Curious here.. does grinding a weld smooth make it lose strength? I see it can and I see it can help. What do you all think?
By removing reinforcement the weld will be weaker.
This is a more complicated topic than it might appear…
First, there’s geometry. A butt weld ground smooth on both sides might be said to weaken the weld, but the material adjacent to the weld is about the same strength as the ground weld, so the practical effect is that there’s no impact on strength. Grinding a fillet weld in a corner will weaken the weld; it may be stronger than the adjacent material, however. In general, these can be left alone.
Second, a as-welded joint that undergoes repeated reversing stresses could well have stress concentrations that would be removed by grinding smooth.
Lastly, obviously some designs require welds be ground smooth for fitment reasons.
So, it depends. The safest thing to do is ensure that the design has an adequate factor of safety. Welds subject to reversing stresses should be ground smooth; otherwise, unless needed for fitment or finish reasons, welds should not be ground (it’s faster to leave them alone, of course).
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Great Answer! Yes, a weld with a little valley between the “dimes” provides a “stress riser” that will initiate cracking long before the same weld would have cracked had it been ground smooth. But injudicious grinding can itself provide the same sort of stress riser. Grind carefully!