FORGING OPERATIONS
=44. The Hammer Blows.=—Metal can be forced into desired shapes or
forms by delivering the hammer blows in different ways. All hammer
blows are not alike; some will have one effect and others will produce
an entirely different result.
=45. The upright blow= is delivered so that the hammer strikes the
metal in an upright position and fully on the anvil. Such blows
force the metal equally in all directions, providing the surrounding
dimensions are equal. They will also reduce the thickness of the metal
in the direction in which they are delivered, the reduction depending
upon the amount of force put into the blows. They are used for drawing
where the metal is supposed to spread equally in all directions and for
making smooth surfaces.
[Illustration: FIG. 22.—THE UPRIGHT BLOW.]
Figure 22 shows an upright blow as delivered on a piece of flat
material. If the material is as wide as the face of the hammer, or
wider, the force of the blow will spread the metal equally, but if it
is narrower, the blow will lengthen the material more rapidly, because
the hammer will cover more in length than in width.
=46. The edge-to-edge blow= is delivered so that the edge or side of
the hammer face will be directly above the edge or side of the anvil.
When blows are delivered in this manner (_a_, Fig. 23), the hammer
forms a depression on the upper side of the metal and the anvil forms
one on the bottom.
[Illustration: FIG. 23.—THE EDGE-TO-EDGE BLOW.]
When a piece of metal is to be drawn to a smaller dimension, with
shoulders opposite each other, on either two or four sides, these blows
will produce the required result to the best advantage. They are more
effective if the metal is held at a slight angle across the edge of the
anvil face, but then the hammer blows must be delivered a little beyond
the anvil edge, so that the upper and lower depressions in the metal
will be formed exactly opposite each other, as shown at _b_, where the
depressions are indicated by the broken lines.
In forming shoulders such as are required on the hasp exercise (page
64) the first pair may be formed as shown at _b_ and the second pair
as shown at _c_. In the latter case the metal is held across the nearer
edge of the anvil face and the blows delivered in a manner similar to
that described in the preceding paragraph. Hammer blows of this class
may be used on any edge of the anvil as required.
=47. The overhanging blow= is delivered so that half the width of the
hammer face extends over the edge of the anvil. (See Fig. 24.)
[Illustration: FIG. 24.—THE OVERHANGING BLOW.]
It is used for forming shoulders on one side of the metal and for
drawling out points of scarfs. When blows are delivered in this manner,
the anvil will form a depression or shoulder on the lower side of the
metal, and the hammer will keep the metal straight on the upper side.
This blow also will be more effective if the metal is held at a slight
angle across the edge of the anvil face, but the blows must always be
delivered squarely on the upper side of the metal to keep it straight.
=48. The beveling or angle blows= are delivered at any angle that the
form of the work may require. When the metal is to be drawn with a
taper on one side, it must be held level on the anvil and the blows
delivered at an angle determined by the amount of taper required.
Figure 25 shows the manner of holding the metal and the way the blows
are to be delivered.
[Illustration: FIG. 25.—THE BEVELING OR ANGLE BLOW.]
When the metal is to be drawn tapering on two opposite sides, it should
be held to the proper angle on the anvil to establish the taper desired
on the bottom, while the hammer blows are delivered so as to form a
similar taper on the upper side. (See Fig. 25.)
[Illustration: FIG. 26.—DRAWING METAL TO A POINT BY BEVELING OR ANGLE
BLOWS.
_A_, correct position; _B_, incorrect position.]
[Illustration: FIG. 27.—THE LEVERAGE BLOW.]
Blows of this kind are used for chamfering corners or edges, and may be
delivered at any required angle. They are also used when drawing metal
to a point, either square, round, hexagonal, or octagonal, but the
metal should be held on the anvil, as shown at _A_, Fig. 26. Then the
hammer will not come in contact with the face of the anvil, as shown at
_B_. If the hammer strikes the anvil, small chips of steel are liable
to break off from the hammer at the place indicated by _c_, and cause
serious injury.
[Illustration: FIG. 28.—BENDING BY LEVERAGE BLOWS.]
=49. The leverage blows= are used mostly for bending, as they will not
leave marks where the bending occurs. For instance, when a ring is to
be formed, the metal is first held in the tongs and rested on the horn
of the anvil, as shown in Fig. 27. Note that the metal will bend at
_a_, providing the heat is uniform. If, therefore, bending is required
at a certain place, that place should rest on the anvil and the blows
should be delivered beyond it.
