Sill Patch Fabrication

Today I spent most of the day fabricating steel patches for the worst-rusted areas of the front fender sills, the area under the front fenders down close to the ground. This is the area where the front fenders bolt to the underside of the body, and an area where the fenders are apt to rust as well as the sills. Although relatively solid, rust holes had begun to penetrate the area and the best course of action was to cut out the rusty sheet metal and replace it with solid steel.

Starting on the driver’s side, I just drew up and cut-out a patch from poster board big enough to cover the rusty area, then I taped the poster board up onto the sill in order to trace the cutting perimeter onto the body.

I traced the outline using a black Sharpie marker.

On the passenger’s side I did the same, and it required a patch of a different shape.

The nice thing about using a poster board template is that I could then lay it flat on my steel stock and trace out the shape the patch would need to be before bending. I used 18-gauge steel for the patches. I cut out the patch using a pair of electric sheet metal shears.

I cut out both the left and right patch panels the same way.

On the driver’s side I made a rough bend in the patch panel so it would have a curve similar to the sill. I just sandwiched the lower edge of the steel between to short lengths of two-by-four and pulled up on the upper edge to bend it.

Then I cut out the rusted sill area from the body just using my Dremmel with the little cut-off wheel. The thin Dremmel cut-off wheels were used up pretty quick so I had to keep switching in new ones.

After cutting halfway around the top I could see that there was plenty of rust inside the sill. In fact, I could see where the bolts that connected the lower fenders into the sill had rusted and broken off in their nuts. I finished cutting out the rest of the area.

Here is the removed rusted-out sill area and a side-by-side with the new patch after I fine-tuned the shape of the patch a little more.

I cleaned up the edges of the remaining surrounding sill using a cleaning wheel on my drill.

Since I had to cut out the nuts that the fenders bolt into at the bottom of the sill, I will need to drill holes and weld in some new nuts onto the patch. I marked the location of the holes in the patch.

Then I moved over to the other side. Instead of using the Dremmel I used my angle grinder furnished with a metal cut-off wheel, which went much faster through the sill. This was definitely a better tool for the job!

There was less rust inside on the passenger’s side but I still had to clean up the remaining metal using a stripping wheel.

Here is the patch panel bent roughly into shape alongside the cutout.

I prepped the inside areas of the sills on both sides by washing them out using Simple Green and also spraying on some Metal Prep to address surface rust. Then I painted on a coat of Eastwood’s Rust Encapsulator. The Rust Encapsulator is supposed to seal in rust and prevent any further deterioration.

I just applied a generous coat of Rust Encapsulator using a brush.

And I did the same on the other side.

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