8 BULLETIN 1259, U. S. DEPARTMENT OF AGEICULTURE. 
round washers having a thickness of 3^ inch shall be 
placed under the nuts. 
20. Riveting. Rivets shall be heated uniformly to a light cherry-red 
color and shall be driven while hot. The heating of the 
points of rivets more than the remainder will not be 
permitted. When ready for driving they shall be free 
from slag, scale and other adhering matter and when 
driven they shall completely fill the holes. Burned, 
burred or othei-wise defective rivets, or rivets which 
throw off sparks when taken from the furnace or forge 
shall not be driven. 
Loose, burned, badly formed or otherwise defective 
rivets shall be cut out. Caulking and recupping of 
rivet heads will not be allowed. In cutting out defective 
rivets care shall be taken not to injure the adjacent 
metal and, if necessary, the rivet shanks shall be removed 
by drilling. 
Countersinking shall be neatly done and countersunk 
rivets shall completely fill the holes. 
Shop rivets snail be driven by direct-acting riveters 
where practicable. The riveting machine shall retain 
the pressure for a short time after the upsetting is com- 
plete. 
Pneumatic hammers shall be used for field riveting 
except when the use of other hand tools for riveting is 
permitted by the engineer. 
21. Edge plan- Sheared edges of material more than ^^ inch in thickness 
shall, when required by the engineer, be planed to a 
depth of not less than 3^ inch. Reentrant cuts shall 
be filleted before cutting. 
beSin^^^^fac^^ Euds of columns taking bearing upon base and cap 
' plates shall be milled to true surfaces and coiTect bevels 
after the main section of these members and the end 
connection angles have been fully riveted. 
Caps and base plates of columns and the sole plates of 
girders and trusses shall have full contact when assem- 
bled. The plates, if warped or deformed, shall be hot- 
straighteneo, planed or otherwise treated to secure an 
accurate, uniform contact. After being riveted in place 
the excess metal of countersunk rivet heads shall be 
chipped smooth and flush with the surrounding metal 
and the surfaces which are to come in contact with 
other metal siirfaces shall be planed or milled, if neces- 
sary, to secure proper contact. Correspondingly, the 
surfaces of base and sole plates which are to come in 
contact with masonry shall be rough-finished if not free 
from warps or other deformations. 
Surfaces of cast pedestals and shoes which are to come 
in contact with metal surfaces shall be planed and those 
which are to take bearing upon the masonry shall be 
rough-finished. 
In planing the surfaces of expansion bearings the cut 
of the tool shall be in the dii*ection of expansion. 
ing 
