Technical Can anyone show how they do the overlay cut & butt weld technique?

I hope to soon start on the roof insert on my 35 5W and want to TIG butt weld it in. I'm still learning to TIG so getting a tight seam is extremely important. I saw on YouTube and heard of the technique of overlapping the panels, cleco them in place then slice through both with a thin cut off wheel in small sections which the scrap is peeled away and the panels tacked. It would seem this method would yield a much better fit then me scribing a line and cutting to it especially for such a large and visible panel. Who uses this method ? Have pics/tips to share ? I expect to do a little hammer dolley work at the seam to tighten up gaps. My plan is to get the insert tacked in the finish trimming up my door gaps , tacking in the tail panel so I can rotate my welding all around the car minimizing warping/heat build up . If I dont have enough real estate to weld around I know I'll screw up welding too much too close.


Thanks
Leon

 

on my avatar, I tack welded the insert every 4 or 5 inches to the inside of that trough, then filled the trough with seam sealer. It looks factory and the tacks can be easily cut and re-welded if you ever need to replace the wood inside.
It has never leaked.
Your description of how to do it your way is accurate. Just do it

 

You are filling the opening?

 

Yes, I want to fill the roof.

 

So the mounting area for the fabric insert will.be removed? And you have the pre-shaped metal at hand?

 

It could be done that way for sure.

Once you have a shaped panel do as you stated, you could even just place a few tacks on the outside perimeter and then cut a slot 6 to 8 inches long, add a tack at each end of that slot then cut some more and just keep following that pattern.

One suggestion I have is instead of a small cut off wheel I'd try one of those harbor freight or ebay cheap little air saws or a jig saw. I think the cheap little reciprocating saws use a smaller blade.

 

I've got sheets of 18ga steel and an English wheel.

 

I have the air body saw but I feel the 4" cut off wheel will be straighter and cleaner.

 

Doing it that way the gap will be more than you desire. Form your panel, make ribs under to brace it. Set it on the roof after your happy with the shape and size, drill holes and cleco it down, then scribe around it as close as you can, ice picks work well for that. The cut the roof, not quite to the line you scribed so you can sneak up to the line to keep a tight gap. Then add little straps clecoed across your edge to hold it flush and start tacking.

https://www.hotrod.com/articles/killer-filler-roof-insert/

Sent from my SM-G973U using The H.A.M.B. mobile app

 

https://www.hotrod.com/articles/killer-filler-roof-insert/

 

I need to do a search on this, be back when I find a HAMB related post. Bob


Found it! Go to page 2 of this 1954 Chevy build Cretin started, he shows this technique on a headlight rim extension. Miss the guy, I haven't seen any of his posts lately.

https://www.jalopyjournal.com/forum/threads/54-chevy-210-post-build.969489/page-2

 

See this video from Walden speed shop. Starts at part 20. Shows complete proceedure.
https://www.waldenspeedshop.com/media

 

That Walden video was Great! bob

 

I've got a friend who has done a number of them just the way you described.
I'm not a fan of the thin cut disks that would make the best cut to have the least gap to fill. They are the ones that tend to explode if they bind up a bit or get damaged the least bit. If you are using those wear the big face shield and a heavy shirt or jacket and forget the tank top and those "Just like what the guys wear on the car shows on tv" safety glasses. Wear a pair those under the face shield.

 

So you actually want to remove the cars Roof insert channel in this process?
I’m not sure I would do that, I’d fit the steel nicely and leave that channel.

When I do the overlay technique I fit it with clecos while it’s being taken on and off 209 times then I switch over to rivets, aluminum pop rivets. It’s riveted in pretty damn good and solid. I use an air body saw with a large air fitting (important) and follow the edge of one panel as a guide cutting thru just one layer. Cutting and tackling as I go. Stay tight and it’s ok to nick up the guide edge.


On the back side the little scrap is just rolled up as I go. It’s easy to hammer dolly the tack because nothing is in the way. Planning the placement of the rivets as needed to hold everything and drilling them as I pass. Aluminum rivets drill easy. That’s how I do it.

