great stuff! can wait for more

 

Just had my first non youtube welding lesson tonight. Now I know what too hot and burn through means.


Up until this point, I thought welding was like a bigger form of soldering. Man was I wrong.

 

Great article thus far, AX. Soaking up a lot of good theory I thought I'd never understand.

 

Great lesson Ax, I didn't know this information until now and it is timely since I am trying to fill all the holes in my fire wall at this point. Awesome.....

 

I learned to weld on the farm with a stick. Later, as a welders helper and pipefitter. Migs were used for welding up brackets and stands for our pumps, boilers and other equipment. Now that I am into this project first off I wish I had paid A LOT more attention to the welders and their techniques and secondly though not necessarily in this order would be I wish I had access to this kind of information. To some of you this may be old hat. To the greenhorns and us with no formal training this is going to be a very valuable thread. I hope you will continue providing this information. Thanks.
Remi

 

Awesome thread! Can't wait for more. Have just bought my first welder and begun teaching myself via youtube and hands on on my 2 project vehicles. Looking forward to more posts!

 

I learned by making the mistake of thinking the mig wire was welding wire. I made some pretty welds a few years ago when I was building my own trailer with my new mig welder. They were merely pretty with nothing to do with actual welding the two parts together as I found out during the build when I turned the trailer frame over and it came apart in two places. When I examined the parts I understood what happened. It was a good lesson and this tutorial from Ax is right on the money. I will be paying attention to this thread, Thanks Ax!

 

Go Ax, great job

 

Lesson 3: What you need to weld sheet metal.
In this lesson we'll look at the equipment and accessories needed/desirable to successfully weld sheet steel. At times I will include and/or contrast less popular welding methods to show there is more than one way to join metal, but will primarily concentrate on MIG welding since it is the most popular welding process with the shortest learning curve using readily available reasonably priced equipment in the home workshop. In certain cases I will identify specific equipment or accessories by brand, model or source. I, have no monitary stake in any of these items, I only have personal experience with the products and find them above average in function and/or cost effectiveness. For the purpose of limiting the discussion to the welding of materials found on our trucks, I define sheet steel as having a thickness between 20 gauge and 9 gauge (the higher the gauge number the thinner the material, for example 20 ga is approximately 1/32” thick, 16 ga. Is approximately 1/16” thick and much thinner than 9 ga which is approximately 1/8” thick). There is very little steel thinner than 20 ga on our trucks that you would ever want to weld, and a machine capable of welding 9 ga can be used to weld thicker metal if needed by utilizing welding tricks we will cover later.

The main piece of equipment, the heat source determines the type of welding:
From our definition of welding in lesson 1, the primary need is a heat source capable of melting steel. The commonly used home workshop heat sources are Oxygen-Acetylene torch (gas welding); AC transformer used to provide a plasma arc between a consumable flux coated rod electrode and the material being welded (stick or SMAW welding); A DC transformer or inverter that converts 115V or 220V AC power to a low voltage/high amperage power to a consumable continuous small diameter steel high resistance wire that when short circuited heats to a very hot ionizing heat (short circuit transfer or short arc Gas Metal Arc Welding or GMAW. GMAW is the “official” name for MIG welding). An ionizing arc can also be generated by a power supply through a non consumable tungsten electrode torch. This type welding is commonly called TIG (Tungsten Inert Gas) or by the old school name heliarc welding. TIG welding has some advantages over MIG, but has a much steeper learning curve and the equipment is several times more expensive (the price has been dropping lately into a range much more attractive for the home shop use)

Since we are learning how to MIG weld we will discuss the MIG machine in more detail. There are 4 major sub assemblies combined in the MIG machine:
1.Power converter
2.Wire feed system
3.Hand piece and cables (also called the stinger or MIG torch)
4.The shielding gas supply system.

Or combines 3 sub assemblies for the machine to be used as a wire feed welder. The shielding gas supply system is not present or is disabled. All true MIG machines can be used as as wire welders, but machine lacking a gas supply system can only be used as a wire feed welder.

1. The Power converter:
To effectively use a power source for MIG welding in the home workshop it needs to input 115V 15-20A or 220V 30-50A, AC the commonly available wall plug power, and convert it to low voltage (12-40V commonly) high amperage (90 – 225 A) DC power needed for welding.

Note: there are specialized DC to DC power supplies available that allows the welder to be connected to 12 or 24V DC battery power supply. There are also dual voltage power supplies that can be plugged into a 115V or 220V power outlet, and automatically sense which it is connected to.

