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Right, this is a bit of a newbie type question really.I need to weld some 50mm square tube together, 3mm wall. I'm having trouble getting sufficient penetration with my borrowed 105 amp mig. I'm welding the two lengths at right angles to each other, one on top of the other (I'm making a trailer, one bit is the axle, the other is the main spine).It doesn't help that the edges are rounded either. I've tried grinding out some of the material from the corner of the tube, and the power is cranked right up.Should I just grind the corners right down to nothing or go hire myself a proper 150 amp welder for the weekend??Cheers Dan
Reply:MS - if it were me, I would not grind the corners down as this may weaken the tubing next to the weld.3mm is equivalent to .118 wall thickness, or a little under 1/8".  Theoretically, 105 amps should be able to weld this but I'll defer to the MIG experts on this forum to chime in, as I am more familiar with TIG and stick.The first thing that I would try is to pre-heat the tubing (where I'm welding) with a torch, to see if this would help the penetration.  I would also check to make sure that I had a very clean ground (grind the metal where the ground clamp is attached).If these don't work,you may have a problem with the welder not achieving it's listed amperage and need to use a more powerful one.Good luck.Scott
Reply:Are you using fluxcore or gas? Preheat with a propane torch will make things go easier on smaller feeders.  Fluxcore gets deeper penetration at any given amperage but requires more cleanup.  Unless you are correcting a poor fitup, I wouldn't grind any more than necessary to clean the surface of the metal.Smithboy...if it ain't broke, you ain't tryin'.
Reply:i HOPE YOU ARE USING .023-.025   WIRE , IF YOU ARE USING HARD WIRE . IF YOU ARE USING THAT CORE WIRE , WELL-  GOOD LUCK. SMALL MACHINES JUST DON'T HAVE THE UMMMPH  TO WELD WITH .035 WIRE , ALMOST NOT ENOUGH   EVEN FOR .030 . i CONSIDER THE LOW POWER 100-130 AMPS MACHINES MOST SUITABLE FOR ADVANCED WELDERS, RATHER THAN A BEGINNER , I WISH THE FACTORIES WOULD TELL THE BUYERS THIS IN THEIR LITERATURE .
Reply:Originally Posted by Roy Hodgesi HOPE YOU ARE USING .023-.025   WIRE , IF YOU ARE USING HARD WIRE . IF YOU ARE USING THAT CORE WIRE , WELL-  GOOD LUCK. SMALL MACHINES JUST DON'T HAVE THE UMMMPH  TO WELD WITH .035 WIRE , ALMOST NOT ENOUGH   EVEN FOR .030 . i CONSIDER THE LOW POWER 100-130 AMPS MACHINES MOST SUITABLE FOR ADVANCED WELDERS, RATHER THAN A BEGINNER , I WISH THE FACTORIES WOULD TELL THE BUYERS THIS IN THEIR LITERATURE .
Reply:I'm using .8mm solid wire ( .03 ish), I changed to straight CO2, added some heat from a blow torch and the welds are looking pretty good now. Thanks for the advice.
Reply:I want Monkeystealer to go to the thread that was started to explain his username! heheheLincoln Power Mig 210MP MIGLincoln Power Mig 350MP - MIG and Push-PullLincoln TIG 300-300Lincoln Hobby-Weld 110v  Thanks JLAMESCK TIG TORCH, gas diffuser, pyrex cupThermal Dynamics Cutmaster 101My brain
Reply:I think monkeystealer might actually want to avoid that thread...just to keep out of legal trouble.  Sounds kinda strange and illegal to me...but...who am I to judge...Smithboy...if it ain't broke, you ain't tryin'.