Hello,
For starters, I DO NOT have a machine running Mach3. I run a commercial shop with Fanuc and Mitsubishi controls. That said, I spend a fair amount of time helping out on the Fusion 360 CAM forum and one question that pops up often enough is this scenario (from people using Mach3 or 4):
"Can I rotate the spindle on my CNC router to make it a horizontal mill"
"I have a home built router that allows me to position the head at 90 degree increments and rotate it around 360 degrees (in 90 deg increments)"

I guess I'm stymied on HOW Mach3 handles machines like these and what sort of g-code format it is looking for.

Couple examples of this question:
https://forums.autodesk.com/t5/fusion-360-computer-aided/mill-the-side-of-a-box/td-p/7940664
https://forums.autodesk.com/t5/fusion-360-computer-aided/setup-wcs-with-different-tool-orientation-wcs/td-p/7804362

In the first scenario, I'd imagine that a vertical/horizontal conversion would be as easy as swapping axis assignments (Y becomes Z, Z becomes Y), but I start to lose clarity of thought when we start moving into other axis arrangements. It seems to me that the easiest thing to do would be to have "Euler Angles" with G68.1 coordinate rotation (much like multi-axis millturn centers use)

So.....
I guess I'm looking for suggestions on how you all handle custom machines like this, and what you would want to see for g-code output.

Thanks in advance!

-Seth

and one question that pops up often enough is this scenario

To be honest, I think this is far more rare than you may think. I've been following this forum for about 10+ years, as well as other forums where Mach3 is used by a majority of the members, and I think I've only seen a machine like this maybe twice?

Mach3 has no special support for this, so it's up to the user how they set up the machine. It's either setup like a traditional machine, with the horizontal spindle moving up and down, or the Z axis becomes X or Y, with the gantry moving along the Z axis. (Basically just rotating the machine 90°)

With the first, getting g-code from a traditional CAM program would be very tricky. With the second, it's just standard code.