The Stovebolt Site Forums The Shop Area Paint and Body Shop Question on welding in a patch panel

So i did my first welding in over 20 years and welded in a patch for a rusted area in the cab. Here is the hole that I ended up with
http://img403.imageshack.us/img403/2126/img4781g.jpg
Here it is with the patch in place
http://imageshack.us/photo/my-images/225/img4783y.jpg/
When I put a light behind it I see a few pinholes where light comes through. I will be sanding and using some body solder. Should I weld up the pinholes first or will the body solder take care of that?
This is my first time doing body work. In the past I have only done mechanical work. So, any advice is greatly appreciated.

Personally, I weld them up, grid the welds down smooth and only use filler minimally, if needed. Others may have a different opinion.

Dale

Pin holes will let moisture in and eventually start rusting. Filler and primer will seal the outter panel. If it's possible I'd seal the inside panel, with a water proof coating.

This is the back of the cab and there is only one panel. I will try to weld up the pinholes tomorrow.

If you are using lead as filler there is no need to fill the pinholes. The lead will not allow moisture to enter the repair if it done correctly......

I am using lead free body solder. Can I assume it will also fill the pinholes? I went out last night after dark and used a light on one side while welding on the other. At this point my neighbors think I have absolutely lost my mind.
Once I use the body solder, should I use a seam sealer on the inside?

Should not be necessary but a good coat of paint would be good insurance. Be sure to neutralize the acid used to clean the steel to get the lead to stick. Why you want to use lead is beyond me as the body filler available now is as good as if not better than lead if used correctly......

The body solder is only because I wanted to try it. If it is too much trouble I will use a modern body filler instead. After I used my grinder on the weld, there is very little filler needed. I guess that's a good thing.

Kary, using a MIG, after I've jumped around with the initial tack welds, I'll planish those to stretch out what's shrunk up from the welding heat, then grind the weld dots down to just above the panel surface. (gets them out of the way for planishing the next ones) When ready for the next weld "dots", rather than centered between the last ones, I go to an overlap of the last dots. Then Lather, rinse, repeat. By overlapping it tends to eliminate the pin holes. Here's a post on a lower fender repair that shows it pretty well...


http://www.trifive.com/forums/showthread.php?t=9511

Robert
Can I ask how you planish the metal. I noticed today that there is a little warpage by one side of the repair. I was thinking of using a hammer and dolly to bring it back to shape. Should I be doing something else? Thanks

To start, any time you weld, you will have some shrinking occur. Basically with the introduction of heat from the welding process, the molecules in the metal expands from the heat. Then, as it cools, the molecular structure will re-align such that they are tighter together than they were previously, or in other words, shrinking has occurred. So yes, a hammer and dolly works wonders to stretch out the area that has shrunk. About the only time you will see any stretching is from a dent during body damage. Welding causes heat that shrinks. Fix the deformity that results by stretching the weld and Heat Affected Zone (HAZ), recognized by the blue discoloration around the weld.

There are a couple different ways to planish the welds:

1- planish out the weld dots as you go, and then grind them down to insure they are out of the way for planishing the next set. If you don't do this step, you may end up with some weld dots taller than others, and as you hammer and dolly, these varying height welds will tend to deflect the panel, possibly causing waves/more distortion.

2- Weld the complete joint and planish afterwards. Following the same philosophy of the varying height weld dots as before, it would be best to grind down the weld to just above the panel surface (both sides) for a consistant, flat weld surface, and then planish. For someone not as adept in grinding consistently, the first version may work best. Someone who can grind to a consistent height could use either, personal preference.

Here are a couple of reads on the topic, some showing the difference between shrinking and stretching, that may help to explain a little better (with pictures!!)

http://www.trifive.com/forums/showthread.php?t=46382

http://www.trifive.com/forums/showthread.php?t=65849

Thank you so much for the info. Your work looks great. I have always done mechanical work and this is my first shot at body work. I am going slow as learning and hoping to get good results. My wife and daughter are actually impressed with how good it looks so far.

Thanks. Lots of practice and not so good looking work to get to that point.
A lot of resources (pictures, videos, etc) online exist today to start you off on the right foot. Wish that was the case when I started...

The other thing I forgot to add in all that other rambling, when setting up your welder you want some weld protrusion on the back side of the panel as well, a full penetration weld. If you don't, you'll lose much of your joint strength as soon as you grind the weld down. Theoretically, with a full penetration weld, as soon as you grind down both sides (and planish as needed) it should be as if it were one panel the whole time.

I spent some time practicing my welding on sheet metal prior to putting the first patch in the truck. It took some adjusting to get a full penetrating weld. I have been getting info from the internet and a lot from my father who did this type of work years ago. Unfortunately he has lost a lot of his vision to macular degeneration or he would be helping with the work. He used to lay down the most beautiful welds.
Again thanks for all your help