Pelican Parts Forums - Butt welding flares vs. lap welding

Pelican Parts Forums (http://forums.pelicanparts.com/)

- Porsche 911 Technical Forum (http://forums.pelicanparts.com/porsche-911-technical-forum/)

- - Butt welding flares vs. lap welding (http://forums.pelicanparts.com/porsche-911-technical-forum/345010-butt-welding-flares-vs-lap-welding.html)

Butt welding flares vs. lap welding

As i am learning to weld i am curious how exactly flares can be butt welded. It seems it would be impossible to perfectly match the cuts on the chassis and flare. What am i missing?

Also curious to know whether those of you who do a lot of 911 metal work prefer Mig or Tig.

Thanks for the input-

Erik

I am in the process of butt welding GT flares on my 914 but it's the same for a 911. I have never done this before but I did a lot of research on the web and then decided to do it. What I am doing is I get the flare clamped in place and take all the vital measurements to determine it is in the right location. Once I know it's good I put 4-5 self-tapping sheet metal screws thru the flare and into the existing body. I then use a jig saw with metal cutting blade and cut thru the edge of the flare and the fender, this leaves a exact seam does that make sense? I'll cut about 10-12 inches and stop. I'll peel away the existing fender and install welding butt clamps to hold the seam tight and do a couple of tack welds. I continue this process until the flare it tacked all the way around. So far I have done the rear flares on both sides and this has worked great. I am doing this with a Hobart 140 mig welder with .025 wire and 75/25 shielding gas. Hope this helps.

I could say do a search.....but after you do butt weld is the ans. Just remember to give it all a good hammering after the job to relax it all

Re: Butt welding flares vs. lap welding

Quote:

Originally posted by berettafan
As i am learning to weld i am curious how exactly flares can be butt welded. It seems it would be impossible to perfectly match the cuts on the chassis and flare. What am i missing?

Also curious to know whether those of you who do a lot of 911 metal work prefer Mig or Tig.

Thanks for the input-

Erik

Whatever you have will work. The trick is to use as little heat as possible to do the work. Only weld a small amount at a time. People always say this, but they don't know how much heat it takes to start a weld. With MIG, the weld is started almost instantly, but MIG welds are hard; not very malleable. TIG works nicely, but not everyone has one or knows how to properly use it. It takes a couple of second to start a bead. This is unwanted heat.

Oxy/gas might be the preferred method of the accomplished welder, but a lot of heat can be introduced if not really good at it. The trick here is to use a real, real small tip and MIG wire as the filler because welding rod smaller than 1/16th is hard to find. And, get some Cool Blue welding heat sink paste.

If a team were to do the welding, that would be ideal. One to weld, the other to hammer and cool. One just doesn't have enough hands to handle the torch, the welding lens over your eyes, find the hammer and dolly, then hit the weld with air or a wet rag. It's like juggling. 3 balls, 2 hands

As an amateur (installing my 5th set of quarters, at this moment on a Buick GS), Milt's thoughts are so accurate. Good luck getting the helmet up, tip down and hammer and dolly ready before the MIG weld cools.

I don't think any amateur should try Oxy/gas on cosmetic thin metal welds.

Use thin wire in your MIG (.25), this is handy.

Take your time, check twice before stitch welding after the tacks. I prefer Clecos to attach panels. You'll likely be proud of your task afterwords.

Grinder: take smooth long passes and don't try to grind down small sections. It may seem to take longer but less likely to form gouges.

Re: Re: Butt welding flares vs. lap welding

Quote:

Originally posted by milt
Whatever you have will work. The trick is to use as little heat as possible to do the work. Only weld a small amount at a time. People always say this, but they don't know how much heat it takes to start a weld. With MIG, the weld is started almost instantly, but MIG welds are hard; not very malleable. TIG works nicely, but not everyone has one or knows how to properly use it. It takes a couple of second to start a bead. This is unwanted heat.

Oxy/gas might be the preferred method of the accomplished welder, but a lot of heat can be introduced if not really good at it. The trick here is to use a real, real small tip and MIG wire as the filler because welding rod smaller than 1/16th is hard to find. And, get some Cool Blue welding heat sink paste.

If a team were to do the welding, that would be ideal. One to weld, the other to hammer and cool. One just doesn't have enough hands to handle the torch, the welding lens over your eyes, find the hammer and dolly, then hit the weld with air or a wet rag. It's like juggling. 3 balls, 2 hands

If you like to gas weld you would really like one of these. I have had the weldit mdl 101 for years - it is a great tool.

http://www.victortorch.com/weldit%20gasaver.htm

Victor, for one, makes the small tips good for this kind of work.

Lukesportsman, I have a 69 Buick GS that I'm restoring also.

what is the purpose of hammering after the weld?

thanks for the links john. that pretty much explains it.

i am not going to be doing flares myself, just have some pan area work to do and a small floor pan hole to patch. i just wanted to understand the process a bit more.

Quote:

Originally posted by rfuerst911sc
What I am doing is I get the flare clamped in place and take all the vital measurements to determine it is in the right location.

What measurements did you take? I would like to get my flares perfectly aligned...I'm ready to weld now. I think that method you described is a great one though...it's gotta be the right way to do it. How much of the new flare did you cut off?

Any pics to share?

