Body Shop Tips & Tricks |
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rocnroll
Member Sponsor Member Joined: 20 July 2005 Location: Tuscumbia, AL Status: Offline Points: 13584 |
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I've seen different articles, videos and company propaganda on those shrinking disks and have always been curious.
My takeaway has always been, in an industrial atmosphere somewhere maybe they would work with a little practice, but home shop.....well, let's just say it wouldn't work for me in my area. The neighbors would REALLY need to be understanding! I'm like you though....they really make it look easy! |
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'47 CJ2A PU
'48 CJ2A Lefty "Common sense is not that common" |
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drm101
Member Joined: 12 Dec. 2012 Location: Clarkston, MI Status: Offline Points: 1470 |
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I've also had some luck shrinking metal by using a thin disc to cut a slot, then welding the slot up with my mig. Usually it works well when there is a large buckle, for example. Sometimes I just drill a hole and weld it up and it will shrink the metal in that area.
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Dean
'47 CJ2A "Ron" '66 CJ5 "Buckie" The less the Power the More the Force |
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WeeWilly
Member Sponsor Member x 2 Joined: 07 May 2009 Location: Clayton IN Status: Offline Points: 3423 |
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I am with Dean on this one. I have wasted hours trying to shrink metal by heating and quenching with wet rags which is supposed to work but hasn't for me. I use a cut off wheel on a angle grinder and cut a "H" pattern through the stretched area and after leveling it out tac weld it back together. I find this way works the best for me.
Jim
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47 CJ2A (Ranch Hand) 48 CJ2A, 48 Willys truck, T3C 3782, M274 (Military Mule)
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rocnroll
Member Sponsor Member Joined: 20 July 2005 Location: Tuscumbia, AL Status: Offline Points: 13584 |
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Never really thought of doing it that way, but it makes sense.....will have to keep that one filed away for next time.
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'47 CJ2A PU
'48 CJ2A Lefty "Common sense is not that common" |
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drm101
Member Joined: 12 Dec. 2012 Location: Clarkston, MI Status: Offline Points: 1470 |
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Not my proudest moment, but sometimes you have to do what you have to do!
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Dean
'47 CJ2A "Ron" '66 CJ5 "Buckie" The less the Power the More the Force |
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rocnroll
Member Sponsor Member Joined: 20 July 2005 Location: Tuscumbia, AL Status: Offline Points: 13584 |
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Otto, have you played with the disc any?
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'47 CJ2A PU
'48 CJ2A Lefty "Common sense is not that common" |
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otto
Member Joined: 26 Feb. 2012 Location: Orygun Status: Offline Points: 2264 |
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Yes, thanks for asking. I have used the disc a little- and enough to arrive at some early opinions. First, it does work somewhat to shrink metal. I mounted it on my air grinder first and tried it on some lumpy, oil- canny parts of the floor after welding the hat channels in. Using it like everyone describes, it got metal hot and when water was sprayed on the hot spot some shrinkage was noted (insert Seinfeld reference here). It took a few tries in some spots to get a good result, while in others one or two attempts was enough. Maybe that was just me getting used to it- I'm still learning with it. One thing I do NOT like about it is the galling. I guess it's a fine line between getting the metal hot and too hot. If it starts throwing sparks, it's too hot and will gall and transfer metal from the panel to the disc. I had to sand off the galling once already which took a while to recondition the disc. I have watched Wray Schelin's(sp?) Proshaper videos (which are pretty good and cover more than just the disc) where he suggests using a heavy felt marker on the panel- he says the ink acts like a lubricant and prevents the galling somewhat. I tried this and it seemed to lessen the galling. I also switched the disc to my electric buffer which has a max RPM of 3200 and it seemed easier to control. Not sure which of these variables worked; maybe both. In Wray's videos, he uses the disc to show highs and lows, but still works small dents out with hammer and dolly. He seems to use it less to shrink metal than others. I'm to the stage of working the lumps and bumps out of my project so I may reach for the disc a little more and experiment. The disc has developed a bit of a wobble so it doesn't run as smooth on the panel. I'll try it again on the air grinder to see if that solves the run-out issue.
Edited by otto - 15 July 2021 at 12:53am |
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47 CJ2A w/fuel injected boat engine
48 CJ2A 64 Ford Econoline Travelwagon If you can't get there in a Jeep, get a motorcycle! |
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rocnroll
Member Sponsor Member Joined: 20 July 2005 Location: Tuscumbia, AL Status: Offline Points: 13584 |
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Thanks.
