A cylinder of lead, of five or six
inches in diameter and about two feet long, is cast with a small
hole through its axis, and an iron triblet of about fifteen feet
in length is forced into the hole. It is then drawn through a
series of holes, until the lead is extended upon the triblet from
one end to the other, and is of the proper thickness in
proportion to the size of the pipe.
144. Iron rolling. When cylinders of iron of greater
thickness than wire are required, they are formed by passing
wrought iron between rollers, each of which has sunk in it a
semi-cylindrical groove; and as such rollers rarely touch
accurately, a longitudinal line will usually be observed in the
cylinders so manufactured. Bar iron is thus shaped into all the
various forms of round, square, half-round, oval, etc. in which
it occurs in commerce. A particular species of moulding is thus
made, which resembles, in its section, that part of the frame of
a window which separates two adjacent panes of glass. Being much
stronger than wood, it can be considerably reduced in thickness,
and consequently offers less obstruction to the light; it is much
used for skylights.
Pages:
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156