[georgebarr]

I am trying to weld a 6" x 2.5" x 0.375" plate on to a 3"x3"x0.25" square tubing all made from mild steel. I have several of these welds to do and I am making a bench stand for my Rong Fu type mill which weighs about 1000+ lbs. I am using a Mig Millermatic 175 (175 Amps max) or a Mig Clarke 180EN (180 Amps max) which are both rated to weld upto 1/4" thick mild steel. Since the 3/8" (0.375") plate is thicker than 1/4" (0.25") welding capacity, my question is how can I do this and be able to support 1+ Ton of weight on the bench? What technique is needed? I will be using Mig solid wire with Argon/Co2 mixture gas.

To avoid the bench not handling the weight and causing damage to the CNC Mill or to a person, I have to get this welding thing done correctly for safety reasons.

Thanks,

[cam1]

Hi: I have the same welder. First of all, remember that the Tensile strength of the weld is 70,000 psi. So, you do not require as much as you think in order to build a brick craphouse. make sure that you remove the rust and scale from the parts you are going to join. For the plate/tube weld crank the welder up to level 4 and set the feed to 50% (this is the factory set sweet spot), and run a bead on a test coupon. Then, tack as usual, run 2 passes, and you will be fine. You may even get away with a single pass if you weave the bead, concentrating more on the 3/8 plate. Try to weld in the horizontal flat position. Most of the welders are capable of more, but for liability reasons, they are underrrated.
Practice on coupons befor you tackle the real part.


regards

[DareBee]

It will not work very well that is not enough amperage to puddle the base metal effectively.
If you can't get a bigger welder or a stick machine at least preheat your metals to help some - torch.
The welder will need to be max amperage and the wire feed will need to be close to max. Your wire needs to be AHEAD of the puddle while welding.

The MIG welding ticket is the highest fail rate when testing. It is easy to make a pretty looking "weld". In a lot of cases not much more effective than a bead of caulking.

It will be really obvious if you have cold lap when you spray paint. The paint will seep away from the cold lapped area, makes the weld look like it is sitting on top.