Smithing, or blacksmithing, is the process of working heated iron, steel or
other metals by forging, bending or welding them.
The Forge.--The metal is heated in a forge consisting of a shallow
pan for holding the fire, in the center of which is an opening from below
through which air is forced to make a hot fire.
Image Figure 48.--Tuyere Construction on a Forge
Air is forced through this hole, called a "tuyere" (Figure 48) by means of
a hand bellows, a rotary fan operated with crank or lever, or with a fan
driven from an electric motor. The harder the air is driven into the fire
above the tuyere the more oxygen is furnished and the hotter the fire
becomes.
Directly below the tuyere is an opening through which the ashes that drop
from the fire may be cleaned out.
The Fire.--The fire is made by placing a small piece of waste soaked
in oil, kerosene or gasoline, over the tuyere, lighting the waste, then
starting the fan or blower slowly. Gradually cover the waste, while it is
burning brightly, with a layer of soft coal. The coal will catch fire and
burn after the waste has been consumed. A piece of waste half the size of a
person's hand is ample for this purpose.
The fuel should be "smithing coal." A lump of smithing coal breaks easily,
shows clean and even on all sides and should not break into layers. The
coal is broken into fine pieces and wet before being used on the fire.
The fire should be kept deep enough so that there is always three or four
inches of fire below the piece of metal to be heated and there should be
enough fire above the work so that no part of the metal being heated comes
in contact with the air. The fire should be kept as small as possible while
following these rules as to depth.
To make the fire larger, loosen the coal around the edges. To make the fire
smaller, pack wet coal around the edges in a compact mass and loosen the
fire in the center. Add fresh coal only around the edges of the fire. It
will turn to coke and can then be raked onto the fire. Blow only enough air
into the fire to keep it burning brightly, not so much that the fire is
blown up through the top of the coal pack. To prevent the fire from going
out between jobs, stick a piece of soft wood into it and cover with fresh
wet coal.
Tools.--The hammer is a ball pene, or blacksmith's hammer,
weighing about a pound and a half.
The sledge is a heavy hammer, weighing from 5 to 20 pounds and
having a handle 30 to 36 inches long.
The anvil is a heavy piece of wrought iron (Figure 49), faced with
steel and having four legs. It has a pointed horn on one end, an
overhanging tail on the other end and a flat top. In the tail there is a
square hole called the "hardie" hole and a round one called the "spud"
hole.
Image Figure 49.--Anvil, Showing Horn, Tail, Hardie Hole and Spud
Hole
Tongs, with handles about one foot long and jaws suitable for
holding the work, are used. To secure a firm grip on the work, the jaws may
be heated red hot and hammered into shape over the piece to be held, thus
giving a properly formed jaw. Jaws should touch the work along their entire
length.
The set hammer is a hammer, one end of whose head is square and
flat, and from this face the head tapers evenly to the other face. The
large face is about 1-1/4 inches square.
The flatter is a hammer having one face of its head flat and about
2-1/2 inches square.
Swages are hammers having specially formed faces for finishing
rounds, squares, hexagons, ovals, tapers, etc.
Fullers are hammers having a rounded face, long in one direction.
They are used for spreading metal in one direction only.
The hardy is a form of chisel with a short, square shank which may
be set into the hardie hole for cutting off hot bars.
Operations.--Blacksmithing consists of bending, drawing or upsetting
with the various hammers, or in punching holes.
Bending is done over the square corners of the anvil if square cornered
bends are desired, or over the horn of the anvil if rounding bends, eyes,
hooks, etc., are wanted.
To bend a ring or eye in the end of a bar, first figure the length of stock
needed by multiplying the diameter of the hole by 31/7, then heat the piece
to a good full red at a point this distance back from the end. Next bend
the iron over at a 90 degree angle (square) at this point. Next, heat the
iron from the bend just made clear to the point and make the eye by laying
the part that was bent square over the horn of the anvil and bending the
extreme tip into part of a circle. Keep pushing the piece farther and
farther over the horn of the anvil, bending it as you go. Do not hammer
directly over the horn of the anvil, but on the side where you are doing
the bending.