When cutting thru 2 layers it’s tricky, and if your lower layer has the channel you can’t get out of the way it’s going to be a nightmare.

 

All good advice.

 

The roof is kinda screwed up already. The channel has been poorly spliced and is far from straight. The PO did a horrible job of filling the roof by overlapping. I would salvage it if there wasn't so much collateral damage. It looks much in person.

 

So the place to start would be removing the part you don't want and tuning up the opening.

 

This one is pretty good.

 

File the new panel edges clean and straight (radius the edges)
Fit the part and cleko in place.
Scribe the new panel edges on to the car. Machinist dye works great for showing the edge. Also make reference marks to orient the part.
Use a quality pair of shears to cut the outline.
You can cleko temporary strips to hold the new pane in place. Start tac welding
Lots it tac welds then weld and hammer.
The better the fit, the better and faster the weld.
I don’t like filling the gap left by a cut off wheel. Especially with a tig.
You can make that part fit together tight with no gap with a little patience.
The time spent to fit it perfectly will pay off by saving time during the weld process.

 

Yup. I watched this a few times.

 

Also, I use these.

 

We always called the process of overlapping two sheets from opposite directions and then cutting through both at the same time a "kiss cut". Keep the cutting tool 90 degrees to the metal and it works really good. It eliminates the problem of having to cut a perfectly straight line since the one sheet of metal will be the mirror opposite of the other and it will fit together perfectly. Thus, making a tight butt weld is fairly easy.

 

https://www.jalopyjournal.com/forum/search/231376421/?q=****&o=relevance&c[node]=5&c[user][0]=46669 Alot of information, Check out his 55 210 wagon build, There is a section where He explains butt welding! Excellent read!! Pete

 

Thats a video from a good friend of mine...fellow HAMBer "fitzee".

 

Holding the panel firmly in place has it's benefits, but there may be times when you want it to "float" a little. Welding causes shrinkage, so if you need to close up a gap that has opened up due to shrinkage, remember that a crowned panel will expand when pushed down. Like, take a cupcake paper thingie, put it upside down on a table and push down on it, and you will see what I mean. The only hard and fast rules there are when welding in a large panel are the fact that it will be difficult, it will warp, you will get pissed off, and each one will be different.

 

The best cut off tool to use for the final cut.

Then I like to use a file to clean up any irregularities.
Don’t worry about warpage. It’s gonna happen. That’s what hammer and dollies fix.

 

The Walden method is probably the best. When I weld two pieces of sheetmetal together with a TIG I try for zero gap. I think even the thinnest saw or wheel will make too much gap.

I usually scribe a line, then rough cut to about 1/4" from the line. Then I can use my sharpest hand shears to cut exactly on the line. Then file and maybe grind a little to tune it up. Some of the time I'm lucky enough to not need any wire to make the weld, but I always have some ready in case there's a little gap. I see Walden uses some MIG wire when he's TIG welding, and I may try that next time I have a good fit up.

 

Haven't tried this, but I'm wondering if it might work. Get metal insert say an inch bigger than what you want to actually install it. Lay it in place and scribe say the back and the passenger side. Remove it and cut it on your workbench. Cut those two sides and lay the metal back in place and check/adjust it till it seems to fit ok.
Once you have it fitting acceptably on those two sides, put 3 tack welds to hold it and then scribe the other two sides (front/drive). Remove the tack welds,take it back to the workbench and cut to the outside of your scribe line.
Lay it back in place and mark any minor interference and then belt sand those imperfections.
The idea is that you are doing it in two steps rather than trying to get all 4 sides perfect at once. Don't know that it will work any better but it seems logical to me.

Edit: After thinking about it a little more, after doing the first two sides, I would do the last two sides.......one at a time. Much easier when you aren't trying to get four things perfect all at the same time.

 

I agree the Walden video is excellent. Will watch more.