10 replies to this topic

[Big_Adam]

Just a question,

Going to (eventually) replace the sills on El Gordo ( oversills of DEATH!) but I don't know how they go.

There's an inner sill and outer right? So do they meet (making a triangle shape) or is the floor double skinned?

Also, how do you attach panels that are normally spot welded with a TIG welder. Just I want to replace the wings too.

Ta for the info.

[nmt_oli]

not sure on the shape to be honest, but i think they make a kinda triangular cross section.

you can either seam weld (stronger, but a pain if you need to replace in the future) or drill a hole in both panels, and fill the hole with weld, imitating a spot weld.

[jack_marshall]

If your replacing the sills to the way they were from the factory (narrow 4 inch sills) you can use same method they used at factory, which is spot welding.

If your patching, it has to be a continuous seam weld.

I guess spot welds would be a little more difficult and time consuming with a Tig, and you would be better off with runs of weld along the edges. Although if your any good with a tig, you can make lovely work of things. Any chance of using a Mig? Tends to be alot easier for this sort of thing.

[Big_Adam]

Ack, not MIG. I'm too simple to do two things at once.

As for spot welding, really can't get the equipment to do it. Well not like the mass I've seen at college that could do the job in 10mins.

[Silicon Skum]

Ack, not MIG. I'm too simple to do two things at once.

As for spot welding, really can't get the equipment to do it. Well not like the mass I've seen at college that could do the job in 10mins.

Have you tried asking the colledge if you could use the tools / workshop for an hour or two when it's not busy, or if they run a night school course (usually at least two hours) if you could use the tools then (asuuming they are not in use) ? Might be worth a try.

You would NEED to have the car finished in that time though, mostly because the college will not be insured to keep your car on site (even outside) - and it could invalidate their insurance if your car caught fire during the night, etc - so they won't allow it. Could be done in time if you drill through half the existing spot welds (just enough to speed up the time, but still be safe to drive there) and complete the job once there. Maybe do one side at a time, and the other a few days / week later when the workshop and tools are free again.

Worth investigating at least.

SS

[Big_Adam]

Have you tried asking the colledge if you could use the tools / workshop for an hour or two when it's not busy, or if they run a night school course (usually at least two hours) if you could use the tools then (asuuming they are not in use) ? Might be worth a try.

Considering they won't let me rifle thro the skips anymore I doubt it. Health and Safety, tis a nightmare.

[dklawson]

I consider the term "inner sill" a misnomer until you've started the body work. As built, the inner sill is a feature of the floor stamping. It isn't a separate part until you find rust and have to cut out the old and weld in the new. Yes, together the inner and outer sills form kind of a wedge shape.

As for spot welding with TIG, it's just like you would do with a MIG but prettier when you're done. Let's talk about where the outer sill joins the floor since it's the worst example. Every two or so inches along the edge of the new sill and about 3/4 inch from its edge punch or drill a small through hole. I used 5/32" [4mm] holes. Clamp the sill up to the car aligning it properly with the doorstep and the front wheel arch. Use a paint marker through the holes you just made to leave marks on the underneath side of the car. Remove the sill and grind away the paint (top and bottom) for about 1/2" diameter around the through holes. Turn your attention to the paint marks left on the floor and do the same, removing the paint in little circles. (Before any welding you'll need to do all of this along the doorstep as well. Don't tack anything in place until you've drilled, marked, and stripped paint from ALL the plug weld locations.) Refit the sill to the car and triple check its alignment. There's no turning back once you start welding.

With the prepped sill clamped in place and the car up high enough in the air that you can crawl under on your back, use wedges, jacks, or other items to push the area for your first plug weld firmly "up" so the sill is in good contact with the floor with little to no gap between the panels. Set your TIG so it will have a maximum power of around 20 Amps and make sure your Tungsten is sharp. (I use MIG wire for filler material. I think for these welds you'll find it's better than the thicker filler rod commonly used with TIG welding.) Draw an arc between your torch and the floor panel THROUGH the hole punched in the sill. You don't want the arc going to the edges of the hole yet. As soon as you see the weld pool starting to form on the floor panel, feed in a little of the MIG wire. As you feed in the filler start moving your torch outward in small, widening circles. Continue feeding wire. As your circles grow the plug/button you're building will quickly reach the edges of the hole punched in the sill. When the plug joins the edges of the hole, go around a couple of times to make sure the joint is solid and then shut off your arc.

Now that sounds like a lot of work, but it's not bad at all if you've prepped the holes and floor. Remember, no rust or paint (unless it's weld-thru primer) around the locations for the plug welds, and make sure you push the panels tightly together. The only bad thing about this process is the number of welds involved. Before doing this on the car though, pick up some scrap metal and practice on the bench. You don't want to be learning and practicing on your car.

[Big_Adam]

Wait.....yes....nope.........nope. Don't get that at all Doc L.

I thought I could stitch weld new outer sill on then weld the gaps.

[Jupitus]

Adam,

DKL is referring to a technique which looks like spot welds, but is done with a mig welder... looky here:

http://www.mig-weldi...k/plug-weld.htm

Clearer?

[Big_Adam]

Oooooooooooooooooooooooooooooow.

Now I get it. So I don't seam weld the front wings on then. Gotcha.

[dklawson]

Seam welding is nice and I know an earlier post mentioned it, but once you seam weld future repairs are much more difficult. You can drill out plug welds just like you can spot welds.

Jupitus, nice link. Thanks for posting it.

Big_Adam, the very bottom picture on that link shows what the plug welds along the doorstep to sill joint would look like. For TIG welding, the 7.5mm through-holes the guy is recommending seem a bit large. I'm sure those holes fill quickly with MIG, but that's a lot to fill with TIG. Practice the technique on the bench and determine what size you are comfortable with. Start small, like the 4mm I was suggesting, and move up to larger hole sizes if necessary.

SIDEBAR:
While restoring my Mini I wanted to replace the rotted out drip edge spot welded to the underneath side of the roof gutter. I don't think this was retained on later Minis but is a nice cosmetic detail on early cars. I didn't want to put too much heat into the roof area plug welding the new drip edge in place. I found another method that worked extremely well and worked very quickly. This is strictly for cosmetic bits NOT structural parts. Instead of using MIG wire for the filler, use copper wire. Apply this just as I described above. The copper will melt and flow into the plug hole VERY quickly without the amount of heat or time required for steel welds. Again, this is for cosmetic parts only but it's a nice trick to apply when you're using a TIG welder. by the way, do NOT try this with brass wire. The zinc in brass will cause it to "pop" out of the pool as soon as it melts. Only try this with copper on non-structural parts.