Originally Posted by
bulgie
The tool he uses is really dangerous in the wrong hands though. I didn't see him making any deep troughs, but using that tool without digging trenches in the tubing adjacent to the fillet takes a lot of skill. Even so, I can guarantee that he has thinned the steel a little there, at least a little.
It's also good reason to dish out a few extra bucks on 631 (or 853 etc) tubes, expert or not, when making big fillets. It's not just that the steel is stronger against breakage, but that the steel is also harder and a bit more abrasion resistant post-brazing. I'd also steer away from the fancy grinding belts.