PART ONE.--WELDING OF CAST IRON
(=66=) In order to know how to weld, it is quite imperative that
the operator first know the kind of metal he is to work on. It is
surprising to find how few welders know their metals thoroughly. An
incident might be cited where some welders depend upon the sparks given
off by the emery wheel in determining the kind of metal they are about
to weld. They will approach the wheel; grind off their work, noting the
sparks; return to their welding table; choose their filler rods and do
their welding without any delay whatsoever, much to the consternation
of their fellow workers. There are four simple ways in common use to
distinguish between cast iron, malleable iron, and steel; they are:
By the cross-section of a fresh break, by application of the welding
torch, by the sparks given off when applied to the emery wheel and by
the chisel test.
[Illustration: FIG. 42.--Characteristic Sparks of Different Irons and
Steels Thrown off by an Emery Wheel. Wheel should be Clean Cutting and
Run about 7000 Feet per Minute.
(1) Shows cast iron. No sparks unless impurities are present.
(2) Is wrought iron almost free from carbon. Heated particles thrown
from wheel follow straight line. These become broader and more luminous
some distance from their source of heat.
(3) Illustrates mild steel action. Small amount of carbon present
causes a division or forking of the luminous streak.
(4) Shows the effect of increasing the carbon from 0.50 to 0.85
per cent in mild steel. The iron spark lines diminish: the forking
of the luminous streak occurs more frequently, being subdivided by
re-explosions from smaller particles.
(5) Is a piece of carbon tool steel. The iron lines are practically
eliminated with the increase of the explosions and subdivisions,
causing display of figures.
(6) Gives the spark of high-speed steel, containing in addition to 65
per cent carbon, other alloying elements, chiefly tungsten and chromium.
(7) Represents a manganese spark. (Occasionally found in cast iron.)
(8) Shows spark thrown from old grade of “Mushett” steel.
(9) Represents a magnet steel spark.]
(=67=) Externally cast iron usually has some sand on its surface and
its cross-section shows the grain to be fine, even, and to have a dull
grayish color. The surface of malleable iron contains no sand and its
grain is very fine, such as cast iron, but slightly darker in color.
A very fine steel veneer is on all surfaces of malleable iron, which
is much lighter in color. When the welding torch is applied to cast
iron, no sparks are given off, but when applied to malleable iron a
bright spark is thrown off which breaks in falling, showing that the
outside material is steel. These sparks soon cease and the metal which
is molten is covered by a heavy oxide or skin which recedes or draws
away from the flame slightly, showing a very porous cast-iron interior.
When brought in contact with the emery wheel steel sparks, which are
very luminous and break in falling, are given off first in the case of
malleable iron, but they soon change to the dull red spark of cast
iron. When a chisel is applied to cast iron, the iron chips off; when
applied to malleable iron the edge will curl up, then chip off when the
cast iron is reached. The cross-section of cast steel shows a bright,
coarse, silvery gray grain. When the torch is applied a distinctively
steel spark which is luminous and breaks in falling is thrown off. When
applied to the emery wheel steel sparks are thrown off; when the edge
is chipped by a chisel it will curl up.
[Illustration: METHODS OF DISTINGUISHING METALS
Here are five methods, any one or all of which may be used to learn
the nature of common castings which might confuse the welder.
---+-----------+--------------------+-----------------+---------------
No.| Test. | Malleable Iron. | Cast Steel. | Cast Iron.
---+-----------+--------------------+-----------------+---------------
1 |Outside |Generally smooth and|Rough surface |Surface fairly
|Appearance.|free from all sand, |with sand in |smooth but
| |weighs about same |evidence, weighs |generally shows
| |as cast iron. |much more |some sand.
| | |than cast iron. |
---+-----------+--------------------+-----------------+---------------
2 |Cross- |Ring of bright steel|Large, bright, |Fine, uniform,
|section |crystals outside, |luminous, silver |dark gray,
|Test. |with darker iron |crystals. |crystals.
| |crystals inside. | |
---+-----------+--------------------+-----------------+---------------
3 |Emery Wheel|Few steel sparks and|Bright, luminous |Dull red sparks
|Test. |then iron sparks |sparks that |that do not
| |from interior. |break in falling.|break.
