It's really good to keep repeating this regarding the actual technique with the abrasive wheel...I'll bet that doesn't get into the equation many times...keeping it localized...I'm sure once the weld is flattened you can do a more typical angled grind BUT near 90 degrees or just sticking to the weld as much as possible seems to be the key initially.
Kudos for having the guts to put your frustrations out there - especially here! Good advice given as well. If all those lines visible are your fit-up - excellent work. It’s a shame to have to use MiG on that! That fit-up is far better than anything I’ve seen on fitzee videos. I’ve only seen a couple as he gets stuff done but it’s often not the right way. I’m sure he has content that is very helpful but I prefer inspiration from Wray Schelin and the like. I would agree that grinding highs around the welds is a trap. Since the bead shrinks, pulling in and down on the seam, the surrounding metal is more exposed. You will seldom get down to the toe of the weld for a perfect surface without severely thinning out the parent metal. Then repairing unforgivingly thin metal becomes your new problem. Far better to planish your welds, grind them down slowly and carefully, and bump the seams around to smooth them for putty. This way you aren’t thinning the surrounding sheet which actually now needs its own full thickness patch - not a MiG wire patch. JMO D
To simplify it a ton... Why are you quenching? Don't. After grinding/sanding, I can still see the interface of the two pieces. You're not getting fusion in these areas. Either you're missing the interface with your weld bead or your technique/parameters aren't sufficient to allow for penetration of the material, and all you're doing is sticking a bead on top. You need more practice dialing in parameters and hitting your target.
I don't quench, but I do keep a damp rag close by if I need to cool something. Like multiple have already said in one way or another, you can fuck up a lot with the same grinder that you're trying to use to make things better lol. If you're trying to master metal finishing, lay down the grinder and grab a body file, practice your hammer and dolly techniques, and post a picture of your welds prior to grinding, maybe you can get a little more heat in there and create less work on yourself ...
Welding requires good technique and patience but grinding of welds requires the same. I don’t know what kind of grinder you are using but in my opinion a side grinder with grinding wheel or flapper disc doesn’t give you enough control and results in removing too much metal from the surrounding area. Those grinders and cutting wheels are great for removing heavy weld on thick steel but not sheet metal. I like to use a die grinder with maybe a 2” RolLoc discs and concentrate on grinding the weld only until it almost flush with the surrounding area. Keep the sanding disc parallel to the surface and don’t use just the edge which a lot of folks seem to do. For practice try putting some masking tape on both sides of weld and grind weld without sanding off tape. Also very important to use new and sharp sanding disc so you are actually cutting the weld and not just creating heat. Once the weld is almost flush with surrounding metal you can switch to a larger diameter disc to blend to surrounding area without excessively removing too much sheet metal and thinning it. Your mileage may vary. I’m sure there are many of you who grind weld to perfection as second nature using any type of grinder and abrasives but just trying to explain basics for someone who asked the question
The key is STOP watching folks on youtube showing bad fabrication and/or habits! Unless their last name is Covell, Fournier or Delay they probably don't know what they are doing.
HA ! Everyone that walks into my shop says I should have a TV show. My helper wants to start a YouTube channel. I told him he ain’t got time, I ain’t got time.
I know people that have had or been on TV shows. In the end they would rather be back in the shop working without the cameras. I watch a TON of stuff on Youtube but virtually no fabrication since most of it is so cringeworthy. A great person to watch however on here and IG is @cornfieldcustoms, very tidy fabrication.
Fitzee, Bad Chad and others v Wray, Walden, Covell and others...... all get the job done in the way they choose. Nobody is necessarily saying which route is better or best, but it does seem to come down to a mig v tig thing. Horses for courses I guess. Chris
Mig VS tig . I’ve got both, I use both and greatly depends on what’s getting welded, how it’s fitted, and budget mostly. Are they paying for metal finish and want my welding to be undetectable or are looking for something that will hold paint. Positional and access concerns play a part too. Plug welds are almost always mig welded, sometimes flushed off and done sometimes finished and dimpled for factory look. Most everything gets tacked with the mig. I can make a good argument for both, I can’t make a good argument that one’s better than the other without the goals and conditions.
I like to grind the weld area only (as others have said, with the edge of a 3" or smaller as it wears grinding disc in my cut-off tool) on both the welded side and the backside. Once both sides of the weld area only, are close to the surrounding metal thickness, I planish/stretch the weld with hammer on dolly along the length of the weld. After this is done, I'll give the welded area a quick pass with a sharp 24-36 grit 3" or 5" sanding disc (needs to be sharp! as you're not trying to generate more heat). After this, the area gets a quick pass with 80 grit on a da sander. Keep at it, you'll get it.
the current "fad" is to finish weld everything, smooth and little or no filler. this is not necessary for a first time or novice just getting the body solid and close enough for an eighth inch or less filler is fine, you can even skip most of the grinding, just bump the weld down, clean thoroughly, prep and put a thin layer of filler on. ever see a factory weld with the lead or plastic removed? stop trying to make it perfect
Use an air gun to cool the tack welds, don't quench with water as it's create warpage and shrink things. Heat is the enemy, so only tack every 6" or so and hit them with the air gun. Keep tacking in between the tacks to get down to a 1/2" between tacks and alternating to reduce hot spots. Again go slow and use the air gun until you can touch the steel by hand and is cool to the touch. From there you can fill the gaps, but cool each gap you weld before you move to another. As stated grind the welds down with a 3" wheel on a die grinder to just above the welded surface piece's. Again go slow and use lots of air because grinding creates a ton of heat also. Do small area's, when you are ready to sand them down, use 24 or 36 grit on an angle grinder and when you get down to the surface and stop, again the air thing and small area's. From that point you can DA it with 80 grit or finer and move on. Problems happen when you want to rush the process. This was almost 6 feet of welding and it was flat when I was done. Took about 2-2 1/2 hours total to weld and smooth. Practice helps and it's never as easy as a YouTube video makes it look when you are just starting out. Han g in there, you'll get it !
