Fig. 2895.
When one piece has to be driven on to the other, the weld is called a pump-weld, for which the ends should be rounded as in [Fig. 2894], so that they will meet at their centres, and will, when struck endways to make the weld, come to the shape shown in [Fig. 2895].
Fig. 2896.
It is obvious that in this case the interior of the iron comes together and is welded, and that dirt, &c., is effectually excluded; hence if the iron is properly heated the weld may be as sound as a lap weld, and is preferred by many as the sounder weld of the two. When a stem requires to be welded to a large flat surface, the pump weld is the only one possible, being formed as in [Fig. 2896], in which the stem is supposed to be welded to a frame. The plate is cupped as shown, and the metal being driven up on the sides as much as possible, the stem overlaps well at c b, so that it may be fullered there. The stem should first meet its seat at a, so that dirt, &c., may squeeze out as the welding proceeds.
Fig. 2897.