G
grogetter
Thanks, Crash.
They did that all day long 5 days a week, with the spot welder suspended on a cable which went up to a pulley on a roller so they could move around. So going from one hood to the next the roller will want to keep going when he stops. He was also working at a fast pace, not trying for perfection.BTW. Does anyone know why some OEM spot welds are just that, spots, while others look more like a smear?
Well, I got to feeling a little big for my britches and decided to try out my new shrinking disc set. After I got the big patch all nice and pretty, at least in my eyes, I had a ridge that ran along the line shown. I figured that it was caused by shrinkage along the weld bead adjacent to the feature line of the hood. So, I said to my self, use the small shrinking disc and start working out the ridge so I used it on the dark rectangle, in the circle, along the feature line.
Im sure that I used the wrong technique because it seemed to stretch the metal, not shrink it so I tried using the disc on the back side and got a little of the "belly" out of the area. I worked on this area most of the day with hammer and dolly, treating it as if it were a ding. Got most of it out but still had the ridge to deal with.
This time I decided to use the 7" disc and try to use more of the surface of the disc rather than the edge like I had on the first attempt.
I worked with light pressure, not getting the metal to the point of discoloration and working in a broader area. Here, you can see the pattern left by the disc.
View attachment 6628
Everything seemed to be going well until this happend. A deluxe oil-can .
View attachment 6629
I'm confused. As I understand it, oil-canning is caused by too much metal for the surrounding metal. So it has to go some where and that causes the metal to bow out, creating the oil-can effect.
If I was shrinking the metal how could shrinking cause this?
Thanks in advance.
The only way we can get good spots with the mig is constantly opening up the butt area. When it shrinks from the last weld, keep cutting it open, trying to get the same size wheel or cutter as the wire you use, so you are actually starting in the middle of the part. You get some better penetration that way.
I also saw the one real good tech on the Kindigit show use an angle grinder with a flat aluminum wheel. He was using it to heat the panel and then quenching it to get it flat again. Has anyone ever seen one of those?
Thank you, John. Just another question, if you don't mind.
Why do you planish before grinding? Seems to me that if you did a rough grind on the spot, top and bottom, making flat surfaces, then planished, it would work better and be easier, too.