Quote:

Originally posted by emptyo
What measurements did you take? I would like to get my flares perfectly aligned...I'm ready to weld now. I think that method you described is a great one though...it's gotta be the right way to do it. How much of the new flare did you cut off?

Any pics to share?

The measurements I took are available on the net for the 914 GT flare install but I'm sure there must be measurements available for the 911? I always have trouble adding pics but if this works here is a pic of one of my flares.http://forums.pelicanparts.com/uploa...1179826584.jpg

I lined up using the torsion bar hole, then rear flange on the back. Put a couple of sheet metal screws to hold in place.

They now have this new MIG wire from Harris called "20 guage" that is powder filled, designed for light sheet metal work.

Does the wire make a big difference bob? I need to see what I have in my MIG before I start this, I think.

I haven't used it, but have been reading about it on various hotrod, welding sites.

Some links:

http://www.millerwelds.com/education/projects/mboard/showthread.php?t=532

http://www.harrisproductsgroup.com/consumables/alloys.asp?id=11

Heres how I do it:

I'll weigh in here as I just did this exact project on a 911 and have done many similar things on other cars...

Background: car is a 79 SC that we're building as an IROC inspired hotrod.

To answer a question in the thread, it is difficult to get the flare to butt nicely-but not impossible. Using the following I can usually get everything nice nice with about a 1/32" max gap. Using the following method you can do door bottoms, etc-any butt welded repair/modification.

Start by using some good measurements-i.e. torsion bar holes, rear lip above the valence, etc. to position the thing roughly.

Line it up, then make a line on the body where the new/repair panel overlaps-then take the flare off and grind off the paint about an inch or so from each side of the line.

ALSO grind off the undercoat on the bottom about the same amount. Take it down to bare, shiny metal. Use one of those resin discs like a Norton Beast-they do not thin the metal like grinding it. You DONT want to thin the metal, its thin enough already...and you'll burn through enough as is...

Anyway, that was your rough line just to get a ballpark idea of where the part will go. NOw you have bare metal to scribe your actual cut line on-its much easier to see and make an accurate cut on bare metal than on painted metal.

Now, working with the flare, trim the edge so the edges are not wandering (from the stamping process) so they form a nice symetrical arch. Wandering lines are tough to weld accurately. Sometimes I do this by stretching a piece of tape along the edge and then tracing the tape edge...trim to the tape edge or the line you made, now you have a nice even edge...

http://s94994139.onlinehome.us/album...8/P1010057.jpg

Line it up as above but more accurately if you did the above just roughly, use some sheet metal screws/cleco's/rivets to hold it nicely tightly.

Scribe the quarter panel on the car thusly:

http://s94994139.onlinehome.us/album...8/P1010077.jpg

I use a super sharp scriber to get teh tip right down at the edge of the flare. Its also a good idea to make some hash marks that will allow you to index the flare once everything has been removed because you will then have no reference point.

Now remove the flare, use a 1/16" or thinner cut off wheel to make the slice on the OUTSIDE of the line you just scribed. If the line has a great curve, you'll want to use a smaller wheel as it will be easier to make follow the curve without making the cut choppy and innacurate-either that or just dont bury the wheel when you're cutting:

http://s94994139.onlinehome.us/album...8/P1010072.jpg

Now your flare is off-and holding it in place will be really tough as you cant clamp it too effectively, so its best to use your index marks and have an assistant who has not been drinking hold it in place while you tack weld it in a few areas.

http://s94994139.onlinehome.us/album...8/P1010082.jpg

Like has been said, you need to work slowly. Each tack weld, until you get them spaced about a half inch apart will need to be hand dollied to make sure the two adjoining panels have no offset between them.

http://s94994139.onlinehome.us/album...8/P1010085.jpg

http://s94994139.onlinehome.us/album...8/P1010001.jpg

Note the use of a small chunk of angle iron to make sure there is no offset between the panels-you could also use padded vise grips to accomplish the same thing.

Keep a clean small wire brush (toothbrush size) handy to clean your welds after you do them to make adjacent welds nice and clean.

http://s94994139.onlinehome.us/album...010014_003.jpg

(note-wheels are "Rollers" that are too narrow and I think we were taking the rear valence off because its hanging a bit low...)

Once you have 100 percent welded the flare, its time for grinding the welds. This is AT LEAST as important as your welding for determining how the end result is.

I grind welds thusly: I use the same cut off tool that I run an .045 cutoff wheel in, but I use an 1/8" so called cutoff wheel. This way you can grind JUST the weld and not the surrounding metal-its very controllable. I dont have a pic of this but its something that does not carry over well in a pic anyway. I hold the tool at a variety of angles to achieve the nice result I want-you just have to learn what works for you.

One thing I do is mark areas where the welds may not have penetrated well enough or where there were spots I missed. I then reweld these areas afterward and grind, etc.

ONce its all ground, you can hit it with a DA with some 80 grit to make it really pretty like this:

http://s94994139.onlinehome.us/album...8/P1010023.jpg

Sit back and marvel at the work you've done!

Thanks Matt...great post. I assume that you go back and stitch weld between the tack welds before you grind it. What do you think about the technique of attaching the panels and cutting them both at the same time with the body saw? Then tacking 10" or so at a time?