After the first end has been bent to the required radius, the other
should be bent by holding it in the manner shown in Fig. 28, because
the joint of the tongs will prevent its being struck out of them while
the blow is being delivered. When both ends have been bent to the
proper radius, the ring should be finished as described in the ring
exercise (page 74), where upright blows are used with a leverage effect.
=50. The backing-up blows= are used to upset metal when it is
impossible to upset it in the usual manner, and in backing up the heel
of a scarf.
[Illustration: FIG. 29.—THE BACKING-UP BLOW, FOR UPSETTING.]
Upsetting with backing-up blows is done in the manner shown in Fig.
29. The metal should be extended over the anvil and thrust forward as
the blow is being delivered, to get the best results. This will also
prevent jarring the hand. The metal should be as hot as possible when
being upset in this manner.
The heel of a scarf is formed with backing-up blows after the metal has
been upset in the usual manner. The blows should be directed so that
they will have an upsetting effect, as indicated in Fig. 30, and not a
drawing one. After a few blows have been delivered with the face of the
hammer, they should then be delivered with the ball to form the heel
better and more rapidly.
[Illustration: FIG. 30.—BACKING-UP BLOWS USED FOR SCARFING.]
=51. The shearing blow= (see Fig. 31) is conveniently used for cutting
off small portions of metal instead of employing the hardy. It is
delivered so that the side or edge of the hammer will pass by and
nearly against the side or edge of the anvil. A blow so delivered will
have a shearing effect and cut the metal. It is perfectly proper to use
this blow for its intended purpose, but it should not be used when the
edge-to-edge blow is the one really required.
=52. Forging.=—Forging is the operation of hammering or compressing
metals into a desired shape. Seven specific operations are used.
Sometimes a piece of work or forging requires two, three, or even
all of them to complete it. These operations are designated by the
following names: drawing, bending, upsetting, forming, straightening,
twisting, and welding.
[Illustration: FIG. 31.—THE SHEARING BLOW.]
=53. Drawing=, the process of spreading or extending metal in a
desired direction, is accomplished by hammering or by pressing the
metal between such tools as the swages and fullers, or by holding it
on the anvil and using either of the set hammers, the flatter, or the
fuller. When using any of these pressing tools for drawing, a helper is
supposed to use the sledge to deliver the blows upon them.
It is always best to draw round metal with the swages, as it will be
smoother when finished than if it were done with the hammer; it should
be rolled in the swage a little after each blow of the sledge, and
after a complete revolution in one direction it should be turned in
the opposite direction, and so alternately continued until finished.
Especially if iron is being drawn, this will prevent twisting of the
fiber, which, if prolonged, would cause the metal to crack. Figure 32
shows the method of drawing with the swages.
When drawing any shape or size of metal to a smaller round diameter, it
is best first to draw it square to about the required size, delivering
the blows by turns on all four sides, then to make it octagonal, and
finally round. The finishing should be done with the swages, if those
of proper size are at hand; if not, light blows should be used, and
the metal revolved constantly in alternate directions, to make an
acceptable shape.
[Illustration: FIG. 32.—DRAWING WITH THE SWAGES.]
[Illustration: FIG. 33.—DRAWING WITH THE FLATTER.]
Drawing with the top and bottom fullers, in the manner shown with the
swages (Fig. 32), ought to be done cautiously, as the metal decreases
in size so rapidly that there is danger of its becoming too small at
the fullered place before the operator is aware of it. When using the
top fuller alone, in the same manner as the flatter (Fig. 33), similar
precautions should be observed. If the metal is to be decreased between
two shoulders, the top fuller may be used to rough it out; but the
fuller marks should be distributed between the shoulders, until one of
the set hammers or the flatter can be used.
If the metal is being drawn and is held crosswise on the anvil, as
shown at _a_, Fig. 34, it will increase in length more rapidly than
it will in width, and if held lengthwise as at _b_, it will increase
more in width than in length. This is due to the fact that the anvil
is slightly convex on its face, so that it has the effect of a large
fuller.
[Illustration: FIG. 34.—DRAWING WITH THE HAND HAMMER.]