---+-----------+--------------------+-----------------+---------------
4 |Chisel |Surface will curl |Will curl before |Will chip off.
|Test. |and interior break |breaking. |
| |off. | |
---+-----------+--------------------+-----------------+---------------
5 |Torch Test.|Gives way before |Gives forth |Gives no sparks
| |flame and delivers |bright sparks |except where
| |few sparks. Metal |that break in |there are
| |becomes porous. |falling. |impurities.
---+-----------+--------------------+-----------------+---------------
FIG. 43.]
(=68=) The metal in the filler-rod should be the same in practically
all cases as the metal to be welded. There are few exceptions to this
rule, but the principal one is that of malleable iron. The cast iron
in the rods is of a very good grade and generally much better than
the piece to be worked upon. To permit the ready flow of the rod and
eliminate oxidation, as much as possible, three per cent of silica is
generally used in the casting of filler-rods for cast iron welding.
Piston rings and other scrap iron should not be used for filler-rods,
as they contain many impurities such as core-sand, dirt, grease, etc.,
which will ruin the weld. It is disheartening to see some operators
attempt to economize on the filler-rod. It is not an uncommon sight to
see several dollars’ worth of gas and the same amount of the welder’s
time, together with a few cents’ worth of filler rods all lost, and the
operator’s reputation ruined. This, because an attempt is made to save
the few cents involved in the filler-rods by substituting a rod of a
very poor grade.
(=69=) A flux is not used, as many suppose, to cement the filler-rod to
the metal. It is used purely as a cleansing agent and may be likened
to the acid used in soldering. It does not act on the metal until the
latter has reached the melting-point, but then it starts to break up
the oxides and clean the surface. This action permits the metal to flow
together more readily. A cast-iron flux is always used in welding cast
iron, to break up the oxide, because the cast iron itself will melt
before the oxide and no matter how hot the metal is it will not flow
together as long as this oxide is present.
(=70=) To obtain the best results, reliable fluxes should always be
used. Occasionally an accident will happen to the flux can, when the
operator is on some isolated job and a substitute flux must be obtained
at once. Equal parts of bicarbonate of soda (cooking soda), and
carbonate of soda (ordinary washing soda), may be purchased from any
grocery in the powdered form and mixed together thoroughly. This will
tide the welder over until he can return to the shop and replenish his
supply.
[Illustration: FIG. 44.--Whenever Possible, the Beginner should “V” His
Work, and Complete His Weld from One Side only. On heavy work, however,
it will be necessary to “V” out from both sides, as is here shown.]
(=71=) The flux is generally applied by means of the filler-rod. One
end is heated and dipped in the flux; enough will adhere to break up
part of the oxides, on the ordinary-sized job. The flux is carried to
the work, which should be at the melting-point and introduced between
the flame and the metal. Oxides will break up immediately and the
metal will flow together, but it must be remembered that the flux has
no action on cold or moderately heated metals. The flux as has been
explained is used to clean the metal and break up the oxides. To the
oft-repeated question, how often should the flux be applied, answer is
made as follows: As often as it is necessary to clean up the metal and
break up the oxides. All fluxes should be kept in airtight containers
when not in use, to keep their chemical contents in the very best
condition and it is best to use only a small quantity of flux on the
welding table at one time.