This is the best answer right here. For a guy that's building his own car as a hobby, it's impossible to rival a professional coach builder with years of experience and tools that cost more than a farm in Texas. Watching a guy do top quality metal work on TV or the internet will do nothing but discourage most guys. Do the best you can and make yourself happy. It's about building hot rods and enjoying them.
Here’s what I’ve found, getting to 85-90% is good, Getting That last 10% takes 90% of the total time and effort involved. From life’s experiences this far, if I were tasked with getting something perfect, I’d practice reaching perfection on something that didn’t matter that much.
There also seems to be some confusion when folks say 3" wheel. It IS NOT a hard 3" wheel like you get with your average angle grinder like the one below. They really have no use in sheet metal work What we are referring to a THIN 3" wheel that you dress the weld down using the thin, fine edge. I prefer to chuck these in an air tool as they are more forgiving and spin slower than electric. Metabo is one of my favorite brands. Notice they are only .040 thick?
100000000% Adding to the above: Even the metal finished cars get skim-coated! We have this unrealistic, idyllic view on what the old hot rods were. Their images were taken at a distance, the photographs and printing didn't show the details like modern images. So, we think they were the standard of perfection. Then, when one of these icons get restored we over-restore them. I can't even recall how many of these icons that are found/saved and as the images show the reality the magazines never showed (because it didn't matter) sometimes crude work and "creative" fixes, tons of filler, bubblegum welds, torch cuts and all sorts of other stuff. It might have been more common than not. Yes, we know better now, and we're lucky to have the resources and technology to help improve our skills. But, the thinking that metal finishing is the standard and any use of filler is hack work is unrealistic. We need more thrasher hot rods in the world! Jimmy White's coupe is the perfect example. Lloyd, you're right on. Some metal finished cars actually end up pretty thin, not just the guys trying to replicate the look at home either. Does it look awesome, for sure, but it's not a requirement.
Mine are around 90% when done and a skim coat for the final 10% is just dandy. The last 10% just ain't worth the time or effort. I shoot for a 1/16" and can live with 3/32". Anymore and I have plenty of hammers to help me out !
Keep in mine....it AIN'T structural it's sheet metal. It ain't gotta be 'strong'....just sewn together. I like to start at the top and down hill the welds...finishing toward the bottom....weld 7 or 8 inches at the time. Going down hill the welds will be flat (er). Less grinding needed. (sometimes even a little concave. Just fill with body filler/bondo) Less heat/warpage because you stop at the bottom and heat travels UP. They do make water proof bondo BTW so the worry of absorbing moisture(and rusting) is gone. Down hill welding is weaker than up hill or a bunch of little tacks BUT...with sheet metal the object is to stitch it together so it can be skim coated and painted ! Now structural welding needs a gap and welded "up-hill" (not trapping slag) and full penetration. 6sally6
So after practice practice practice you’ve got to know your machine. Settings and is it a “soft start” or not. Will you have a backup, will you have a gap, will there be free air behind. Every condition will be different. Most sheet metal mig work is Tack tack tack tack. Sometimes there’s a pause between sometimes not much. In quick progression my machine will give me 6 “cold start” tacks, number 7 is not cold start and likely to blow a hole. Because of the “cold start” I set the machine much hotter so I get the tack I want not what the machine thinks, I out smarted it up to tack 7, if there’s pause it’s always the same. If I’ve got a back up ( copper, aluminum, leaf spring dolly) I get better results with HOT setting and 0.035 wire with low wire speed and that’s because I’m outsmarting the cold start. Flat weld less grinding and full penetration on sheet metal. Don’t do it without a back up. Can do it with 0.30 but there’s a higher grind and not always full penetration. 0.030 is better for plug welds, or lap welds. If I’m welding with free air space 0.023 is more forgiving on blowing holes and always more grinding. If you don’t have access to the back the last thing you want is a blow thru. They are UGLY on the backside. Rust Whiskers and lumps and all kinds of nonsense. Also handy to have around is some 0.045 tig rod to aid in filling a bigger gap or blow out.
Enjoying this thread. As a hack welder I'm getting plenty of great info from those who are very good at welding.
Thanks, it was necessary because I channeled the body 2" over the frame. Took my time and plodded it out, hardest part was making the first cut because there was no turning back after that. Also when I decided to channel the body I had to move it forward 1 3/8" to clear the frame comfortably. So it was twofold, up and rearward. I wanted to maintain the wheelbase as is, so you have to do, what you have to do ! The end goal was to make it subtle enough so that many won't really even notice it and not make it look off . Glad that part is done ! Don't want to hi-jack this thread so I'll stop while I'm behind...
That’s hi jack is ok I think. I went thru the same mental gymnastics with mine. Obviously it’s doable as you did but I couldn’t get my head around the cut and how to bring it all back together. Matter of fact talking about that cut and reaching out for help is how I met a friend, a very good friend. I chickened out and took a different approach and added 2” to the bottom. Custom built the frame following 33-34 profiles, with model A top view. Funny I never used photo bucket Lol
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