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  #11  
Old 07-10-2017, 03:22 PM
toreadorxlt toreadorxlt is offline
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Quote:
Originally Posted by Lee T View Post
I have heard of ghost lines in butt welds, what might cause a ghost line in a butt weld with tig torch?
Are you talking about the subtle color variance on butt welded tig seams? That is caused by the tig welded seam tempering at a different temperature than the surrounding metal. Or atleast thats the answer Fay Butler gave me when i posed him the question.
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  #12  
Old 07-10-2017, 07:51 PM
John Buchtenkirch John Buchtenkirch is offline
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Quote:
Originally Posted by toreadorxlt View Post
Are you talking about the subtle color variance on butt welded tig seams? That is caused by the tig welded seam tempering at a different temperature than the surrounding metal. Or atleast thats the answer Fay Butler gave me when i posed him the question.
A ghost is actually a pretty good name for the problem. It’s any indication of a previous repair that shows thru the final finished paint work. It may be so subtle that only you can see it because you know where your repair work is (welcome to the curse of the “body man’s eye”). Or it may be so noticeable that you have to change your repair methods on future jobs. Worst is the panel may look fine for several months but a ghost shows up a year or two later to haunt you. Maybe not spooky scary stuff but the kind of stuff that haunts craftsmen if they worry about their reputation . ~ John Buchtenkirch
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  #13  
Old 07-11-2017, 01:07 AM
Oldnek Oldnek is offline
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You see those lines all the time when the panel shop just spots the panel to the flange, and not weld it as per John's illustration. I have done a few repairs where the guys just spot weld rather than fully weld, and most of the time you have to cut that whole piece out and butt weld a piece in due to rust under that flange.
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  #14  
Old 07-14-2017, 02:34 AM
FritzCustom FritzCustom is offline
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I remember reading an article Ron Covell did in his "Professor Hammer" column in Street Rodder years back explaining this, I have also noticed this on lots of beautifully painted cars.

He stated that the added thickness of a lapped seam will cause the outer body metal to expand and contract at slightly different rates, this is more prevalent when the car is exposed to high temperatures.

I have also seen this on shaved door handles as well, since some guys simply will mig weld in a patch and leave the stamped surround lip in place rather than cutting it out and butt welding in a piece.

I make sure that all outer skin body metal is the same thickness. Im a bit superstitious and will try to sand down the back side of the weld flush if I can get to it as to not add any additional thickness to the metal.

Just my two pennies
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