_Lap welding_ is the process used when two pieces of metal are caused
to overlap and when brought to a welding heat are forced together by
passing through rollers, or under a press, thus leaving the welded joint
practically the same thickness as the balance of the work.
Where it is desirable to make a continuous seam, a special machine is
required, or an attachment for one of the other types. In this form of work
the stock must be thoroughly cleaned and is then passed between copper
rollers which act in the same capacity as the copper dies.
_Other Applications._--Hardening and tempering can be done by clamping
the work in the welding dies and setting the control and time to bring the
metal to the proper color, when it is cooled in the usual manner.
Brazing is done by clamping the work in the jaws and heating until the
flux, then the spelter has melted and run into the joint. Riveting and
heading of rivets can be done by bringing the dies down on opposite ends of
the rivet after it has been inserted in the hole, the dies being shaped to
form the heads properly.
Hardened steel may be softened and annealed so that it can be machined by
connecting the dies of the welder to each side of the point to be softened.
The current is then applied until the work has reached a point at which it
will soften when cooled.
_Troubles and Remedies._--The following methods have been furnished by
the Toledo Electric Welder Company and are recommended for this class of
work whenever necessary.
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