Welding thick steel, smaller welder

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What considerations or techniques are there when you are welding thicker steel than a welder is rated capable of?So for instance, if you are making a press finger brake and are using 1/2 inch bar for the downforce bar, you might weld 1/2 bar to 1/2 bar spacers to 1/2 bar sandwiched together.   Is it okay to use something like a hobart 190 if that's all you have?  Or is that plain stupid?  Should you bevel the edges?  Can you make multiple passes on each layer?How about when welding a size within the limits to something outside the limit.  Such at 1/4 to 1/2 inch? Thanks
Reply:You need higher amps to acheive the desired penetration, base metal dilution into the puddle. The thicker the metal, the less chance of this. The rule of thumb is one amp per .001" of legal thickness.You can increase your odds with a preheat up to 400 degrees or so,  using gasless wire(flux core), and 220 volt input.As far as welding .250 to .500 inch,  you have to take the average and then concentrate your arc on the thicker member and was the bead to the thinner.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:The pros weld really thick metal all the time.  They don't  use a 4000 amp welder to weld to an 4 inch  thick plate. The keys are prep, preheat, proper filler and multi pass.   You'd probably end up welding from both sides.  You might find that your hobart has a short duty cycle of only a few minutes at full output.  That makes it more of a hassle, but still doable.I saw a picture of the cross section of a weld yesterday that used 32 passes to achieve the required thickness.   If you have limited experience, you will want to learn about how to make welds that will withstand the forces that the press brake will exert.   A T joint welded from one side will break more easily when pressure comes from the unwelded side.Good luck.  I'd like to see your plans.----------------------------Measure twice.  Weld once.  Grind to size.MIG:  Lincoln SP100 TIG/STICK:  AHP Alphatig 200X
Reply:preheat like they said.   an uphill weld will give you the most penetration, so position your part accordingly
Reply:Originally Posted by 123weldan uphill weld will give you the most penetration, so position your part accordingly
Reply:well OK, you got a point.    If he cant handle an uphill weld, he may not be able to handle the molten slag from mixing in his puddle in a flat weld.   How much slope can you handle Mike?
Reply:Don't know, as all of my welds have been flat on a table, rotating the piece to accommodate.  But I can start practicing with scrap and see if I have a difficult time.When you are doing multiple passes, do you keep amps high, but wire feed low?  I would expect that if you kept it at full rate, you'd end up with a big amount of filler and each pass would have to work through previous filler and steel. No?I plan on purchasing the Swag Offroad Finger brake kit.  Details on welding here http://www.swagoffroad.com/assets/im...STRUCTIONS.pdf
Reply:Originally Posted by whiskeymikeWhen you are doing multiple passes, do you keep amps high, but wire feed low?  I would expect that if you kept it at full rate, you'd end up with a big amount of filler and each pass would have to work through previous filler and steel. No?
Reply:Looking at those instructions I don't see any really critical welds that need to be done. Almost all are simply locating welds. You shouldn't need super heavy welds in any of the locations I looked at. 1/4" welds should be more than adequate, and massive welds may cause issues with warpage..No government ever voluntarily reduces itself in size. Government programs, once launched, never disappear. Actually, a government bureau is the nearest thing to eternal life we'll ever see on this earth! Ronald Reagan
Reply:There you go, do some practice and make your own call.   You want to end up w/ at least a half fluent looking weld, w/o holes in it.   As for dialing in your welder for heat and feed, your going to have to know that by sight and sound, or there might be literature wrote on the machine, giving you a ballpark for different settings w/ the particular sizes and types of wires.  I doubt that little machine would be much of a match on .500" material to make any undercut to speak of.    If you don't like your vertical up, try it at 45 degrees + or -.   Or if you weld it flat, give it at least 10+ degrees incline, it will help keep your puddle and weld cleaner, providing your using fluxcore like the first post reccamended.
Reply:That Hobart will be fine for that. Run it hot and do some multipass if necessary. 1 amp per every .001 is a good guide up to a certain point. You won't use 1000 amps for 1" material. You use enough amps to get good fusion into the base material and run multiple passes until you reach the required size of weld.Lone Star Mobile Welding, LLC2006 Ram 3500Lincoln Ranger 250GXTHypertherm 30 AirK2000 CAG ESAB Rebel 215ic Milwaukee mag drillDewalt dry cut sawMilwaukee metal cutting circular sawMilwaukee M18 Fuel Chisholm Lead Reels
Reply:Originally Posted by DSWThat's why with small machines, multiple passes doesn't mean you can weld thick material. The underlying passes that aren't well fused to the base material are still the weak point. More metal on top doesn't gain you anything if the root passes aren't well bonded.
Reply:Originally Posted by dbstooThey don't  use a 4000 amp welder to weld to an 4 inch  thick plate.
Reply:Originally Posted by whiskeymikeDon't know, as all of my welds have been flat on a table, rotating the piece to accommodate.  But I can start practicing with scrap and see if I have a difficult time.
Reply:Originally Posted by CEPDon't be too disillusioned. That's how it's done out on the job site. You don't have to know how to weld out of position. Things can be rolled, so all welds are flat.
Reply:Originally Posted by mad welder 4True, but the welding web answer should be something to the effect of:you need a welder capable of jump starting a planet with a dead core and that the right way to do it is with a single pass.
Reply:Originally Posted by dbstooYeah, it's amazing how many things are rotated in order to work on them.   Doing some body work?   Try this!  ( from accessiblesystems.com )There appears to be an industry built around automated positioners. Dan
Reply:Consider stick welding?  You need the amps for a particular rod (rod thickness) but you can always go smaller rod.BTW, let us know how the project turned out.  I'm looking at the same kit.  40" wide? Or?Con Fuse!Miller Dynasty 350Millermatic 350P-Spoolmatic 30AMiller Multimatic 200Hypertherm PowerMax 1000G3Miller Maxstar 200DX
Reply:Originally Posted by con_fuse9Consider stick welding?  You need the amps for a particular rod (rod thickness) but you can always go smaller rod.BTW, let us know how the project turned out.  I'm looking at the same kit.  40" wide? Or?
Reply:If you are really concerned, post up your location and maybe someone (myself included) will offer up a few minutes use of a larger machine...I ordered the same brake last night as well.....MillerMatic 252, HTP 221 w/cooler, Hypertherm PM45, Lincoln IdealArc 250 AC/DC"I'd like to believe as many true things and as few false things as possible"
Reply:I'm in Austin, TX(Cedar Creek/Bastrop) if anyone wants to have a brake building party I'm not to concerned having read the comments above.  Looking forward to getting the kit.  Should open up some new projects.  Also seems like there are some good mods for the HF 20T press as well.