The most difficult drawing for the beginner is to form metal into a
square or hexagonal shape. To draw it into a square form, the metal
must always be turned either one quarter or one half of a revolution to
prevent its becoming diamond-shaped, and the blows must be delivered
equally on the four sides to prevent its becoming oblong. If it does
become diamond-shaped, it can be made square by delivering blows at a
slight angle on the corners and sides of its long diagonal as shown
at _A_, _B_, and _C_, Fig. 35. If it is but slightly diamond-shaped,
the method shown at _B_ will prove satisfactory, but if badly out of
square, the method at _A_ will be the best.
[Illustration: FIG. 35.—SQUARING UP A DIAMOND-SHAPED PIECE.]
In drawing the hexagonal form, the metal should be turned by sixths of
a revolution. If it becomes distorted, it may be forged with such blows
as are shown at _B_ and _C_; if held as at _A_, it would be marred by
the edge _e_.
=54. Bending= is the operation of deflecting metal from a straight line
or changing its form by increasing the deflection already present. Iron
of any cross-sectional shape can be bent, but some shapes are much more
difficult than others.
The easiest to bend is the round, the only difficulty being to prevent
the hammer blows from showing. If the metal is to be round in section
when finished, the work will not have a good appearance if the cross
section is oval at some places and round at others, and unless the
hammer blows are cautiously delivered this will be the result.
Bending metal of a square section at right angles with the sides is not
very difficult, but bending such a section in line with the diagonal is
quite difficult, because the edges are liable to be marred where they
rest on the anvil and where the blows are delivered. The best method of
making bends of this kind is to heat the metal only where the bend is
to be, and then to bend it by pressure or pulling, while the work is
held securely in the vise, hardy hole, or swage block. If the heating
cannot be confined to the desired space, all excessively heated parts
should be cooled.
Oval sections are easily bent through their short diameters, but in
bending through the long diameters, the same method should be pursued
as described above for bending the square section in the plane of its
diagonal. Further explanations for bending are given on pages 118-121.
=55. Upsetting= is the operation of enlarging metal at some desired
point or place. It is done by hammering, ramming, or jarring. When a
piece of metal is too long it can be shortened by upsetting, or when it
is too thin at a certain place it can be thickened by the same method.
This is done by having the metal hot only at the point or place where
the upsetting is required. It is frequently necessary to cool the metal
where the heat is not needed in order to confine the upsetting to the
desired place.
Upsetting is not a very difficult operation as long as the metal is
kept perfectly straight; otherwise the task will prove tedious and the
metal may break from the constant bending back and forth. Bending will
always take place, but breaking generally can be prevented by having
the metal hot when it is straightened. The greatest difficulty in this
respect will be experienced when operating on common wrought iron.
Upsetting by hammering is done by holding the metal perpendicularly on
the anvil or something solid enough to withstand the blows which will
be delivered upon it. Figure 36 shows this method.
[Illustration: FIG. 36.—UPSETTING BY HAMMERING.]
If the end of a bar is being upset, and the upsetting is supposed to
extend up through the bar for some distance, the heated end should be
placed on the anvil as shown in the figure, because the anvil will
slightly chill the end of the bar, and the upsetting will continue much
farther than if the blows were delivered on the hot end. Striking the
hot end with the hammer increases the diameter of the end excessively,
because the contact of the hammer does not have a tendency to cool the
metal.
[Illustration: FIG. 37.—“BACKING UP” METAL.]
Another method of upsetting with the hammer, which is called “backing
up” the metal, is shown in Fig. 37. This method does not upset the
metal so rapidly, because the force of the hammer blows jars the hand
and arm which hold the bar.
Upsetting by ramming or jarring is thrusting the metal forcibly against
some heavy object like the surface plate, the swage block, or the
anvil. Figure 38 shows upsetting by this process. This method is very
effective and is used mostly when the metal is long enough to be held
with the hands, as shown.
[Illustration: FIG. 38.—UPSETTING BY RAMMING.]
=56. Forming= is a term generally applied to the making of a forging
with special tools, dies, or forms. This process may include bending,
punching, and other operations.
Swages are used for forming. A block of steel with a depression of a
special design is known as a forming die; a number of other tools and
appliances may be used for forming, but it is needless to mention them
here.