To make the outside of a bend square, sharp and full, rather than slightly
rounding, the bent piece must be laid edgewise on the face of the anvil.
That is, after making the bend over the corner of the anvil, lay the piece
on top of the anvil so that its edge and not the flat side rests on the
anvil top. With the work in this position, strike directly against the
corner with the hammer so that the blows come in line, first with one leg
of the work, then the other, and always directly on the corner of the
piece. This operation cannot be performed by laying the work so that one
leg hangs over the anvil's corner.
To make a shoulder on a rod or bar, heat the work and lay flat across the
top of the anvil with the point at which the shoulder is desired at the
edge of the anvil. Then place the set hammer on top of the piece, with the
outside edge of the set hammer directly over the edge of the anvil. While
hammering in this position keep the work turning continually.
To draw stock means to make it longer and thinner by hammering. A piece to
be drawn out is usually laid across the horn of the anvil while being
struck with the hammer. The metal is then spread in only one direction in
place of being spread in every direction, as it would be if laid on the
anvil face. To draw the work, heat it to as high a temperature as it will
stand without throwing sparks and burning. The fuller may be used for
drawing metal in place of laying the work over the horn of the anvil.
When drawing round stock, it should be first drawn out square, and when
almost down to size it may be rounded. When pointing stock, the same rule
of first drawing out square applies.
Upsetting means to make a piece shorter in length and greater in thickness
or width, or both shorter and thicker. To upset short pieces, heat to a
bright red at the place to be upset, then stand on end on the anvil face
and hammer directly down on top until of the right form. Longer pieces may
be swung against the anvil or placed upright on a heavy piece of metal
lying on the floor or that is sunk into the floor. While standing on this
heavy piece the metal may be upset by striking down on the end with a heavy
hammer or the sledge. If a bend appears while upsetting, it should be
straightened by hammering back into shape on the anvil face.
Light blows affect the metal for only a short distance from the point of
striking, but heavy blows tend to swell the metal more equally through its
entire length. In driving rivets that should fill the holes, heavy blows
should be struck, but to shape the end of a rivet or to make a head on a
rod, light blows should be used.
The part of the piece that is heated most will upset the most.
To punch a hole through metal, use a tool steel punch with its end slightly
tapering to a size a little smaller than the hole to be punched. The end of
the punch must be square across and never pointed or rounded.
First drive the punch part way through from one side and then turn the work
over. When you turn it over, notice where the bulge appears and in that way
locate the hole and drive the punch through from the second side. This
makes a cleaner and more even hole than to drive completely through from
one side. When the punch is driven in from the second side, the place to be
punched through should be laid over the spud hole in the tail of the anvil
and the piece driven out of the work.
Work when hot is larger than it will be after cooling. This must be
remembered when fitting parts or trouble will result. A two-foot bar of
steel will be 1/4 inch longer when red hot than when cold.
The temperatures of iron correspond to the following colors:
Dullest red seen in the dark... 878°
Dullest red seen in daylight... 887°
Dull red....................... 1100°
Full red....................... 1370°
Light red...................... 1550°
Orange......................... 1650°
Light orange................... 1725°
Yellow......................... 1825°
Light yellow................... 1950°
Bending Pipes and Tubes.--It is difficult to make bends or curves in
pipes and tubing without leaving a noticeable bulge at some point of the
work. Seamless steel tubing may be handled without very great danger of
this trouble if care is used, but iron pipe, having a seam running
lengthwise, must be given special attention to avoid opening the seam.
Bends may be made without kinking if the tube or pipe is brought to a full
red heat all the way around its circumference and at the place where the
bend is desired. Hold the cool portion solidly in a vise and, by taking
hold of the free end, bend very slowly and with a steady pull. The pipe
must be kept at full red heat with the flames from one or more torches and
must not be hammered to produce the bend. If a sufficient purchase cannot
be secured on the free end by the hand, insert a piece of rod or a smaller
pipe into the opening.
While making the bend, should small bulges appear, they may be hammered
back into shape before proceeding with the work.
