The practice of driving rivets into a punched rivet hole from which
the fin or cold drag, caused by the movement of the punch, has not
been removed by reaming with a countersunk reamer, or better still a
countersunk set, should be condemned, as by driving the hot rivet head
down against the fin around the hole in the cold plate caused by the
action of punching the countersunk fillet is not only destroyed, but
it is liable to be driven into the head of the rivet, partially
cutting the head from the shank. If the rivet is driven into a hole
that has been punched with a sharp punch and sharp die, the result is
that the fillet is cut off under the head, and the riveted end is also
cut, and does not give the clinch or hold desired. That is to say,
rivet holes in plates to be riveted should have the burr or sharp edge
taken off, either by countersinking, by reamer, or set.

_Heating of Rivets._--Iron rivets are generally heated in an ordinary
blacksmith's or rivet fire having a forced blast; they are inserted
with the points down into the fire, so that the heads are kept
practically cool.

Steel rivets should be heated in the hearth of a reverberatory furnace
so arranged that the flame shall play over the top of the rivets, and
should be heated uniformly throughout the entire length of the rivet
to a cherry red. Particular attention must be given to the thickness
of the fire in which they are heated.

Steel, of whatever kind, should never be heated in a thin fire,
especially in one having a forced blast, such as an ordinary
blacksmith's or iron rivet furnace fire. The reason for this is that
more air passes through the fire than is needed for combustion, and in
consequence there is a considerable quantity of free oxygen in the