=57. Straightening= is one of the most frequent operations. When metal
is being forged, the various blows have a tendency to make it crooked,
and if the work is supposed to be straight when finished, it should be
so.
[Illustration: FIG. 39.—_A_, STRAIGHTENING WITH THE HAMMER; _B_,
STRAIGHTENING WITH THE SWAGE.]
There is as much skill required to straighten properly a piece of metal
as there is to bend it. The most common method (_A_, Fig. 39) is to
hold the metal lengthwise on the anvil with the bowed side or edge
upwards, then to deliver the blows at the highest point of the bow. The
blows will be most effective at the point where they are delivered,
so they should be distributed in order to get the object perfectly
straight and to avoid making unsightly hammer marks.
If the metal to be straightened is round, or if it is flat with round
edges, it is best to use a top swage of the proper size and deliver
the blows on the swage as shown at _B_, Fig. 39. Then the surface of
the round or the edges of the flat stock will not show any marks. The
flatter or round-edged set hammer may be used in the same manner on
flat or square material.
[Illustration: FIG. 40.—STRAIGHTENING WIDE METAL.]
When wide pieces of flat metal are to be straightened edgewise, and
such blows as are shown at _A_, Fig. 39, are not effective, then the
blows should be delivered along the concave edge as shown in Fig.
40, and distributed as indicated by the dotted circular lines. Blows
delivered in this manner will stretch or lengthen the metal on the
concave edge and straighten it.
=58. Twisting= is the operation of rotating metal to give it a spiral
appearance. It may be done either hot or cold, as the dimensions of the
material may require. It is done by holding the material in the vise,
the hardy hole, or the swage block, and turning one end of it with a
pair of tongs or a monkey wrench as many times as may be required. The
twisting will be confined between the places where it is held with the
vise, and where it is seized by the tongs or wrench.
If the material to be twisted is heavy enough to require heating,
a uniform heat is necessary or the twist will be irregular, and, as
an artistic appearance is usually desired, this operation should be
carried out with that result in view.
[Illustration: FIG. 41.—_A_, METAL TWISTED WHILE HOT; _B_, METAL
TWISTED WHILE COLD.]
_A_, Fig. 41, illustrates a piece of 1/2-inch square stock that has
been twisted while hot. _B_ shows a piece of 1/2 × 1/8-inch material
that has been twisted cold.
Another difficulty met with in twisting a piece of metal is that of its
becoming crooked. It can be straightened by laying the twisted portion
on a wooden block and striking it with a wooden mallet. This will
prevent the corners from becoming marred. A good method of avoiding
this trouble is to twist the metal inside of a piece of pipe whose
inside diameter is equal to the diameter of the metal.
=59. Welding=, the most difficult operation in the art of forging, is
the process of joining two or more pieces of metal into one solid mass.
All the previous operations allow some time for thought; in welding,
the worker must determine instantly where each blow is to be delivered,
as the welding heat of the metal vanishes rapidly; therefore, he is
compelled to think and act very quickly.
A scientific analysis of a perfect weld shows that it consists of
several processes, and that each one must be perfectly executed. If any
of these operations are improperly done, the result will be a partial
failure; if they are essential ones, the weld may readily be considered
as totally unfit.
=60. The Material for Welding.=—This must be considered, because there
are different qualities in each metal to be operated upon, and some
metals can be worked more easily than others.
A cross section of a bar of iron viewed through the microscope is seen
to be made up of a great number of layers or fibers, called laminæ,
resembling the grain or fiber in wood. These were cemented together
in the process of rolling or welding in the mill where the iron was
manufactured, and are continuous through its length. This makes the bar
of uniform quality throughout.
In welding, these fibers are joined diagonally at the ends,
consequently the strength of the weld depends entirely on how closely
or perfectly this cohesion is made. Careful hammering at the proper
heat brings the fibers in as close contact as possible, squeezes out
the slag and scale, and therefore greatly assists in strengthening the
weld.
Iron is an easy metal to weld. To prove this, place two pieces of
iron in a clean, non-oxidizing fire, allowing them to attain a white
or welding heat; then place them in contact and notice how readily
they stick together, proving that iron is easily welded at the proper
temperature. But in order to make the contact thorough, the pieces must
be hammered. This shows that hammering is a secondary operation, and
that iron cannot be joined by either heating or hammering alone.
