Have an ax to grind
Have an ax to grind
to have a strong opinion about something, which you often try to persuade other people is correct, to have a private reason for doing something, to have a selfish motive in the background:
Environmentalists have no political ax to grind – they just want to save the planet.
Fre: avoir une hache à acérer
Fa: نظری شخصی و خودخواهانه داشتن