48 BRIDGES AND CULVERTS. 



be done without breaking out metal. Chipped edges must be 

 finished off with a file, and all concave corners must be 

 rounded off. Chipping with a sledge will only be permitted in 

 exceptional cases, and must be done without leaving fractured 

 edges. 



RIVETING. In driving rivets, the dolly and die should be 

 placed directly opposite each other, at right angles to the riv- 

 eted surface, to insure straight driving. Rivets must be driven 

 while at an orange heat, and no burnt rivets should be used. 



After riveting, each rivet must be tapped with a hammer to 

 insure that they are tight, and the heads must be well formed, 

 concentric with center of rivet, and closely fitted against the 

 riveted surface. 



Defective rivets can usually be detected by their color, or by 

 sound when tapped with a hammer, and all loose or burnt 

 rivets must be immediately cut out and replaced. 



In cutting out rivets be careful to ascertain that other rivets 

 In proximity have not been loosened. 



Tightening up, recupping or calking old rivets will not be 

 tolerated, except that occasional recupping of shop rivets do 

 not form part of important connections, or do not directly 

 transmit stresses. 



Countersunk rivets must be inspected after chipping heads, 

 and no unnecessary chipping should be permitted. 



PAINTING. The specifications under the head of cleaning, 

 oiling and painting must be strictly carried out 



An accurate account should be kept of the quantities and 

 proportions used, of pigments, oils and other ingredients, and 

 the quantities by weight or fluid measure, of the resulting 

 mixtures, ascertained. A record should be kept of the quan- 

 tity of paint applied, of each coat, and its proportion ascer- 

 tained to area or weight of material covered. 



Paint should be thoroughly worked in all corners of joints, 

 and narrow openings, covering edges and sealing up all lines 

 of contact between parts. 



Unless otherwise specified, the ingredients and proportions 

 of the mixture, for the three coats, shall be as follows: 



First Coat 30 Ibs. pure lead to 1 gallon pure boiled linseed 

 oil, 1-3 pint pure turpentine. 



