Originally Posted by
Michael Angelo
All very good points, take a home made airplane. Which many of them are made of welded tubing and the welding is some of the most accurate and perfect to be seen. NONE of them are ground down and smoothed over, because it WEAKENS the joint. Oh... and it won't be air worthy. So the question still is, will grinding a perfect weld bead that has very good penetration weaken it? Yep. If you need more scientific data on this, I guess I have to look for my school books from when I went to aircraft mechanic school and got my A&P licence back in the early 70's. Still, if you want to build anything with welded joints and grind them down even to the base metal, that's YOUR choice. I, would cover the weld bead with a filler metal and grind that smooth so as not to compromise the weld. Again, YOU can do what YOU want on you weld beads.
Mike
Interesting, but contradicted by
THESE LECTURE NOTES on commonly used weld improvement techniques and their effects on the fatigue performance of welded joints. As long as smoothing doesn't remove too much material, fatigue performance is actually improved by smoothing since stress risers caused by undercutting and rough weld beads are eliminated (see Figure 8 - Fatigue strength improvements due to burr toe grinding and disc grinding).
These seat stays were TIG welded and the beads were then smoothed by grinding and polishing. The result is a joint that has superior fatigue performance and the pleasing aesthetics of a smooth fillet.
