How best to preserve the rear quarter flange after drilling?

[RobFrost]

Not a picture of my car - just for reference. Along the double red lines I have some rust, for which I plan to drill out the spot welds and remove the bottom x inches of the door shut panel. After drilling out the spot welds, there'll only be say 60% of the flange marked with an arrow left. Upon plug-welding back together through the drill holes, the welds would be likely to absorb the thin metal and foul the edge of the quarter panel. What's the best way to keep this edge of the rear quarter panel flange tidy where it overlaps the door shut panel? A bigger job would be to cut the flange off and weld on a new one. An easier job would probably be to plug weld the holes and then carefully tidy the edge with a grinder - although I'd rather not do it that way and end up grinding a groove into the shut panel to be filled. Just wondering what has brought people the best results.

[Gary71]

I preserved the flange for on one side when removing the quarter by cutting the panel off so there was only the spot welded strip left.

As drilling out the spotwelds (even with the proper drill) can destroy the metal underneath I only drilled maybe half way through each weld.

Then with a combination of tickling it with a grinder and bending the remaining panel back and forth gradually unpicked it.

This preserved the flange on the RHS, the LHS had rotted away so I had to replace it anyway.

This pic is a bit higher up the same flange but you get the idea. Get it down to a little strip then you can see what you are doing

[RobFrost]

Thanks Gary. I see what you're saying - I'll try that for that flange. If I'm reading your picture correctly, that's the opposite flange to the one I've pointed an arrow at, which I'm less sure about, and which is more important cosmetically.

[Gary71]

Ah, sorry. You are trying to preserve the bottom of the quarter panel?

If you’ve got rot down there you will probably need to slice the bottom of the quarter panel off to get to the kidney bowl area.

If you remove the bottom of the quarter with the bottom of the lock post in one piece then you can tackle the spot welds from the back to reduce damage to the quarter section.

If not then it’s just careful drilling from the A surface using a new sharp 6mm spot weld drill and then plug welding back through the holes.

[RobFrost]

Hmmn... I like the idea of drilling from the back. I wonder if that's possible in situ? I may at least be able to drill some from the back to minimise damage.

My kidney bowls are made of two separate members - the vertical part is intact with no water thrown up from the back wheels. But the forward-section welded on to that has been rusted by water dropping in from the door opening. It could still be more severe than it looks once I get in there.