(=72=) Oxy-acetylene welding is purely a fusing process and the most
important points to remember in executing a weld are, to eliminate
the entire crack in the fracture and to add the filler-rod without
changing the character of the metal. On thin pieces of metal it is
possible to depend upon the force of the flame to entirely penetrate to
the depth of the crack but on work three-eighths of an inch thick or
over, it is well to “V” out or remove some of the surface metal around
the crack in order to get down to the bottom. By “V-ing” we mean to
chip or grind off each edge at an angle of approximately 45 degrees, so
that the opening will form an angle of 90 degrees where the two pieces
come together, with the crack at the bottom portion of the “V.” This
should NOT be ground down to a knife edge, for it will readily burn
up. It is preferable to leave about one-eighth inch along the line in
order that the pieces will fit together and the proper alignment may
be obtained. If two pieces of cast iron have been prepared in this
manner the neutral flame of the welding torch is brought down in such a
manner that the tip of the cone just licks the metal. The heat is not
applied directly to the line of weld to start with, but rather to the
surrounding part. This is done in order to get the entire locality in
a condition which will not withdraw too much of the heat from the line
of the weld, once the fusing is begun. If it is found that the tip will
not produce enough heat to bring the metal to a red heat in a fairly
short time, a larger tip should be used.
[Illustration: FIG. 45.--Starting a Cast-iron Weld.]
[Illustration: FIG. 46.--Reinforcing a Cast-iron Weld.]
(=73=) No set rule can be given as to the sized tip to be used on
various kinds of metal. It will largely depend upon the welder’s
ability and judgment. When the metal is brought to red-heat, the
neutral flame or cone is brought into contact with the lowest portion
of the “V” and held there until it is seen that the metal is melted on
both sides. The filler-rod, which has previously been heated at one
end and dipped into the flux so that an amount adheres to the end of
the rod, then carries this flux to that portion of the weld which is
under way. Enough flux is blown off the rod into the weld to clean up
the surface and permit the metal flowing together. The crack should be
melted together all along before any additional metal is added, for the
elimination of the crack is extremely important. It might be noted that
as soon as the metal begins to flow freely the neutral flame should
be raised a short distance from the work in order to better control
the molten metal. In order to build up the metal to the original state
along the line of weld or perhaps reinforce it, the sides and bottom of
this “V-ed” out part are then brought to a molten state and held there
while the filler-rod which brings up more flux is stirred into this
metal and the end melted off. In this way the flame does not come in
direct contact with the filler-rod and is used only to keep the metal
in a molten condition. As much of the filler-rod can be melted off as
is thought necessary to bring the weld to the normal condition of the
metal or an additional reinforcement can be built up, if it is thought
advisable. If care is taken in the above procedure, many of the blow
holes and hard spots in the weld will be eliminated, for any impurities
that might gather will be displaced by the melted metal and will float
to the top. In cooling a weld of this kind, care should be taken not to
permit any sudden chilling for this will tend to harden the weld. It is
best to cool it slowly by burying it in slack lime, ashes, or wrap it
with asbestos paper to keep the air from it as much as possible.
[Illustration: FIG. 47.--This Problem does not Require Preheating to
Care for Contraction, as the Ends of _A_ and _B_ are not Confined.]
(=74=) There may be a great many causes for blow holes and hard spots
in the weld, but probably they can all be traced directly to the
lack of heat. It must be remembered that welding is a fusing process
and heat is absolutely essential. Therefore it should not be used
sparingly. The application of heat always causes expansion. There are
no exceptions to this rule, likewise upon cooling the metal there will
be a contraction. Outside of the actual welding, that is, the fusing
of the metal into a homogeneous mass, perhaps the greatest problem
that the welder has to confront is the expansion and contraction of
his metals. Whenever the ends of two pieces of metal which are to be
welded are free to move, or even one end, there will be no difficulty
encountered with contraction and expansion, but if these ends are
confined, it is an entirely different problem.
[Illustration: FIG. 48.--Preheating Problem. Ends of Bars _A′_ and _B′_
are Confined.]
