Advice on which way to weld my car's outer sill.

[MalcolmB]

Thanks for the advice. It's just I thought if the outer sill was only welded to the middle sill and not the inner sill it wouldn't be as strong.
I'll definitely practice first. Thanks also for the hole size info too. The original spot welds look quite small so I thought I'd get away with something like a 5mm hole but what you said makes sense and I'll use a bigger drill bit.

Also I can repair the rear part of the inner sill without removing the outer sill so I am thinking that as it's only the very rear of the car and mostly just the flange area I shouldn't need to brace the car.

 

[tom2207]

Thanks for the advice. It's just I thought if the outer sill was only welded to the middle sill and not the inner sill it wouldn't be as strong.
I'll definitely practice first. Thanks also for the hole size info too. The original spot welds look quite small so I thought I'd get away with something like a 5mm hole but what you said makes sense and I'll use a bigger drill bit.

Also I can repair the rear part of the inner sill without removing the outer sill so I am thinking that as it's only the very rear of the car and mostly just the flange area I shouldn't need to brace the car.

I loose track of how many times I post this ,,,, but ,,, try a 6.5 or 7mm hole for plug , weld across the hole start at one side and weld slowly , put a weave from bottom to top into the middle section and finish at the opposite edge , that way the middle of the hole which is further away will be hot when you get there and will get good pen and the whole plug will be good ,,, the extra heat will suck back and the whole thing will end flat , or very near it . the whole plug is done in one operation and really only takes a couple of seconds , it becomes second nature after a while very fast and very repeatable with results you can stand by.

if you start in the middle of a plug with a small hole , the farther away sheet will be blocked by the wire before its really hot , you wont see the hole fill and the outside will sit proud but ,,, you will think its a great job , unless you have a lot of experience doing it its easy to get caught out .

Give it a go and see ,,, anyone Ive shown this too tends to convert over to this method . Plenty will tell you its all wrong , but try it and see ,,,,

 

[BrokenBiker]

Actually I have another thing I've been wondering. If there's a middle layer sandwiched between the inner and outer sills what would be the best way of plug welding it all together?

I mean if I plug weld the outer sill to the centre one that might be loose from the inner sill if I don't do it right on the old spot weld and it wouldn't be strong enough.
If I drill through the outer and centre one while the new sill is on the car to make sure the weld goes all the way to the back I might drill too far and drill a hole in the inner sill and there'd be a hole all the way through.
If I drill out the spot weld in the centre sill while I am drilling and removing the old outer sill how can I line up the hole in the new sill with that properly?

Put the middle section in and plug weld that, grind flush then drill holes in the outer sill and plug weld that to the middle bit

 

[Keithmac]

I ended up doing a partial sill on both sides of the Golf after some consideration.

The floor was also in poor shape where it met the sill so used some angle iron as a full sill / floor support (a bit overkill as you can jack the car up from the middle of the sill!).

I have arch trims so ultimately the welding would always be under a cover, and above my cut line all the original bodywork was in great condition.

You have to weigh up all options really. I nearly fitted the entire sill panels, would probably not have been a lot more work but cutting the lot out would have required a lot of bracing before hand (plus I didn't want to chop decent original bodywork off).

 

[MalcolmB]

At least I know why the inner sill seemed thicker earlier. After getting under properly and cleaning off the protection stuff the inner sill actually becomes double skinned about 1/2 an inch up from where it curves out to the flange.
It appears the inner sill damage is mostly the flange and that bit that comes out to it. The vertical bit is just surface rust and it seems pretty strong. The very rear end of the inner sill, nearest the rear wheel, has a curved corner which adds to it's strength. I am going to keep that and the sliver of a bit where the vertical part starts to curve out towards the flange as that's solid and weld my replacement flange onto that.

When cutting off the outer sill I'll have to open or take off the doors as they are in the way so I can't use them for rigidity purposes but as it's just the outer sill it should be fine I hope. Well that depends on what the rest of the inner sill is like when I take the outer off I suppose.

I am just including more info in case people in the future perusing this thread could benefit from it.