Thursday, September 13, 2012

Tech Tip - Sheet Metal Repair

Sheet metal repair can seem like a huge out or reach project for a beginner, but this article should show you its not as bad as you might think. Tools you'll need: sand paper (80-160-220 grit), hammer and dolly, some filler, a mig or tig welder (we are using a mig), some various clamps or sheet metal clips if available, some metal shears and a diegrinder.

Start by location the rusted and wrongly patched areas. Once located using the diegrinder and a cutoff wheel we cut the infected areas out. Unfortunately for us that include most the the drivers side but that's okay, this car has tons of aftermarket support and we easily found patch panels at for next to nothing. After cutting away the rusted areas, use the 80 grit to remove the paint and clean up your cut edges. Afterwards use a coat of weld through primer to seal and prevent any future rust if you don't finish.

Using the old pieces as a template, use a marker to trace the basic outline onto the new panel and use the metal sheers to trim off the excess, its better to leave a little extra at this point.

Once trimmed use clamps to hold onto the car in the correct position, this will allow you to make and final trim marks with your marker. Its important to not overlap your metal, you want your panel to come about 16th away from each other. This way once welded you can grind smooth and have a perfectly flush piece. Overlapping would cause an unwanted ridge.

Using clamps again to secure your panels in place. start by making a few spot welds around the perimeter. This will hold your piece on so you can remove your clamps, allowing more room to work. Since these are large shaped flat areas, be sure to make small spot welds a good distance apart allowing metal to cool, so it doesn't loose shape and distort. For the in fender well, we drilled a few hold and made flush spot weld to join the two and used a sheet metal join compound to fill the small gap between rather then try and seam weld the fine edge. The same technique is use in the door jamb as well. While welding it maybe necessary to use the hammer and dolly to make adjustments to get your fit flush. Take your time here small adjustment will make large differences.

Once welded use a 4" grinder if available to take down the high spots, making sure not to over heat the metal. Doing so will be just like the welding process causing distortion. To finish the grind, I recommend a heavy grit sanding disc on the diegrinder to make quick work or the remaining welds. You should be left with a panel similar to this.

A little filler and a block sander will take out any hi or low spots, you weren't able to get with hammer and dolly. For this we used an aluminum based metal filler, since we will be adding some more mods to this area later. For the sanding we used the three step process, stepping down from 80 grit to take the high parts down to 160 for the majority of the sanding and finishing for primer with 220. This form of filler is more difficult to work with. The aluminum makes the sanding a lot tougher and more time consuming, so make sure you use small thin layers. Piling it on will only waste your money and time.

With sanding completed the final product is a new side completely un-noticeable from the original worn out panels.

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