A little help

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First, this is only my 2nd post and as my alias suggest, I am so far away from being a good welder, its not even funny. With that said, I have been practicing (welding, grinding, welding, grinding,...) and reading this forum for over a year.I recently acquired an old grill guard for my vintage truck and I need to do some modifications. It is made from 1/4 inch flat bar. I am using a Lincoln 140, mig welder with the gas attachment. I purchased it before I ever knew this forum existed, so I know it is under powered for the job. I have the option of having it done by a professional, but I want to do the job myself. My question is: Can I preheat to compensate for the lower power or make multiple passes? I guess I want to know how you would do if you had the same conditions.Thanks for your insights.
Reply:Well if I were in your position, I would sell the 140 and get a proper mig. A 110volt unit just does not have the guts to do 1/4"But if you are stuck, prep all the joints like you  would eat off them. Then tack a cleanly as possible, and then preheat up to at least 500 F.Good Luck on that. A 220volt mig is so much easier to use.Weld like a "WELDOR", not a wel-"DERR" MillerDynasty700DX,Dynasty350DX4ea,Dynasty200DX,Li  ncolnSW200-2ea.,MillerMatic350P,MillerMatic200w/spoolgun,MKCobraMig260,Lincoln SP-170T,PlasmaCam/Hypertherm1250,HFProTig2ea,MigMax1ea.
Reply:With some preheat and some mild beveling you should be just fine. (I know I could confidently weld 1/4" Flat bar steel with that setup)The 500F preheat temp is excessive 250F would do fine, with an interpass temp of 300-400Remember a fillet weld need only penetrate to the root. As long as you have clean steel a shallow bevel and some preheat all will be well.
Reply:Thanks to you both. I'm going to give it a shot. If it comes out looking OK, then I'll post pictures and give you credit. If not, you'll see the pictures on "what was he thinking?", or in the "Bird poop of the month" calendar.
Reply:I got rid of my 110v mig shortly after getting it.  I found a used mm251 pretty cheap, and that thing is AWESOME.  I have never worried about not putting enough heat into anything, and I have never cranked it up to its limits either.  Due to the state of the economy, you may be able to pick up a 220v welder cheaper that you would otherwise.The Lord has declared, "This is my work and my glory--to bring to pass the immortality and eternal life of man"  Moses 1:39Link: My name is John, and I am a member of The Church of Jesus Christ of Latter-Day Saints.-- ColdCreekWorks.com --
Reply:Really go to your LWS and get some tempil sticks. Get it preheated to 500 degrees F. And you aren't going to get penetration to the root on fillets unless you run flux-core. Which is a whole different world.What wire are you running?Weld like a "WELDOR", not a wel-"DERR" MillerDynasty700DX,Dynasty350DX4ea,Dynasty200DX,Li  ncolnSW200-2ea.,MillerMatic350P,MillerMatic200w/spoolgun,MKCobraMig260,Lincoln SP-170T,PlasmaCam/Hypertherm1250,HFProTig2ea,MigMax1ea.
Reply:definitely use fluxcore
Reply:FCAW not required for fillets on 1/4" flat stock until you start welding on some seriously heavy weldment. The assumption is you are talking about Flat BAR 1/4" X 4" OR LESS.
Reply:I thought about using fluxcore and I have a spool I've used in the past. Shovelon, I'm using .025 wire.FB, the flat bar is 1.5" wide. I looked at 220V welders last night on craigslist. There were some Lincoln 180's from $550 to $800.There were a lot of stick welders for much less. Unfortunatly I'm not much of a stick welder. I have proven that serveral times.Thanks again for all your help and comments.
Reply:Stick welding could be used, if you want to spend the money on a welder.Otherwise, Flux Core, welder cranked all the way up, a bevel & adding some heat to the joint, that 140 MIG will weld the flat bar just fine.Stick welding on the other hand can be done without the additional heat, it just takes practice to learn how to run the rod.MarkI haven't always been a nurse........Craftsman 12"x36" LatheEnco G-30B MillHobart Handler 175Lincoln WeldandPower 225 AC/DC G-7 CV/CCAdd a Foot Pedal to a Harbor Freight Chicago Electric 165A DC TIG PapaLion's Gate Build