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'47 CJ2A PU
'48 CJ2A Lefty "Common sense is not that common" |
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Bob W
Member Sponsor Member x 4 Joined: 08 Aug. 2005 Location: Monticello, NY Status: Offline Points: 1691 |
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I have a shrinking disc that I use in my angle grinder. I like it. Using a torch to heat the metal required experience to put the heat in the correct location. I don't have enough experience to get it right so I was shrinking in the wrong places. With the shrinking disc the heat was in the high spots, where it needed to be. I did not have any problem with galling.
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otto
Member Joined: 26 Feb. 2012 Location: Orygun Status: Offline Points: 2264 |
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This thread has been badly neglected, so I’ll talk some more about the shrinking disc. I’ve worked with the disc a little more, mostly on the sides of the tub where the lower metal was replaced and warped from the welding. The disc wasn’t working very well on the driver’s side after repeated attempts to bring down some high spots. I looked a little closer and could feel some proud weld edges where I didn’t grind them thoroughly enough. After giving them a little attention with some 36 grit, the weld was the same thickness as the surrounding sheet metal and reacted like a single sheet of steel. I mentioned this a ways back and should be listening to my own advice a little more. Next time I'll try to share some photos. |
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47 CJ2A w/fuel injected boat engine
48 CJ2A 64 Ford Econoline Travelwagon If you can't get there in a Jeep, get a motorcycle! |
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otto
Member Joined: 26 Feb. 2012 Location: Orygun Status: Offline Points: 2264 |
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I guess I should mention that before using the disc the metal should be fairly straight- the disc is not a magic wand or able to perform miracles. So, first I’ll work the low spot at the weld, using my flat dolly on the low side of the panel and working the high side with a hammer or slapping file. I can tell when it’s flat when the hammer makes a “ting” sound when the low has been brought up to the dolly. If I was a bit too exuberant working from the inside and created a high spot on the outside, I’ll switch the hammer and dolly and work from the outside. Be careful to not work the metal too much and stretch it creating one of those fun oil cans. Jeeps have flat panels so a straight edge or a body file can show you where the highs/lows are if you can’t feel them with your hand. Flat panels are both a blessing and curse because while you can check them with a straight edge, they’ll need to be straight to look good once painted. I also like to run a large grinding disc over the panel to see where I’m high or low as it will take down some high spots. Reserve this for when you have things really straight and be careful here to not grind a thin spot or hole if you try this! |
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47 CJ2A w/fuel injected boat engine
48 CJ2A 64 Ford Econoline Travelwagon If you can't get there in a Jeep, get a motorcycle! |
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ggordon49
Member Sponsor Member Joined: 30 June 2017 Location: Connecticut Status: Offline Points: 1436 |
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Hello otto, do you have any advice on when it's best to replace an entire panel, fender, etc. rather than patch work and hammer and dolly? I suppose it depends on your level of skill, but I was just wondering when you would say it's just too far gone.. Is it time vs money? Thank you!
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- Don't Let The Fatherless Ones Grind You Down -
- I like them stock, survivor's with original paint are my favorites - |
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otto
Member Joined: 26 Feb. 2012 Location: Orygun Status: Offline Points: 2264 |
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Hmmm...interesting question. Well you asked when I would say something is too far gone, so that may be subjective to my level of motivation at the time I'm pondering a repair. In the olden times when I worked in collision repair, that was easy, if it costs more to repair than the replacement part it got replaced. In a jeep restoration situation, rust would drive the decision and just how beat up the panel was. For me, difficulty of replacement, cost, can of worms, etc. would play into my thinking. Also if I can fabricate the part myself or have to order and wait, pay shipping...will play into it too. I guess in the end I would consider what would make the best end result and that is not always replacement. A lot of times repair is better for the vehicle than replacement because factory sealers and rustproofing is not disturbed. This probably applies more to modern vehicles than vintage jeeps but the principle still stands. If you can repair it well, why not? A little bondo never hurt anything. With my own project, I chose to try and keep as much of the original steel as possible, cutting out the rusty stuff and patching. Just out of preservation I suppose. HTH
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47 CJ2A w/fuel injected boat engine
48 CJ2A 64 Ford Econoline Travelwagon If you can't get there in a Jeep, get a motorcycle! |
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ggordon49
Member Sponsor Member Joined: 30 June 2017 Location: Connecticut Status: Offline Points: 1436 |
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With these two points of discussion, you completely answered my question and firmed-up in my mind what direction to proceed in. Thank you kindly for taking the time to respond!
