have an ax to grind
US /hæv ən æks tuː ɡraɪnd/
UK /hæv ən æks tuː ɡraɪnd/
1.
to have a private reason for doing or being involved in something, especially a selfish one
:
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He seems to have an ax to grind with the company, always criticizing their policies.
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I don't have an ax to grind; I'm just stating the facts.