(=75=) To illustrate this point more clearly, the following very simple
example will be given. In Fig. 47 we have two bars of metal _A_ and
_B_ which have been beveled off or “V-ed” out as shown at the point
_C_. Now as soon as the heat is introduced at _C_ there is bound to
be an expansion of the metal at that point. Naturally if the pieces
were heated slowly and for a considerable distance, the cool ends of
these bars would be forced outward. We will assume that the heat is
introduced very rapidly and the metal is brought to a molten state;
that instead of the contraction forcing the cool ends outward, whatever
expansion there is, is taken care of, at the weld, for the metal when
melted will readily push together. It is also assumed that the bars are
heavy enough to overcome what slight force might be in evidence from
the expansion. A weld is then made and allowed to cool. As it cools,
there is bound to be a contraction along the line of the weld and the
welded piece will be slightly shorter than the work before the weld,
for it will draw in the pieces _A_ and _B_. As can be seen, there is no
particular force preventing the contraction of such a weld for the ends
are free to move. However, let us turn to Fig. 48, which constitutes
an entirely different problem. It might seem that the ends _A′_ and
_B′_ appear the same as _A_ and _B_ in Fig. 47, but such is not the
case. The ends farthest from the weld are confined, held in place by
a heavy frame which does not permit their free movement. When heat is
introduced at the point of welding _C′_, about the same action takes
place as in the previous problem, but as soon as the weld commences
to cool let us see what happens. The bar _A′B′_ must be shortened so
there is an inward pull on the bars _D′_ and _E′_. If this work were
cast iron or aluminum it would certainly be broken by the strains
set to working and would naturally break at _C′_, where the metal is
still hot. If it were steel or one of the ductile metals, it might
twist and warp in its endeavor to overcome these internal strains.
This illustrates in a very simple manner the difference between what
is known as a “cold” and a “preheating” job. In the first no provision
is made for expansion and contraction. In the second means are taken
to overcome these important factors. In order to provide for the
successful welding of the second problem, it is only necessary to heat
up the bars _X_ and _Y_ about the same distance as the center will be
heated, and keep them in that condition while executing the weld at
_C′_, then allowing the whole to cool gradually.
PART TWO.--WELDING OF CAST IRON
(=76=) Before commencing to weld, or even turning on the gas, it is
well to see that all preparations have been made and all materials on
hand to bring the weld or whatever job it may be, to a finished state.
[Illustration:
(_Courtesy of Ben K. Smith, U. S. Welding Co._)
FIG. 49.--This Locomotive Cylinder was Welded at the Saddle, near the
Frame.]
(=77=) As a specific example of a simple welding operation let us
consider that two cast-iron bars, measuring one by six inches and
twenty-four inches long are to be welded end to end. To start with it
would be necessary to “V” off the ends that were to be joined at an
angle of about 45 degrees, leaving about one-eighth inch along the
bottom edge to line the metals up with and to see whether they are in
proper position. If the bar were to measure exactly forty-eight inches
when finished it would be necessary to move these bars apart about
one-sixteenth of an inch in order to provide for their contraction. It
is assumed that the weight of the bars would be sufficient to prevent
their pushing apart when the line of the weld is brought to a molten
state and that the expansion will be taken care of within the weld.
The bars after being lined up are ready for welding, but there are such
things as filler-rods, flux and goggles that are necessary to have on
hand before starting to work. It is well to have a few fire bricks, a
little asbestos paper and a bucket of water convenient, in case these
things are needed. The acetylene gas should then be turned on and
ignited. A sufficient pressure should be passing through the regulator,
when using a medium, or high-pressure apparatus, to cause the flame to
leave the torch tip about twice the distance of the diameter of the
orifice of that particular tip. Then turn on the oxygen until a neutral
flame is obtained. On some torches it is necessary to make a second
adjustment by turning on a little more acetylene gas and still more
oxygen, until a goodly sized neutral flame results. Apply the flame to
the pieces, so that the neutral flame will just lick the surface of the
metal. Move the torch slowly forward and backward on each side of the
