I hate to disagree but I would like to give another side of your post Buzz.
If you have properly welded with full penetration there is no reason what so ever that you can't grind the weld all the way down flush. If it fails after one ground the weld down, it was not welded properly, PERIOD, end of story.
I mean, let's go to the metal masters. They will make a fender out of many pieces, butt welded together and metal finish them with no filler what so ever. If you want to see this in action, I HIGHLY recommend getting the video/dvd "Making the Model A fender".
http://www.fournierenterprises.com/cart/product.php?productid=16252&cat=2&page=2 Amazing stuff I don't expect to be able to do anything like this any time soon, but amazing to watch. Split the cost among some friends and have a movie night.
And I don't mean one needs to be a "Metal master" to do it, not in the least. If one is not penatrating one needs to learn how to weld properly. The bead should NEVER be expected to "hold" it together. The WHOLE POINT of welding is joining the metal making ONE piece. If one is relying on the bead, one has mearly "glued" it with some filler rod.
On the spot welder, I use a $20,000 Squeeze Type Resistance Spot Welder (STRSW) at work and I have to say, it barely reproduces an OEM type spot weld under PERFECT conditions and settings. That $100 welder from HF is just not going to get it done. I have tried a few of these economy spot welders, they DON'T work. I have not tried this one, it may be the anomaly.
Now, I totally agree in that grinding the welds down flush by someone not comfortable with their welding, and having done destructive tests to see how well they are penatrating is probably a bad idea.
A butt weld on a panel being "bondoed" might as well be left semi ground, being you are covering it with filler anyway.
However, one REALLY should be doing test welds, and destroying them to see if they are welding properly.
Brian
