INTO THE STRENGTH OF WROUGHT-IRON PLATES. 
689 
This property of unvarying soundness in the work, constitutes the superiority of 
the machine over the hand-riveting. The machine produces much sounder work, as 
the time occupied in the hand process allows the rivet to cool, and thus by destroying 
its ductility, the rivet is imperfectly closed, and hence follow the defects of leaky rivets 
and imperfect joints. It is evident that an instrument, such as the riveting-machine, 
having sufficient force to compress the rivet at once, or within an almost infinitely 
short period of time, must obviate, if not entirely remedy, these evils, as the force of 
compression being nearly instantaneous, the heads on both sides cannot be formed 
until the body of the rivet is squeezed tight into the hole ; and in every case (even 
where the holes are not exactly straight) the compressed rivets are never loose, but 
fill the holes with the same degree of tightness as if placed directly opposite to each 
other. If, for example, we take a circular boiler, such as represented at A*, Plate 
LVI. fig. 3, and having all the perforations made and the plates attached to each 
other by temporary bolts and suspended over the machine in the position as shown 
at A, and having brought the holes in a line with the die marked ^, h, the machine 
then is set to work, and by means of the cam or excentric raising the pulley of the 
elbow-joint C, the die /r is advanced against the fixed die i in the wrought-iron stem, 
and the rivet is compressed into the required form with an increasing force as the die 
advances which gives the nip,” or greatest pressure, at the required time, namely, 
at the closing of the rivet. 
From this description it will appear that a very limited portion of time is occupied 
in the process, and as twelve rivets can be inserted and finished by the machine in a 
minute, it follows, from the rapidity of the operation and the absence of hammering, 
that the ductility of the rivets is retained, and their subsequent contraction upon the 
plate renders the joint perfectly tight and the rivets sound in every respect. Under 
all the circumstances the machine-riveting is preferable to that executed by the 
hammer; it saves much time and labour, and that in proportion of 12 to 1, when com- 
pared to a long series of impacts applied by the hammer. 
Having described the process of uniting wrought-iron plates by rivets, it may be of 
some importance to know the value of joints thus formed as regards their strength 
when compared with the plates themselves. To attain this object, and satisfactorily 
to determine their powers of resistance to a tensile strain, a great variety of joints 
were made, and having prepared the different specimens with the utmost care and 
attention, they were submitted to the test of experiment as follows ; — 
* The plan represents the machine in the act of riveting the corners of a square cistern or a locomotive fire- 
box. 
4 T 
MDCCCL. 
