18 / 10 line graver which I believe is the proper tool to use.
Laurie, I’ve generally used #14 liners or sometimes #12. The second
number is how many lines there are, of course. That doesn’t mean not
to use an 18, if you want to. 45 degree angle, just start cutting all
the way around. You’ll find it easier to push off the edges from the
inside - instead of trying to catch the edge in the beginning, do
what you can and then go back and touch them up so the graver goes
over the edge from the field of the ring. (You’ll see). Just push,
don’t wiggle the tool - not so easy, and the bigger the tool, the
harder it is. Do the whole ring one direction, touch up any holidays,
and then go back at 45 degrees the other way, ideally just cutting to
the same depth or you can obliterate your previous work.
By the way, florentine is a complete finish - 100% both ways - but
there are others. “Linen” is 100% the first way, and then skip a bit
on the second pass, which takes a bit of artistry to do well. And
there are some others…Florentine is pretty easy, it’s just a lot
of work. I won’t say you need a sharp tool because you never don’t
need a sharp tool.