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- Don't Let The Fatherless Ones Grind You Down -
- I like them stock, survivor's with original paint are my favorites - |
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otto
Member Joined: 26 Feb. 2012 Location: Orygun Status: Offline Points: 2264 |
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You're welcome. I must admit that I re-read your question after answering and thought I completely missed your point! But if that works for you, great! Another thing I consider is the quality of the replacement parts. I've dealt with enough aftermarket parts that I will spend some extra time and effort on repairing OE sheet metal over replacing with aftermarket stuff that may not fit well. |
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47 CJ2A w/fuel injected boat engine
48 CJ2A 64 Ford Econoline Travelwagon If you can't get there in a Jeep, get a motorcycle! |
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otto
Member Joined: 26 Feb. 2012 Location: Orygun Status: Offline Points: 2264 |
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More with the shrinking disc Tonight’s efforts were a carbon copy of the last session; I didn’t grind the weld down enough- if you look closely you will see the proud edge as a dark spot. Went over the weld with a small 36 grit disc and brought the weld down to the metal’s height so it’s flush. Now that the metal was uniform, I felt a little ~ in the panel so had to work the metal a little more to iron it out. Now that the panel was flat, it had developed a bit of an oil can and felt a little “fat” so I grabbed the felt marker and inked up the spot where the oil can was most prevalent. You can see the area where the disc was hitting the high spot and removed the ink. I ran the disc over the welded area a handful of times cooling with water each time, and slowly the oil canning went away and the panel stiffened up where it wouldn’t move in and out. It feels pretty good at this point. I was super skeptical about shrinking discs before using one, but I’m glad I gave it a try. For specific tasks it works far better than I thought it might so at this point it was a good gamble.
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47 CJ2A w/fuel injected boat engine
48 CJ2A 64 Ford Econoline Travelwagon If you can't get there in a Jeep, get a motorcycle! |
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otto
Member Joined: 26 Feb. 2012 Location: Orygun Status: Offline Points: 2264 |
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With the metal work done on the tub, we’re moving on to plastic filler. This is something that folks were interested in early on, so I’m finally ready to share some of my techniques. These work for me, your mileage may vary. Prepping the metal- grind off all the paint around the repair to get the metal roughed up so the filler will stick well and to give room to featheredge the paint. Don’t apply filler over paint because it makes it impossible to featheredge the paint back, creating a smooth transition from metal to paint. My tub is stripped to metal on the outside, but the interior repairs will be in painted areas. We’ll talk about feathering paint when we get to that stage. Mixing: my rule of thumb- apply a ribbon of the hardener across the blob on the mixing board; it usually works out perfectly. Get it on the car! It doesn’t do any good hardened up on your board, so work fast to get all of your filler on the panel before it sets up. You can make it pretty after it’s all on- the smoother it’s applied, the easier it is to sand. Try to get enough on to fill the imperfections- the goal is “one wipe”, but it rarely happens that way. This project will most likely get “sheeted” with filler as it’s fairly straight but riddled with dents, repairs, ripples, imperfections, etc., so the panels will be completely covered with filler and mostly sanded off leaving just a thin layer where it’s needed. This is far more efficient than trying to deal with many, separate repairs. If you’ve attended car shows and seen muscle cars and street rods that are perfectly straight with nary a ripple or wave, this is how the prep work for those cars was done. I would also like to mention that plastic filler is the best value in the paint store. The gallon I just bought was $26, so do as much as you can with it because all the other products will cost far more to straighten panels than using filler. Don’t think “I’ll just load it up with primer and block it out later”. Primer will shrink as it dries, is far more expensive than filler, takes longer, etc. Here’s another one of my practices: leave the worst spot to repair for last. Why? If you have a spot that you know will take a lot of filler to repair, use that real estate for when you mix a bit too much and apply the excess there. It’s better than throwing it in the garbage. Edited by otto - 05 Aug. 2021 at 11:50pm |
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47 CJ2A w/fuel injected boat engine
48 CJ2A 64 Ford Econoline Travelwagon If you can't get there in a Jeep, get a motorcycle! |
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nofender
Member Sponsor Member x 3 Joined: 10 May 2016 Location: Maryland Status: Offline Points: 2035 |
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I see you applied filler directly to the bare steel. I've been researching the topic - whether to apply filler to bare steel or seal prime first.
I've been leaning towards your method. What's the pros/cons, in your opinion of both methods.
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46 CJ2a rockcrawler
46 CJ2a - 26819 46 Bantam T3c "4366" 47 Bantam T3C - 11800 68-ish CJ5 |
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