Bolt to the rotor, don't weld there. That way you will have no worries about a cracked weld or incomplete fusion/penetration or any other weld-related 'issues'.
And with currently only 120V power to run the welder? Forget about welding to the 1/2" thick plate. Especially with GMAW (aka MIG). Even running straight CO2 shielding gas, on 120V input power you will
never get enough output power in short-circuit transfer mode to adequately weld to some 1/2" thick plate (1500F preheat notwithstanding). On 'maximum', the machine can only ouput ~130 amps using 120V input power. And that amperage is what you would use for some ~1/8" plate (rule of thumb : use 1 amp welding current per each 0.001" thickness of the work piece). Nowhere near enough output power to weld some 1/2" thick plate.
RTFM or look at the parameter chart inside the wire-compartment door. Using 120V input power, maximum workpiece thickness is listed as 3/16" thick steel. Using 240V input power, maximum workpiece thickness is listed as 3/8" thick steel.
Unlike SMAW (aka stick), you can not just try and run multiple passes to weld a thicker workpiece when using wire-feed machines. Sometimes, you just run out of output power to adequately melt a thick workpiece. The wire will (almost
) always melt, but without enough total ouput power you might not melt any/enough of the workpiece to get anything other than a weld bead that is just piled on top of the workpiece. Classic cold lap, aka inadequate fusion, aka inadequate penetration.
And if using Lincoln Innershield NR-211-MP FCAW wire, note that the wire itself is only rated for use on workpiece thicknesses 5/16" or less (with wire sizes 0.045" or smaller, all you would be running on that class machine anyway).
Doesn't matter how many passes you use or how 'big' a machine you have, Lincoln flat-out says do
NOT use NR-211-MP on workpieces thicker than 5/16" if using 0.035 or 0.045 wire. (if using 0.068" or larger NR-211-MP wire, the workpiece thickness limitation is 1/2" max).
The MM211 is a nice machine and all, but it is
NOT a machine with enough ouput power to weld 1/2" thick plate. And no way does it have enough ouput power to weld 1/2" thick plate when using 120V input power. Nope, nada, nichts, nyet, nope.
IMNSHO.
Bolt to the rotor, if using the 1/2" thick bottom plate then use a stick welder to weld the 4x4 vertical post to the 1/2" thick baseplate (get the puddle going on the 1/2" thick plate and then 'wash' it onto the thinner-walled 4x4 post, standard thick-to-thin procedure) and bolt the baseplate to the rotor.
