Welding Basics, Part 4
Oxy-Acetylene Torches - Part Two
Our ongoing series is discussing some basics in barnyard welding. The
previous article gave some introductory material on the equipment and
safety factors when working with an oxyacetylene unit. This portion
will try to deal with the gas welding procedure and what we can use it
for.
We've been working slowly but surely on our bushog repair over the past
several months. Let's pretend for a moment that our natural talent for
stick welding has surpassed all our dreams and our heavy framing and
reinforcement is complete. Now we need to weld on the sheetmetal so we
can wrap this thing up and paint it. But to our surprise the arc tends
to melt the sheetmetal faster than the metal framework. The difference
in metal thickness makes the thinner metal blow away before a puddle
can be formed. Here is a great example of how gas welding can come in
handy. Let's take a quick review before we start.
Our oxygen and acetylene tank are secured to the wall, stand, or cart
with a chain. The regulators are in the off position or are unscrewed
all the way so no pressure is present on the diaphragm. The hoses are
safely wound away from the weld-site. We have our gloves, goggles,
leather wear, and safety shoes on and our uncoated steel rod is lying
to the side, easily accessible within our reach. The repair has been
wirebrushed and cleaned of debris and is ready to weld.
When gas welding with thin tin like on our bushog we want to keep the
pressures on the regulators quite low so we don't make a blowing flame.
We are also using a smaller orifice on the torch to help keep the heat
level low. In general the thin metal we are welding will require a rod
about the same thickness. If the sheet metal is 1/8 inch in thickness,
then we need a 1/8th uncoated rod. The torch orifice size is equated
to a numbered drill size, in this case a size 54 -57 tip drill size.
The pressures on the regs are low: 5 psi for the oxygen and 5 psi for
the acetylene. Remember these are pressures for gas welding with a
single orifice torch. Pressures for the cutting torch are different
and are not for this type of repair. Remember to open the gas tank
cylinders slowly to prevent regulator damage and then screw down the
diaphragm adjusters to the appropriate pressure settings. It can be
helpful to open the corresponding torch valve at the same time to bleed
the gas in the line off and to ensure the correct gauge setting.
Now we are ready to light up. Open the acetylene torch valve no more
than 1/16 of a turn. Cup the flint lighter over the tip to collect a
little gas and ignite. Next, turn the acetylene torch valve on slowly
until the acetylene flame becomes turbulent a distance of 3/4 inch to
one inch away from the orifice. Note that at this distance the flame
will stop smoking. When proper turbulence is recognized open the
oxygen valve a little bit. Note the color change in the flame and the
slow development of an double inner cone within the acetylene flame.
As oxygen is increased the larger middle flame will merge with the
inner greenish hued cone. When there is only one lightish green/blue
cone established then the flame is called a neutral flame. If the
secondary or middle flame is still visible then the flame is called a
carburizing flame; a cooler flame with too much acetylene is being
consumed. If the inner cone is established and then additional oxygen
is added it becomes an oxidizing flame. This is also characterized by
a hissing sound to the torch and more of a bluish tinge to the flame.
Too much oxygen will burn or oxidize the metal being welded. The
neutral flame has a soft purring sound to the torch, has a well defined
inner cone with the greenish/blue tinge, and is the hottest part of the
flame produced. This is the flame we are looking for.
Next step is to heat the metal we are going to weld. In the case of
our bushog we want to preheat the thickest metal first. Hold the torch
at a 30 to 45 degree angle to the work. The flame spreads over the
work in the direction in which the weld is progressing and acts as
preheater to the material. Rotate the torch tip in a circular motion
for even heating and puddle control; hold the inner cone just above the
developing molten puddle of metal. This motion should be contained
within the parameters of the created molten puddle and not stray
outside the welding area. If the puddle starts to sag or burn through
then adjust the distance of the flame to the weld by increasing the
angle of the flame rather than by pulling the flame away from the
puddle. The molten puddle that you create with the flame is what will
make the weld between the metals. When working with the different
thickness’ of metal it is necessary to form the puddle on the thickest
portion of steel and then float the puddle onto the thinner steel so as
to not burn through. Adding extra metal to the puddle with a rod may
or may not be necessary. If the parent steel is thick enough then the
puddle may flow easily to the thinner steel and form a great weld. If
additional metal is needed then the rod may be added. Move the rod
towards the flame so it is preheated then place the rod end into the
puddle as more metal is required. The flame will melt the rod
accordingly. Try to avoid a dripping rod as this only creates a weaker
weld. As with most things it takes some practice, trial and error.
