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Removing Dents

Removing Dents

by Wray Schelin


In the last post I described the tools neccessary to completely remove dents, waves, and dings in your body panels. In this post I will share with you how I use the tools to achieve a panel smoothness that will require very little or no bondo filler. It is best to keep your bondo use down for two reasons. One,bondo use is not craftsmanship, its just a cheap substitute. If your trying to achieve a high standard restoration- in my opinion it is best to have the craftsmanship on more than just what you see. The value of these cars is more than just the dollar amount. The second reason is, if you keep your substrates (bondo fillers and primers) to a very minimum and apply just enough topcoats you will have an ideal thickness of paint coatings. With an ideal thickness your paint system will be able to expand and contract with the steel and aluminum surfaces of your cars body as it heats and cools. This correct thickness insures you against an early paint failure. Coatings can fail for many other reasons, but too much paint and filler I believe is the most common culprit. The most surprizing thing about high quality metal finishing, is that is not that difficult to do; but it does take patience, good eyesight, a fine sense of touch, and the tools that I previously mentioned. First what's fixable and what's not. If you have, say, a 120 front fender that was severely damaged in a accident many years ago on its leading surfaces, an was quickly repaired by sewing up tears with brazing rod, crudely hammered out, ground very thin, and then filled with bondo, forget it; in that case you are probably better served by replacing that heavily damaged section. Another impossibilty is an area that has been incorrectly torch shrunk; what had started out as an earnest limited attempt, inadvertantly expanded to large area, leaving heat damage with heavy intractable waves. Fixable dents and damage, listed in a descending order of severity: Bodged past repairs that are still fixable, because the metal has not been ground too thin, Collision damage with stretching and tearing, Sandblasting with excessive pressure causing a wave effect, Smoothing out the seam of a butt welded patch panel, Small dents with little or no stretching, I 'll share with you how I remove a small dent . An easy example will work best, so lets say, its the rear fender of a XK120. The dent is in the middle of the rear section of the fender, and its is about the size of your fist, sunken in about 3/4" in the center. All paint and undercoating should be removed first. I would first select a dolly that has a crown that is close to the fender; in this case that would be a medium crown. Using a glove to protect my fingers I would palm the dolly and lightly tap it against the bump on the inside of the fender; carefully watching the progress of the rising depression. I would use this process until I got the dent up to within 1/8" of the surface. This will happen within minutes- this is called roughing out the dent. Next I would hold the dolly tightly against the center of the damage , on the backside, while I use the slapper on the front, tapping the circumference of the dent. This is a dolly off action, the slapper and dolly are not clashing with each other, they are beside one another. I would keep tapping away with the slapper, moving the dolly tightly with some force, against the lowest area of the dent. Slowly the dent will rise to very close to the surface level. The slapper does this operation very effectivly because it has such a large surface area, compared to a hammer. With a hammer you're hitting a smaller area and you might dent the area you're hammering against because it will yield easier than the center of the dent. Roughing and slapping the dent has reduced the dent by about 90% and progress was swift. The next stage of metal finishing requires the bag of tricks and the tools. The problem that you encounter at this final stage is, you have trouble seeing what you're doing because your actions have to be small. When you were roughing you could easily see the metal move closer to the surface; but now you might only have to move the metal forty thousands of an inch or less to reach the true surface. At this stage a common practice is to use a pick hammer. In my opinion a pick hammer has many drawbacks: one- you need room to be able to swing it; and generally the hammer itself might be 6" or more across the head. Two- it is very easy to over hit with a pick hammer and cause irrepairable damage. Three- more likely than not you will not be able to strike the low spot, instead you will hit the high spot worsening the problem. The safest bet is to retire your pick hammer. This verdict also applies to the bulls-eye gimmick tools which use a C shaped frame to guide you to the elusive low spot. If you go down the bulls-eye road you will find your garage populated with many expensive sizes and versions abslolutely needed to remove all those pesky dents and dings. You will allways be one bulls-eye tool short. What I do at this stage is coat the damaged area entirely with the 1/2" wide red magic marker ( thats a US trade name for those who might not be familar with them- there is no magic, its just a felt ink marker) Next I draw the fine body file over the area, just lightly skimming the surface, this will quickly reveal the high and low spots. The object now is to raise the low spots. You can do this by placing a dolly with a high crown surface tightly against the low spot. You will only be guessing at this point unless you have x-ray vision . You find out where you really are with the dolly by lightly slapping the surface, with the the slapper a few times, trying deliberately to strike the dollies crown. If you are successfull - and you probably will be, because of the slappers large working surface- you will hear the ring of the contact of the metals. Slide the slapper to the side, but leave the dolly where it is. You should be able to see a 1/8" diameter ( a 1/8" inch affected area will raise quickly with little force , the size of the mark made when you slap it determines the speed of the metal rise. 1/8" is fast 1/2" is slow) clear spot, or slightly less inked, in a region of the small low spot that you were raising. If you goofed and hit a high area instead you should be able to see a difference there too. Whether you were in the right area or not is not important, what is most important, is establishing where you are and being able to adjust . Watch the trail marks left in the inked surface and you can steer the dolly, on the backside, easily to where it is needed. Slap lightly, slowly raising the low spot. After a few minutes, refile the area and your progress will become apparent. You might have to wash off the marker ink ; re-ink, and refile several times. Each working of the area will reduce the size of the low spots. Remember that the filing is meant just to scrape off the ink and not to reduce the thickness of the metal. The force and stroke of the slapper will be less as you progress. When you have reduced the low areas to less than 1/2" in diameter, and when you rub your hand over the area you still slightly feel them, you are ready to use the shrinking disc. The condition of the metal at this point is stressed and springy as a result of all the trauma inflicted on it. The original damage has been raised but in the process the metal has been stretched a little. If you applied bondo at this stage some of the bondo would surround the damaged area, feathering in the new surface height. With the marker ink still on, and a wet rag handy, crank up the body grinder with the shrinking disc and rub the area. You vary the pressure according to how much you need to shrink. On the first pass I usually apply light pressure. The metal will quickly begin to rise and expand from the heat build-up. Remove the disc and wipe the area with a wet rag. With that operation you have started to shrink, stress relieve and further fine tune the outline of the low spots. You can now re-mark with ink, file and further tap out the low spots with the slapper and dolly. Some dents might require several cycles, but as you hone your technique you should be able to remove most dents in fewer cycles . At this stage an obvious high spot might have developed. You can easily remove it by rubbing the shrinking disc over it; it will heat to a blue condition in seconds, and then cool with the wet rag. After I'm satisfied that I can no longer effectivly raise any remaining tiny low spots (depressions only a few thousands of an inch deep). I then install the very dull 120 grit 9" grinding disc and proceed to work the area with it. The grinding disc will level the area leaving a almost polished surface, it will heat the area quickly also, so cool it with a rag after you done grinding. If you have done everything correctly you should have a very smoooth surface , that is stress free and in no need of bondo. If you practice these tecniques on some old , damaged, and unimportant sheetmetal parts you will quickly hone your skill. On some areas of the XK Jaguars it is almost impossible to get a conventional dolly into the area; in those cases you have to be resourceful and fashion something that will snake into the damaged area, it will be effective as long as it resists the blows of the slapper causing the metal to rise. When working aluminum, I use all of the same techniques except, I do not use the shrinking disc. Aluminum is much softer and requires less force to work it. Regards, Wray E. Schelin WES PARTS phone 508-347-7749 e-mail wesparts@hey.net P.O. Box 652 Charlton City, MA 01508

If you have any questions or comments send e-mail to: ted@jag-lovers.org
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