Butt weld vs. flange weld - Chevelle Tech
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post #1 of 42 (permalink) Old Jan 19th, 15, 9:55 PM Thread Starter
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George
 
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Butt weld vs. flange weld

Guys, watched many videos where a flange tool is used to "crimp" about 5/8", cut new panel to lay on that, sheet metal screws to "tighten" new/old panel together, then start welding that line. Then that 5/8 overlap just is tapped down in trunk once done? Is this the way to go? I'm going to be doing this the first time on a car and this looked "safer" than a true butt weld... For a non-show but still want a long term quality result, is this good?
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post #2 of 42 (permalink) Old Jan 20th, 15, 8:39 AM Thread Starter
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George
 
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Re: Butt weld vs. flange weld

What I should have said a "lap" weld after using a flanging tool to create a crimp where 5/8 of old metal will be beneath the new panel, then weld... Is this the correct method?
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post #3 of 42 (permalink) Old Jan 20th, 15, 8:56 AM
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Re: Butt weld vs. flange weld

If that area is prone to moisture it leaves room for rust, much better to butt weld.

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post #4 of 42 (permalink) Old Jan 20th, 15, 9:15 AM
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Rich
 
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Butt weld vs. flange weld

Admittedly, I've been doing this kind of research as I have been working on my trunk floorpan and planning to redo the seams on the rear quarters. Among welders, it becomes almost a religious debate as to which way is better (almost like a windows vs Apple debate). Both have their benefits and downsides. Mind you, I'm no welder and haven't ever held a MIG in my life (not one that was on, anyway), I can't do anything more than pass on the information I've collected. I expect that to start changing in the next few weeks as I start down the road of learning to weld small stuff.

From what I have been told by various people experienced with welding (I can be a research junkie at times), doing a small flange/overlap requires more prep and cleanup, but it is generally easier to do and it will be stronger. I've been assured by many that any fear of moisture collection at the overlap is unfounded when "done right," which has been described to me as a small 1/2-5/8" overlap (which will sandwich the steel together) combined with sealer, plastic filler, undercoating, etc.

Doing a butt weld isn't as strong, but is generally much harder (requires more patience and experience) to do right and it requires a lot less cleanup and blending. The finished produce won't require as much plastic filler or effort to smooth out the seam.

Again the disclaimer.. I don't know any of the above through first hand experience...

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post #5 of 42 (permalink) Old Jan 20th, 15, 9:42 AM
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Re: Butt weld vs. flange weld

Quote:
Originally Posted by Mikes64 View Post
If that area is prone to moisture it leaves room for rust, much better to butt weld.

I flange welded my quarters on 5 years ago. No signs of rust. I sealed the inside and the outside. The reason I did it that way is I felt it was stronger to butt weld. If you are not a great welder, do the flange weld. You will burn holes thru the metal if you butt weld.

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post #6 of 42 (permalink) Old Jan 20th, 15, 10:18 AM
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Terrence
 
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Re: Butt weld vs. flange weld

Rookie welder here. decided to do butt welds and stand by the decision. The flange approach for some reason seems less daunting but butt weld is fusing metal at the molecular level so just like what was there originally. takes a little more patience to spot weld it. My 69's quarters I wanted to put skins on at the top body line. came out almost perfect without body filler. I was worried the flange would show on the curve I was welding.

if you do butt weld here are some tips
don't buy those panel alignment things. I bought them and never used them.
I zip screwed the quarter to the existing above where I wanted to weld and used a body saw to cut through both. then welded this perfectly matched pattern removing the old cut off piece as I went.
use a small screwdriver and something to push to align these two perfectly before tack welding.
use a light behind the panel to see any pinholes you miss.(can't do this with flange)

This project is the 2nd thing I ever mig welded so if I can do it most anyone can with a little practice

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post #7 of 42 (permalink) Old Jan 20th, 15, 11:22 AM
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Re: Butt weld vs. flange weld

it depends what panel or where the weld is. if you lap weld, use weld thru primer before welding and seam sealer if you can before paint. I did both on different parts of the car. each weld technique has its purpose.
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post #8 of 42 (permalink) Old Jan 20th, 15, 12:53 PM
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Re: Butt weld vs. flange weld

Butt welding as a rookie seems intimidating. It takes time to fit the work and clean it up. The results are superior in looks when finished. I knew from my OCD that I would only butt weld. I was surprised when I got into it that I really enjoyed the fitting of the patches. Grinding sucks for me. There are some posts on TC here that give great advice about grinding, sanding and finishing fast.


