Grinding exhaust welds

[siggyfreud]

Anyone here grind their welds when making an exhaust system? I am MIG welding an exhaust system together for my 66 GMC. I have a set of mandrel bent pipe. My mig skills are OKAY. I can get fairly good penetration and not a lot of burn through, but still learning. That said, they aren't always the prettiest.

I am considering grinding them smooth, but not sure how much integrity I give up by doing so. If they're going to be more prone to cracking that way, I'll not do it.

Eventually I'll buy a TIG, but really want to get to a point where my skills surpass my MIG machine before I go buying more tools .

[NONHOG]

Might look up V8TV on Youtube and see how they MIG'd and ground some exhaust. Made me want to but I just left well enough alone.
My thoughts are if properly supported by hangers ground or not shouldn't be much of an issue.

[GASoline71]

I have MIG'd many an exhaust system. Never ground any welds. Well... except when I did my 3" system and forgot to slide the collector flange on before I welded the collector to the pipe. Had to grind the welds a little to get it to slide over.

No TIG needed, unless you're lookin' for some show quality "stack of dimes" welds. Which some cats can do with a MIG too.

Gary

[Gumby]

Maybe only do the spots you can see, ive stuck to tacks, one time I went all out, fully welding up a system, it pinged n tinged like crazy, so much people would stare at my car like " is a bomb about to go off?" Took several long drives then shocking with cold water to stress it.

[siggyfreud]

A lot of my stuff will be butt-welded, so only tacking won't suffice to seal it. I'll keep going and see how things turn out without grinding. I may do like was suggested and only grind stuff visible, perhaps around the tailpipes.

[vidman]

I ground all mine just because. I know not many will see them but they all look clean

[cableguy0]

Practice,Practice,Practice and then Practice some more and you will be able to lay dimes with a mig. No need for a tig welder at all to make a pretty weld. I do it everyday with a mig. Aside from that Tig welding a bunch of exhaust seams will take half the day. You can do weld entire system in 20 minutes with a mig and have it look good.

[crazy longhorn]

A butt weld on thin tubing, is hard to make real pretty, with a mig? Most of my time in the muffler shop was spent welding lap joints, & I can make them really nice Just a thought on the butt slices...put an inch long "weld ring', inside of the pipe & leave about 1/32 to 1/16"gap tween the 2 pcs that you are welding. If she don't weld as pretty as you like, grind it & you will still have plenty strength on the weld joint? Longhorn

[Redcap]

Nope. I got better things to do after I burn together exhaust on something than waste my time grinding the welds.

[crazy longhorn]

Originally Posted by Redcap

Nope. I got better things to do after I burn together exhaust on something than waste my time grinding the welds.

Totally agree! Just burn it like I showed you...my bet is that you wont need to grind it longhorn

[burnin oil]

Don't waste your time. I am a decent home welder and welding pipe is about the biggest pain in the butt other than overhead. It is about gaurenteed that there will be a thin spot or pin hole wherever you start/stop. It is round so you will start and stop alot! I have a few minor leaks on my 72 that are witnessed by carbon leaks but small enough that you don't hear them over the mufflers so I let them be. Another truck I built a custom adapter for an exhaust brake on a diesel that remote mounts it at the end of the turbo downpipe. Now it has a few miles on it I need to drop it and do some patch work on the seams. There are literally over 100' of weld on this creation and it needs to hold 65PSI of back pressure. Its very quiet but you can tell a seam spit somewhere with the brake is on as the hold back got weaker.

[siggyfreud]

Originally Posted by crazy longhorn

A butt weld on thin tubing, is hard to make real pretty, with a mig? Most of my time in the muffler shop was spent welding lap joints, & I can make them really nice Just a thought on the butt slices...put an inch long "weld ring', inside of the pipe & leave about 1/32 to 1/16"gap tween the 2 pcs that you are welding. If she don't weld as pretty as you like, grind it & you will still have plenty strength on the weld joint? Longhorn

They make these weld rings to use externally? Honestly I'd probably rather have a ring on the outside with nice welds than to reduce the internal size of the pipe in certain spots.

[crazy longhorn]

Originally Posted by siggyfreud

They make these weld rings to use externally? Honestly I'd probably rather have a ring on the outside with nice welds than to reduce the internal size of the pipe in certain spots.

No sir,the weld rings come from the "Harley experience"....I<MHO, if you cut the inside diameter of the pipe, by 1/8", I would doubt that you will notice that on the street, or street /strip? For your flat out strip toy, I will subscribe to your method...yes. it will flow better? My bet is that you wont see anything, unless you are running 7000+ rpms tho...Longhorn

[Captainfab]

If you leave a slight gap on your butt joint, you will get 100% penetration and a smoother weld on the top side. A continuous series of tacks work good enough for strength and look better than trying to run a continuous bead around an exhaust pipe. Also using a small wire such as .023 is much easier than .030 or .035.

[crazy longhorn]

Captain....right on spot, as usuall Longhorn

[Gumby]

If you could roll the pipe at a continuous speed, could play weld machine with a steady hand