Welding Patches?

[dhungerf]

When repairing a rusted section (Floor, Inner Fender, etc.) is it acceptable practice to overlapand weld the new metal 1/2" or so on top of the existing section and feather the edge in, or would it be better to create perfect but welds that do not show a step?

Thanks for any help

Cheers

 

[Mark Jones]

To me, if its an area that is not going to be seen then an overlapping weld would be fine. When I welded the new floors into my Spitfire this past winter I used overlapping welds.

 

[dklawson]

I believe lap joints in hidden areas are the norm. They are much easier to produce.

 

[NickMorgan]

I think your only worry here would be that you may be providing a moisure trap. As long as you seal it up you should have no problems.

 

[martx-5]

I used both flange lap joints and butt joints when doing my car. For the flanging, I got this tool from Harbor Freight. With the tool, you create a lip that is lower and therefore the two pieces of sheet metal are the same height. For any of the exterior panels, I butt welded them if possible. They have small clamps for that job that makes butt welding much easier. I didn't do any straight overlap joints.

 

[glemon]

I took an autobody class at the local community college last winter, the guy there said they always overlap, I think it is a matter of time more than anything else. He said thye don't flange it, as the metal is not that thick and it is not that hard to blend it out with filler.

I am have been doing a lot of rust repair on my car as well, and have done both kinds of welds, the biggest difference for me anyway is that to do a butt weld you need to cut the patch darn near perfect, the actual welding of a butt weld with a MIG was relatively easy for me at least.

The other concern with the butt weld is that it may be more likely to warp than the thicker two layer bond created by the overlap.

Of course if done well it looks better top and bottom, really thought it was pretty cool when I butt welded a couple parts and then grinded them out and it was like the rust was never there.

Important thing with the overlaps is to seal them--paintable seem sealer on the bottom is good, on the top they make fiberglass reinforced filler which is both stronger and doesn't absorb water.

Lastly, there is a relatively new body metal, they say if done right it is stronger than a weld, you need to over lap to apply it, but the neat thing is that it acts as both the bond and a very strong tight permanent seal on the joint. I haven't tried it but have seen it used--apparently not cheap, but your local auto body place should have it.

Greg

 

[tdskip]

Thanks Greg.

Sounds like you have been busy! Any pictures for us?

 

[glemon]

You know I posted a progress report a while back, progress has not been going super fast, but may be time for an update. I am getting ready to paint the engine compartment (as well as rebuilding the motor and the latest working on the alternator and starter), had to patch up the battery box which had become a big hole--The weekend it spoken for, but maybe next week I will get some new pics of the 250 restoration up.

Greg

 

[Simon TR4a]

It would be better to use a plasma cutter to cut out the old floor completely and replace it with a new one- but i guess you already knew that!
Simon.

 

[hilsideser]

ah! Yes, a plasma cutter. How cheaply can one get into a plasma cutter?

 

[Guest]

Not cheap. I bought a Hypertherm Powermax 380 that would run on either 110 or 220. Well, at least they said it would run on 110. Kept kicking the breaker. Had to have an electrician come install a 220 20amp plug in my garage. Then had to buy the moisture filter for the unit. Then need plenty of air pressure (had that). Then need a place to cut, those things produce something that approaches the heat of the sun (for real!) and are tricky to use. Takes lots of practice. Tends to vaporize the metal around the cut (that is the idea) and makes for difficult welds. I would simply recommend getting a high cfm air compressor (which everyone needs) from Home Depot (American made!) and buy a cheap air cutting disk tool. Those things do need lots of air so a small compressor won't work.

 

[74WannaB]

My bid for a plasma cutter couldn't get through the procurement officer, so I still use a cutoff wheel with my 4-1/2" grinder. Works well for most cuts.

As for panels, I also got a flanging tool from either harbor freight or eastwood (I can't remember which). It works well for body panels.