ST ae 
™ " 
‘ | r) 
‘ 
284 WILLIAM FIELD HOW. 
To obtain sound rivetting when hydraulic machinery is employed, 
the rivets are the exact length required to fill the holes and form 
the correctly shaped heads. If they are too short, mere buttons 
are formed instead of heads, and the bodies of the rivets are not 
forced out laterally—the consequence being loose rivets. When 
the rivets have been correctly made, it is usual, in boiler work, to 
keep the pressure on them until they have become slightly cold. 
In some well known firms steam rivetting for boilers is still 
employed, and the manufacturers maintain that by so closing the 
rivets, they ensure tighter work than could be obtained from 
hydraulic pressure, the blows from the steam rivetter being sharp 
and decided, whereas the hydraulic machine forms the rivet more 
slowly. 
Before concluding these remarks about rivetting, the author 
desires to state that he is satisfied too much attention is usually 
given by inspectors to the perfect shape and appearance of rivets. 
It is of course, advisable to insist upon manufacturers paying 
particular attention to the neatness and finish of the rivets, but 
practical engineers would prefer sound and reliable work to that 
having a neat appearance but being of a less substantial character. 
‘When it is remembered that rivets in the flange plates of a bridge 
are mostly in shear, and that many of those put in principally 
serve the purpose of keeping the plates together and weather- 
tight, it will be acknowledged that, to cut out a rivet in a tension 
member of a bridge which has been put in by hydraulic machinery, 
only serves to injure the plate around the rivet hole, and that, 
when such a rivet has been replaced, the actual strength of the 
work is seriously impaired by the injury done to the plates when 
the rivet was being removed. Again, when work has been rivetted 
by hand, in many cases it would be better to leave a few loose 
rivets in place, rather than cut them out and loosen the adjacent 
ones during the operation, and this nearly always happens. 
In manufacturing girders of small spans, it is usual to completely 
erect them at the manufacturer’s works. The main girders, cross 
girders, &c., being in position, every possible care is taken that 
