This is just an introduction to various welding methods and their application to motorcycle restoration.
Incidentally for electric welding of any type, “DC” means direct current and is often used in either DC reverse polarity (electrode negative). “AC” means alternating current. Both DC in straight or reverse polarity and AC, on cheaper machines, are fine for steel, but not necessarily for aluminum and exotic materials. More on this in a moment. But before you run off to buy a shiny new welder, beware – inexpensive “multi-function” welders most often will only work on steel. Especially for TIG functions on aluminum and other non-ferrous metals, you will NEED a unit that provides advanced functions like balance control and pulse.
| Format | Method | Uses |
|---|---|---|
| Gas Fuel | Oxy/Acetylene | Braze, weld, cut steel and even weld light aluminum |
| Gas Fuel | Oxy/Propane | Braze, weld, cut steel |
| Electric | Wire Feed Flux Core | Basic Steel Welding |
| Electric | Wire Feed Gas Shield | MIG Steel & Aluminum Welding |
| Electric | Stick | Steel welding & cutting |
| Electric | Tungsten Inert Gas | Steel & Nonferrous welding |
| Electric | Plasma Cutting | Cut steel and nonferrous metals |
Note that the above table defines only the most common types of welding. Hardly a year goes by without some new innovation – at least a new tweak to an existing method. So for example in some situations you can use both flux core wire and gas shielding for Wire feed welding.
Some terms can be misleading – “MIG” welding really means “Metal Inert Gas” but in reality the more inexpensive wire feed units do not use gas, they rely on the flux in the wire. Sometimes flux core wire is used along with gas shielding. For aluminum work with wire feed, you MUST use argon shielding gas, and a special gun with the wire spool attached. Aluminum wire tends to stick in the cabling used for steel wire, hence the spool gun for aluminum.
TIG or Tungsten Inert Gas welding (originally called Heli-arc or helium shielded arc welding) involves use of a tungsten electrode to create and hold an arc with gas shielding blowing from around the tungsten to envelope the weld area. In a manner very similar to oxy/acetylene or oxy/propane brazing or welding, filler rod is introduced into the arc under the shield of the gas. Though argon is typically the gas to use for steel or aluminum, sometimes helium is still used, often mixed about 50/50 with argon, for greater penetration on aluminum or other exotic metals.
Newer type TIG welders capable of doing aluminum and exotic materials actually use AC (alternating current) but with a twist – you can control the “balance”. Normally AC means one cycle of DC followed by one cycle of DC reverse. But now we can use balance control and say “Give me 75% DC reverse and 25% DC”. Not exactly your Grandad’s view of AC welding from an old buzz box! And to add more control, you can use “pulse” which literally shuts off the power momentarily. Usually used at 1 to 1.5 pulses per second, it becomes very distracting like a strobe, if you crank up the pulses per second. It’s much like when you weld on steel and pause to let the puddle cool, only in much faster cycling.
Rule 1 Amperage for any electric form of welding – it’s pretty simple to find a starting point. Determine the thickness of the material in decimal format to three decimals – i.e. 1/8 inch thick material is 0.125″ thick – so you should start with 100 to 125 amps, regardless of whether you’re doing MIG, Stick or TIG welding. This rule falls off as you get to material 1/4″ thick. You can often weld this material at 150-175 amps. It varies a lot. With thicker materials you’ll probably make more than one pass. Your best option is to use some scrap, properly prepared and do a few test runs, adjusting your amperage and technique. On a good TIG machine, you can also adjust things like pulse mode, etc.
Rule 2 “Physically clean, Chemically clean” – these are buzz words drummed into me in shop class in junior high school when we learned to do soldering. This is a mandatory approach to all welding preparation. Usually you’ll do only the physical cleaning, then leave it to flux and/or gas shielding to keep the weld clean. And clean your work where the ground clamp will attach (see next).
Rule 3 For all forms of electric welding, grounding your work seems pretty obvious, just put the ground clamp in place, maybe wiggle it around to ensure it’s contacting the work well. For wire feed and stick welding, difficulty establishing a good arc are almost always caused by poor grounding or the work. This situation is even more problematic with TIG welding.
Note for working with aluminum and exotic materials, all wire brushes, flap/grinding/cutting wheels should be used ONLY for that type of material. The best wire brushes for all such work are those made with stainless steel wire.
About purchasing equipment – don’t buy a welding machine from an online or catalog source without knowing for sure what you need and how well that machine suits your needs.
For example, inexpensive “multi purpose” welders often are advertised as capable of MIG, Stick & TIG welding. And they are – for steel. However the TIG setup on cheaper machines is only DC. That’s fine for steel. If you want to weld aluminum or other non-ferrous metals, you need AC with pulse and balance control. Unless you know clearly what you want, enlist the help of an experienced welder or spend a bit more and buy from a reputable dealer.