By a similar experiment with soft steel, you will notice that the
pieces do not adhere like iron. If borax is applied while they are
heating, then slight indications of adhesion will be noticeable. This
shows that borax, sand, or something of a like nature must be used in
welding steel. In this case hammering is not a secondary operation, but
an essential one.
A higher carbon or tool steel may be experimented upon, with nearly the
same result. The noticeable difference between the lower and higher
qualities of steel proves that the greater the quantity of carbon, the
harder will be the welding, and if the experiments were extended to
still higher carbon steels, it would be discovered that they could not
be joined except by the use of a specially prepared flux. There are
indeed some high carbon steels that cannot be welded.
If a forging is to be made of a special quality of material, it is
frequently advisable to avoid welds, because two pieces that are welded
can hardly be considered so strong as a piece of the same material that
has not been welded.
The weldings which are alluded to here are such as are used by
practical blacksmiths in their general work without any special
appliances or apparatus whatever. The majority of the exercises on
welding in this book require the use of iron; for this reason this
preliminary consideration of metals need not have any further special
attention.
=61. Heating.=—When the word “fuel” is used here, either coal or coke
may be meant. Coal is the original in either case, for coke is formed
from it by the removal of gaseous substances. It is better that the
coal first be converted into coke, and that only the coke should come
in direct contact with the heating metals.
[Illustration: FIG. 42.—SECTIONAL VIEW OF A BLACKSMITHING FIRE.]
Figure 42 shows a sectional view of a blacksmithing fire: _d_ is the
bed of hot coke; _c_ is the dampened and unburned coal which surrounds
the fire, continually forming more coke as it is needed and also
holding the fire in a compact form; _a_ shows the proper way of placing
the metal in the fire, _b_, the improper way because the metal is
too near the entrance of the blast. As heating is such an important
operation, a thorough understanding of what causes imperfect heats, as
well as how to prevent them, is necessary.
The best fire for perfect heating is a reducing one, that is, one in
which the combustion of the fuel is rapid enough to use entirely the
oxygen in the air which is supplied. An oxidizing fire is one that does
not use all the oxygen in the blast for the combustion of the fuel.
The surplus oxygen will produce, on the surface of the metal, oxide of
iron, or a black scale, which is extremely injurious. This scale will
prevent welding, so all possible precautions should be taken to avoid
its forming.
A reducing fire can be maintained, and an oxidizing one avoided, by
having plenty of fuel surrounding the metal, equally, and allowing
the entrance of only sufficient air or blast to provide the necessary
heating.
If a piece of metal is left in a fixed position while heating, the
lower side will become the hottest. For that reason, all metals to be
welded are placed with scarfs downward. If the required heat is to be a
penetrating and thorough one, the metal is turned frequently to bring
all surfaces in contact with the most intense point of heat.
Even though every possible precaution is taken in all other steps of
the welding, the pieces cannot be joined perfectly if the heating is
carelessly done.
=62. Scarfing.=—This is the operation of preparing or shaping metal for
welding. There are five general kinds of welds, the distinct form of
each depending either on the quality of the material or on the shape of
the desired forging. They are called the lap weld, the cleft weld, the
butt weld, the jump weld, and the V weld.
=63. The lap weld= (Fig. 43) is so called because the pieces lap over
each other when placed in contact. It is most commonly used in general
practice, and all welds formed in a similar manner belong to this
class, regardless of the sectional form of the material or the shape of
the completed weld.
[Illustration: FIG. 43.—LAP WELD SCARFS.]
The pieces should always be upset where the scarfs are to be formed, to
provide excess metal for welding. They should be formed with their end
surfaces convex, and at an angle of about 45 degrees, which would not
make the joining surfaces too long.
When the fire and all tools are ready, place both scarfs face down in
the fire; when they are removed to the anvil, the piece held in the
right hand should be turned face up and rest on the anvil, in order
that the other may be placed in position on top of it.
The left-hand scarf should be placed carefully, with its point
meeting the heel of the other. If placed too high and overlapping,
it will increase the surface to be welded and perhaps decrease the
dimensions of the material where the points are welded down upon the
exterior. If placed too low, in all probability the surplus metal
provided by upsetting will not be sufficient to form the weld to a
uniform dimension. A little practice with the scarfs before heating is
advisable to prevent this difficulty.
