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OK - so doing rust repair on external panels how many of you butt weld your outward facing rust repair panels so they are flush vs. welding the new metal in from behind and then lightly skimming the difference?
 
If you do a butt weld it less likely you'll have rust return.

Any kind of overlappiing weld is an invitation for water and dirt to accumulate...

I always TRY to do a butt weld...
 
I'd like to hear more. So I can learn more. What are you working on? What kind of welding machine? How big is the panel?
 
It depends on the repair. I just finished fixing the area around my headlights on the BMW. It required several small pieces butt welded and then ground smooth to make the panel. On the MGB floor pan repairs, I overlapped and seem welded both edges. It made the car stiffer than when it had a crude showroom stock style bolt in cage. In general small home made pieces get butt welded, and large replacement panels get an overlap, drill, and spot weld. Some panels just get extra metal laid over the existing metal for reinforcement. The rear control arm mounting points on a TR8 is a perfect example of a place that just gets extra metal.
 
So far in my project, I have butt and plug welded. The equipment available to me is an old sputter box AC arc welder for heavy gauge and frame metal, and oxy-acetylene to weld and braze panels. I have yet to do a flange weld but I am considering it for the driver's floor if I decide to do just a partial replacement.
 
Pictures would really be great on this topic.
 
Butt weld body panels, overlap and plug weld things like floorpans...
 
Thanks guys - I was mainly asking about fenders and valances. I've come across a number of folks that simply welded the repair panel in from behind and it seems like really easy fix, albeit a bit of a hack...

How do you get a nice squared off hole for the new panel insert? I'm having trouble getting a nice straight edge to butt weld the panel to.
 
Tom, shape the patch first. Then, cover the area to be patched, and scribe a line around the patch. Cut the hole slightly small, then file to fit the patch. You'll want a small gap all around to allow for expansion of the metal.
Jeff
 
I prefer stay away from from square pieces, especially corners as corners have a tendency to pucker as you weld it in. My patches tend to be circular or oval, or at the minimum square with well rounded edges.

What is important is to have some gap around the patch to allow the metal from the welder to fill into, hopefully insuring a well penetrating joint. You must avoid welding in long continuous strokes. Instead, make small spot like welds alternating from side to side until the joint is filled. It is also a good idea to use a hammer and dolly to planish (hammer til smooth) the welded joint as you go to stretch the weld which will have shrunk as it cooled.

Practice a lot on some scrape pieces to gain confindence in the process.
 
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Exactly. I guess I should have clarified those points in my previous response.
Jeff
 
Hello all,

yes, I go with the flush repair panels. I don't know about the U.S.A. but here in the U.K. most amateur restorers use MIG welders which do not lend themselves to dressing as the weld seems to be heavy and 'hard'. I personally prefer my oxy\acetylene torch which is better suited to outer panel repairs.

Alec
 
piman said:
Hello all,

yes, I go with the flush repair panels. I don't know about the U.S.A. but here in the U.K. most amateur restorers use MIG welders which do not lend themselves to dressing as the weld seems to be heavy and 'hard'. I personally prefer my oxy\acetylene torch which is better suited to outer panel repairs.

Alec
Click to expand...
Years ago I used a "new" type of wire that was softer and easier to hammer weld...but I sold my welder that had it on the spool and never found it again. Now I can't even remember the name of the product!
 
I use an inverter TIG. TIG welding is somewhat analogous to the oxy torch welding mentioned by Piman. Like Jeff and Ray, I cut rounded patches that I butt weld in place. With the TIG I can fuse the panel in place with minimal filler so there is less to dress down. However, some body filler is always required to restore the panel contour.
 
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