I was railroaded into doing a simple engraving job for a friend. Well you know how those simple jobs turn out sometimes... this one did.I used the 4th axis CNC mill with a spring loaded carbide scribe to scratch the artwork on the rings.
Because of the small diameter (.625) of the parts I was spending more time trying to rotate the part and reposition it to keep the area to be engraved located at 12 o'clock . Every time I loosened the jaws on the engraving vise the part would usually fall down between the jaws and require reinstalling it in the vise.
I fabricated a holder to go into the engraving vise to keep the rings from falling and to provide an easier mouse trap to better rotate the ring as required while engraving. The first step was to drill one hole in the face of each of the 2 engraving vise jaws (very soft) . I used the same size hole as those on the top of the jaws (factory drilled).
The pictures show two holding adapters ,one is for rings or ferrules that have one end capped with a small hole that the scribe or cutting tool goes through ,the other holder is for normal rings. The pictures show both style holders being put into the vise and shots showing the vise closed. The beauty of this fixture is all it takes is a small loosing of the vise to enable you to rotate the ring to the new position to be engraved. A few different holders could be made to handle a wide inside ring diameter and if the 2 holes drilled in the jaws that support the rod were properly registered it would accommodate some gun cylinders.
Another thing that made the operation easier was to remove the captive retainer from the vise tightening screw (the one that keeps the vise jaws centered). This enables you to slide both jaws at the same time and position the ring under the microscope center.