What MIG Welding Tip Should I Buy?

Choosing the correct MIG Welding Tip requires you to consider multiple factors including the alloy being welded, the gas being used, the wire being used, the position of the weld and more.

Tip for Alloys:Low Carbon AlloysAluminum AlloysCopper AlloysStainless Steel Alloys (300 Series)Flux Cored Stainless Steel Alloys
With cylinder gas supply, use a high integrity gas delivery system in place of a standard rubber diaphragm regulator flowmeterXXXXX
Use a large gas nozzle if possible (4/3" or greater)XXXXX
Depending on the welding position and current setting, use gas glow rates in the 35 - 45 cfh rangeXXXXX
Ascertain raw material is clean before weldingX
 X 
Use a large filler metal diameter when possible (0.035 or greater) as this will enhance wire feedability X
 X 
Use a larger filler metal diameter when possible (0.045 or greater) as this will enhance deposition rates and wire feedability. For out-of-position welding, select a .045 or .052 diameter wire    X
Use a high integrity gas supply line from the flowmeter to the gas solenoid on the welder. Conventional rubber hoses may leak.XXXX 
If a central gas supply or distribution pipeline is utilized, use a high flow moisture trap and an oxygen trap     
To control splatter, use an argon-based gas mixture. Options include Argon/CO2, Argon/Oxygen/CO2, and Argon/Co2/Helium X    
Use ultra-high purity argon when possible (Grade 5.0 or better), 99.999% purity XX  
Use a three-part gas mixture for stainless steel welding. Options include Helium/Argon/CO2, Argon/Nitrogen/CO2, and Argon/CO2/Hydrogen   X 
Hydrogen or Nitrogen-enhanced shielding gases should not be used when welding stainless to carbon steel   X 
Hydrogen-enhanced shielding gases will offer an improved color match and should be selected when surface appearance is critical   X 
For a gas-shielded wire, match filler metal to shielding gas. Always consult filler metal manufacture's recommendations. Failure to do so could result in loss of weld metal ductility and cracking. Use pure CO2 or argon/CO2 gas mixtures. Note, some wires are designed to operate with 100% CO2 only    X
Usa a two-part gas mixture - argon/CO2. Pure CO2 can be utilized with some stainless flux-cored wires but it can contribute to additional welding fumes and increase distortion rates     
On thicker materials (> 1/8"), consider the use of an argon/helium shielding gas mixture (<90% He). As base metal thickness increases, helium content should also increase XX  
With materials greater than 1/8", consider use of spray or pulsed spray transfer for improved penetration. When pulse arc transfer is selected, move up to the next larger wire diameterXXXX 
Use post and pre-flow when possible (1-2 seconds for pre-flow and 1 second for every 50 amps of welding current for post-flow). Keep torch in the weld zone until gas has stopped flowingX    
Use post and pre-flow when possible (1-2 seconds for pre-flow and 1 second for every 10 amps of welding current for post-flow). Keep torch in the weld zone until gas has stopped flowing XXXX
Perform inter-pass cleaning with a 300 series stainless steel brushXXXX 
Perform inter-pass cleaning with a steel brush to reduce the incidence of subsurface porosity    X
Remove surface contamination when possible (rust and mill scale)X    
Remove surface oxide in the weld zone using a clean stainless steel brush prior to welding. Be sure to use a SS brush that has not been used on carbon steel XXX 
Match filler metal to base metal - consult AWS or CWB guidelinesXXXXX
Match filler metal to the application at hand. Follow recommendations of wire manufacturer     
Use a water-cooled MIG torch when welding thicker material (>1/8") to prevent wire feed problemsXXXXX
Use an enclosed feeder when possible to prevent contamination of the filler metal. If the feeder is exposed to the atmosphere, remove the spool when welding is complete and place it back into the shipping box or clean storage area XXX 
Use a V-groove drive roll that is adjusted properly to prevent the wire from being deformed or crushed, and for improving wire feeding. Polish drive roll with stainless steel brush prior to useX  XX
Use a U-groove drive roll that is adjusted properly to prevent the wire from being deformed or crushed, and for improving wire feeding. Polish drive roll with a stainless steel brush prior to use XX  
Use Direct Current Reverse Polarity (DCRP) electrode positive when possible. Gasless wires may operate on DCSP (Direct Current Straight Polarity). Consult filler metal manufacturer's recommendationsXXXXX
Heat input should be minimized and tacking intervals should be every 4 inches due to the thermal expansion rates of stainless steel. This will also improve corrosion resistance by preventing carbide precipitation   X 
Heat input should be minimized and tacking intervals should be every 8 inches due to the thermal expansion rates of steelX    
Use fume extraction systems. Consult MSDS of the electrode manufacturer. The use of pulsed transfer combined with argon-enhanted shielding gases will help to lower the fume rate. In stainless welding, air-born chromium may be breathed by operator. A respirator is highly recommendedXXXXX
To minimize surface discoloration, maintain close nozzle-to-work distances (maximum 1/2" from work piece).XXXX 
To minimize surface porosity, maintain close nozzle-to-work distances (maximum 3/4" from work piece)    X
To limit weld spatter, use spray or pulsed spray transfer when possible X X 
To limit weld spatter, consider the use of metal-cored wires which facilitate the use of spray or pulsed spray transfer. For flat or horizontal welding, this family of wires offers improved deposition rates, as well as reduced post-weld clean up    X
GMAW is not recommended for cladding applications. Use FCAW or SAWX  X 
FCAW is recommended for cladding applications. Be sure to remove the residual slag deposit off the surface of the weld metal prior to multi-pass welding    X
Aluminum and copper alloys have high thermal conductivity. Preheating may be required on thick sections XX  
Use a teflon liner to improve wire feedability XX  
If the weld needs to be anodized, use a 5000 series filler metal X   
Use a contact tip that is slightly larger than the wire diameter selected X X 
Do not use tools that have been utilized on carbon steel structures. Grinding sparks from steel must not touch aluminum or stainless steel structures X X 
Use a shorter MIG gun (8 ft) or a push/pull system to improve wire feedability XX  
Circulate wire stock and do not open shipping package until ready to use the wire. Wire stored for extended periods of time must be oven baked to remove excess moisture    X