I have m20 romi cnc lathe. I have chased right hand threads of all different types: pipe taper, double lead, straight, hydrill. I just can't seem to figure out how to chase left hand of any type. I have tried it with the thread repair cycle by running the tool from back to front with a right hand internal tool cw and from front to back with a left hand tool ccw. Neither way worked. If anybody has any suggestions it would be appreciated.