Tex Gore Posted October 11, 2011 Share Posted October 11, 2011 Sorry if this is the wrong area - but its my Disco that needs welding after all I suppose... What's the general technique for welding thinner to thicker plate steel? For example, the floor on the disco is thinner than the box I'm using for sill repairs, and owing to the interesting way in which the floor has gone and the fact it's a bobtailed 5-door (so what's left of the rear doors get in the way and won't open) I'll be seam welding the floor to the box (plug welding won't be enough). It's not a load bearing section, but want to get it right, so any advice gratefully received. TG Quote Link to comment Share on other sites More sharing options...
Les Henson Posted October 12, 2011 Share Posted October 12, 2011 You need to weld more on the thicker metal than on the thinner stuff, so that the weld just catches the thinner metal. This is only suitable for an over lap or butt weld. I don't know about a corner, but I would guess you weld it fast - so that the thinner stuff doesn't blow through. Short bursts might work as well. Les. Quote Link to comment Share on other sites More sharing options...
FridgeFreezer Posted October 12, 2011 Share Posted October 12, 2011 Short bursts to reduce the heat you're putting into the thin stuff, and aim more toward the thick stuff. Quote Link to comment Share on other sites More sharing options...
Tex Gore Posted October 12, 2011 Author Share Posted October 12, 2011 Cheers both - makes sense. Why do spare welding tips go the same place as pens and sellotape. Quote Link to comment Share on other sites More sharing options...
pete3000 Posted October 12, 2011 Share Posted October 12, 2011 clamp a lump of flat copper behind the thinner stuff to prevent as much blow through. It acts as a heatsink. Quote Link to comment Share on other sites More sharing options...
Tex Gore Posted October 12, 2011 Author Share Posted October 12, 2011 Pete - nice one. Never would have thought of that. Don't have a big lump of copper either but I'll steal some off some local pikeys. Well, before I can try any of that tomorrow is a major cleaning day. Lots of chopping out and grinding back to metal to do. No point in worrying about the weld if it's not prepared. TG Quote Link to comment Share on other sites More sharing options...
simonr Posted October 12, 2011 Share Posted October 12, 2011 Move the torch in a pattern like this - UUUUUUU Following the lines of the U's. The upper pointy bits of the U's are on the thinner sheet and the curved part on the thicker. This means the torch spends more time on the thick plate than the thin. Also, like Fridge suggested, weld in short bursts and let it cool a little in-between. The combination will give good penetration in both without blowing (too many) holes in the thin sheet. Si Quote Link to comment Share on other sites More sharing options...
Tex Gore Posted October 13, 2011 Author Share Posted October 13, 2011 Thanks Si - I'm getting good value out of you at the moment! Quote Link to comment Share on other sites More sharing options...
Tex Gore Posted October 15, 2011 Author Share Posted October 15, 2011 The problems continue. My welder isn't behaving itself. It's a Cosmo 200. Whilst trying to weld two pieces of 5mm together (into a T shape) I am not getting any penetration; only big blobs that I can twist off with pliers. I've tried all power settings, I've tried varying the gas output, a new tip, and wire speed - nothing seems to work. It's supposed to weld up to 6mm, but with the maximum setting and the wire speed set to auto it just chucks more spatters about and still doesn't penetrate. The metal is clean, as is the welder earth clamp. I've got the torch at the right distance and angle (I did an evening class, would you believe). Has my welder gone wrong, and is there a way I can test it? TG Quote Link to comment Share on other sites More sharing options...
Landy-Novice Posted October 15, 2011 Share Posted October 15, 2011 i had the exact same problem, came down to a faulty reg! have you tried reverse polarity? Quote Link to comment Share on other sites More sharing options...
Boro Posted October 15, 2011 Share Posted October 15, 2011 How to put this nicely, the cosmo welders dont have the best reputation... how old is it? could be an issue with the liner, try keeping the torch leads (between torch and welder) straight and seeing if that improves things as they dont like being kinked especially on the cheaper machines Quote Link to comment Share on other sites More sharing options...
Tex Gore Posted October 15, 2011 Author Share Posted October 15, 2011 Hmm - there is no way of reversing the polarity that I know of? As for kinks - you could be right Boro. It does seem to be struggling to get the wire out smoothly. Oh well, a new welder is well beyond my means at present. Guess project rotten Disco will have to go on hold. Cheers Quote Link to comment Share on other sites More sharing options...
Boro Posted October 15, 2011 Share Posted October 15, 2011 An old sip i once owned was really fussy when it came to kinks and it would have a huge effect on the welders performance (similar to what you describe), get the torch held right and it would do a good job, cheap little upgrade for you would be a metal torch liner, makes a big difference Quote Link to comment Share on other sites More sharing options...
Tex Gore Posted October 15, 2011 Author Share Posted October 15, 2011 Hmm, might give that a go. If Cosmos are that bad, what brands are worth considering. I don't tend to use the welder often, but when I do it's for relatively extensive stuff.... I guess Clarke are worth considering, what other brands give good, reliable performance for the occasional user? Quote Link to comment Share on other sites More sharing options...
Landy-Novice Posted October 15, 2011 Share Posted October 15, 2011 oh sorry, i assumed it was a gas/gasless MIG, Quote Link to comment Share on other sites More sharing options...
Tex Gore Posted October 15, 2011 Author Share Posted October 15, 2011 oh sorry, i assumed it was a gas/gasless MIG, It is a gas/gasless Mig - but no polarity switch Quote Link to comment Share on other sites More sharing options...
Team Idris Posted October 16, 2011 Share Posted October 16, 2011 I'm jumping back in the thread a bit, but another trick for thin-to-thick welding is to fold back an edge on the thin, so your welding double thickness. Quote Link to comment Share on other sites More sharing options...
Landy-Novice Posted October 16, 2011 Share Posted October 16, 2011 but no polarity switch it wont be a switch, it will be two cables connected to two terminals inside the spool compartment. if not then i don't no.. Quote Link to comment Share on other sites More sharing options...
reb78 Posted October 16, 2011 Share Posted October 16, 2011 it wont be a switch, it will be two cables connected to two terminals inside the spool compartment. if not then i don't no.. What he said ^^^ you reverse the polarity of the cables in the compartment to switch between gas and gasless. If you are looking for another welder, there is a thread in the tech archive on whats good and whats not. Links are all here: http://forums.lr4x4.com/index.php?showtopic=19017 I got a Butters AMT 180 (i think) after reading those threads and its a nice machine for the money (~£400) Quote Link to comment Share on other sites More sharing options...
Tex Gore Posted October 16, 2011 Author Share Posted October 16, 2011 What he said ^^^ you reverse the polarity of the cables in the compartment to switch between gas and gasless. Why on earth didn't I know that! I'll take a look. It did seem to be working much better when I was using gasless wire...although I was using a touch of gas with it to try and counteract the wind outside.. Quote Link to comment Share on other sites More sharing options...
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