The power supply typically uses one of two technologies to convert the power, The older technology uses a copper wire wound transformer plus a diode bridge. The secondary wire winding is brought out at intervals to provide different voltages and it corresponding amperage. A transformer uses a lot of fine copper wire windings around a laminated steel core. That makes the transformer expensive to make, large, heavy, and generates a lot of heat that is difficult to keep cool. The wire is only insulated with a lacquer coating and if it overheats the coating melts, shorting out the transformer, destroying the unit. This was the most common way to build a welder until just a few years ago. Today all but the big industrial units are built with solid state inverter technology replacing the transformer. This makes the units light weight, small, inexpensive and easier to keep cool. The machines have a heat sensor on the inverters that should they start to overheat from heavy use, the machine shuts off until it cools back down to a safe temperature.
One has to be careful buying a used unit. First because of the high original cost of transformer units, the sellers often have an unrealistic expectation of value often asking more than the cost of a brand new unit. Second there is no way to assess if a unit has been overheated and/or how many times. Overheating damage to a transformer is cumulative.
Just because a 386 processor computer originally cost $5K new 15 years ago doesn't make it worth $3K today, no matter how little it was used or how good condition it's in, when you can buy a brand new laptop with the latest high powered CPU for <1K! Even if the price is cheap, should that used computer suddenly quit working there's no place to buy repair parts or find anyone willing to work on it. Same goes for buying a unit that doesn't come with gas capability but requires buying a conversion kit. By the time you buy both the wire welder and gas conversion kit, the price is usually more than a unit with the gas capability built in.
If you only have 115V power available in your shop, don't dispair! Just buy yourself a 135-140A 115 V unit with gas. It will do all the welding you are likely to need to do. I use a Hobart 140 in my own shop, when I first got it I didn't even have a shop, I plugged it in on my back porch and welded in the backyard. I stored it in a kitchen closet between uses. If I was shopping right now for a 115V unit I would definitely buy the 135A machine from Eastwood. I have used it and was quite impressed and the price is super low. I suspect it is made by the same factory that makes Lincoln or is a direct clone. If you have 220V 30A outlet available I'd recommend the Eastwood 175A since it also comes with a free spool gun for welding aluminum, typically a 300.00 + extra cost accessory with other units. Don't buy more than a 225A unit no matter how cheap, it won't be able to be set low enough for welding the thinner body metals.

2.The wire feed system.

The most suitable units can use both the standard 4” and 8” wire spools, and be easily switched between at least 0.024” (sometimes listed as 0.023” or 0.025” size and can all be considered the same) and 0.030” wire sizes. Most units have a stepless variable wire feed speed ****, or is auto setting when you set the voltage and wire size. IMHO the auto setting feature is a sales gimmick with very limited usefullness. I can't emphasize strongly enough my recommendation to use nothing but ESAB “Spoolarc Easy Grind solid wire for MIG welding!!!! It is available, usually by special order from a local ESAB dealer, or online. Weldingsupply.com / ESAB / 69130051]Weldingsupply.com / ESAB / 69130051 ACCEPT NO SUBSTITUTE or “EQUIVILENT”, none exists for this amazing wire. You want the 0.023 wire size for sure for body sheet metal and a spool of 0.030 for welding 12 ga and thicker.

That's enough for this lesson. We'll continue with the equipment and accessories in the next installment.

 

I am excited to read about the next lesson. Thanks!

 

Thank you AX. Very informative and well written.

 

Thanks AX! I look forward to your future installments.

 

I've been welding for quite awhile, both with mig and smaw. Had classes in high school and even went throught the certification tests. I'm still finding this very informative and would like to thank you for it.

 

Lesson 4: What you need con't.

Let's finish up discussing the machine and then what accessories to have on hand.

3. Hand piece and cables.

The hand piece, “stinger” or MIG torch is the business end of the machine.
The multi-function cable connects the stinger to the machine, the ground cable provides the return path for the electricity to flow between the work and the machine, the power cord allows the machine to be plugged into an electrical outlet to power the unit. The torch and cables are usually supplied with the machine.

The stinger consists of a handle, a push button trigger switch (this switch is an on or off switch, not a throttle, it should be pressed fully and held firmly while welding), a removable gas concentrating nozzle around the end of the stinger (the nozzle is typically a tapering brass tube that directs and concentrates the shielding gas around the molten metal puddle). If you pull the concentrator nozzle off the end of the stinger, underneath there are gas outlets surrounding a screw in replaceable copper rod with a hole down the center. This copper piece is called the contact tip. It is electrified when you press the trigger and the filler wire is in turn electrified from rubbing on the inside of the contact tip while being fed out the end of the stinger. To help conduct electricity to the wire, the wire itself has a flash plating of copper, and the contact tips come with different size center holes matched to the wire sizes (the contact tip hole size is stamped on the side of the contact tip). The contact tip size should be changed any time you change wire size. The hole wears larger through use, and can get dirty, so it should be kept clean by wiping with a clean dry rag and/or using “tip dip” (discussed later) or replaced when the weld fails to start immediately when the trigger is pressed or sputters while welding. A package of contact tips in the wire sizes you use should be stocked at your welding or maintenance station, they are inexpensive.

Connecting the stinger to the machine is a multifunction cable. This cable is about 10' long on most machines, rubber covered and somewhat stiff. It has a teflon lined tube down the center that guides the filler wire through the cable to the stinger. It also has a tube that feeds shielding gas to the nozzle and an electrical conductor that feeds electricity to the contact tip. Finally it has wires that connect the trigger switch to the machine. This cable is critical to the proper functioning of the welder and somewhat easily damaged, so it should be cared for accordingly: it should be uncoiled completely and arranged as straight as possible between the machine and the weld site to reduce wear on the liner and resistance to the filler wire feed. It should be protected from being stepped on, rolled over, snarled or kinked. It should be stored in as large a coil as possible without dragging on the ground. Avoid dropping or pulling the stinger to the floor.

