Josh's FIAT 1500 Cabrio

I’ve been working on removing dents and prior damage from several parts of the car. For the most part though, it’s not a very photogenic process. It takes forever, and improvement is very slow. But it really is an interesting process, and i’m slowly getting better at it. I figured i’d share the basics by doing a writeup on one part of the car, the upper nose panel.

It seems that these cars often get smacked in the nose at some point in their lives.. It seems like all the parts cars I see are in similar condition. However, while my car has damage spread across most of the nose, the parts car’s damage is more localized and was previously repaired reasonably well.

nose of my car

nose of the parts car

To get a better look at it, I cut the nose section out of my parts car and drilled and ground out all of the spot welds to remove the outer skin from the inner structure.

This skin is indeed somewhat dented in one area, but overall it’s definitely in better shape than the one that is on the car. So i decided to go ahead and try to straighten out the dents.

I’m not yet sure if i’ll actually use this panel as a patch for my car, but I think that if i can get it straightened out, i may use it to replace the more extensively dented piece that’s on my car. Unfortunately this panel is a little rusty on the back side, so i will have to see how thin it ends up being when this rust is fully cleaned out.

I used a large, low crown dolly and a slapper to raise the larger overall low area of the dented area, then used the shrinking disc to level it a bit (more on this later).

After repeating this process several times, the surface started to resemble the right curve, but there are a bunch of small dimples left over from the prior repair that was done on this car.

cover with sharpie ink

sand with 220 grit on flat board

highs and lows are highlighted

To smooth these out, i need some way to planish the panel. Planishing is basically just smoothing a panel by using repeated small hammer blows (or something like an english wheel, but I don’t have one)

Since I don’t have an air-powered planishing hammer or english wheel, I’ll use the low-cost manual alternative, a post dolly:

A post dolly is really just a hard smooth die that’s clamped in place (on a post, or whatever). You hold the panel over this and tap out the imperfections in the panel by hitting the die with a smooth hammer or slapper.

The same basic principles apply as when using a regular hand-held hammer dolly. When you work the metal “on-dolly”, the steel effectively being smashed between two hard surfaces, and so it stretches.

If you work the metal “off-dolly”, (that is, the dolly is under the low spot and you only hit the high spots with the hammer), this stretching effect is minimized, because the low spot is pushed up, in effect shrinking the trapped metal somewhat by forcing it together as it’s rearranged.

The die i’m using (clamped in a vise) is actually one of the ends from this hammer kit. I don’t find this hammer all that useful, but the ends are pretty good for this use.

I ground the sharp edges off the hammer end (you never want a sharp edge on a hammer- one false move and it will dig into the metal and leave a mark) and clamped it in the vise. I then mounted a cheap laser pointer to my ceiling above the vise and wired in a remote switch so that i can easily turn it on and off. (ideally, i’d have this hooked to a foot pedal, but i didn’t have one to use, so for now it’s just a microswitch i can nudge with a hand or knee.)

To allow for adjustment, I screwed a piece of metal to my ceiling, and mounted the laser pointer to a magnet. This works really well, actually.

laser above vise	align the laser	highlight the low spot
	slap it lightly	mostly gone

So, to raise small low areas in the panel, i point the laser at the center of the crown of the dolly, then put the panel in place and line up the laser dot with the low spot. Then when i hit the panel with a hammer or slapper, i know that it’s centered on the low spot, so that’s what will be planished out.

If I hit too hard, it stretches the metal a bit, making a larger high spot in place of the small low spot. This is in fact what happened, but it’s not a problem to fix.

Once I’ve raised most of the low spots, i then reapply the sharpie and sand to get a look at things. As you can see, the low spots are reduced, but there’s one big high area now.

To shrink this stretched metal down and lower this high area, I use the shrinking disc. This selectively heats up the high spots. When it’s cooled off back to room temperature (you can use water or compressed air to speed this cooling), the metal shrinks slightly beyond its initial shape.

Here’s the result of that:

As you can see, it’s starting to level out now. There are some low spots remaining near the edges of the panel.

Basically, by repeating the steps above over and over, i can refine the surface until all the dents are essentially gone. There are still going to be some rust pits and scrapes on the surface which I can’t eliminate, but those can always be filled later if I do decide to use this panel.

For more information on the techniques I am using, see metalmeet.com, and in particular this tutorial.

Some of the tools I am using, and where I got them:

• Shrinking Disc - Wray Schelin
  These are available from several other sources. It’s just a flat stanless steel disc with a lip on the edge and a dimple in the middle, so several folks make them. Espect to spend about $50 on them. A very inexpensive 9” grinder is available from Harbor Freight that works fine with these discs. I use a 7” rubber backing plate from home depot or similar and a 9” phenolic backing bad behind the plate to provide support.
• 7 pc. Hammer/Dolly Set - Martin Tools
  I really like this set of hammers and dollies. They are *MUCH* harder and better polished than the cheapie chinese sets you can find at harbor freight (and everywhere else). I found that sears’s web store had a good price on this set (here).
• Slapper
  A slapper can be used like a broad hammer to spread out a blow over a larger area. This works great for raising small dents, because you’re effectively hitting simultaneously all the way around the outside of the dent when you hit it with a slapper. Slappers can be made from a car’s leaf spring, bent into proper shape and polished. Since I don’t have a torch (or a leaf spring), i instead bought one from autobodystore. A light slapper also comes with the martin tool set, which is good for fine work, but not really heavy enough for a lot of the stuff i’m doing.
• 3M Roloc Discs
  I use the 2” discs on an angle die grinder for general cleanup of metal parts, stripping paint and rust, etc. I also use the roloc bristle brush and sandpaper for some tasks.
• Random-Orbit or D/A Sander
  Ideally i’d use an air-driven D/A sander for final metal surface preparation and light paint removal, but I find that my little compressor can’t put out enough air to drive one. So for now i’m using a dewalt electric sander for this kind of thing.
• Markers/Flat Sanding Block
  I’m just using a bit of relatively-flat plywood with a piece of 220 grit “stickit” style sandpaper on it. I’m just copying what Wray Schelin uses, and it seems to work well for me. As he said in a metalmeet post:

  I have tried Dykem, and many other highlighters. The best by far is a Magnum Magic marker. These are monster sized markers.

  When I wrote that original article about taking dents out at that time I used a file to skate across the metal to highlight the highs and lows. I no longer use a file. I use stickit 220 or 150 sandpaper on a 6 inch round by3/8” thick disc of baltic birch plywood. For large low crown panels I use a 2.5” wide x 16” piece of 3/8” aluminum with a boardfile 150 or 220 stickit paper.

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