“V” until the two edges are a dull red color, or better still a bright
cherry red, then hold the torch stationary until the metal in the “V”
nearest to the operator commences to melt. Then bring the filler-rod
end in contact with the flame to get it heated and plunge it into the
flux which should be near at hand. Enough flux will adhere to break
up the oxides and by placing the rod between the flame and the metal,
enough flux will be introduced to allow fusing of the metal. Proceed
in this manner until the metal in the bottom of the “V” is properly
fused throughout its length. Do not add the filler-rod, up to this
point unless necessary. In holding the flame, see that the preheating
flame will heat the parts yet to be welded. The weld should be made
away from the operator. After the metals along the bottom have united
and a good foundation has been obtained, then start the weld at the
beginning once more, working the flame across the piece, in the same
manner as before; bringing the metal to the molten state and stirring
the filler-rod in it. As the filler-rod melts, the amount of molten
metal naturally increases and the flame is moved along the weld as fast
as the metal is added. It is important that the metal is in a molten
condition. It is almost impossible to get too much heat on this type
of work. Build up the weld slightly higher than the original piece. It
may be found in finishing up the corners that the velocity of the gases
or the force of the flame will be sufficient to blow the melted metal
away. This may be overcome by directing the flame at a different angle,
and will cause no difficulty after a little practice. Trouble, too, may
be experienced on thin cast-iron sections by having the metal collapse
through the force of the flame, but this can be remedied in the same
manner. While the weld is still in a heated condition, it is possible
to finish it by scraping the surplus metal off with the side of the
filler-rod, the chill of which has been taken off before it is allowed
to come in contact with the molten metal. Another popular method that
will produce even better results is to use a very heavy rasp file to
bring the weld down to the measurements desired. During all of the
previous operations the flame never leaves the line of weld. When the
weld is completed, the torch is shut down by turning off the oxygen
first, and then the acetylene, and the welded bar is covered up to
prevent its cooling too rapidly.
PART THREE.--WELDING OF CAST IRON
(=78=) Problems in expansion and contraction should not be difficult,
if it is remembered that heat causes expansion and the withdrawal of
heat, or cooling causes contraction. As previously stated, when the
ends of the pieces which are being welded are free to move, there is
not much danger of having contraction strains set up. Where the ends
are confined, measures must be taken to overcome this. In welding
large pulley wheels, for example, it may be advisable to do the job
without taking time to preheat. Breaks may be in evidence at any part
of the wheel and generally the ends are confined, such as in the case
of a spoke. If it is borne in mind that the expansion will take care
of itself, the contraction is the only consideration, in a case of
this kind. The welder will see that if he can spring the edges apart a
sufficient amount to provide for the spoke coming back to normal when
welded, he will have no difficulty. The way to proceed in a case of
this kind would be to open the rim by sawing it and then introduce a
jack or some sort of a wedge between the hub and the rim. This will
open the crack in the spoke the amount desired. As soon as the weld
is executed and while still hot, the jack is removed to permit the
rim being drawn in. Later the rim can be welded, by introducing jacks
between the spokes and the same procedure followed. It always must be
remembered that provision must be made for the contraction, even though
it be only one thirty-second or one-sixteenth of an inch. The distance
will depend entirely upon the welder, as some operators use small tips
and cover a small area, while others employ larger tips and cover twice
the area. It is therefore impossible to set any specific distance and
each welder should try to figure this out for himself.
[Illustration:
(_Courtesy of Torchweld Equipment Co._)
FIG. 50.--Large Cast-iron Gear Wheels. Although the Face on These Gears
Measured 10 Inches, New Teeth were Added by Blanking In, as Shown in
the Right-hand View, and Later Machined.]
(=79=) There are many jobs not of a preheating nature that at times
cause perplexity on the part of the welder. A good example of this is
a cast-iron gear wheel. A number of its teeth have been broken out.
