That's a good question! this has never come up before, and is something of a mystery to me. I am familiar with a number of lathes around here, both conventional and otherwise, Mach3 and Siemens controllers, all using Ezilathe Correctly. Hopefully, Someone out there reading this can rule on this point.

However, I can state the following :-
Ezilathe DXF selection is inline with Cad system Coordinates, where Cad Y axis is positive above Center (0). This means that I do have to mirror Arcs to suit a conventional lathe.

Ezilathe Arc direction is in line with the Mach3 Wizards. On my lathe, the "Reversed arcs in front toolpost" checkbox is always checked, as expected with a lathe like mine (Boxford 125TCL). Removing this checkmark and both Ezilathe and Mach3 wizards display and cut incorrectly. I note that this particular wizard always generates G3 (Counterclockwise) - Convex radius cut from OD to center. What I don't understand here is why the mach3 display also changes? I cannot see another setting working in concert with this checkbox.

To me, G2 is Clockwise, and G3 is Counterclockwise, as viewed from above on a conventional lathe using the front toolpost, but I could be wrong. This is what Ezilathe is designed to do.

That said, I can certainly add a checkbox to "Invert Arc Direction" if there is a need for it, as it would be a simple addition. I will have to find a free viewer and play with that.