Take some scrap pieces to practice on before doing a finished job which
will show your skill; or lack thereof.
Here are a couple of tips to keep in mind as you weld. The appearance
of the puddle will be a good indicator as to your progress. A good
puddle will have a smooth, glossy appearance. The edge away from the
torch will have a small bright incandescent spot which will move
actively around the edge of the puddle. If this spot is oversize the
flame is not neutral. If there are weld bubbles and excessive sparks
then there is either a poorly adjusted flame or a poor quality/dirty
metal/rod that you are working with. If the torch pops and spits then
try to increase the pressures in the regulators just a little bit. The
gases are preigniting and may be corrected by a somewhat higher
pressure from both tanks. The tip also may become overheated by
operating it too close to the molten puddle; try extending that
distance. Another possibility of torch popping is that the tip may
have some carbon deposits or hot metal particles in the orifice. Using
a properly sized tip cleaner will open the passage back up. Avoid
submerging the inner cone into the molten metal as this can create a
flashback condition where the gas burns back into the regulator.
All in all the more time spent practicing with the puddle the better
the weld seams that will be produced. Take your time and slowly move
the puddle forward along the metal seams making sure the circular
motion of the torch is consistent. Heat control by this method ensures
that the puddle will not grow out of hand or that a burn through will
result. With a little practice one will find that this type of welding
is real handy when working with thinner metals because it offers quite
a bit of creative control in the weld.
In the last installment of this series we will give some tips and
instruction on using a cutting torch.
Welding Basics, Part 5
Oxy-Acetylene Torches
My favorite tool in my arsenal of welding stuff is the cutting torch.
It seems that whenever I get into a difficult situation the cutting
torch comes running to the rescue. The versatility of this tool is
amazing. It can be used for making tools, freeing stuck nuts, heating
and bending things to fit, not to mention the regular cutting of steel
parts for fabricating and repairing things. The cutting torch is
indeed a universal tool in the field of welding.
Put simply the cutting torch is like a whole bunch of regular gas
torches all bundled into one. In addition there is a single, large
orifice in the center of the tip that delivers pure oxygen to the weld
when actuated with the cutting lever. This oxygen, under the proper
circumstances, will immediately oxidize the pre-heated metal and, put
simply, make it disappear. Let's take a quick look at how this really
works.
As mentioned the cutting torch assembly is rather similar to the
oxy-acetylene torch. In fact many torches have interchangeable ends,
which makes the changeover from a welding torch to a cutting torch a
quick and easy swap. For our purposes the torch base, hoses, regulator
gauges, valves and tanks are the same for welding and cutting. The
safety procedures and equipment are also the same and should be
thoroughly checked before using the unit. The main difference between
the torches is that the cutting torch attachment has an additional
oxygen pre-heat valve, an oxygen-cutting valve with cutting lever, and
a different type of configuration in the gas delivery and flame
expulsion, and a multi-ported tip. To put it all in simple terms the
acetylene gas flow is still controlled in the same location as the
welding torch. But the oxygen control has moved from the lower valve
to a new position up farther onto the body of the cutting torch
assembly. When using the torch this lower oxygen valve is opened all
the way while the 'new' upper valve is used to control the throttling
or neutral flame control setting required for operation. The oxygen-
cutting lever, now under full pressure through the lower valve, is used
to deliver a blast of pure oxygen at the appropriate time to the metal
we are cutting.
The settings, as with regular gas welding, are determined by the
thickness of the metal that you want to cut. A typical example for
cutting 3/8 inch to 3/4 inch steel would be the following: a preheat
orifice drill size of 58, a cutting orifice drill size of 62, oxygen
pressure of 30-40 psi, acetylene around 5 psi. The multi-preheat
flames, as with the single welding flame, need to be ignited with a
sparkler and set to a neutral flame using the same techniques described
in our previous series. Give visual consideration to optimizing the
neutral flame as an oxidizing flame will be harder to work with.