As far as rust goes, this is only an issue if your car will be a winter driven car or if the paint prep is poor. Restored cars seem to lead charmed lives.

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post #9 of 42 (permalink) Old Jan 20th, 15, 1:04 PM
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Re: Butt weld vs. flange weld

First off I am no body guy at all.....I am a welder, however Industrial welder with stick. Again big difference. I do own a mig and can repair and fix things. Have never done any body work ever. So I had my car farmed out......I have both butt and lap welds in my car. My body guy said the lap weld is stronger and used them on the floors and trunk areas. Butt welded anything visible. The lap weld gets weld on top and bottom. So its bonding to both sides but you have the piece thats double in the middle. So instead of a single weld joining the 2 you have 2 welds joining the 2. Well that's what he says. Not to mention used 3M sealer on both sides....no way moisture getting in there. Body sealer wasn't even used in the 60's. Plus how many of you are going to be driving these cars in the winter bad areas? When you know its going to be poor weather and rain? so lighten up have fun and enjoy the car. Unless you got a very rare numbers matching car who cares? In the end if its done correctly how you feel comfortable that's all that matters.

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post #10 of 42 (permalink) Old Jan 20th, 15, 2:46 PM
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Re: Butt weld vs. flange weld

Lots of good info already but I'll just add my $.02 to it, I prefer butt welds. In my mind I feel it is less of a chance for rust to live somewhere else, it requires less work trying to hide the fact it was done, and I just feel better about it.
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post #11 of 42 (permalink) Old Jan 20th, 15, 3:04 PM
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Re: Butt weld vs. flange weld

As a novice welder, I found lap welds much easier to do, but created problems on curved panels. Butt welds required much less filler, and I had fewer problems with warpage. I did the quarter patches on my brother's 67 using lap welds, learned from my mistakes and did mine with butt welds. Was kinda nice having a guinea pig to learn on.

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post #12 of 42 (permalink) Old Jan 20th, 15, 4:47 PM
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Re: Butt weld vs. flange weld

Terrence -

I like your method - I've always been nervous about getting a long cut to line up, but I had read somewhere that the cutting itself creates too much gap between the two panels. Sounds like this wasn't an issue for you? What width of a cut does your body saw make?

I know I have quarter skins in my future to install, so this is good info to have.

Thanks -

jim

I zip screwed the quarter to the existing above where I wanted to weld and used a body saw to cut through both. then welded this perfectly matched pattern removing the old cut off piece as I went.
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post #13 of 42 (permalink) Old Jan 20th, 15, 5:02 PM
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Re: Butt weld vs. flange weld

I prefer butt welds, I also have a flanger but I have found that sometimes it puts a bow in the metal edge. When butt welding You will notice the gap gets tighter because the molten metal contracts as it cools, after each tac weld I use a hammer and dollie to flatten it out a little and maintain the gap. The longer the butt weld the more this helps. Also prevents peaking and reduces grinding.
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post #14 of 42 (permalink) Old Jan 20th, 15, 7:43 PM
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Re: Butt weld vs. flange weld

Quote:
Originally Posted by Jim's69Ragtop View Post
Terrence -



I like your method - I've always been nervous about getting a long cut to line up, but I had read somewhere that the cutting itself creates too much gap between the two panels. Sounds like this wasn't an issue for you? What width of a cut does your body saw make?



I know I have quarter skins in my future to install, so this is good info to have.



Thanks -



jim



I zip screwed the quarter to the existing above where I wanted to weld and used a body saw to cut through both. then welded this perfectly matched pattern removing the old cut off piece as I went.
It's less then an eighth of an inch. Maybe a sixteenth. Because it's not a perfect cut some areas are a little bigger. Using 025 wire it is the best welds I have made.



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post #15 of 42 (permalink) Old Jan 20th, 15, 8:27 PM
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Re: Butt weld vs. flange weld

Quote:
Originally Posted by Kaizen View Post
It's less then an eighth of an inch. Maybe a sixteenth. Because it's not a perfect cut some areas are a little bigger. Using 025 wire it is the best welds I have made.



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Gap should not be wider than wire, I use .023 and like zero gaps. 1/16" is .0625 which is way too much.
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