I have two areas on my Model A Coupe where the sheetmetal is bulged out. I'm not exactly sure what's the best practice to hammer/dolly the repair. One spot is from a bullet hole on the rear quarter where a bullet exited and was filled in (long ago) without attending to the damage first. It's raised enough that I could see shrinking it down but still moving the issue outward. It's all very smooth and "tight" in the quarter. The other spot is on the lower third of the door. That area has a bunch of work to be done but the bulge is noticeably larger than the mess around it. So, a better question would be how to tackle it, biggest issue and work my way through or a little bit at a time throughout? The bullet hole portion I'd like to work down as close as possible. Everything else in the area is clean/straight. The door... I'd just like to make it better than it is. It will still get filler but I'd like to improve the area first. As I've practiced, I've gotten a few more tools. I'm posting so you can see what I have at my disposal. Also, I have a larger shrinking disc, not shown. I do feel more comfortable with the small one at this point - but it's 6s, really. I'm a novice with all the metalworking tools. All said, how would you work out the issues with what I have at my disposal?
That appears to be stretched. That being the case, you cannot "hammer it out". If you want it metal-finished it will need to be shrunk. In my experience, a common "shrinking hammer" does not actually shrink. The cross-waffle face creates "double corduroy" wrinkles in the metal, which may, or may not be able to be sanded smooth. They would otherwise need to be covered with a little bit of filler. If you are ok with a little filler, you can carefully hammer it down to where the bottoms of the wrinkles are just below the intended surface, and then fill. What you have in that drawer rivals my collection, and I have been doing this for about 40-years. Take it slow, see how the metal responds. It's just metal. It is not smarter than you.
I would try shrinking it with the heat and shrink method. I've had good luck doing it on areas just like what you're dealing with.
@gimpyshotrods thanks. Yes, both areas are stretched. I do have shrinking discs. I can see how I could work the smaller one... but damn, it scares me to mess that area up in the quarter.
Pretty hard to over shrink with a shrinking disk that's what makes them work so well you can sneak up on the amount of shrinking required. That and they concentrate the heat on the highs more so than a torch.
Get a cast off fender or panel from a local body shop/u pull-it etc. & re-create a stretched area close to what you are dealing with to give it the trial & error practice method .. ..if the first attempt is unsatisfactory recreate an additional 2nd. or 3 rd. stretch for another go at it. While you may be practicing on metal of slightly thinner gage depending on what cast off parts your able to come up with it will provide the ability or not to tackle the real deal. The real fact of the matter is how the hole was patched, welded closed, patched, etc. metal may move arround differently in each case. most bullet holes are probably best repaired with fresh metal.
This looks like it might be a good application for a “donut dolly”. I believe that’s what @MP&C called his PVC pipe dolly. Paging @MP&C for a tutorial
For me, I’d use a small tip torch, heat the stretched spot, hammer/dolly then quick cool. In my experience, the shrink disc is a straightening tool as you work a dent. You hammer the dent (usually from the back side outward), use the disc, quick cool then hammer the spots not touched by the disc. Repeat. It’s steel not gl***. Ya ain’t gonna break it.
I've had good luck with the shrinking disc...and a squirt bottle of water...it's kind of hard to screw up with a shrinking disc in my experience... @flynbrian48 had good luck with his wagon roof after he got after it with a shrinking disc, as I recall Also have used an oxcy/acetylene torch and shrunk that way but you need to work fast and back it up with a dolly We shall see what you do
Yes. I've had some success and made some messes using heat. In the beginning, I overdid it with the heat.
Use a soft hammer with a dolly, or a shrinking hammer with a wooden block behind it. One of the surfaces needs to be soft, so it thickens when being hammered. Hitting it between 2 hard surfaces will stretch it
This is a very informative book and explains the process of shrinking dents using heat. It's my go-to for understanding the various processes of straightening bent metal.
Flat dolly and wood (or plastic) hammer, or even a flat dolly and one of your *******s. Go slowly, monitoring progress, work carefully. Holding, hitting the surface with the ******* angled will put nasty marks in the panel.
Thanks for the heads up @ClutchDumpinDan, missed this one... Here's a luggage door skin we repaired for a school bus. With primed replacements over $1000, it made sense to try and save this one. I used the BF618 Snap-on crowned body hammer and a donut dolly to remove the long stretch in a damaged aluminum skinned school bus luggage door. The donut dolly provides off dolly theory with a more focused precision as the panel is supported all around the dent. For a flat panel such as this, a crowned hammer works better for pushing the metal into the donut dolly and capturing the excess for an effective shrink. (for a high crowned area the flat hammer can be used) The point where the tool is the most effective is just shy of leaving a dent. Too light a hammer swing, and you’re not capturing the excess. Too heavy a swing and you leave dents. But for those not familiar with the tool, I encourage you to practice, gradually increasing the hammer swing until you leave a dent. Now that you know how much effort it took, you can back up from that slightly for a more effective shrink without adding any more damage. The only tools used here were a crowned body hammer, a PVC plumbing fitting, and a straight rule to check out progress. A grid was laid out on either side to better monitor location for accuracy which = more effective shrink. Not that it's needed in a smaller confined (more manageable) area, but for the size of the door we had it was used more as a periodic reference that we were lined up well over the dolly. On this next picture note the hammer marks in the background (off to the right of the hammer head), this shows where the strikes took place... This shows how much more "push" a crowned hammer has over a flat one to push the excess into the dolly, capture and shrink the stretch.. The light reflection shows the difference over the first picture above.. You can't fake that... This is the small amount of filler needed prior to paint... Here's a simulation of using the donut dolly on a goose egg..