The real key to cutting metal with a torch is to always heat the
working metal to cherry red. If the metal is too cool it won't cut.
If it is too hot, as in white hot, it splatters, undercuts, and reduces
the quality of the cut. Laying the base metal on a pair of vee blocks
or steel spacers will help facilitate the cutting process. Preheat the
metal edge to a dull cherry red using the tip of the multi-flame cones
for maximum heat. A tight circular pattern over the starting area will
even out the preheating. When a small cherry red dot appears apply the
oxygen cutting valve lever. The metal will blow away like a stream of
butter as the oxygen oxidizes and melts the metal in contact with the
high pressure stream of gas. While holding a vertical attack angle
slowly follow the melt line with the torch until the cut is complete.
Prescribing the cut line with welders chalk makes following the cut
line a lot easier.
As with anything once the basics are understood practice makes the
best teacher. With time (and a good piece of chalk to mark your
cutting lines) further skills can be realized. One of these skills is
being able to fabricate parts for repairs. Many times, such as our
bushog, a piece of plate steel has to be cut and fit over a cracked
section or hole in order to make the repair. The cutting torch is
ideal for making these custom fabrications. By chalking the lines of
the desired filler piece on a section of steel the cutting torch can
make exact repair plates of virtually any type and size. With
additional time and skill one can also learn to make angle cuts with
the torch to create a ‘pre-cut’ chamfer in the plate for stronger
welds. After the cuts are made the magic of a hand grinder can make
the plate look like a factory part.
One great feature of the torch is that it can be used to ‘make stuff
fit’. By heating parts to cherry red they can be bent and tweaked to
various angles. Support rods or plate reinforcing can be bent to mate
perfectly to matching parts. Rebar can be bent to perfect and tight
90-degree angles for support cages. Plates that have to be placed over
obstructions can be heated and tweaked to have bumps, ridges, or
chamfers in them. When heated to the right temperatures it is amazing
to see just how pliable steel becomes. Steel tubing can be filled with
sand, heated, and then gradually bent to strange angles. Done slowly
and with care the pipe integrity will not be sacrificed.
Sometimes in the shop one can run across a huge nut or bolt that
requires an expensive wrench to remove. A piece of scrap steel, some
carefully scribed chalk lines, and a steady torch hand can create a
make-shift wrench that will comfortably work. Of course you will
probably have to do some grinder touch up work on your new tool
addition before it will fit close enough to use. In addition the
‘working end’ can be roasted to cherry red and quenched in some water
to obtain some tempered features.
Frequently one will run across a nut that won't budge with a
well-fitted wrench. Even a pipe extension, commonly called a cheater
bar, won’t crack it free. By taking our torch and heating the nut to
our famous cherry red it will usually break free with only the effort
of our wrench. Granted you might have to install a larger torch tip to
release the amount of heat needed to toast that much steel. But it is
amazing to see what a little heat can do on stubborn nuts. The key is
to heat only the nut cherry red so it expands over the stud. On most
stuck nuts there is a layer of rust between the bolt and nut that has
caused the seizure. This layer can act as an insulator and retard the
transfer of heat to the stud. If the nut is heated too long then the
stud will also receive too much heat, start to get red, and then
probably snap off when torque is applied. Focus the heat only on the
nut and, when it releases and starts to turn, get it off quickly. If
it seizes up again reheat it back to red and try again.
Sometimes it is a stubborn bolt that is stuck in a component. Try
heating the surrounding metal and then backing the bolt out with a
wrench or vise grips. Be especially careful if it is a cast iron
component. It is recommended that drilling and using an easy-out first
be tried as cast iron can do strange things if too much heat is
applied. In a case of a broken stud in an engine block sometimes the
stud can be heated cherry red, then quenched quickly with some ice
wrapped in a rag. The sudden temperature change can sometimes break
the rust layer free and give some space to rotation of the stud. If
all else fails a very small torch tip, a steady hand, and nerves of
steel can sometimes be used to cut a problem stud out of a cast
component. This last gasp tactic is best reserved for the experienced.
All in all the cutting torch is one of the most universal and versatile
tools in the arsenal of the home repairman. Make sure and keep it
clean and tidy so it will be ready to serve when most needed.