The hand hammer should be placed conveniently on the anvil, with the
handle projecting sufficiently over the heel so that it can be grasped
quickly with the right hand as soon as the two pieces are in position.
If this precaution is not taken, the welding heat may disappear before
any blows can be struck.
The first blows after the pieces are placed should be directed toward
the center of the scarfs; when the center has been thoroughly united,
the blows should be directed toward the points to complete the
operation, if this can possibly be done in one heating.
It is impossible to give an invariable routine of blows; those given
are sufficient for the beginning, the rest must be left to the
observation and skill of the operator. Practice and judgment will
determine where the blows should be delivered, and when they should
cease.
As the welding heat vanishes very rapidly, it requires careful judgment
to determine when the pieces cease to unite. All blows delivered
after this will reduce the dimensions of the metal; if reheating
is necessary, there should be no metal sacrificed by unnecessary
hammering. Welds are generally weaker than the metal from which they
are made; consequently if the stock is made smaller at the weld, its
strength is greatly decreased.
The old adage “Haste makes waste” does not always apply. If you hasten
the operation of welding while the pieces are sufficiently hot, you
will not waste the metal. If through want of haste you are compelled to
reheat, you will waste metal, for every time a piece is heated it loses
a fractional part of its area, regardless of any hammering.
Welds made with scarfs of this kind are considered to be nearly as
strong as the metal itself, because they allow of a more thorough
lamination by hammering than other welds, consequently they are
frequently used on various qualities of metal when strength is
considered a chief requirement.
[Illustration: FIG. 44.—_A_, CLEFT WELD SCARFS; _B_, BUTT WELD SCARFS.]
=64. The cleft weld= (_A_, Fig. 44) is so called because one piece of
metal is split to receive the other. It is used for welding iron to
iron or steel to iron (the inserted portion being the steel). Whatever
the metal, the inserted portion is usually roughened with a hot cutter
on the pointed surfaces and the cleft hammered down and securely fitted
before the whole is heated. The pieces should not be placed in the fire
separately, but together, as they have been fitted.
When a welding heat appears, if possible, light blows should be
delivered on the end of the inserted portion while the two are in the
fire; these blows will partly join the pieces and make them secure
before removal. If this cannot be done, the first blows after removal
from the fire should be on the end. When a final and thorough welding
heat has been attained, they should be removed to the anvil and
securely joined. If heavy pieces are being operated upon, they may be
welded with the steam hammer.
=65. The butt weld= (_B_, Fig. 44) is so called because the pieces are
butted together and almost thoroughly joined by ramming or backing-up
blows before any blows are delivered on the exterior surface. The
scarfs are easily formed. The outer edges of the pieces are backed up
to form a rounded or convex end to insure their being joined at the
center first. As the blows are delivered on the end, the metal will
upset and the pieces will be joined from the center to the outer edges.
After they have been quite thoroughly joined with these blows, they
should be hammered on their exterior to weld them securely.
When scarfed in this manner, the pieces are frequently placed in the
fire for heating with the ends in contact, then partly joined while in
the fire and removed to the anvil or the steam hammer for final welding.
[Illustration: FIG. 45.—JUMP WELD SCARFS.]
=66. The jump weld= is shown in Fig. 45. The scarfs require perfect
forming, because the opportunity for hammering is limited, as blows
can be delivered only at certain places: on the end of the scarf 1
driving it into the concave groove 3; on a fuller which is held in the
fillet 4; and on both the edges indicated at 3.
The groove at 3 should be formed with sufficient metal at points 0, to
meet the projections _X_, and form a fillet. The convex scarf 1 should
first come in contact at 3, so that welding will proceed from that
place.
Welds made in this way are considered the weakest of those here
described, on account of the limited assistance which can be provided
by hammering. Still they are frequently used to avoid the laborious
operations required to make such forgings out of solid metal.
[Illustration: FIG. 46.—V WELD SCARFS.]
=67. The V weld= (Fig. 46) is a very important but difficult one. It is
generally used on extremely heavy work, such as locomotive frames (Fig.
47), beam straps, rudder stems, and all cumbersome forgings.
