Philbur, It sounds like you have been answering many of your own questions. Here are a couple of real world videos of the 2L engraving on a curved surface. As far as eliminating the 4th axis, I would say it certainly reduces the need for it.
[ame=http://www.youtube.com/watch?v=gjVpr_u0PVo]cnc spring loaded engraving tool scorpion - YouTube[/ame]
[ame="http://www.youtube.com/watch?v=_1f4w9VOyaI"]hammer of thor engraved whisky flask titanium - YouTube[/ame]
Magma-joe
That still doesn't entirely solve the problem. Since Z is spring-loaded, if you spend more time in one place than another, it gets cut deeper. So Z-feeds especially end up deeper than desired. As do places where engraving lines cross each other.
It's still a handy thing for uneven surfaces since those are a real pain without something like that, but it's not the answer to everything.
Philbur, Its called a depth control control engraving system. It is an accessory for the spring loaded tool, adjustable by .001 depth and used for very soft metals. I don't have one so I can't comment on how well it works.
I can say this, spring loaded engraving tools are nothing new and have been used for a long time on dedicated engraving machines. They work well and are used on different types of materials.
2L just happened to patent a tool to fit in a mill. I attached a video of a rotary spring loaded engraving spindle commonly used on router / engraving machines. Same concept and they are adjustable by .001 increments as well. The engraving bits are loaded from the top of the spindle. The spring loaded spindle in the video sells for about $400.00 US.
2L depth control
Depth Control Engraving with the Spring Loaded Engraving Tools
Vision Engraving Spindle Video
[ame=http://www.youtube.com/watch?v=WCEcTeI4054]Vision Engraver 24 Series - YouTube[/ame]
Magma-joe
Don't get me started on 2L's patent...
I've not tried the 'nose' piece, but it sort of defeats the purpose of engraving on uneven surfaces.
Check out Harvey Tool - Harvey Tool > Carbide Miniature End Mills, Diamond End Mills, Carbide Long Flute End Mills, Carbide Long Reach End Mills
I use many of their engraving tools - excellent quality.
Your cut looks a lot deeper then .010". Can I confirm your numbers here? Thx
The entire thread is over 10 years old so you may not a response.