After the riveting of a boiler is completed, the various lapped seams are made tight by caulking the beveled edges of the sheets. A flanged joint is usually made, as shown in Fig. 240, with the lap of the end D on the outer face of the flange and not on the inner face B except for a particular reason.

This arrangement enables the beveled edge of each sheet to be set down against the adjacent surface tightly, as shown at KK.

Fig. 240. - Example of Caulking.

This operation of caulking is preceded by cutting the edge of the plate to a uniform bevel. Flat-plate edges may be beveled by planing, though edges of curved flange plates are beveled by chipping with the cold chisel driven by the hammer or better by the pneumatic holder. Chipping may be done before or after the joint is riveted, and, if done after riveting, great care must be taken to avoid gashing the surface of the adjacent plate.

A caulking tool is virtually a cold chisel with a blunt end. Two styles of caulking-tool ends are shown at R and S in Fig. 240.