lanherbert, I typically use 316L on all my stainless, 304,309 & 316L,

Weldonwelding, Your right about the filler metal thing, Thats why sinks that are welded into counter tops have a bad habit of dropping out.

One thing that no one mentioned and thats to use the biggest cup you can stand.
Using a small cup and turning your pressure up to compensate creates problems.