I made a beginner's mistake welding my first flange to the exhaust pipe. Because I want the pipe to turn ASAP out of the collector, I welded the flange to the very end of a bend instead of a straight section. The pipe wasn't fully round, so I welded one side, and then stretched the other half with a torch and hammer, welding an inch at a time, then reheating and stretching until it fit.
Then today, I put the other flange against it and the one I welded was about 1/8 inch unflat (new word, thank-you). I guess I'll have to cut it completely off and re-weld it. Maybe because the pipe will be round now, I can tack the flange all around and it won't warp when I finish-weld it.
I see a lot of talk about v-bands, but I don't recall anybody mentioning that they did the welding themselves.
Any tips? If not, thanks for listening to my dumb-assedness (I should write Mikester's Dictionary, huh?).
Oh, yeah, they're 3-inch stainless.

 

tack weld are key. they spot welded mine ( just like tac weld all the way around)

 

Mine were welded from the inside then the bead ground down so it didnt impeded flow. Here is how mine look

dont mine the bead about an inch from the flange I had to cut my exhaust there when modifying the the crossover pipe on my ypipe.

 

1) tack it in 6 places
2) do a c-stitch weld to keep the gas on the current puddle (and don't do the circle stitch -- too much heat). Also, try to get most of the C on the pipe and just drag the tip up and over the edge of the v-band to get the puddle.
3) keep moving at a good pace -- get your penetrating heat, puddle a little and move.

Also, there are quality v-bands, and not-so-quality. I bought from 2 different vendors. One vendor's stuff was nice and thick, the other... eh.

 

My flanges are almost 1/8 inch thick at the part that gets welded to the tube. Would that rank as quality or not-so-quality?
Are you describing a TIG method?

 

Yes he described a TIG method, are you MIG'ing stainless?

 

No, I TIGGED it, but with poor fit-up. I think part of the reason that it warped was because of the excessive heat that adding all that filler caused. I was thinking of trying MIG next time, though. Any reason why not? I have some 308 wire.

 

No big deal, I cut it off (1/2 last night, 1/2 tonight), tacked it about every 1 1/4 inches, and tigged it with tig-size welds instead of big-*** mig-looking beads. I keep forgetting that because I don't weld very often, I am a beginner at the start of every project, and will therefore make beginner mistakes. Thanks for your replies.

 

The C stitch works both ways (TIG and MIG -- which ends up looking like TIG if you control the wire feed).

I think the extra tacks help a lot. I always do at least 4, and with a thick to thin join and do 6 or so.