tighten the screws (on somebody)to try to force someone to do something, by threatening them or making things difficult for them – used in news reports
[TahlilGaran] Dictionary of Contemporary English ▲
tighten the screws v. phr. To try to make someone do something by making it more and more difficult not to do it; apply pressure.
When many students still missed class after he began giving daily quizzes, the teacher tightened the screws by failing anyone absent four times. [TahlilGaran] English Idioms Dictionary ▲