Fullering denotes the preliminary roughing-down of the material
between tools having convex edges; swaging, the completion or
finishing process between swages, or dies of definite shape,
nearly hemispherical in form. When a bar has to be reduced
from larger to smaller dimensions, it is laid upon a
Fullering and swaging.
fuller or round-faced stake, set in the anvil, or, in some
cases, on a flat face (fig. 1), and blows are dealt upon that portion
of the face which lies exactly
opposite with a fullering
tool A, grasped by a rather
loosely-fitting handle and
struck on its head by a
sledge. The position of the
piece of work is quickly
changed at brief intervals
in order to bring successive
portions under the action
of the swages until the reduction
is completed; the
upper face, and if a bottom
fuller is used the under face also, is thus left corrugated slightly.
These corrugations are then removed either by a flatter, if the surfaces
are plane (fig. 2), or by hollow swages, if the cross section is
circular (fig. 3). Spring swages (fig. 4) are frequently used instead
of separate “top and bottom tools.” Frequently swaging is practised
at once, without the preliminary detail of fullering. It is
adopted when the amount of reduction is slight, and also when a
steam hammer or other type of power hammer is available. This
process of drawing down or fullering is, when practicable, adopted in
preference to either upsetting or welding, because it is open to no
objection, and involves no risk of damage to the material, while it
improves the metal
by consolidating its
fibres. But its
limitations in anvil
work lie in the
tediousness of the
operation, when the part to be reduced is very much less in
diameter, and very much longer, than the original piece of bar.
Then there are other alternatives.
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Fig. 2. |
Fig. 3. |
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Fig. 4. |
If a long bar is required to have an enlargement at any portion of
its length, not very much larger in diameter than the bar, nor of
great length, upsetting is the method adopted. The part
to be enlarged is heated, the parts adjacent remaining
cold, and an end is hammered, or else lifted and dropped heavily
Upsetting.
on the anvil or on an iron plate, with the result that the heated portion
becomes both shortened and enlarged (figs. 5 and 6). This
process is only suitable for relatively short lengths, and has the disadvantage
that the fibres of wrought iron are liable to open, and so
cause weakening of the upset portion. But steel, which has no
direction of fibre, can be upset without injury; this method is
therefore commonly adopted in steel work, in power presses to an
equal extent with drawing down. The alternative to upsetting is
generally to weld a larger to a smaller bar or section, or to encircle
the bar with a ring and weld the two (fig. 7), and then to impart
any shape desired to the ring in swages.
Bending is effected either by the hammer or by the simple exercise
of leverage, the heated bar being pulled round a fulcrum. It is
always, when practicable, preferable to cutting out a curved or
angular shape with a hot sett or to welding. The continuity of
the fibre in iron is preserved by bending, and the risk of an Bending.
imperfect
weld is avoided. Hence it is a simple and safe
process which is constantly being performed at the anvil.
An objection to sharp bends, or those having a small radius, is that
the fibres become extended on the outer radius, the cross section being
at the same time reduced below that of the bar itself. This is met by
imparting a preliminary amount of upsetting to the part to be bent,
sufficient to counteract the amount of reduction due to extension
of the fibres. A familiar example is seen in the corners of dip
cranks.
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Fig. 5. |
Fig. 6. |
Fig. 7. |
The property possessed by pieces of iron or steel of uniting autogeneously
while in a condition of semi-fusion is very valuable.
When portions which differ greatly in dimensions have to
be united, welding is the only method practicable at the
anvil. It is also generally the best to adopt when union has to be
Welding.
made between pieces at right angles, or when a piece on which
much work has to be done is required at the end of a long plain bar,
as in the tension rods of cranes and other structures with eyes.
The art of welding depends chiefly on having perfectly clean joint
faces, free from scale, so that metal can unite to metal; union
would be prevented by the presence of oxide or of dirt. Also it is
essential to have a temperature sufficiently high, yet not such as to
overheat the metal. A dazzling white, at which small particles of
metal begin to drop off, is suitable for iron, but steel must not be
made so hot. A very few hammer blows suffice to effect the actual
union; if the joint be faulty, no amount of subsequent hammering
will weld it. The forms of weld-joints include the scarf (figs. 8 and
9), the butt (fig. 10), the V (fig. 11) and the glut, one form of which
is shown in fig. 12; the illustrations are of bars prepared for welding.
These forms give the smith a suitable choice for different conditions.
A convexity is imparted to the joint faces in order to favour the
expulsion of slag and dirt during the closing of the joint; these
undesirable matters become entangled between concave faces.
The ends are upset or enlarged in order to leave enough metal to be
dressed down flush, by swaging or by flattering. The proportional
lengths of the joint faces shown are those which conform to good
practice. The fluxes used for welding are numerous. Sand alone
is generally dusted on wrought iron, but
steel requires borax applied on the joint
while in the fire, and also dusted on the
joint at the anvil and on the face of the
latter itself. Electric welding is largely
taking the place of the hand process,
but machines are required to maintain
the parts in contact during the passage
of the current. Butt joints are employed,
and a large quantity of power is absorbed, but the output is immensely
greater than that of hand-made welds.
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Fig. 8. |
Fig. 9. |
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Fig. 10. |
Fig. 11. |
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Fig. 12. |
When holes are not very large they are formed by punching,
but large holes are preferably produced by bending a rod round
and welding it, so forming an eye (fig. 13). Small holes
are often punched simply as a preliminary stage in the
formation of a larger hole by a process of drifting. A piece of Punching.
work
to be punched is supported either on the anvil or on a ring of metal
termed a bolster, laid on the anvil, through which the burr, when
severed, falls. But in making small holes through a thick mass,
no burr is produced, the metal yielding sideways and forming an
enlargement or boss. Examples occur in the wrought iron stanchions