Can someone make me smart about this?

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I have been welding a while now but it has all been AC arc with a Lincoln Tombstone welder (Had to be this welder, I am from Tombstone, Arizona).Anyway, I just picked up a Miller Thunderbird AC/DC stick welder.I can use the AC side without problems but am not familiar with the DC side. I tested the welder and it works. I got a 7018 rod and tried to weld a bead on a plate. I just grabbed a hunk of steel and it was really coroded but tried it anyway. With the ground in the negative and the stinger in the positive I tried to weld but just kept getting stuck. I was using 1/8" rod at 125 amps.So, what is the best setup for DC? I know I should clean up the steel, that is a given but I just wanted to see if it worked. How picky should I be with cleaning the metal? Does DC require really clean metal or just pretty clean?Should I use the ground in the positive or negative side?7018 is a DC rod from what I understand, is this correct?Any pointers would be great.Bob
Reply:Bob, it sounds like you got it set up alright(positive stinger) and the amps are close(1/8rod@125) You could go hotter but thats close,amp range being relative to material thickness. The mat should be clean so you don't get contaminants in the weld but for just goofing off you can run a pass over 'bout anything. Give it a quick wire brush and bump up your heat a taste. 7018 is not the easiest rod to use so it could just be operator malfunction(no offense)If the rod is old and has gotten damp sometimes they are hard to get lit. Are you poking/stabbing to start or dragging,like striking a match?Either will work so try both. Try long arcing it once it starts just to see if there is a machine problem.
Reply:I am dragging. Once the arc starts I try to start a bead and that is when I get stuck. Long arcing works fine. It could be that the piece is just too dirty because when I get down to the right position to start the bead it builds up very quickly and before I know it I am stuck.I just tried it playing around. I will go back out this afternoon and use a cleaner piece of metal and give it a "Proper" try.Just wanted to be sure I was setting it up right.Thanks
Reply:7018, as mentioned, isn't the easiest rod to run, but you'll get the hang of it and then you'll really like it.  It's a rod that draws moisture from the air, though, and should never be used for structural (critical) welding unless it comes from a fresh container.Even your AC rods will usually run on DC, though, so try some of them.  I still like 6011, even though I always run it on DC.Calling the work clamp a "ground" can lead to confusion.  It is not grounded and can be any polarity, depending on process.7018, more than many others, really wants clean metal to work best.
Reply:7018 is what they use at the local vo-tech.  We were made to grind off the mill scale before welding.DennisThermal Arc 185-TSWMillermatic Challenger 172VictorO/AAtlas Craftsman 12 by 24 LatheEsab PCM-875Wholesalem Tool Mill-Drill
Reply:the cleaner the better applies to any welding..i use 7018 for alot of journal repair thats just a mess with grease and months of abuse..it'll blow thru anything as far as yuck goes..and usually it just takes a tap and off you go when the heat is right..no matter how crappy it is..but on the other hand if its not tap and off to the races?it gets stuck..you bend it.. the flux comes off..it heats up red..you get the piece goes flying if its light enough to move.. if not you try to get it out of the holder as fast as you can so you can beat the crap out of it with the chipping hammer...sound about right? ...zap!I am not completely insane..Some parts are missing Professional Driver on a closed course....Do not attempt.Just because I'm a  dumbass don't mean that you can be too.So DON'T try any of this **** l do at home.
Reply:Originally Posted by zapstersound about right? ...zap!
Reply:Originally Posted by TEKYeeuuupppp!!! You been there.
Reply:Here is the welder.  I still need to try it out on clean steel.Notice the cables? The stinger (red) is plugged into the negative and the clamp (black) is in the positive. This is how it came from the machine shop I got it from. I traded them and tried my first weld (that did not go well).Bob
Reply:Bob, looking at your pics the machine is set @approx  100 amps. Try turning it up to 125 or a little more.I've found on a lot of welders the #'s on the front are not what the welder is putting out. Keep adjusting to find the "sweet spot".        MikeOl' Stonebreaker  "Experience is the name everyone gives to their mistakes"Hobart G-213 portableMiller 175 migMiller thunderbolt ac/dc stick Victor O/A setupMakita chop saw
Reply:As said 7018 is a pain to get to run right. But once you figure it out I think it is the right choice. Less tendency to crack. And I think it is easier to keep in position because you can almost see through the slag it produces.  Again my opinion. I really like running 6010 on anything rusty and cracked then run 18's as cover and fill
Reply:When in doubt, switch polarity. someone before you might have done something to the machines inside wiring. AKA, try something different until it works. And, using 3/32" will  be easier for you to learn on.Last edited by tessdad; 09-08-2006 at 10:29 PM.Just my  opinion, not from a book, just from the road.Howes Welding Inc.www.howesweldinginc.com
Reply:Thanks guys. I will play with it this weekend after getting a proper plug. Had to remove the old one because it is not like my outlets. Couldnot resist cheating and cramming the wires into the outlet to test it.If there were any internal changes made, it was done a LOOOOOOg time ago. The thing looks like it was never touched inside, not even blown out.Thanks again.
Reply:Bob, any possibility that your wires crammed into the receptacle were dropping too much voltage?  Did you notice if the wires were hot after welding for a while?  If so, just getting the proper plug might cure the problem.  It's a hassle, but you could put a VOM across the junction of the wire and the receptacle and see if any significant show up when you try to draw an arc.  Have someone else read the meter as you try to weld.Good luck.awright
Reply:Awrite,It is VERY possible. I plan on getting a plug tomorrow (oops! I mean today).I will try with decent steel and see what happens.Thanks,Bob