Now there are three very common ways of building up or repairing such
castings. First by aid of carbon blocks, cut to form and the teeth cast
in by the use of the torch; second, by blanking in the space between
the teeth and then sawing out the individual tooth or cutting it out
with a milling machine or shaper; third, by building up each tooth
with the welding rod and torch, and later dressing it down with a
file. One very important point must be uppermost, when dental work on
gears is being done, a good foundation is necessary, for regardless of
how well the tooth may be shaped, if it is not firmly secured to the
wheel itself, it will be of very little value. Another very important
point is in the finishing of such gears, to see that the teeth which
have been added correspond in the pitch and mesh exactly as the others
do. The importance of seeing that things of this nature are machined
correctly should not require mention, but it has often been found that
machinists are very careless about finishing this kind of work and if
anything goes wrong, the welder is naturally at fault. Therefore it is
always well to put the gears which have been welded back into place and
turn them over slowly by hand to see that they are in good condition
before the power is turned on. In allowing this kind of work to cool
after it has been welded, some operators permit it to be hurried, with
the result that there may be hard spots to confront the machinist when
finishing. If he ruins one or two of his cutters he will naturally
frown upon all welding work. It is therefore desirable for this and
many other reasons to have the weld come out as soft as possible, and
great care should be exercised in cooling. Any weld that is subjected
to machining, allow it to cool slowly in slack lime, in ashes, or cover
it securely with asbestos paper. Occasionally it may be found difficult
to find sections of carbon blocks which will take care of a job of
this kind. Many welders who have had to run around the country, and do
jobs in isolated places, have found that the carbon centers, from the
ordinary dry cell batteries, which may be found practically everywhere
in a discarded condition, can be shaped on an emery wheel and patched
together in a manner that will permit their use. However, when such are
used, it is quite necessary that they be heated a little with a torch
beforehand, in order to drive out any chemicals or acids that may be
contained in them. Unless these chemicals are removed, the molten metal
coming in direct contact with them might be injured to a considerable
extent.
[Illustration:
(_Courtesy of the Oxweld Acetylene Co._)
FIG. 51.--This View Shows new Teeth being Welded in an 8¹⁄₂-ft.
Cast-iron Gear, Weighing over 5 Tons. Note the Improvised Preheating
Oven.]
(=80=) Ofttimes there are castings upon which parts wear off in a very
short time. There may be very little strain upon these parts, yet
the constant wear will weaken them in time. It is well to remember
the action of a carbonizing flame when executing work of this kind.
Introduce an excess of acetylene when finishing up the work. It will be
found that with a strongly carbonizing flame, carbon will be taken up
by the molten metal and the finished weld will be considerably harder
and will wear longer than if it were executed by a neutral flame. An
abrupt cooling will chill the metal on the surface and make it wear
longer than it would otherwise.
PART FOUR.--WELDING OF CAST IRON
[Illustration:
(_Courtesy of Ben K. Smith, U. S. Welding Co._)
FIG. 52.--View of Locomotive Cylinder with Three Jackets 3 Inches
Thick. This job weighed over 16 Tons and Required Fifty-six Hours of
Welding.]
[Illustration:
(_Courtesy of Torchweld Equipment Co._)
FIG. 53.--Various Types of Cylinders before and after Welding.]
(=81=) The true index as to the success of a weld will depend entirely
upon the finished job. If it is usable, i.e., if it can be put back
into service again and give satisfaction, it may be considered a
successful weld. If a piece were to be warped, distorted, contain hard
spots which could not be machined, or have internal strains, which
would not make it safe for use (such as fly-wheels), it could not then
be considered satisfactory and it would be only wasted energy. Perhaps
one of the most common jobs in the ordinary commercial shop, and one
which is the most abused, is the common cast-iron cylinder block found
on the gasoline engine. This is so constructed that there are two
walls of metal, very thinly cast; the innermost being the cylinder
wall, and the outermost a water-jacket. The cylinder wall is machined
very accurately to accommodate pistons moving at a very rapid rate, up
and down and yet holding compression. The upper part of the cylinder
is called the head, and generally has two or more valve seats which
must be in alignment with the valve guides to make an airtight seat
for the valves. Now this water-jacket is usually very thin, perhaps
three-sixteenths to one-quarter inch in thickness, and when there are
two, three, four, or more cylinders cast in one block, there are bound
to be internal strains set up in casting within the piece itself. These
strains are removed to a large extent by baking the rough casting
before machining. Generally there are some strains left in every
cylinder block of this nature. If the water in the water-jacket freezes
or some other force comes in contact with the thin castings which
constitute a block, the metal will give way at its weakest point, and
the welder is usually called upon to repair it. At times these cracks
are exceedingly small and the temptation is to braze or attempt to weld
the small portions. However, as soon as there is heat introduced into
the water-jacket and not into the cylinder wall, there are certain
to be strains set up which, if sufficient, will distort the cylinder
and make it useless unless it is rebored. The sooner welders realize
that work of this nature must be preheated throughout, to a point as
near melting as they can approach without causing the metal to scale,
before any welding is attempted, the better success will be obtained in
these lines. It is quite necessary to line up the work well, so that it
will not sag when heated. It is best to heat very slowly and cool in
the same manner to insure the best results. There are many preheating
agencies, such as oil-ovens, preheating torches and the like, but
about the best and most reliable agent known is charcoal, which heats
up very gradually, makes a good even fire and dies down slowly which
is the manner desired. Occasionally cracks will be found in the
combustion head of the cylinder. It is very difficult to get the torch
down inside the cylinder to execute this weld unless the operator has a
special torch for this purpose. Even then it is difficult to keep the
torch lighted when working over a newly made charcoal fire. For this
reason, other means must be used when working on a job of this kind.
