I am not sure how to take these bumps out of my 39 Plymouth fender. I do ok indents but the array of tiny bumps has me stumped. Thanks for the help
in 1978 a body man named Juan, who lived in Mexico,, told me, Bring everything up then work down the bumps
It all takes practice and sometimes we don't actually get enough or steady enough to get great at it. I gave this fender to a kid who showed up on the Hamb a few years ago when he smashed his fender the first day he had the truck. Before I sent it I ground the bondo out of it, knocked the dents out and probably spent an hour sitting in a chair with a hammer and dolly working the fender that had 3/8 inch bondo in it in one area and turned it into a mud free fender that just needed finish metal work to be really nice. No shrinking disk though.
Metal has its on language You have to listen to it. it will tell you what to do. An old guy once told me “bump up the lows, knock down the highs” Sounds simple. It kinda is. The shrink disc isn’t magic, just another tool. before I ever used a disc, I turned grinding discs backwards to heat up sheet metal. Didn’t have a torch. It worked or at least a young me thought it did. The fender I posted took several hours after roughing out on a frame bench. Someone previously tried to fix that fender with a large hammer only. Stretched the***** out of it. The disc method works for me. I use a small and medium size ball peen. Both can act as a hammer and a dolly. The metal need to be bare. Bump up the lows, tap down obvious highs and use the disc. Cool as shown in the videos. Then tap up the areas not touched by the disc. Repeat with the disc. You don’t have to work the entire area at one time.
looks like one of those easy dents to fix where someone "fixed it" with a pointy hammer so now there are 50 tiny dents to fix instead of one crease. it did not get that damage from an accident. how much are shrinking discs these days? if I did not have one I'd just hammer and dolly it out. surprised we have not heard of anyone slicing the heck out of themselves. I think new ones have a curved edge to avoid bleeding out all over the shop floor.
The channel I like is Carter's Auto Restyling. His most recent one is an Auburn he worked the fenders on. He's also done his Chevy truck fenders and the Chicken Truck. I'm sure there are others that show their own process. Try a few different ones and find the one that works for you. Patience and willingness to keep at it is more important than any single tool.
Hamer and dolly use black guide coat on the bear steel then sand with 80 grit on a long block will show your high and low spots I have a shrinking disk and it dose work I dont know how a guy could get his hand in the disk.
if you don't how a shrinking disc can hurt you you should not be using one. mine is a 9" rippled disc with a pretty sharp edge. I could use it to cut a persons head off if I had a good reason to do so. I said nothing about your hand, but if you slice your inner thigh and hit the femoral artery you will be dead in less than a minute.
No doubt the wavy disc is dangerous, the newer style with the turned up edge is much safer. Of course a person wants to have their wits about them when using anything on a big angle grinder. I think both Wolf Fabrication and Pro Shaper sell this style.
Kyle is one of the best instructors you're going to find for free. Go back and look at his older videos on straightening out dents, this one is a good example.
I don't have a lot of body work experience but a little. I've also had success with "bumping up the lows and knocking down the highs". Once you realize that bending the metal stretches it and once you shrink it the correct amount, a lot of the adjacent area issues are solved. Torch quench, off dolly or shrinking disk all work. I have a relatively flat hood that looked like it was tire chained or similar. brought the lows up, did some off dolly work to shrink the worst stuff, then did some shrink disk work. Found more low areas to bump up, then shrink disk. Got it really pretty good in a few hours. This is just one of many areas. Not great pics, but indicative.
Please help me understand the science behind the shrink disc.. Does it heat the metal and cause it to shrink because the dents stretch the metal?
Essentially yes. It uses friction to heat the metal which will then shrink once it cools. The nice thing about them compared to other methods is they only heat the high spots because it only rubs on those.
It does shrink the highs. It also creates a great visual for working up lows roughed out dent from a previous repair that just filled it up with filler. a couple passes with the disc. Shiny areas are low. Bump those up. Then more disc repeat Clean up with a DA the heavy grinding marks was from the previous repair
Wray schelin videos on YouTube taught me a lot about working out dents/ripples including how to use a shrinking disc.
Great save on that shoebox fender Ant Knee. It was ragged and you (and your students presumably) brought it all the way back. Hell yeah.
Hands held pneumatic plannishing hammer will make short work of that. But they're pricey things. Mine is a butchered Harbour Freight item. Works great. Can't find a pic of if right now!! Edit. Found it! Chris
The Jalopy Journal
