why is my welding inconsistent?

Couple of things some already said:

1. Clean Clean Clean BOTH SIDES IF POSSIBLE, any contamination will cause problems even if it is on the reverse side.

2. The temperature of the material. Thirty or Forty degrees can have a real impact on the welding. So if the temp of the material starts at room temp and then as you weld is raised from 70 degrees to 110 degrees it makes it a lot easier to burn through.

3. Trim the wire EVERY time you weld. If you look at the end of the wire when you stop welding, you'll see a little ball, this ball is slag. When you weld thick material it doesn't really matter, but on thin sheet metal this can make starting a stable arc more difficult. Which in turn makes you hold the gun in the starting position longer, thus increasing the possibility of burn through.

4. Slow down.

Hope this helps,

Regards,

Joe Dokes