process shall follow punching 