Tubing or pipes may be bent while being held between two flat metal
surfaces while at a bright red heat. The metal plates at each side of the
work prevent bulging.
Another method by which tubing may be bent consists of filling completely
with tightly packed sand and fitting a solid cap or plug at each end.
Thin brass tubing may be filled with melted resin and may be bent after the
resin cools. To remove the resin it is necessary to heat the tube, allowing
it to run out.
Large jobs of bending should be handled in special pipe bending machines in
which the work is forced through formed rolls which prevent its bulging.
WELDING
Welding with the heat of a blacksmith forge fire, or a coal or illuminating
gas fire, can only be performed with iron and steel because of the low heat
which is not localized as with the oxy-acetylene and electric processes.
Iron to be welded in this manner is heated until it reaches the temperature
indicated by an orange color, not white, as is often stated, this orange
color being slightly above 3600 degrees Fahrenheit. Steel is usually welded
at a bright red heat because of the danger of oxidizing or burning the
metal if the temperature is carried above this point.
The Fire.--If made in a forge, the fire should be built from good
smithing coal or, better still, from coke. Gas fires are, of course,
produced by suitable burners and require no special preparation except
adjustment of the heat to the proper degree for the size and thickness of
the metal being welded so that it will not be burned.
A coal fire used for ordinary forging operations should not be used for
welding because of the impurities it contains. A fresh fire should be built
with a rather deep bed of coal, four to eight inches being about right for
work ordinarily met with. The fire should be kept burning until the coal
around the edges has been thoroughly coked and a sufficient quantity of
fuel should be on and around the fire so that no fresh coal will have to
be added while working.
After the coking process has progressed sufficiently, the edges should be
packed down and the fire made as small as possible while still surrounding
the ends to be joined. The fire should not be altered by poking it while
the metal is being heated. The best form of fire to use is one having
rather high banks of coked coal on each side of the mass, leaving an
opening or channel from end to end. This will allow the added fuel to be
brought down on top of the fire with a small amount of disturbance.
Preparing to Weld.--If the operator is not familiar with the metal
to be handled, it is best to secure a test piece if at all possible and try
heating it and joining the ends. Various grades of iron and steel call for
different methods of handling and for different degrees of heat, the proper
method and temperature being determined best by actual test under the
hammer.
The form of the pieces also has a great deal to do with their handling,
especially in the case of a more or less inexperienced workman. If the
pieces are at all irregular in shape, the motions should be gone through
with before the metal is heated and the best positions on the anvil as well
as in the fire determined with regard to the convenience of the workman and
speed of handling the work after being brought to a welding temperature.
Unnatural positions at the anvil should be avoided as good work is most
difficult of performance under these conditions.
Scarfing.--While there are many forms of welds, depending on the
relative shape of the pieces to be joined, the portions that are to meet
and form one piece are always shaped in the same general way, this shape
being called a "scarf." The end of a piece of work, when scarfed, is
tapered off on one side so that the extremity comes to a rather sharp edge.
The other side of the piece is left flat and a continuation in the same
straight plane with its side of the whole piece of work. The end is then in
the form of a bevel or mitre joint (Figure 50).
Image Figure 50.--Scarfing Ends of Work Ready for Welding
Scarfing may be produced in any one of several ways. The usual method is to
bring the ends to a forging heat, at which time they are upset to give a
larger body of metal at the ends to be joined. This body of metal is then
hammered down to the taper on one side, the length of the tapered portion
being about one and a half times the thickness of the whole piece being
handled. Each piece should be given this shape before proceeding farther.
The scarf may be produced by filing, sawing or chiseling the ends, although
this is not good practice because it is then impossible to give the desired
upset and additional metal for the weld. This added thickness is called for
by the fact that the metal burns away to a certain extent or turns to
scale, which is removed before welding.
When the two ends have been given this shape they should not fit as closely
together as might be expected, but should touch only at the center of the
area to be joined (Figure 51). That is to say, the surface of the beveled
portion should bulge in the middle or should be convex in shape so that the
edges are separated by a little distance when the pieces are laid together
with the bevels toward each other. This is done so that the scale which is
formed on the metal by the heat of the fire can have a chance to escape
from the interior of the weld as the two parts are forced together.
