I emgrave stuffprofesionally for a living and i do not think you need a 4th axis unless your design raps the barrel
New Hermes was sold to Gravograph like 20 years ago.Peter what do you recommend to engrave .003"-.005" with letters 1/16" of an inch or larger on a 1.200" to 1.250" circumference surface. A spring loaded engraving bit? I have two New Hermes engravers with the tooling that came with the machines it engraves shallow on letters taller than 1/16" inch on barrel tenons.
Nat Lambeth