Here’s another post I did on the donut dolly, this one shows using it on a more crowned panel. Compared to the typical off-dolly bumping, the donut dolly works more proficiently in off-dolly shrinking a crowned panel because it supports the bottom side in more than one spot (around the perimeter) as the panel is bumped from the top in the center of the donut dolly. This would seem to be useful in body repair, especially to address high spots found after blocking primer where heat would not be as feasible. Some time ago, someone on another forum asked for advice in removing an outward roof dent, a result of some over-eager on-dolly stretching in removing dents... I suggested a low-buck alternative to the donut dolly, simply using a PVC pipe fitting. Where it may not work as aggressively as the donut dolly which has more m***, sometimes slower is better, especially when trying something new. Trying this process for myself in the shop, and rather than use the roof of something sitting here, we will use a piece of 18 ga CRS to simulate a roof. Grid layout for the Wheeling Machine, and completed "sample" roof... The first order of business should be to make some profile templates. In the case of an actual dented roof, use the opposite, undamaged side. This will allow you to check your progress as you go, and easily find the remaining high spots. Using a crowned body hammer, a "dent" will be added from the back side, crossing both directions where the templates were taken. With the dent added: I chose to use a PVC elbow, a "tool" readily available and economical. As with any body tool, they should be free of any burrs that may mar the metal surface, so I sanded a slight radius into the edges... Here are the tools we will use today, our dolly, a flat faced body hammer, and out profile templates: After some off-dolly bumping: Check with the templates Progress....your taps with the hammer need to be hard enough swing to bring down the high spots but not create craters or inward dents Here's where I finished up... I have a little over an hour in making the panel, denting, and removing the dent. Where I still could have gone a bit more, it was about to a point where high build primer should have masked any remaining imperfections. This dent removal could also have been accomplished with heat shrinking using an O/A torch, etc, but for those times where you may not wish to use heat (primer is already sprayed) and want another option, this seems to work well.
Brady, it’s simply off dolly theory on Steroids. Your typical off dolly does little to shrink a stretched panel, it does more moving things around than anything. If the panel has little stretch, it’s not as much an issue, but if there is significant stretch the off dolly will just push the extra metal outward and may affect panel crown or promote a tight oil can. The donut dolly is ideal in situations like this as it shrinks while it bumps the metal panel in the direction we need it to go. Referring back to the original post, a bullet hole through sheet metal adds quite a bit of stretch. If someone at some point used a hammer and dolly in on-dolly, the minute you hear that ping of the hammer striking through to the dolly you are adding even more stretch. So at this point the panel needs some shrinking. I would add that if we’re using heat (torch) we don’t need to heat something up red hot (as that just creates mill scale, something else to clean up), a straw color up to blue is sufficient to provide shrink without adding more cleanup of mill scale. The additional plus of using a donut dolly is that if something has already been epoxy primed, you can work to shrink the damage without degrading the paint finish. Torch doesn’t play nice at all with paint.
I wish all the awesome pics were still in this thread. Anyhow, I tackled that stretched bullet hole area and got it into much better shape. I used my small shrinking disc, a sharpie, and compressed air to cool off the worked area as I went. I did hammer a bit from the back when everything was much closer. It's a lot better. The filler will take care of the rest. It won't be all that much. Before: After: There's a little more work I could do from the back but right now the low spots are very thin and wouldn't need much filler. Thanks for the help, fellas. I learned a bunch.
MP&C, thanks a LOT for that tutorial on using a “doughnut dolly”! I’m really just getting into the metal bumping art and going VERY slowly and when I have some time I’m going to try out your method. So in short I’d need a doughnut dolly and a crowned hammer and patience? Secondly, place the dolly beneath the area to be bumped and hammer/tap into the doughnut, or do I have it absolutely incorrect? Thanks fo the advice!
Sorry so long to respond, just saw your post. Here's another quick and dirty video I did on donut dolly.. And it's more a use what you have tool as shown in the video..
the important fact to get across to the students is that any misses using steel (large socket) will stretch when we don’t want to, but it will also give and indicator ping so they can learn hand movement/alignment. This is where the plastic or PVC works better for less chance of stretching on any mis-strikes. For the novices, a bit larger diameter than the hammer head helps here. For smaller dings (blisters? Depends what side you’re on) you want the donut dolly sized about the size of the halo ring around the dent. for the most effective capturing Of the excess metal you need to be able to push it inside of the donut, or more accurately, the donut should support the metal as the bulge or excess is pushed below the level of the parent metal. That’s why on the flat bus door above we used a crowned hammer and the blister just above works perfectly fine with a flatter hammer.
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