The process is as follows: Pieces 5 and 6 are to be welded. They are
held in a rigid position with heavy straps and bolts, as shown on the
locomotive frame in Fig. 47, sometimes while the V-shaped opening
is being formed; however, they must always be held secure while the
welding heat is being obtained. The V-shaped opening formed by the
scarfs on 5 and 6 should penetrate about two thirds of their thickness
and form an angle of about 50 degrees, with sufficient metal at _9_ to
provide for the waste which will occur while a welding heat is being
procured.
The wedge 7 is formed with some surplus metal for filling the V-shaped
opening. It is handled by a bar which is welded to it. The angle of the
wedge should be not less than 5 degrees smaller than the angle of the
opening. This will insure that the welding proceeds from the apex or
point of the wedge outward.
Two fires are required; 5 and 6, securely strapped and bolted together,
are placed in one with the V-shaped opening turned downward. Plenty of
coke is placed around this opening, completely covered with moistened
coal, and securely packed with a shovel; then two openings or vents are
made through the coal with a poker, one on each side of the metal and
leading to the scarfs. This is called a covered fire. The blast is now
turned on and slowly increased until the proper heat is attained. The
progress of heating can be observed through the openings thus made, and
the fire replenished with coke when necessary.
These operations are supervised by the smith who has the work in
charge, with two or more helpers or assistants, according to the size
of the forging. The wedge 7 also is heated in a covered fire with only
one opening on the workman’s side of the forge; the wedge is inserted
in that opening, and is attended and handled by another smith, who
watches its progress in heating.
When the supervising and attending smiths have signaled to each other
that the heats are ready, 5 and 6 are removed, turned over, and placed
on the anvil or on the steam hammer die to receive the wedge which is
placed in position by the attending smith. After the wedge has been
thoroughly welded into place with either sledges or steam hammer, the
handle and all surplus metal surrounding the openings are removed by
the aid of hot cutters and sledges.
This procedure must now be repeated and another wedge welded into place
on the opposite side indicated by the broken lines. With these two
wedges 5 and 6 will be securely joined.
To insure a perfect weld, a good quality of material should be selected
for the wedges. It should be thoroughly hammered to produce good
texture, and if iron is operated upon, the fiber of the wedges should
run parallel to the fiber of the piece to be welded. As this is not
generally observed, welds of this character often break through the
centers of the two wedges.
[Illustration: FIG. 47.—A BROKEN LOCOMOTIVE FRAME.]
The broken locomotive frame shown in Fig. 47 would be repaired by the
above method. The irregular line at _A_ shows where the break has
occurred. The straps and bolts at _B_ indicate the method of holding
the parts in alignment. Two tie rods at _C_ prevent the parts from
separating.
QUESTIONS FOR REVIEW
What effect is produced by the upright blow? By the edge-to-edge
blow? By the overhanging blow? By the beveling or angle blow? By the
leverage blows? What are the backing-up blows used for? The shearing
blows?
What is meant by forging? How many different operations are used
in forging? Name them. What is meant by drawing? What tools may be
employed in drawing metal? If you desire to increase the length more
than the width, how should you hold the metal on the anvil? Why? What
precaution should be observed in revolving metal when it is being
drawn into a round form? What is meant by bending? Can iron of any
sectional shape be bent? Which is the easiest to bend? What shapes
are difficult to bend? How are these difficulties overcome? What is
meant by upsetting? Explain how it is done. What difficulty is often
experienced in upsetting? What is the difference in effect between
resting the heated end on the anvil, and striking on the heated end
while upsetting?
What is meant by forming? What other operations may be involved? What
special tools or appliances are sometimes used for forming? State
what has been said about straightening? Does it require much skill?
Would it be as easy to straighten a wide flat piece of metal, as it
would a round one? Why? Explain the operation of twisting. Why is it
generally done? How can twisting be done and keep the work perfectly
straight? Explain the essential parts of a weld. Is a weld as strong
as the original unwelded bar? Can all iron and steel be welded? What
kind of fire is best for heating? What is meant by an oxidizing
fire? What effect does it have on the metal? How can an oxidizing
fire be prevented? How should scarfs be placed in the fire? Why? If
a penetrating and thorough heat is desired on a piece of metal, how
can it be obtained? What is meant by scarfing? Are all scarfs formed
alike? Name and describe the different kinds of scarfs and welds.
Which one is considered the weakest? Why? On what kind of work is the
V weld used?