Image Figure 51.--Proper Shape of Scarfed Ends
If the scarf were to be formed with one or more of the edges touching each
other at the same time or before the centers did so, the scale would be
imprisoned within the body of the weld and would cause the finished work to
be weak, while possibly giving a satisfactory appearance from the outside.
Fluxes.--In order to assist in removing the scale and other
impurities and to make the welding surfaces as clean as possible while
being joined, various fluxing materials are used as in other methods of
welding.
For welding iron, a flux of white sand is usually used, this material being
placed on the metal after it has been brought to a red heat in the fire.
Steel is welded with dry borax powder, this flux being applied at the same
time as the iron flux just mentioned. Borax may also be used for iron
welding and a mixture of borax with steel borings may also be used for
either class of work. Mixtures of sal ammoniac with borax have been
successfully used, the proportions being about four parts of borax to one
of sal ammoniac. Various prepared fluxing powders are on the market for
this work, practically all of them producing satisfactory results.
After the metal has been in the fire long enough to reach a red heat, it is
removed temporarily and, if small enough in size, the ends are dipped into
a box of flux. If the pieces are large, they may simply be pulled to the
edge of the fire and the flux then sprinkled on the portions to be joined.
A greater quantity of flux is required in forge welding than in electric or
oxy-acetylene processes because of the losses in the fire. After the powder
has been applied to the surfaces, the work is returned to the fire and
heated to the welding temperature.
Heating the Work.--After being scarfed, the two pieces to be welded
are placed in the fire and brought to the correct temperature. This
temperature can only be recognized by experiment and experience. The metal
must be just below that point at which small sparks begin to be thrown out
of the fire and naturally this is a hard point to distinguish. At the
welding heat the metal is almost ready to flow and is about the consistency
of putty. Against the background of the fire and coal the color appears to
be a cream or very light yellow and the work feels soft as it is handled.
It is absolutely necessary that both parts be heated uniformly and so that
they reach the welding temperature at the same time. For this reason they
should be as close together in the fire as possible and side by side. When
removed to be hammered together, time is saved if they are picked up in
such a way that when laid together naturally the beveled surfaces come
together. This makes it necessary that the workman remember whether the
scarfed side is up or down, and to assist in this it is a good thing to
mark the scarfed side with chalk or in some other noticeable manner, so
that no mistake will be made in the hurry of placing the work on the anvil.
The common practice in heating allows the temperature to rise until the
small white sparks are seen to come from the fire. Any heating above this
point will surely result in burning that will ruin the iron or steel being
handled. The best welding heat can be discerned by the appearance of the
metal and its color after experience has been gained with this particular
material. Test welds can be made and then broken, if possible, so that the
strength gained through different degrees of heat can be known before
attempting more important work.
Welding.--When the work has reached the welding temperature after
having been replaced in the fire with the flux applied, the two parts are
quickly tapped to remove the loose scale from their surfaces. They are then
immediately laid across the top of the anvil, being placed in a diagonal
position if both pieces are straight. The lower piece is rested on the
anvil first with the scarf turned up and ready to receive the top piece in
the position desired. The second piece must be laid in exactly the position
it is to finally occupy because the two parts will stick together as soon
as they touch and they cannot well be moved after having once been allowed
to come in contact with each other. This part of the work must be done
without any unnecessary loss of time because the comparatively low heat at
which the parts weld allows them to cool below the working temperature in
a few seconds.
The greatest difficulty will be experienced in withdrawing the metal from
the fire before it becomes burned and in getting it joined before it cools
below this critical point. The beveled edges of the scarf are, of course,
the first parts to cool and the weld must be made before they reach a point
at which they will not join, or else the work will be defective in
appearance and in fact.
If the parts being handled are of such a shape that there is danger of
bending a portion back of the weld, this part may be cooled by quickly
dipping it into water before laying the work on the anvil to be joined.
