Thank y'all for all the useful, informative postings. It's a sad (I suppose) bit of irony that materials that are so wonderful in some respects are difficult to deal with in other respects.
I've done a bit of titanium (TIG) welding with great results, but no machining of it. I did a little sanding on some once, using
a belt sander, and did notice the bright white sparks. Kinda scary looking. I urge an abundance of caution, and always try to
practice what I preach. This helped me become quite an old guy (well, maybe not so old in land speed racing circles).