CHAPTER XII. 

 SHOP -PRACTICE AND ERECTION. 



Laying Out Work. As soon as the metal sheets or 

 plates for tank or stand-pipe work are received at the shop, 

 they should be immediately and carefully unloaded and 

 stored awaiting- the earliest moment when they may be 

 " laid out." This process consists in marking off the plates 

 for shearing, machining, punching, and rolling. 



The object of shearing or machining is to put a bevel- 

 edge upon the opposite face of the plate where two plates are 

 to be in contact, and in order that the thin edge so formed 

 may be properly and easily calked after riveting and that a 

 water-tight joint may thus be secured. 



For the reason that such work upon heavy plates has 

 been shown to exert a force tending to change the molecular 

 arrangement of the metal, this shearing of plates is usually 

 not permitted upon plates that are thicker than f of an inch, 

 all plates above that thickness being planed to a bevel by a 

 machine. 



In laying out, the rivet-hole spacing is indicated by mark- 

 ing with a sharp-pointed cold-chisel, the widths from centre 

 to centre, or the pitch, having first been calculated as has 

 been described and explained. 



Realizing that a greater comparative efficiency of joint- 

 strength may be secured, with fewer rivets and wider spac- 

 ing, where the largest possible rivet is used, this inclination 

 is sometimes stretched to the limit, the requirement for tight- 



275 