The workman uses a heavy hand hammer in making the joint, and his helper,
if one is employed, uses a sledge. With the two parts of the work in place
on the anvil, the workman strikes several light blows, the first ones being
at a point directly over the center of the weld, so that the joint will
start from this point and be worked toward the edges. After the pieces have
united the helper strikes alternate blows with his sledge, always striking
in exactly the same place as the last stroke of the workman. The hammer
blows are carried nearer and nearer to the edges of the weld and are made
steadily heavier as the work progresses.
The aim during the first part of the operation should be to make a perfect
joint, with every part of the surfaces united, and too much attention
should not be paid to appearance, at least not enough to take any chance
with the strength of the work.
It will be found, after completion of the weld, that there has been a loss
in length equal to one-half the thickness of the metal being welded. This
loss is occasioned by the burned metal and the scale which has been formed.
Finishing the Weld.--If it is possible to do so, the material should
be hammered into the shape that it should remain with the same heat that
was used for welding. It will usually be found, however, that the metal has
cooled below the point at which it can be worked to advantage. It should
then be replaced in the fire and brought back to a forging heat.
Image Figure 52.--Upsetting and Scarfing the End of a Rod
While shaping the work at this forging heat every part that has been at a
red heat should be hammered with uniformly light and even blows as it
cools. This restores the grain and strength of the iron or steel to a great
extent and makes the unavoidable weakness as small as possible.
Forms of Welds.--The simplest of all welds is that called a "lap
weld." This is made between the ends of two pieces of equal size and
similar form by scarfing them as described and then laying one on top of
the other while they are hammered together.
A butt weld (Figure 52) is made between the ends of two pieces of shaft or
other bar shapes by upsetting the ends so that they have a considerable
flare and shaping the face of the end so that it is slightly higher in the
center than around the edges, this being done to make the centers come
together first. The pieces are heated and pushed into contact, after which
the hammering is done as with any other weld.
Image Figure 53.--Scarfing for a T Weld
A form similar to the butt weld in some ways is used for joining the end of
a bar to a flat surface and is called a jump weld. The bar is shaped in the
same way as for a butt weld. The flat plate may be left as it is, but if
possible a depression should be made at the point where the shaft is to be
placed. With the two parts heated as usual, the bar is dropped into
position and hammered from above. As soon as the center of the weld has
been made perfect, the joint may be finished with a fuller driven all the
way around the edge of the joint.
When it is required to join a bar to another bar or to the edge of any
piece at right angles the work is called a "T" weld from its shape when
complete (Figure 53). The end of the bar is scarfed as described and the
point of the other bar or piece where the weld is to be made is hammered so
that it tapers to a thin edge like one-half of a circular depression. The
pieces are then laid together and hammered as for a lap weld.
The ends of heavy bar shapes are often joined with a "V," or cleft, weld.
One bar end is shaped so that it is tapering on both sides and comes to a
broad edge like the end of a chisel. The other bar is heated to a forging
temperature and then slit open in a lengthwise direction so that the
V-shaped opening which is formed will just receive the pointed edge of the
first piece. With the work at welding heat, the two parts are driven
together by hammering on the rear ends and the hammering then continues as
with a lap weld, except that the work is turned over to complete both sides
of the joint.
Image Figure 54.-Splitting Ends to Be Welded in Thin Work
The forms so far described all require that the pieces be laid together in
the proper position after removal from the fire, and this always causes a
slight loss of time and a consequent lowering of the temperature. With very
light stock, this fall of temperature would be so rapid that the weld would
be unsuccessful, and in this case the "lock" weld is resorted to. The ends
of the two pieces to be joined are split for some distance back, and
one-half of each end is bent up and the other half down (Figure 54). The
two are then pushed together and placed in the fire in this position. When
the welding heat is reached, it is only necessary to take the work out of
the fire and hammer the parts together, inasmuch as they are already in the
correct position.
Other forms of welds in which the parts are too small to retain their heat,
can be made by first riveting them together or cutting them so that they
can be temporarily fastened in any convenient way when first placed in the
fire.
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