Clint,
As Grigg pointed out, material thickness to be welded is usually limited by the 'oink' of the machine...the maximum output in amps, and type of wire used.
If your MIG had instructions with it, take a look at them. I just bought a little Lincoln 140C and it tops out on 5/16" material...and this is with flux core.
A 135 amp machine might be hard pressed to properly weld a thick spring perch to a heavy walled axle tube. The welder not only melts the filler wire, it must also melt some of the parent material so all that soup can joint together as one.
I'm sure your job is OK, but for general info, this is how it sort of works.
Stuart
Last edited by atomarc; 01/28/2008 7:10 PM.