The ground cable connects the machine's power ground terminal to the part being welded to provide the return path for the welding current. The end of the ground cable has a clamp on it similar to one on a jumper cable on the smaller machines. I'd recommend changing it to a solid brass welding ground clamp as found on larger welders to make attaching easier and provide better conductivity. They are available at a welding supply and are easy to change. Always attach the ground clamp to bare metal that is connected to and is as close as possible to the weld. When welding small parts or precise assemblies it is often easier to lay or clamp the work on a steel topped welding bench (discussed later) and attach the ground to the bench top instead of to the piece.

Finally the power cable and plug allows the machine to be plugged into one of several different outlets to provide the power to the unit. Different outlet/plug prong configurations are used depending on the voltage/ amperage capacity of the circuit. Be sure to match the outlet to the plug, do not change the outlet to match the machine plug without being sure the circuit wiring is sized properly. If you are not 100% sure you know what you are doing it is best to consult a licensed electrician before changing or adding a special circuit. It's much cheaper than a fire and/or denial of your homeowners insurance coverage after a loss!

4. The shielding gas supply system.

As discussed previously the use of shielding gas is what distinguishes a MIG welder from a wire feed welder. A wire feed welder may be better than no welder(just barely IMHO), but with a good serviceable MIG welder being available for <300.00, I would avoid investing in a wire feed only unit. The shielding gas supply system consists of a storage cylinder containing the shielding gas of choice under high pressure, a regulator or gas flow meter, a hose to feed the reduced pressure gas from the tank to the unit and on to the line in the multifuction cable, and an electrical solenoid in the unit to turn the gas flow on and off.

The best shielding gas choice for welding steel is a 75%-25% mix of Argon and Carbon Dioxide.

There are a number of sizes of storage cylinders available, from ones the size of a small fire extinguisher to large industrial supply size than must be moved with a fork lift. I recommend a 140 cu ft size as being the best choice for a home shop. This size cylinder is about 4' tall and 9” in diameter. It is small enough to be luggable or mounted onto a roll around welding cart, but large enough to last a good while under average shop use and most economical to refill. The major cost to refill is the handling and inspection charges, which is about the same for all the home shop sized tanks, so it is nearly as expensive to fill a miniature tank as a larger one. The first tank can be purchased outright plus the gas inside, leased monthly or yearly, or secured under a demurage agreement where you agree to buy so many refills per year. The highest up front costs will be the purchased tank, but unless you are welding at least half a day, 5 or 6 days a week, will be the cheapest in the long run. In all cases you return or have picked up the empty tank, and exchange it for a different full tank, paying for the contents. Tanks and refills are available from your local welding supply and from some farm supply outlets. Shop around, but be sure you are comparing the same size tanks.
No matter what size tank you end up with, always secure it to a stationary solid object like a wall or bench or to a sturdy welding cart with a steel cable or chain higher than ½ way up the cylinder. Shielding gas is stored under extreme pressure > 2000# per sq in.. Should an unsecured cylinder accidentally be bumped or fall over, the valve could easily be knocked off resulting in the cylinder launching like a rocket. Such a tank is easily capable of flying through a concrete block or several wood framed walls and killing an individual in it's path several rooms away or outside. I have personally witnessed the aftermath of the destructive force involved!

That high pressure must be reduced down to a much lower working pressure and flow rate before being fed through the unit to the stinger. That is accomplished with a regulator or flow meter. Functionally they are similar in function, but differ in what and how they measure their respective output. We want to use as little shielding gas flow as possible to just just gently blow away the air around the weld puddle without being so strong as to blow away the molten metal or cause eddying which could pull air in rather than keeping it away. If you put the gas cup up near your cheek (on a machine that has a purge only setting!) and press the trigger you would barely feel a breeze of shielding gas. To measure this small flow accurately we need to use a relatively accurate 2 stage regulator or a flow meter.
A 2 stage regulator has one gauge that reads the tank pressure (think of it as a gas gauge, it reads about 2000# when the tank is full, and goes down as the tank empties. The second gauge actually reads the output pressure, so it has a reading if the gas is flowing or not, but it reads on the face in cu ft/hr, a flow rate indication. This leads to some confusion, that we'll cover in setting up our machine.
A flow meter has a calibrated glass or plastic tube with a colored ball inside that lifts up the tube when the gas is flowing to indicate the flow rate directly. The flow meter is more accurate, but the regulator is sufficiently functional if set properly.

Finally the gas is fed through a rubber hose to a gas solenoid in the unit that turns the gas flow to the stinger on and off when the trigger is pressed on or released off.

That covers the basics of the MIG welding machine. We will end this lesson here, and take up what accessories you want to have along with your welding machine to make welding easier and better in the next lesson. Hang on, I promise we'll be melting metal soon!

 

Wow,> 1400 views, almost 100 views since I posted lesson 4 last night! It is encouraging that so many are reading this. Lesson 5 is in process.