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  #61  
Old 05-14-2019, 06:03 PM
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05snopro440 05snopro440 is offline
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Holy! I just saw the last page of the thread and at first thought you were making 39-46 Chevy fenders. Great work on the fenders and even the buck! I wish I had a quarter of your skill and half of your ambition!
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  #62  
Old 05-14-2019, 06:56 PM
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Quote:
Originally Posted by dutch View Post
oxi/acethylene with no filler rod... just for the occasional hole
Quote:
Originally Posted by dutch View Post
Single pass not planished yet...
Your photo below... how do you avoid distortion while welding a joint of this length?



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  #63  
Old 05-14-2019, 08:30 PM
bob w bob w is offline
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Hopefully Dutch will explain. However, I did watch a video tape by an English metal man who gas welds without filler rod too. He states that by moving at a constant pace distortion is minimized. Notice the consistent width of the heat discoloration in the pic above.

I've tried it on flat test pieces and it works.
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  #64  
Old 05-15-2019, 01:18 AM
dutch dutch is offline
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I`ll try to explain how I work...
there`s always some distortion, but real problems occur when the distortion is uneven. Single most important thing is to cut the panels to a seamless fit so when placing the tack welds you wont need any filler rod and you`re able to steer the panel and hold the torch in the other hand. Tacking takes every bit of focus I can find. Correct level on both, heat/tack, check and correct height for next tack, look at gap closing, set next tack before panels start to overlay etc... I dont use clamps since I already know the panel fits seamless to the other so it will end up in the right position anyway. I place a tack at the edge of the blue of the tack before, so about every 3/4".

After that, it`s hammering the seam flat and the panel to the shape it should be. Wirebrush the seam clean on both sides and weld in one pass. Takes some practice to get the penetration right, but what you get is a crater on the top side and bead hanging on the other side of the weld. Work that flat and 90% of the shrink/distortion will be gone.
By welding in a single pass the discoloration is very even, so the shrink is very even ,so the distortion is minimal.

You do need to understand the reason why sheetmetal will distort after heat.

When heated it expands, when cooled down after heat, the surface area has shrunk more than it was before heat. So uneven heat = uneven shrink = distortion = very hard to correct.

Hammering these a/o welds is no problem because they are as soft as the surrounding metal. I can cut them with snips no problem and I can use the e-wheel to stretch larger area`s.

hope this makes any sense and / or helps
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  #65  
Old 05-15-2019, 05:21 AM
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Thanks for the explanation Dutch. I presume you use a small brazing tip?
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  #66  
Old 05-15-2019, 05:55 AM
dutch dutch is offline
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Quote:
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Thanks for the explanation Dutch. I presume you use a small brazing tip?
Usually I use a #1 welding tip. #0 also works fine for 19gauge but is too small for 16gauge . I use 16gauge for fuel tanks and I dont have to switch tips that way.
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  #67  
Old 05-15-2019, 09:03 AM
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Thanks for the details.
I never knew why this process worked so well either.
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  #68  
Old 05-15-2019, 10:09 AM
kenny c kenny c is offline
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Very nice explanation. Thanks. If I tried it, it would look like Swiss cheese.
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  #69  
Old 05-15-2019, 12:36 PM
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Thank you for the explanation, Dutch.
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  #70  
Old 05-15-2019, 08:17 PM
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Thanks, dutch!

I'm a "heavy metal" fabricator and welder, with an early (abbreviated) career in collision repair. I can iron out some damage, but I'm nobody's "coach builder".

Unfortunately, I never learned how to do what you do, but I hope to learn before I die. (Little demand for custom work in my corner of the world.)

Another question:

- Have you tried TIG welding the same joints? I don't see a huge difference between the two processes, especially when performing a fusion weld with no filler rod... I'd appreciate your opinion on the subject...

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