Thanks David,
The machine only came with one 6mm collet and a few cutters and stylus . It also has a set of New Hermes 5/8 Double line fonts.
I can't quite understand how to engrave on the slight radius of a barrel. I have tried on flat aluminum plate and get a pretty good result. Do you somehow have to manualy hold pressure on the cutter spindle over a radius? Thanks Again , bison-j

Jim,

Unless you have a way to rotate (automatically) the barrel, you'd have to engrave at the top of the curve, where even though only slightly perceptable, the depth of the letter at the center, would be deeper than the tops and bottoms of the letters.

Most often, a single-line typeface would be used, not that double-line Century (probably what you have) wouldn't work.

The other consideration, if you don't have a cutter grinder, you'll want to make friends with someone who does. Routing into steel takes a pretty quick toll on cutters, especially those with small tip sizes, i.e. .010-.015.