[Illustration: Fig. 156.]
Fig. 156 represents a pair of jack screws. These are invaluable devices
for use in boiler-shops, and also in establishments where ponderous
machinery has to be shifted or otherwise handled.
But few machine tools are used in making steam boilers, and they are
generally as follows:
1st.—_The Rolls_, operated either by hand levers or power; used for
bending the iron or steel plates into circular form.
2d.—A wide _power planer_ for trimming the edges of the sheet perfectly
straight and true.
3d.—_Heavy Shears_ for trimming and cutting the plates.
4th.—A _Power Punch_ for making the rivet holes.
5th.—A _Disc_ for making the large holes in the tube sheets to receive
the ends of the tubes.
6th.—_Rivet heating furnaces_ and frequently _steam riveting machines_.
The hand tools needed by boiler makers are equally few, consisting of
_riveting hammers_ and hammers for striking the chisels, _tongs_ to
handle hot rivets, _chipping chisels_ used in trimming the edges of
plates, _cape chisels_ for cutting off iron or making holes in the
sheets, _expanders_ to set the tubes, and also _drift pins_ to bring
the punched sheet exactly in line.
Fig. 157 exhibits an improved pattern of the well-known tool—dudgeon
expander.
[Illustration: Fig. 157.]