As i understand the ABC orientation definition the C angle defines the turn of the tool around its own X'' axis .
If this is the case then for symmetric tool like drills turning the tool around its own X axis has no meaning as it symmetric .
Am i correct in this understanding.
By relative coordinate system i assume that before the "A" turn the tool axis are defined by vectors X=(1,0,0),Y=(0,1,0) and Z=(0,0,1). After the first turn the toll is a new system defined by X',Y',Z' and after the second turn we are in X'',Y'',Z''.