First the crack is accurately located, then a piece is cut out of the
water-jacket just over the crack by means of a chisel, hack-saw or
drill press. Never attempt to remove a piece of this nature with the
flame, for the introduction of heat may distort the piece at this time.
“V” out the crack in the combustion head and scrape off as much of the
brown oxide and dirt formation as possible. It is well to clean off
more than needed and to even “V” out the crack a greater distance than
is thought necessary. This will insure a good weld being made in one
operation. The cylinder is then preheated with the crack uppermost so
that welding can be executed with the least possible difficulty. While
preheating is taking place it is well to tack the small section of the
water-jacket which has been removed, to the end of the filler-rod, and
place it too, in the preheating oven, with the end of the filler-rod
projecting so that it will be available whenever needed. When the
cylinder is red hot the weld should be executed; particular attention
being given to see that each part of the metal is actually fused to
prevent any leaks occurring later. As a rule the welder can tell when
he has made a successful weld by observing the flow of his metal,
and it will not be necessary for him to test out this cylinder weld
before adding the water-jacket. The piece of the water-jacket is then
replaced; it can be very easily handled by means of the filler-rod
which has been tacked on. Weld this section securely in place and
cover the piece of work with asbestos paper and permit it to cool
with the dying fire. When cold, all port holes in the water-jacket
should be closed and the cylinder tested for leaks. This can be done
by introducing water into the water-jacket and applying about fifteen
pounds of air pressure. Wet spots will appear if there are any leaks.
If the cylinder is found tight it should be polished, then oiled, and
the outside given a coat of filler or painted to make it presentable.
Work is generally very much discolored when coming out of the fire. A
simple device for polishing the cylinder bore may be made by turning
out a hardwood block about three inches long and a little less in
diameter than the size of the piston. This should be split as shown in
Fig. 54, and wrapped with very fine emery cloth, then put into the
cylinder and a wedge placed between the two halves. Spread them apart
so they will come in contact with the cylinder wall on all sides. A
screwdriver may be used for this purpose if necessary. By screwing this
into the cylinder its full depth, with the aid of a little oil, a very
highly polished surface may be obtained.
[Illustration: FIG. 54.--Suggested Method of Polishing Cylinder Walls
of Cast-iron Cylinder Block after it has been Preheated.]
[Illustration: FIG. 55.--Cast-iron Cylinder Block with Part Broken Off.]
[Illustration: FIG. 56.--Showing how Broken Part on Cast-iron Block
should be Lined up before Welding. Position Greatly Exaggerated.]
(=82=) Another cylinder block job that generally causes more confusion
than is necessary is brought about when welding on small lugs, such as
shown in Fig. 55. When welding these lugs on from the outside only,
they generally warp upwards in cooling and it is either necessary to
build up the bottom side of this lug or to machine off the entire
face in order to have the end square. This can easily be overcome by
permitting the lug to sag before welding and then dress off the small
portion that continues to sag, after it is welded, rather than face off
the whole surface. See Fig. 56.